Category Archives: PoCUS Pearl

PoCUS in Early Pregnancy – a review

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PoCUS in Early Pregnancy – a Resident Clinical Pearl (RCP)

Dr. Victoria Landry, R3

Integrated Family Medicine Emergency Medicine Program

Saint John, NB

Edited by Dr. Rawan AlRashed, PoCUS fellow

Copyedited by Dr. Mandy Peach

PoCUS use by the emergency physician for the diagnosis of uncomplicated intrauterine pregnancy have been proven to be affective in expiditing patient management and decreasing the length of stay in the emergency department. In a metanlaysis done by Stein et.al. emergency physiscain performed PoCUS was found to be 99.3% sensitive in ruling out ectopic pregnancy by detecting an Intauterine pregnancy (IUP). In this review, ultrasound findings in the first trimester will be highlighted.

Indication: Confirmed or suspected pregnancy with abdominal pain, vaginal bleeding, syncope, or hypotension(2)

Technique

Start with trans-abdominal ultrasound (TAUS) (1,2)

  • Use abdominal probe (deep penetration, wide field view; use “obstetrics” or “gynecology” preset)
  • Acoustic window is a full bladder (anechoic structure in the near field). Uterus is a homogenous structure beneath bladder
  • Place abdominal probe midline longitudinally/sagitally immediately superior to symphysis pubis with probe marker toward patient’s head. Adjust depth so uterus is in middle of screen. Sweep left and right till uterus disappears in each view.
  • Rotate probe 90° into transverse plane with marker toward patient’s right side. Sweep up and down till uterus disappears in each view.
  • To improve image: Turn the gain down, sweep slowly

Then Consider the use of transvaginal ultrasound (TVUS) if available, and qualified to use  (1)

  • Requires empty bladder, Patient in lithotomy position.
  • Ultrasound gel on probe, latex condom over top (ensure no air bubbles), then sterile lubricant
  • Reference mark toward ceiling (in sagittal orientation), insert 4-5cm into vagina, sweep left and right
  • Turn probe 90° C to be in coronal plane and marker to the right of the patient – sweep anterior and posterior

General principles (1)

  • follow the endometrial stripe (echogenic line within uterus) along its entire course (left to right in longitudinal view, cervix to fundus in transverse view), looking for evidence of a pregnancy
  • You are trying to rule in an intrauterine pregnancy (IUP) (as opposed to rule out an ectopic) – assume all pregnancies are ectopic until proven otherwise(2)

 

Figure 1 – Longitudinal/sagittal view (TAUS): (1)

Figure 2 – Transverse view (TAUS): (1)

Discrimination zone (βHCG levels below which you cannot see an IUP)(2, 3)

  • TVUS – βHCG 1500-2000 mlU/ml
  • TAUS – βHCG 5000-6000 mlU/ml
  • If No definite IUP (NDIUP) above these levels, strongly consider ectopic!

Findings:

Inutrauterine pregnancy

  • The “double ring sign” is the earliest sign of a definitive IUP. Diagnosing an intrauterine pregnancy (IUP) requires visualization of all 3 structures inside the uterus. (1,2)
  • Decidual reaction – hyperechoic (white) line in uterus (2) represents endometrium thickening – begins around day 14 post-fertilization (1)
  • Gestational sac – anechoic (black) round area within decidual reaction, contains amniotic fluid, seen at 4-5wks (TVUS), 6wks (TAUS) (2)
  • Yolk sac +/- fetal pole within the gestational sac(2)
    • Yolk sac: circular echogenic layer, looks like a cheerio, visible when gestational sac is 10mm by TVUS (~5-6wks GA), 20mm by TAUS (~6-7wks GA) (1)
    • Fetal pole: echogenic structure; develops around the same time as yolk sac but visualized on US ~1wk later(1)

Figure 3 – Double ring sign(1)

Figure 4 – Double ring sign(4)

Figure 5 – Fetal pole(1)

Measurements

Mean sac diameter

  • Obtain sagittal view of gestational sac, measure height and length of sac using mean sac diameter calculation package, rotate probe 90º to obtain transverse view of gestational sac, measure width of sac
  • MSD (mm) + 30 = Gestational age (days)

 

Crown-rump length (CRL) = Top of skull to base of pelvis(1)

  • >5mm without visible fetal heart = unlikely to proceed to viability
  • CRL (mm) + 42 = gestational age (days)
  • The most accurate method of dating the pregnancy(3)

 

Fetal cardiac activity = proof of live IUP(1)

  • detectable ~6wks on TVUS (fetal pole is >5mm), 7-8wks on TAUS (fetal pole is >10mm) (1)
  • Normal IUP with fetal cardiac activity is reassuring!
    • absence of cardiac activity will likely result in miscarriage, presence of cardiac activity reduces risk of miscarriage (HR >100 consistent with good fetal outcome)
  • Technique(3)
    • Locate fetal pole, optimize depth, turn on M-mode (never doppler as it subjects fetus to high US energy and may be harmful)(1,2), place caliper over beating heart, measure and calculate heart rate
    • Note: must be within gestational sac, well away from uterine wall (don’t confuse with highly vascular decidual reaction)(1)
    • Normal FHR Ranges
      • 6-7wks: 100-120bpm
      • 8wks: 145-170bpm
      • 9+wks: 120-160bpm

 

Other findings and descriptions

No definitive intrauterine pregnancy (NDIUP) (2)

  • if any single criteria of IUP is missing

DDx for NDIUP(2):

  • Early normal pregnancy (βHCG below discrimination zone)
  • Threatened/spontaneous abortion
  • Anembryonic pregnancy (blighted ovum)
  • Molar pregnancy
  • Ectopic pregnancy

Threatened abortion: abnormal bleeding during pregnancy; normal IUP on US(3)

Inevitable abortion: vaginal bleeding with open os; normal IUP or product of conception (POC) near cervix on US(3)

Incomplete abortion: open os with retained POC; US shows anything from debris to embryo; abnormal uterine contents confirms dx(1)

Complete abortion: empty uterus + positive βHCG +/- closed os; same findings as for ectopic therefore requires formal US + serial βHCG(1)

Ectopic pregnancy (3)

  • NDIUP (no definitive intrauterine pregnancy) above βHCG in discriminatory zone
  • Scan adnexa for signs of ectopic
    • Tubal ring sign (thick hyperechoic ring around a tubal mass)
    • Ring of fire sign (also seen in corpus luteum cysts; high velocity flow seen on color doppler around the
    • gestational sac + fetal pole with cardiac activity outside the uterus is diagnostic of an ectopic
  • assess pouch of douglas for free fluid
  • suspicious for ectopic: ectopic mass, fluid in cul de sac, absent IUP, abnormal βHCG pattern (normally rises at least 50% in 48hr period)

Corpus luteal cyst(2,3)

  • develops due to growth, instead of normal regression, of corpus luteum
  • appears very similar to ectopic, but will move with the ovary in response to transducer manipulation instead of independent, tubal ring is thinner and less echogenic, cystic fluid is more clear and anechoic (rather than “clumpy” with echoes)
  • ovarian cyst characteristics: outside the uterus, circular, well circumscribed, do not taper to solid organs

Blighted ovum (anembryonic pregnancy)(1,2)

  • abnormally large gestational sac with no embryonic contents
    • gestational sac >20mm without yolk sac visible à suspect blighted ovum
    • >25mm without yolk sac visible à blighted ovum virtually certain (Eliminates diagnosis of ectopic)
  • Positive βHCG (higher than expected for GA)
  • Confirm with formal US

Molar pregnancy (1,3)

  • Tumor due to uncontrolled proliferation of trophoblasts (cells that surround blastocyst and later become the placenta)
  • Complete mole: no fetal/embryonic tissue; abnormally elevated βHCG >100,000 mIU/ml
  • Partial mole: may contain (abnormal) fetal structures
  • Presentation: hyperemesis, larger uterus than expected, vaginal bleeding, anemia, signs of hyperthyroidism, pregnancy-induced hypertension
  • US: appears as a “snowstorm” or “cluster of grapes” in uterus – fairly homogenous mass full of small, fluid-filled (black) holes; no detectable fetal cardiac activity
  • Needs gyne referral for surgical evacuation(2)

Pitfalls

  • Pseudogestational sac (1, 3)
    • contains no yolk sac, usually more irregularly shaped or pointy-edged than a true gestational sac, border is not as echogenic, and fluid may contain some echoes
    • Intrauterine fluid collections occur in 9-20% of ectopic pregnancies
    • Unless all 3 criteria met for double ring sign, pt requires formal US
  • Extrauterine pregnancy(1)
    • Recognize uterine tissue and always confirm bladder-uterus juxtaposition(2)
  • Interstitial and cornual ectopic pregnancies(1)
    • Rare but dangerous – tend to rupture later therefore produce more rapid hemorrhage than other ectopics
    • Myometrium around interstitial and cornual pregnancies is thin and uneven(2)
    • Measure the “myometrial mantle” (the thinnest part of myometrium around the gestational sac) – should be >5-7mm thick (thinner is concerning for cornual or interstitial ectopic pregnancy) (2)
  • Multiple pregnancies(2)
    • In multiple gestation, each fetus needs to meet the criteria for IUP
    • Heterotopic pregnancies = combined IUP and ectopic pregnancy
      • Risk is 1:30,000 in general population
      • Risk increases to 1:100 with fertility treatment (e.g. IVF)

Figure 7 – Extrauterine pregnancy(1)

Figure 8 – Normal myometrial mantle(1)

Figure 9 – Cornual ectopic pregnancy(1)

Key points(1)

  • False positive IUP can have devastating consequences
  • Any positive βHCG + no definitive IUP = presumed ectopic
    • Pt stable + no free fluid à formal US + quantitative βHCG
      • If no ectopic mass, repeat formal US and βHCG in 48hrs with consideration of patient risk of ectopic pregnancy
      • Follow up with OB to be arranged
    • Always consider other diffrerntail diagnosis for patient presentation before discharging them home.

Figure 10 – Clinical application(2)

 

References:

  1. Socransky, S., & Wiss, R. (2016). Obstetrical EDE. In Essentials of point-of-care ultrasound: The EDE book (pp. 61-90). The EDE 2 Course.
  2. Long, N. (2020, March 02). VanPOCUS: 1st Trimester Obstetrics • LITFL • Ultrasound Library. Retrieved October 15, 2020, from https://litfl.com/vanpocus-1st-trimester-obstetrics/
  3. Dinh, V. (n.d.). Obstetric/OB Ultrasound Made Easy: Step-By-Step Guide. Retrieved October 15, 2020, from https://www.pocus101.com/obstetric-ob-ultrasound-made-easy-step-by-step-guide/
  4. Flores, B., Smith, T., & Joseph, J. (n.d.). OB/Gyn. Retrieved October 15, 2020, from https://www.thepocusatlas.com/obgyn-1

 

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Advanced cardiac echo – a review of E-point septal separation

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Dr. Kyle Traboulsee, PoCUS Fellow

Reviewed by Dr. David Lewis

Copyedited by Dr. Mandy Peach

Background:

Often hypotensive, or acutely dyspneic patients, present to the emergency department in significant distress, and emergency physicians must work quickly to evaluate, stabilize, and treat these patients. In the past, determining whether there was a cardiac etiology to these presentations often relied solely on history, physical exam, and varies biochemical markers. Point-of-care ultrasound has increasingly been adopted as a tool to assess cardiac function, and specifically left ventricular ejection fraction (LVEF). Different methods can be used to estimate LVEF (such as “eyeballing”, and the Simpson method), but they can have large inter-reader variability, and require significant cardiac PoCUS experience. E-point septal separation is a measurement of how close the anterior mitral valve leaflet comes towards the interventricular septum and has been shown to be a quick and easy method for estimating LVEF. (1)(2)

 

Anatomy/pathophysiology

               Blood flow is determined by pressure gradients, where blood will travel from areas of high pressure to low pressure. Such a pressure gradient exists between the left atrium and left ventricle. During diastole, the left ventricle relaxes, and the intraventricular pressure decreases until the pressure falls below that of the left intra-atrial pressure. When the left atrial pressure exceeds the left ventricular pressure, the mitral valve opens, and blood passively flows from the high(er) pressure atrium to the lower pressure ventricle. This occurs early in diastole, and the flow of blood from atrium to ventricle is further assisted by an atrial contraction (termed atrial kick) later in diastole. In a healthy individual the atrial-ventricular (A-V) gradient is sufficient to open the mitral valves and bring the anterior mitral leaflet in proximity (or contact) with the intraventricular septum. (1)(2)(3)

In the case of reduced LVEF, the diastolic pressure inside the left ventricle increases due to a decreased ability to eject blood during systole. This can occur due to several reasons, but often result in left ventricular dilation to compensate and preserve LVEF. As LVEF decreases, the ventricular diastolic pressure increases, and the atrial-ventricular (A-V) gradient decreases, leading to a decreased flow rate from atrium to ventricle during diastole, and thus a decreased mitral valve opening. That, paired with LV dilation, leads to an increased (measurable) distance between the anterior mitral valve leaflet and the intraventricular septum during diastole, which can be used as a surrogate marker for left ventricular function. (1)(2)(3).

 

PoCUS Technique

The E-point septal separation measurements will be made using a parasternal long axis (PLAX) view

Obtaining PLAX view

Steps:

  • Place probe at the left parasternal border, just caudal to manubrium (second intercostal space), perpendicular to the chest. Ensure the probe indicator is placed towards to the patient’s right shoulder.
  • Slowly slide the probe down each successive intercostal space, as well as medially (not exceeding patient midline), and laterally, until the highest quality images are obtained (this will likely be around 3-5th intercostal space, left parasternal border, but may differ from patient to patient)
  • Once the best view has been located from step 2, slowly rotate the probe to elongate the left ventricle as much as possible. The probe may need to be rocked (heeled) to center the image.

The optimal PSL image includes the left ventricle (LV) in continuity with the aortic outflow tract. The right ventricle will be near field, the left atrium far field, and the mitral valve, aortic valve, and LV cavity are in between (in the middle of the field).  The apex of the left ventricle will be screen left. (4)(5).

Parasternal long axis view- probe orientation (6)              Parasternal long axis view-anatomy (7)

Parasternal long axis view: normal (own image)

EPSS measurements

EPSS measurements are commonly obtained using M-mode.

  • Once a parasternal long axis view (PLAX) is obtained, turn on M-mode, and place the cursor over the apical tip of the anterior mitral valve leaflet.
  • The M-mode will demonstrate movement of the anterior mitral leaflet, with respect to the intraventricular septum. The image should show 2 peaks per heart cycle, under a hyperechoic line. The first, larger peak (E), represents the initial opening of the mitral valve from passive blood flow in early diastole caused by the A-V gradient. The second, usually smaller peak (A), represents the atrial kick, occurring later in diastole. This M mode image is commonly referred to as a “cloudy sky over two hills”
  • Measure the distance from the top of the E wave to the intraventricular septum. (1)(5)

A normal EPSS measurement with M-mode (8)

PSL: normal EPSS, M-mode (own image)

An abnormal EPSS measurement with M-mode (8)

EPSS measurements can alternatively be measured in B mode

  • Once a parasternal long axis view (PLAX) is obtained, ensure anterior mitral valve leaflet and septum are well visualized over 3-5 cardiac cycles
  • Freeze the image and cycle through the previous 3-5 cardiac cycles, stopping on the image where the anterior mitral valve leaflet lies closest to the intraventricular septum.
  • Measure the distance between the tip of the anterior mitral valve leaflet and the intraventricular septum.

PSL-Poor mitral valve opening (own image)

PSL view- abnormal EPSS measurement in B mode (9)

 

Interpretation

An EPSS < 7mm is considered normal

An EPSS >7 mm has been suggested as 87% sensitive and 75% specific for an EF <50% (10)

Another study suggested that an EPSS >7 mm was 100% sensitive and 51.6% specific for an EF<30% (11).

One MRI study came up with the following formula to calculate EF (4):

EF=75.5 – (2.5 x EPSS in mm)

 

Pitfalls

               Although a quick and relatively simple surrogate measurement for LVEF, there are some patient populations and situations in which EPSS may give in inaccurate estimate of cardiac function. Patients with mitral stenosis may have poor valve opening, leading to a high EPSS, in the context of an otherwise normally functioning left ventricle. Patients with aortic regurgitation may also have poor anterior mitral valve leaflet motion, and thus have a falsely high EPSS. For these reasons, it would be reasonable to apply color doppler across the mitral and aortic valves to assess for signs of regurgitant jets, as well as close assessment of the valves for signs of calcification. Off-axis measurement, regional wall motion abnormalities, and left ventricular hypertrophy may also result in false interpretations concerning LVEF (1)(3)(4).

 

Bottom line

               E-point septal separation is a relatively easy and reproducible technique that can be used to generate a quick estimation of left ventricular function and can help point towards a cardiac etiology in the undifferentiated patient.  It is important to keep in mind factors (as discussed) that may lead to false EPSS interpretations, and EPSS results should not preclude a more global cardiac assessment.

 

References:

  • Boon, S. C., Lopez Matta, J. E., Elzo Kraemer, C. V., Tuinman, P. R., & van Westerloo, D. J. (2020). POCUS series: E-point septal separation, a quick assessment of reduced left ventricular ejection fraction in a POCUS setting. Netherlands Journal of Critical Care, 28(3), 139–141.
  • Cisewski , D., & Alerhand, S. (2018, December). Fellow corner: E-point septal separation in the patient with congestive heart failure. ACEP // Home Page. Retrieved October 18, 2021, from https://www.acep.org/how-we-serve/sections/emergency-ultrasound/news/dece/fellow-corner-e-point-septal-separation-in-the-patient-with-congestive-heart-failure/.
  • Miller, T., Salerno, A., & Slagle, D. (2021, May 25). Advanced Critical Care Ultrasound: E-Point Septal Separation to Estimate Left Ventricular Ejection Fraction. EM resident . Retrieved October 2021, from https://www.emra.org/emresident/article/epss/.
  • Atkinson, P., Bowra, J., Harris, T., Jarman, B., & Lewis, D. (2019). Point-of-care ultrasound for Emergency Medicine and Resuscitation. Oxford University Press.
  • Socransky, S., & Wiss, R. (2016). Essentials of point-of-care ultrasound: The ede book. The EDE 2 Course, Inc.
  • SonoSpot, & SonoSpot. (2012, September 17). Sonotip&Trick: “I can’t get a good parasternal long view.” really? well, try this… Retrieved October 18, 2021, from https://sonospot.wordpress.com/2012/08/07/sonotiptrick-i-cant-get-a-good-parasternal-long-view-really-well-try-this/.
  • Roma, Ak, Sparks, M., Kelly, C., (@NephroP), A. K., Dowd, R., Crosson, D. A., Deepali, D., Singh, N., Andreea, Aya, S.A., A., Panchal, L. M. R., & Murthy, J. (2019, June 7). Introduction to focused cardiac ultrasound: The parasternal long axis view. Renal Fellow Network. Retrieved October 18, 2021, from https://www.renalfellow.org/2019/06/07/introduction-to-focused-cardiac-ultrasound-the-parasternal-long-axis-view/.
  • Miller, T., Salerno, A., & Slagle, D. (2021, May 25). Advanced Critical Care Ultrasound: E-Point Septal Separation to Estimate Left Ventricular Ejection Fraction. EM resident . Retrieved October 2021, from https://www.emra.org/emresident/article/epss/.
  • Satılmış Siliv, N., Yamanoglu, A., Pınar, P., Celebi Yamanoglu, N. G., Torlak, F., & Parlak, I. (2018). Estimation of cardiac systolic function based on mitral valve movements: An accurate bedside tool for emergency physicians in DYSPNEIC patients. Journal of Ultrasound in Medicine, 38(4), 1027–1038. https://doi.org/10.1002/jum.14791
  • Ahmadpour H, Shah AA, Allen JW, et al. Mitral E point septal separation: a reliable index of left ventricular performance in coronary artery disease. Am Heart J. 1983;106(1 Pt 1):21-8
  • McKaigney, C. J., Krantz, M. J., La Rocque, C. L., Hurst, N. D., Buchanan, M. S., & Kendall, J. L. (2014). E-point septal separation: A bedside tool for emergency physician assessment of left ventricular ejection fraction. The American Journal of Emergency Medicine, 32(6), 493–497. https://doi.org/10.1016/j.ajem.2014.01.045
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Alternative Rib Fracture Management in the ED

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Alternative Rib Fracture Management in the ED – A Medical Student Clinical Pearl

Victoria Mercer, Clinical Clerk 3, DMNB

Reviewed and Copyedited by Dr. Mandy Peach

Rib fractures are a frequent presentation in the ED, occuring in approximately 10% of all injured patients with the primary causes being blunt chest trauma and MVAs(1,2).  The mainstay of treatment for rib fractures is analgesic control(1). When pain cannot be adequately managed, the patient is at a heightened risk of hypoventilation due to decreased thoracic mobility and secretion clearance, predisposing the patient to significant atelectasis(1,2).

Historically the pain from rib fractures has been managed with acetaminophen or NSAIDS and if these do not sufficiently alleviate the pain, opioids are used(1,3). Unfortunately, these methods often do not provide adequate pain control or in the case of opioids, come with a myriad of side effects such as nausea, vomiting, constipation, respiratory depression and the potential for dependency and abuse (1,4).

An alternative to traditional methods include regional techniques such as paravertebral or epidural nerve blocks. These interventions have been shown to effectively control pain in rib fractures(3,4). The downside to these interventions include being technically challenging and time consuming with significant complication risks and contraindications such as coagulation disorders (1,3).

The solution? A serratus anterior block 

An ultrasound guided blockade of the lateral cutaneous branches of the thoracic intercostal nerves was first described by Blanco et al. in 2013 for patients following breast surgery to manage their postoperative pain(5). This procedure has been adopted by many emergency departments for its convenience and practicality compared to epidural or paravertebral nerve blocks(3).

Serratus anterior blocks are less invasive and considerably more practical in the ED setting, providing paresthesia to the ipsilateral hemithorax for 12-36 hours (6).

The only absolute contraindications are patient refusal, allergy to local anesthetic and local infection(1).

Complications of a serratus anterior block include pneumothorax, vascular puncture, nerve damage, failure/inadequate block, local anesthetic toxicity and infection(1).

Serratus anterior blocks are only effective for the anterior two-thirds of the chest wall (3).

 

Figure 1. Ultrasound image of serratus anterior muscle and surrounding tissues with superficial or deep needle guides. Image from Thiruvenkatarajan V, Cruz Eng H, Adhikary SD. An update on regional analgesia for rib fractures. Current Opinion in Anaesthesiology. 2018;31(5):601–607.

How do you do it?

The procedure is usually performed with the patient laying supine however the patient could also lay in a lateral decubitus position (1,3). Using a high frequency linear ultrasound probe (6-13MHz), identify the serratus anterior and latissimus dorsi muscles over the fifth rib in the mid-axillary line(1,3). Using an in-plane approach, insert the needle either superficial or deep to the serratus anterior and confirm correct needle placement by visualizing anaesthetic spread via ultrasound(1,3). According to May et al., superficial spreading tends to have a longer lasting analgesic effect(1). Place and secure a catheter to infuse the remainder of the bolus(1,3). Thiruvenkatarajan et al. recommend a bolus of 40ml of 0.25% levobupivacaine and a 50mm 18G Tuohy catheter needle(3).

See this excellent review by Dr. David Lewis on identifying rib fractures and their complications using ultrasound (start 3:08) as well as a review of the block and procedure (start 8:00)

Rib Fractures and Serratus Anterior Plane Block

References

  1.         May L, Hillermann C, Patil S. Rib fracture management. BJA Education. 2016 Jan 1;16(1):26–32.
  2.         Malekpour M, Hashmi A, Dove J, Torres D, Wild J. Analgesic choice in management of rib fractures: Paravertebral block or epidural analgesia? Anesthesia and Analgesia. 2017 Jun 1;124(6):1906–11.
  3.         Thiruvenkatarajan V, Cruz Eng H, Adhikary S das. An update on regional analgesia for rib fractures. Vol. 31, Current opinion in anaesthesiology. 2018. p. 601–7.
  4.         Tekşen Ş, Öksüz G, Öksüz H, Sayan M, Arslan M, Urfalıoğlu A, et al. Analgesic efficacy of the serratus anterior plane block in rib fractures pain: A randomized controlled trial. American Journal of Emergency Medicine. 2021 Mar 1;41:16–20.
  5.         Blanco R, Parras T, McDonnell JG, Prats-Galino A. Serratus plane block: A novel ultrasound-guided thoracic wall nerve block. Anaesthesia. 2013 Nov;68(11):1107–13.
  6.         Mayes J, Davison E, Panahi P, Patten D, Eljelani F, Womack J, et al. An anatomical evaluation of the serratus anterior plane block. Anaesthesia [Internet]. 2016 Sep 1 [cited 2021 Apr 18];71(9):1064–9. Available from: http://doi.wiley.com/10.1111/anae.13549

 

 

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PoCUS & COVID Severity

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Dal PoCUS Fellowship Journal Club March 2021

Dr. Mandy Peach

PoCUS Fellow

Dalhousie University Department of Emergency Medicine

Zieleskiewicz L, Markarian T, Lopez A, Taguet C, Mohammedi N, Boucekine M, Baumstarck K, Besch G, Mathon G, Duclos G, Bouvet L, Michelet P, Allaouchiche B, Chaumoître K, Di Bisceglie M, Leone M; AZUREA Network. Comparative study of lung ultrasound and chest computed tomography scan in the assessment of severity of confirmed COVID-19 pneumonia. Intensive Care Med. 2020 Sep;46(9):1707-1713. doi: 10.1007/s00134-020-06186-0. Epub 2020 Jul 29. PMID: 32728966; PMCID: PMC7388119.

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Rib Fractures and Serratus Anterior Plane Block

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Saint John EM Rounds – March 2021

Dr. David Lewis

@e_med_doc

 

View PDF here

Further Reading and Links

 

 

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Scaphoid Fracture – Can PoCUS disrupt the traditional ‘splint and wait’ pathway?

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PoCUS Fellow Pearl

Dr. Melanie Leclerc, CCFP-EM

MSK PoCUS Fellow

Dalhousie University Department of Emergency Medicine

 

Reviewed & Edited by Dr David Lewis (@e_med_doc)

All case histories are illustrative and not based on any individual

 

Case:

A 37 year old, right hand dominant, carpenter presents to your local ED with a complaint of right wrist pain. He was on a step-stool and lost his balance earlier today. He fell landing on his outstretched arm and had an acute-onset of radial-sided wrist pain. He denies any other injury. There are no neurologic complaints.

On exam, there is no visible deformity. The skin is closed and there is some swelling noted. The patient is tender over the anatomic snuff box as well as volarly over the scaphoid. There is pain noted with axial loading of the thumb. There is no other tenderness. ROM is within normal limits. The limb is distally neurovascularly intact.

X-rays are normal.

An occult scaphoid fracture is suspected. At this institution, patients with suspected occult scaphoid fracture are placed in a thumb spica splint and referred to the local hand surgeon to be seen in ~10-14 days for repeat assessment and X-ray.

Can Point of Care Ultrasound change this traditional “splint and wait” patient pathway?

 

Background:

Scaphoid fracture is a common presentation to the Emergency Department accounting for approximately 15% of all wrist injuries and 70% of carpal fractures. Up to 30% of the time, radiographs at initial presentation appear normal making fracture a commonly missed injury for Emergency physicians. A failure to recognize this injury can lead to chronic pain and functional impairment for patients. Particularly, fractures of the proximal pole (most distant to the blood supply) can lead to avascular necrosis (AVN) at high rates. Non-union can lead to scaphoid non-union advanced collapse (SNAC wrist) which can perpetuate further degenerative changes throughout the carpus. This can cause a significant impact on quality of life and occupation. Early detection of fracture could expedite fixation and possibly results in better outcomes. Further study in this area is needed.

 

Anatomy:

The scaphoid bone lies in the radial aspect of the proximal carpal row. It’s unique shape (“twisted peanut”), lends to easy recognition. It articulates proximally with the distal radius, distally with the trapezium, and on its’ ulnar aspect with the lunate to form the scapho-lunate interval. The blood supply to the scaphoid is unique in that the majority of it is retrograde. The dorsal carpal branch of the radial artery supplies the bone from distal to proximal. A small proportion of the blood supply originates at the proximal end. The boundary between the two supplies creates a “watershed” area prone to non-union and AVN.

 

Classification of Fractures:

Scaphoid fractures are classified by location. These regions are the proximal, middle and distal thirds which account for 20%, 75%, and 5% of the fractures respectively. The stability of fractures is determined by the displacement (>1mm) and angulation (scapholunate angle >60 and radiolunate angle >15). The Hebert Classification as endorsed by Traumapedia can be found below.

 

Traditional Imaging:

Imaging of these suspected injuries varies. Traditionally serial X-rays were used, but have been found to be poorly sensitive even several weeks after injury. Bone scan has also been used as an alternative due to it’s high sensitivity, but has poor specificity and provides no further information regarding the nature of the fracture. CT is relatively sensitive and specific and provides information for pre-operative planning. MRI is considered the gold standard, but is difficult to obtain in a timely manner in Canada.

Bäcker HC, Wu CH, Strauch RJ. Systematic Review of Diagnosis of Clinically Suspected Scaphoid Fractures. J Wrist Surg. 2020 Feb;9(1):81-89. doi: 10.1055/s-0039-1693147. Epub 2019 Jul 21. PMID: 32025360; PMCID: PMC7000269.

 

PoCUS Technique:

  • Linear probe

  • Consider waterbath, gel standoff pad, or bag of IV fluid

  • Scan with the wrist ulnarly deviated

  • Scan in the longitudinal and transverse orientations of volar, lateral and dorsal aspects

  • Place the probe in longitudinal orientation dorsally over lister’s tubercle of the radius and scan distally until the scaphoid is visualized in the snuff box. Scan radial to ulnar.

  • Rotate to the transverse orientation and scan through proximal to distal

  • Volarly, in the transverse plane, identify the tendon of the flexor carpi radialis (this lies radial to the easily identifiable palmaris longus tendon on exam). The scaphoid is found deep to this. Scan proximal to distal.

  • Rotate to the longitudinal orientation and scan radial to ulnar

 

 

Video Demonstration:

 

 

Findings:

  • Cortical disruption

  • Periosteal elevation

  • Hematoma

 

The Evidence:

  • Early advanced imaging (CT or MRI) compared to initial 2 week immobilisation proved more cost effective and had better patient oriented outcomes (ie. missed work).(7)
  • A systematic review and meta analysis of moderate to high quality studies published in 2018 found that ultrasound had a mean sensitivity of ~89% and specificity of ~90% for detection of occult scaphoid fractures.(1)
  • Similar results were also reported by another systematic review in 2018.(8)
  • Pocus was shown to have a comparable sensitivity to CT for occult scaphoid in a systematic review published in 2020.(2)

 

Limitations:

  • Only useful if positive
  • Operator experience dependent
  • US probe and frequency dependant
  • Potential for false positives due to injury of nearby structure causing hematoma
  • Potential for false positives in context of arthritis or remote trauma

 

Bottom line:

  • Useful if positive
  • Still need definitive test to further delineate fracture (ie: for operative planning)
  • Could expedite CT
  • Could expedite specialist follow-up
  • May improve ER physician diagnostic certainty
  • May improve patient trust and compliance with splinting
  • Further study is needed

 

Case Conclusion:

Scaphoid cortical disruption was visualized using PoCUS. After discussion with the hand surgeon, a CT Scan of the wrist was performed which confirmed a minimally displaced waste fracture of the scaphoid. The patient was splinted and seen the next day in clinic for discussion regarding operative management.

 

Further Review:

 

 

 

References

  1. Ali M, Ali M, Mohamed A, Mannan S, Fallahi F. The role of ultrasonography in the diagnosis of occult scaphoid fractures J Ultrason 2018; 18: 325–331.
  2. Bäcker HC, Wu CH, Strauch RJ. Systematic Review of Diagnosis of Clinically Suspected Scaphoid Fractures. J Wrist Surg. 2020 Feb;9(1):81-89.
  3. Bakur A. Jamjoom, Tim R.C. Davis. Why scaphoid fractures are missed. A review of 52 medical negligence cases, Injury, Volume 50, Issue 7, 2019, Pages 1306-1308.
  4. Carpenter CR et al. Adult Scaphoid Fracture. Acad Emerg Med 2014; 21(2): 101-121.
  5. Gibney B, Smith B, Moughty A, Kavanagh EC, Hynes D and MacMahon PJ American Journal of Roentgenology 2019 213:5, 1117-1123
  1. Jenkins PJ, Slade K, Huntley JS, Robinson CM. A comparative analysis of the accuracy, diagnostic uncertainty and cost of imaging modalities in suspected scaphoid fractures. Injury. 2008;39:768–774.
  2. Karl, John W. MD, MPH1; Swart, Eric MD1; Strauch, Robert J. MD1 Diagnosis of Occult Scaphoid Fractures, The Journal of Bone and Joint Surgery: November 18, 2015 – Volume 97 – Issue 22 – p 1860-1868.
  3. Kwee, R.M., Kwee, T.C. Ultrasound for diagnosing radiographically occult scaphoid fracture. Skeletal Radiol 47, 1205–1212 (2018).
  4. Malahias MA, Nikolaou VS, Chytas D, Kaseta MK, Babis GC. Accuracy and Interobserver and Intraobserver Reliability of Ultrasound in the Early Diagnosis of Occult Scaphoid Fractures: Diagnostic Criteria and a Way of Interpretation. Journal of Surgical Orthopaedic Advances. 2019 ;28(1):1-9.
  5. Mallee WH, Wang J, Poolman RW, Kloen P, Maas M, de Vet HCW, Doornberg JN. Computed tomography versus magnetic resonance imaging versus bone scintigraphy for clinically suspected scaphoid fractures in patients with negative plain radiographs. Cochrane Database of Systematic Reviews 2015, Issue 6.
  6. Mallee, W.H., Mellema, J.J., Guitton, T.G. et al. 6-week radiographs unsuitable for diagnosis of suspected scaphoid fractures. Arch Orthop Trauma Surg 136, 771–778 (2016).
  7. Melville, D., Jacobson, J.A., Haase, S. et al. Ultrasound of displaced ulnar collateral ligament tears of the thumb: the Stener lesion revisited. Skeletal Radiol 42, 667–673 (2013).
  8. Meyer, P., Lintingre, P.-F., Pesquer, L., Poussange, N., Silvestre, A., & Dallaudiere, B. (2018). Imaging of Wrist Injuries: A Standardized US Examination in Daily Practice. Journal of the Belgian Society of Radiology, 102(1), 9.
  9. Mohomad et al. 2019. Accuracy of the common practice of doing X-rays after two weeks in detecting scaphoid fractures. A retrospective cohort study. Hong Kong Journal of Orthopaedic Research 2019; 2(1): 01-06.
  10. Neubauer J, Benndorf M, Ehritt-Braun C, et al. Comparison of the diagnostic accuracy of cone beam computed tomography and radiography for scaphoid fractures. Sci Rep 2018; 8:3906.
  11. Ravikant Jain, Nikhil Jain, Tanveer Sheikh, Charanjeet Yadav. 2018. Early scaphoid fractures are better diagnosed with ultrasonography than X-rays: A prospective study over 114 patients, Chinese Journal of Traumatology, Volume 21, Issue 4, Pages 206-210.
  12. Senall, JA, Failla, JM, Bouffard, JL. 2004. Ultrasound for the early diagnosis of clinically suspected scaphoid fracture. J Hand Surg Am, 29:400-405.
  13. https://essr.org/content-essr/uploads/2016/10/wrist.pdf
  14. http://www.bonetalks.com/scaphoid
  15. https://radiopaedia.org/articles/scaphoid-fracture
  16. https://sketchymedicine.com/2014/07/scaphoid-bone-anatomy-and-fractures/
  17. https://radiopaedia.org/cases/scaphoid-fracture-11?lang=gb
  18. https://www.orthobullets.com/hand/6034/scaphoid-fracture
  19. https://meeting.handsurgery.org/abstracts/2018/EP15.cgi
  20. https://www.researchgate.net/figure/Bone-scintigraphy-patient-C-of-the-hands-the-patient-with-a-scaphoid-fracture-on-the_fig4_50399987
  21. https://www.youtube.com/watch?v=7pCXiRQMRKo&t=5s&ab_channel=UltrasoundPod
  22. https://litfl.com/terry-thomas-sign
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A Case of Posterior Vitreous Detachment

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A Case of Posterior Vitreous Detachment – Medical Student Clinical Pearl

Ben McMullin, Clinical Clerk III

Dalhousie Medicine New Brunswick, Saint John

Reviewed by Dr. David Lewis

Copyedited by Dr. Mandy Peach

Case Presentation

A 61 year old female presented to the emergency department complaining of a floater in her right eye, which appeared 3 days prior to presentation. The floater moved with her eye movements. The patient claimed that her vision in the right eye was slightly blurry over the past 3 days but denied any significant decline in visual acuity. She denied any trauma, eye pain, discharge, or redness, but was particularly concerned since she was blind in her left eye since childhood.

On examination, the patients right eye appeared normal, with no discharge or conjunctival injection. Her pupil was roughly 3 mm and reactive to light. Her visual acuity was 20/30 in the right eye, and extraocular eye movements as well as visual field testing were normal. The intraocular pressure in her right eye was 9 mmHg.

Anatomy of the Eye

Figure 1: Normal eye anatomy as seen with ultrasound imaging.1

 

The cornea is the most superficial convex membrane, and immediately posterior to this is the anterior chamber, which is seen as anechoic on sonography. Posterior to the anterior chamber is the iris. Immediately posterior to the lens is the posterior chamber, which is also anechoic on sonography. The outer membrane of the eye from the inner most layer to the outer consists of the retina, choroid, and sclera.2

 

Differential Diagnosis for Non-Traumatic Visual Disturbance
• Posterior vitreous detachment
• Retinal tear
• Vitreous hemorrhage
• Vitreous inflammation
• Ocular lymphoma
• Intraocular foreign body
• Uveitis3

POCUS Ocular Exam

Advantages of POCUS

Ultrasound is a useful tool in the evaluation of some ocular complaints in the ED. Dilated fundoscopic examination is not always easily performed in the ED, but bedside ultrasound is becoming more readily available to physicians.4,5 Ultrasound can be useful in diagnosis of a wide range of ocular complaints, such as retinal detachment, posterior vitreous detachment (PVD), vitreous hemorrhage, and intraocular foreign body.4

Technique

Depending on the clinical history, a bedside ultrasound examination of the eye may be performed with the patient either supine or sitting in a chair.4 A high frequency probe should be used for this exam.1

Liberal amounts of gel should be used when performing a POCUS ocular exam, so as to minimize the amount of pressure placed on the eye.4 The gel does not need to be sterile, however for patient comfort, some physicians place tegaderm over the eye being examined. In order to orient the probe properly, ensure that the indicator on the probe is pointing towards the patients head when performing a longitudinal scan, and to the patients right when performing a transverse scan.1

To ensure that the entire eye is assessed, the eye should be examined in both the longitudinal and transverse planes, and it is important to sweep through in both directions. If the patient is able, it is also helpful to ask them to look to the right and left, as well as up and down with the probe on the eye.1 It is imperative to maximize brightness – if the field is too dark pathology like vitreous detachment can be easily missed.

PVD vs Retinal Detachment on POCUS

Complete retinal detachment will often appear as a V shape on ultrasound, with the apex seen at the optic nerve.5 Partial detachments can be more subtle and can appear differently from case to case.6

PVD is less echogenic than retinal detachment. PVD can often be seen moving with eye movements, more so than with retinal detachment.5 There is often a lag seen between movement of the globe, and movement of the vitreous appendage. In PVD, the detached vitreous is not connected to the optic disc, which contrasts with retinal detatchment.6 PVD can vary widely in size and can be seen with or without vitreous hemorrhage.2

Figure 2: Retinal detachment visualized on point of care ultrasound.6

Figure 3: Retinal detachment on ultrasound. (PoCUS Atlas)

 

Figure 4: Posterior vitreous detachment visualized on point of care ultrasound.2

Figure 5: Vitreous detachment on ultrasound (PoCUS Atlas).

 

Management

In the ED, retinal detachment requires urgent referral to ophthalmology. Retinal detachment can progress to total vision loss and should be seen and treated within 24 hours.3 In contrast, isolated PVD has a much better prognosis. Typically, floaters resolve within 3 to 12 months, but patients should still be referred for follow-up within 3 months to ensure no retinal tear is detected.3

Case Conclusion

Bedside ocular ultrasound showed PVD in the patient’s right eye, with no evidence of vitreous hemorrhage or retinal detachment. The patient was reassured of the prognosis but given that she was completely dependent on her right eye for vision, ophthalmology agreed to assess her the following week.

References

  1. Roque PJ, Hatch N, Barr L, Wu TS. Bedside Ocular Ultrasound. Crit Care Clin 2014; 30(2): 227-241.
  2. Southern, Simon. Ultrasound of the Eye. Australas J Ultrasound Med 2009; 12(1): 32-37.
  3. Arroyo, Jorge G. “Retinal detachment” last modified March 19, 2020, https://www.uptodate.com/contents/retinal-detachment?search=vitreous%20detachment&sectionRank=1&usage_type=default&anchor=H3491968696&source=machineLearning&selectedTitle=1~11&display_rank=1#H1505785278.
  4. Lahham S, Qumber A, Bea MP, Lee C, Fox JC. Role of point of care ultrasound in the diagnosis of retinal detachment in the emergency department. Open Access Emergency Medicine 2019; 11: 265-270. Retrieved from https://search-proquest-com.ezproxy.library.dal.ca/docview/2314891088?accountid=%24%24CLIENTID&pq-origsite=primo.
  5. Botwin A, Engel A, Wasyliw C. The use of ocular ultrasound to diagnose retinal detachment: a case demonstrating sonographic findings. Emerg Radiol 2018; 25: 445-447.
  6. Gandhi K, Shyy W, Knight S, Teismann N. Point of care ultrasound for the evaluation of non traumatic visual disturbances in the emergency department: the VIGMO protocol. Am J Emerg Med 2019; 37 (8): 1547-1553.
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Lisfranc Injury – We have PoCUS but do we still need the cavalry?

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PoCUS Fellow Pearl

Dr. Melanie Leclerc, CCFP-EM

MSK PoCUS Fellow

Dalhousie University Department of Emergency Medicine

 

Reviewed & Edited by Dr David Lewis (@e_med_doc)

All case histories are illustrative and not based on any individual

 

Case Report

A 32 year old male presents to a rural Emergency Department with a complaint of traumatic left foot pain. He was playing recreational football this evening. While crouching, the patient was tackled by another player who landed on his hyper-plantar flexed left foot from behind. The patient had immediate onset of pain in the middle of his foot and was unable to weight-bear. 

On physical examination, you notice significant bruising and swelling of the mid-foot. There is tenderness to the medial mid-foot specifically at the 1st-2nd tarsal-metatarsal articulations. X-rays of the foot appear normal. You are concerned about the possibility of a ligamentous Lisfranc injury.

https://www.footandanklesurgery.com.au/lisfranc-injuries

 

 

Lisfranc injuries

Lisfranc injuries are those that involve the tarsal-metatarsal joints. A spectrum of injury exists from ligamentous to fracture-dislocation. Up to 20% – 40% of injuries to the Lisfranc complex are missed in the Emergency Department. Unrecognized and untreated injuries can lead to long-term instability through the midfoot. As this region of the foot is responsible for a significant load during weight bearing, instability can accelerate degenerative changes in the foot resulting in chronic pain and disability

The injury is named after Jacques Lisfranc de St. Martin, a French surgeon and gynecologist performed forefoot amputations at the tarsometatarsal joint on cavalrymen, during the 1815 Napoleonic wars. Although he didn’t specifically describe the injury, it has since been recognised in equestrians and occurring as a result of a trapped plantar flexed foot in the stirrup during a fall.

 

Other mechanisms have been described including high velocity injuries (sports injuries, foot on brake pedal MVA) and low velocity injuries (Stepping off a curb awkwardly). Low velocity injuries are more likely to be missed than high velocity injuries.

Further Reading – OrthoBullets

 

Anatomy

The Lisfranc ligament complex is comprised of 3 ligaments. The dorsal (red), interosseous (blue) and the plantar (green) Lisfranc ligaments. The  Interosseous ligament is the largest and the dorsal ligament is the smallest.

The first and second rays have unique ligamentous anatomy wherein no intermetatarsal ligaments exist, but extreme strength is imparted by dorsal, interosseous, and plantar bundles of ligament binding the lateral aspect of the medial cuneiform bone with the medial head of the second metatarsal bone—the Lisfranc ligamentous complex. Only the dorsal and plantar Lisfranc ligaments are accessible to ultrasound.

 

 

 

PoCUS of the Lisfranc joint and dorsal lisfranc ligament (DLL)

Lisfranc injuries are one of the most commonly missed orthopaedic injuries in the Emergency Department. Normal X-rays are often falsely reassuring to providers and patients are discharged with a diagnosis of “soft-tissue injury”. These injuries result in midfoot instability and often require definitive surgical management.

PoCUS has been studied as a method of early detection of these injuries. Specifically, assessment of the dorsal lisfranc ligament (DLL) between the second metatarsal (M2) and the medial cuneiform(C1). PoCUS also has the advantages of being significantly cheaper and more accessible than CT and MRI. Further investigation is needed to validate this method of diagnosis, however ultrasound findings of a disrupted DLL and a widened C1-M2 interval compared to the contralateral side may increase your suspicion when pre-test probability is high.

 

Technique

  1. Linear probe-MSK setting starting at a depth of 2cm
  2. Place probe in transverse orientation over the proximal aspect of the 1st-2nd metatarsals with the probe indicator to the patient’s right
  3. Slide the transducer proximally until you locate the medial cuneiform and identify the junction between the medial cuneiform (C1) and the 2nd metatarsal (M2)
  4. The medial cuneiform will have an angulated contour appearance in contrast to the round appearance of the metatarsals
  5. Sweep to identify the dorsal lisfranc ligament (DLL)
  6. Assess the DLL for a fibrillar pattern, normal echogenicity and contour
  7. Measure the DLL width and the C1-M2 distance compare to the contralateral side
  8. Measure the C1-M2 distance with weightbearing (if patient tolerates) to compare
  9. Apply colour doppler to assess for hyperemia

 

PoCUS Findings

Medial Cuneiform (C1), 2nd Metatarsal (M2)

Note the angulated contour of C1 and the smooth contour of M2 – this sectional plane is important when locating the dorsal Lisfranc ligament. The ligament appears hypoechoic with a fibrillar pattern, typical for other ligaments more commonly visualized with PoCUS e.g MCL, ATFL.

1. Normal image – Arrows = dorsal Lisfranc ligament

2. Normal Clip and annotated image. Note how the dorsalis pedis a. frequently overlies the dorsal Lisfranc ligament (yellow lines)

3. Normal clip. Note how there is no separation of C1/M2 while counterstressing the 1st and 2nd rays

 

4. Thickened, convex contour

5. DLL disrupted, wide joint space

6. Widening C1-M2 with weightbearing

Video Case

 

Limitations

  1. Anisotropy – Irregular dorsal contour of foot can result in difficult perpendicular imaging of doral Lisfranc ligament. Stand-off gel pad may help.
  2. History of prior trauma – chronic Lisfranc injury may result in joint widening
  3. Bilateral injuries – inability to compare sides to judge joint space widening

Application

Standard foot radiographs should be performed in all cases of suspicion for Lisfranc Injury. Weight bearing radiographs should also be performed if tolerated (the ability to fully weight bear is often limited in the acute setting)

HIgh velocity injuries result in significant soft tissue swelling, and although non-weight bearing radiographs may not be diagnostic, the index of suspicion for Lisfranc injury will be high. Immobilization +/- early CT and follow up with foot and ankle specialist is recommended. For these, high pretest probability injuries, PoCUS findings are unlikely to change management significantly. A clear Lisfranc ligament rupture on PoCUS may trigger a request for CT/MRI earlier than otherwise considered. In most cases advanced imaging and a clear diagnosis is not usually possible until the swelling has subsided.

In low velocity injuries, soft tissue swelling is less pronounced. in the acute presentation the ability to perform weight bearing radiographs is limited by pain. Index of suspicion for Lisfranc injury may be low-moderate and the decision to immobilize and refer for specialist follow up can be difficult. While there is limited published evidence for PoCUS test characteristics in Lisfranc injury, a positive scan (injury + disrupted ligament / widening of C1/M2) is likely to be highly specific. Patients with positive PoCUS findings should therefore be immobilized and referred for specialist follow up. In those with negative or inconclusive findings, management and disposition will depend on degree of clinical suspicion and correlated with radiographic findings.

In summary, PoCUS provides a useful additional piece of information that can be plugged into a bayesian diagnostic pathway. What is the pretest probability of a particular diagnosis? After reviewing radiographs and performing PoCUS is the diagnosis more or less likely?

More evidence is required to fully understand the test characteristics of PoCUS for Lisfranc injury. Would the addition of plantar views improve sensitivity?

Although the performing the scan takes only a few minutes, it is quite technically challenging for the novice. As with all MSK PoCUS, repeated practice in numerous patient presentations will increase operator speed and accuracy.

 

Finally, although we still need the cavalry, PoCUS can help us decide which regiment and how quickly we need them!

 

References

  1. Mayich DJ, Mayich MS, Daniels TR. Effective detection and management of low-velocity Lisfranc injuries in the emergency setting: principles for a subtle and commonly missed entity. Can Fam Physician. 2012;58(11):1199-e625. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3498011
  2. Woodward, S., Jacobson, J.A., Femino, J.E., Morag, Y., Fessell, D.P. and Dong, Q. (2009), Sonographic Evaluation of Lisfranc Ligament Injuries. Journal of Ultrasound in Medicine, 28: 351-357.
  3. Döring, S., Provyn, S., Marcelis, S., Shahabpour, M., Boulet, C., de Mey, J., De Smet, A., De Maeseneer, M. (2018). Ankle and midfoot ligaments: Ultrasound with anatomical correlation: A review. Eur J Radiol.107:216-226.
  4. Kaicker, J., Zajac, M., Shergill, R., & Choudur, H. N. (2016). Ultrasound appearance of the normal Lisfranc ligament. Emergency Radiology, 23(6), 609-614.
  5. DeLuca, M.K., Walrod, B. and Boucher, L.C. (2020). Ultrasound as a Diagnostic Tool in the Assessment of Lisfranc Joint Injuries. J Ultrasound Med, 39: 579-587.
  6. Marshall, J., Graves, N.C., Rettedal, D.D., Frush, K., Vardaxis. V. (2013). Ultrasound Assessment of Bilateral Symmetry in Dorsal Lisfranc Ligament. The Journal of Foot and Ankle Surgery, 52(3): 319-323.
  7. Rettedal, D.D., Graves, N.C., Marshall, J.J. et al. Reliability of ultrasound imaging in the assessment of the dorsal Lisfranc ligament. J Foot Ankle Res 6, 7 (2013).
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Detection of Foreign Bodies in Soft Tissue – A PoCUS-Guided Approach

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Medical Student Clinical Pearl

Sophia Miao, CC4

MD Candidate, Class of 2021

Dalhousie University

 

Reviewed & Edited by Dr David Lewis (@e_med_doc)

All case histories are illustrative and not based on any individual.

 

Case Report

A 33-year-old woman presents to the ED with pain and swelling over the third digit of her right hand.  One week prior to this, she had shattered a jar and a small glass splinter lodged into her finger.  This was promptly removed at home, and the puncture wound healed without intervention.

She presented to the emergency room 7 days later with new pain and swelling surrounding the initial puncture wound.  There is no significant past medical history and most recent Td booster was given 2 years ago.  On examination, there was some mild erythema, swelling, and tenderness on palpation of the lateral aspect of the middle phalanx of the right hand.  She is otherwise well.  You wonder about the possibility of a retained foreign body.

 

PoCUS-Guided Approach to the Detection of Foreign Bodies in Soft Tissue

Foreign bodies in soft tissue are a common complaint in the emergency department, with open wounds comprising 5.7 million (or 4.5% of total) visits to the ED in 2010.[1]  Foreign bodies were found in up to 15% of wounds.[2]  If retained, complications of these include allergic reaction, inflammation, delayed wound healing, damage to adjacent tissue structures, neurovascular damage, tetanus, and infectious complications including cellulitis, necrotizing fasciitis, synovitis, and abscess formation.[3],[4]  Proper detection, and subsequent removal, of retained foreign bodies is therefore essential to evaluate the wound and prevent associated complications.

Diagnosis of a retained FB requires a high index of suspicion.  Clinical suspicion should be raised when there is a compelling history and physical exam.  The latter may include signs of inflammation and/or infection, including warmth, swelling, erythema, tenderness, abscess formation, and discharging wound).[5],[6]

Conventional radiography is known to commonly miss radiolucent materials such as wood and plastic.  It has been shown that plain radiographs have only a 7.4% sensitivity in the detection of wood foreign bodies.5  Remarkably, even glass – a radiopaque material – has been demonstrated to have been missed in up to 35% of x-ray film studies.[7]  There is increasingly compelling evidence for the clinical usefulness and accuracy of bedside ultrasonography in the detection of soft-tissue foreign bodies.  It has been shown to have a specificity of 92% (95% CI = 88%-95%) and sensitivity ranging from 83.3% to 100%.[8],[9]

PoCUS Technique

Probe selection: the use of a high-frequency ultrasound probe is recommended.  This allows for greater axial resolution at the expense of less penetration, which is suitable for the detection of small foreign bodies, as they typically lodge in superficial tissues.[10]

If the wound is open, a transparent covering such as a Tegaderm or probe cover can be used to cover either the wound or probe before scanning.[11]

Medium: standard technique for assessment of soft-tissue structures by ultrasound involves the use of a standoff pad or gel mound.  However, this is not always possible due to the irregular curvature of extremities such as fingers and feet, which may result in poor contact between the probe and skin, decreased field of view, and patient discomfort.  A water-bath technique can circumvent this and has been shown to be superior in such cases.[12]

Method: the area of interest should be scanned in both longitudinal and transverse planes.  Foreign bodies are best detected when the transducer aligns with the longitudinal axis of the foreign body, and therefore revealing the span of the object.[13]  As foreign bodies tend to embed less than 2 cm below the surface of the skin, the depth of field should remain superficial in order to avoid false positives.

US Probe: Ultrasound Water Bath for Distal Extremity Evaluation

 

Findings

Ultrasonography and plain film findings of foreign bodies in soft tissue are summarized in the table below.

Table 1. Ultrasound and x-ray findings of foreign bodies.6,[14],[15],[16]

Material Ultrasound findings X-ray findings
Wood Hyperechoic; may become isoechoic with surrounding tissue as it denatures over time

Posterior acoustic shadowing

 Radiolucent, often undetectable
Glass Hyperechoic, bright

Posterior acoustic shadowing

± Posterior comet tail reverberation, diffuse beam scattering

 Radiopaque
Plastic Hyperechoic

Posterior acoustic shadowing

 Radiolucent, often undetectable
Metal Hyperechoic, bright

Posterior acoustic shadowing

± Posterior comet tail reverberation

 Radiopaque

 

Foreign bodies may also display a straight or regular contour.6

 

Image 1 – Wood splinter in volar aspect digit, mildly hyperechoic, surrounding hypoechoic halo, irregular acoustic shadowing

Image 2 – Plastic FB, within tendon sheath, volar aspect digit, brightly hyperechoic, long axis

Image 3 – Plastic FB, within tendon sheath, volar aspect digit, brightly hyperechoic, short axis

 

Image 4 – Glass FB – brightly echogenic, posterior reverberation, FB long axis

 

Image 5 – Metal FB – brightly echogenic, posterior reverberation, FB long axis

 

 

It is important to note that the acoustic shadowing may be complete or partial, as this is dependent on the angle of sonography and foreign body material.[17]  It is also possible to see a hypoechoic halo around the FB, which may be suggest edema, abscess formation, granulation tissue, or other inflammatory process.[18]  As the inflammatory reaction develops, the halo effect becomes more apparent; therefore the foreign body is therefore best visualized by PoCUS several days after the initial injury.6

PoCUS-Guided Foreign Body Removal

There are several options for removal of a foreign body with PoCUS:[19]

  1. Needle localization. Once the foreign body has been identified on PoCUS, a hollow injection needle can be inserted under ultrasound guidance and local anesthetic is delivered through this.  This can be done in either the transverse or longitudinal plane.  The ultrasound probe is then removed, and an incision is made along the needle.  Through the incision site, tweezers or forceps can be used to remove the foreign body.
  2. Real-time ultrasound-guided extraction. This technique is similar to the needle localization method. However, rather than removing the transducer following the needle insertion, the entire procedure is done under direct ultrasound visualization.  The probe is held in the longitudinal plane to visualize both the forceps and the foreign body during the extraction process.

 

There is a risk of obscuring the view of the foreign body on ultrasound with air as a result of the incision itself or through anesthetic delivery.  Saline may be used to irrigate and therefore mitigate the issue.19

The patient’s tetanus status should be verified and updated, if required.  Antibiotic therapy may also be provided, should the risk of infection justify it.

Limitations

There is the possibility of false positives.  Foreign bodies must be differentiated from other hyperechoic body structures, including ossified cartilage, sesamoid bones, scar tissue, gas bubbles, and intermuscular fascia.14  Visualization is therefore important in both longitudinal and transverse planes, as well as comparison with the opposite side.  Acoustic shadowing, hypoechoic halo, and posterior comet tails, if present, can also be indicative of a FB rather than organic body tissue.

Traumatic air injection as a result of penetrating injury can create a scatter artifact on ultrasound, which can be misinterpreted as an acoustic shadow associated with a foreign body.  To differentiate this from a true acoustic shadow, pressure may be applied through the transducer to displace the scatter artifact.6

As is commonplace with all emergency ultrasonography, limitations also include the technical skill of the operator.[20]  A foreign body may also be too small to be detectable by ultrasound.  It is therefore important to remember that a negative scan does not necessarily rule out the possibility of a retained foreign body, and the history and physical examination must be considered in conjunction with the ultrasound findings.

 

 

References

[1] National Center for Health Statistics. Emergency Department Visits. Available from: http://www.cdc.gov/nchs/fastats/emergency-department.htm.

[2] Steele MT, Tran LV, Watson WA, Muelleman RL. Retained glass foreign bodies in wounds: predictive value of wound characteristics, patient perception, and wound exploration. Am J Emerg Med. 1998 Nov;16(7):627-30. DOI: 10.1016/s0735-6757(98)90161-9. PMID: 9827733.

[3] Skinner EJ, Morrison CA. Wound Foreign Body Removal. In:StatPearls. Treasure Island (FL): StatPearls Publishing; 2020. Available from: https://www.ncbi.nlm.nih.gov/books/NBK554447/.

[4] Ebrahimi A, Radmanesh M, Rabiei S, Kavoussi H. Surgical removal of neglected soft tissue foreign bodies by needle-guided technique. Iran J Otorhinolaryngol. 2013 Winter;25(70):29-36. PMID: 24303416; PMCID: PMC3846242.

[5] Levine MR, Gorman SM, Young CF, Courtney DM. Clinical characteristics and management of wound foreign bodies in the ED. Am J Emerg Med. 2008 Oct;26(8):918-22. DOI: 10.1016/j.ajem.2007.11.026. PMID: 18926353.

[6] Atkinson P, Bowra J, Harris T, Jarman B, Lewis D. Point of Care Ultrasound for Emergency Medicine and Resuscitation. Oxford, United Kingdom: Oxford University Press; 2019. DOI: 10.1093/med/9780198777540.001.0001.

[7] Kaiser, C. William MD; Slowick, Timothy MBA; Spurling, Kathleen Pfeifer RN, JD; Friedman, Sissie MA. Retained Foreign Bodies, The Journal of Trauma: Injury, Infection, and Critical Care: July 1997 – Volume 43 – Issue 1 – p 107-111.

[8] Davis J, Czerniski B, Au A, Adhikari S, Farrell I, Fields JM. Diagnostic Accuracy of Ultrasonography in Retained Soft Tissue Foreign Bodies: A Systematic Review and Meta-analysis. Acad Emerg Med. 2015 Jul;22(7):777-87. DOI: 10.1111/acem.12714. Epub 2015 Jun 25. PMID: 26111545.

[9] Atkinson P, Madan R, Kendall R, Fraser J, Lewis D. Detection of soft tissue foreign bodies by nurse practitioner-performed ultrasound. Crit Ultrasound J. 2014 Jan 29;6(1):2. DOI: 10.1186/2036-7902-6-2. PMID: 24476553; PMCID: PMC3922659.

[10] Dean AJ, Gronczewski CA, Costantino TG. Technique for emergency medicine bedside ultrasound identification of a radiolucent foreign body. The Journal of Emergency Medicine. 2003;24(3):303–8. DOI: 10.1016/S0736-4679(02)00765-5.

[11] Chen KC, Lin AC, Chong CF, Wang TL. An overview of point-of-care ultrasound for soft tissue and musculoskeletal applications in the emergency department. J Intensive Care. 2016 Aug 15;4:55. DOI: 10.1186/s40560-016-0173-0. PMID: 27529031; PMCID: PMC4983782.

[12] Krishnamurthy R, Yoo JH, Thapa M, Callahan MJ. Water-bath method for sonographic evaluation of superficial structures of the extremities in children. Pediatr Radiol. 2013 Mar;43 Suppl 1:S41-7. DOI: 10.1007/s00247-012-2592-y. Epub 2013 Mar 12. PMID: 23478918.

[13] Rooks VJ, Shiels WE 3rd, Murakami JW. Soft tissue foreign bodies: A training manual for sonographic diagnosis and guided removal. J Clin Ultrasound. 2020 Jul;48(6):330-336. DOI: 10.1002/jcu.22856. Epub 2020 May 8. PMID: 32385865.

[14] Mohammadi A, Ghasemi-Rad M, Khodabakhsh M. Non-opaque soft tissue foreign body: sonographic findings. BMC Med Imaging. 2011 Apr 10;11:9. DOI: 10.1186/1471-2342-11-9. PMID: 21477360; PMCID: PMC3079678.

[15] Lewis D, Jivraj A, Atkinson P, Jarman R. My patient is injured: identifying foreign bodies with ultrasound. Ultrasound. 2015 Aug;23(3):174-80. DOI: 10.1177/1742271X15579950. Epub 2015 Mar 26. PMID: 27433254; PMCID: PMC4760591.

[16] Campbell EA, Wilbert CD. Foreign Body Imaging. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470294/.

[17] Anderson MA, Newmeyer WL 3rd, Kilgore ES Jr. Diagnosis and treatment of retained foreign bodies in the hand. Am J Surg. 1982 Jul;144(1):63-7. DOI: 10.1016/0002-9610(82)90603-1. PMID: 7091533.

[18] Little CM, Parker MG, Callowich MC, Sartori JC. The ultrasonic detection of soft tissue foreign bodies. Invest Radiol. 1986 Mar;21(3):275-7. DOI: 10.1097/00004424-198603000-00014. PMID: 3514541.

[19] Paziana K, Fields JM, Rotte M, Au A, Ku B. Soft tissue foreign body removal technique using portable ultrasonography. Wilderness Environ Med. 2012 Dec;23(4):343-8. DOI: 10.1016/j.wem.2012.04.006. Epub 2012 Jul 25. PMID: 22835803.

[20] Pinto A, Pinto F, Faggian A, Rubini G, Caranci F, Macarini L, Genovese EA, Brunese L. Sources of error in emergency ultrasonography. Crit Ultrasound J. 2013 Jul 15;5 Suppl 1(Suppl 1):S1. DOI: 10.1186/2036-7902-5-S1-S1. Epub 2013 Jul 15. PMID: 23902656; PMCID: PMC3711733.

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A Case of Ectopic Pregnancy

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Medical Student Clinical Pearl – December 2020

Marisa O’Brien

@mbob58

MD Candidate, Class of 2021

Memorial University of Newfoundland

Reviewed and Edited by Dr. David Lewis

All case histories are illustrative and not based on any individual

 

Case Report

A 36-year-old G2P1 female presented to the Emergency Department following a pre-syncopal episode at work. The patient noted a sudden onset of significant abdominal cramping, nausea, and vaginal bleeding with clots that morning followed by an episode of lightheadedness while sitting at her desk. The patient denied any loss of consciousness, no dyspnea, no chest pain, no palpitations, and no fevers/chills. She had no known allergies and no current medications. She was a non-smoker and denied any alcohol or drug usage.

The patient’s past medical history was significant for recent treatment with methotrexate for an ectopic pregnancy eight days prior. The patient had a history of amenorrhea for 7 weeks and a serum β-hCG of 302 mlU/mL at that time. A transvaginal ultrasound was performed at 8 weeks for abdominal pain and light spotting which revealed an IUD in situ with no evidence of an intrauterine pregnancy. An early ectopic pregnancy was diagnosed and the patient was consented to receive medical management with methotrexate. She was followed up with serial β-hCG’s which gradually, but slowly, trended down to 110 mIU/ml by day 6. The patient noted slight abdominal cramping and PV bleeding following the methotrexate however this had settled after 3 days with no ongoing symptoms until today.

On initial assessment, the patient appeared well, no acute distress, and all vital signs were stable.  The abdominal exam revealed bowel sounds present in all four quadrants and the abdomen was tympanic to percussion. On palpation the abdomen was soft and nondistended with LLQ and suprapubic tenderness however, no guarding or rebound tenderness was appreciated.

Initial investigations included a CBC, β-hCG, PT & PTT, type and screen, urinalysis, EKG, & POCUS.

 

Definition

An ectopic pregnancy occurs when a fertilized egg implants at a site other then the endometrium of the uterus, most commonly the fallopian tubes. They often present as vaginal bleeding and/or abdominal pain in the setting of a positive β-hCG.1

A critical complication is a ruptured ectopic pregnancy which occurs by erosion through the tissue the zygote has implanted in resulting in intraabdominal bleeding from the exposed vessel and possible hypovolemic shock.2 Rupture should be suspected in patients presenting with hemodynamic instability including syncope, hypotension, and tachycardia. However, young healthy females may appear vitally stable initially due to compensatory mechanisms. Additional physical exam findings suggestive of a ruptured ectopic pregnancy include severe abdominal pain with guarding or rebound tenderness and abdominal distention. Pain may radiate to the shoulder due to irritation of the diaphragm from blood in the peritoneal cavity.1,3

 

Risk factors for ectopic pregnancy4

  • Previous ectopic pregnancy
  • Prior fallopian tube surgery
  • Previous pelvic or abdominal surgery
  • Sexually transmitted infections
  • Pelvic inflammatory disease
  • Endometriosis
  • Cigarette smoking
  • Maternal age > 35 years
  • History of infertility
  • Assisted reproductive technology (IVF)

 

 

Differential diagnosis for vaginal bleeding in early pregnancy1:

  • Physiologic
  • Spontaneous abortion
  • Cervical, vaginal, or uterine pathology
  • Subchorionic hematoma
  • Heterotopic pregnancy
  • Gestational trophoblastic disease

 

Sonography

According to the discriminatory zones, an intrauterine pregnancy is expected to be visualized on a transvaginal ultrasound at β-hCG levels of 1500 – 2000 mlU/mL and on a transabdominal ultrasound at levels of 4000 – 6500 mlU/mL.5

Gestational Age Β-hCG range (mlU/mL)
<1 week 5 – 50
1-2 weeks 50 – 500
2-3 weeks 100 – 5000
3-4 weeks 500 – 10,000
4-5 weeks 1000 – 50,000
5-6 weeks 10,000 – 100,000
6-8 weeks 15,000 – 200,000
8-12 weeks 10,000 – 100,000

Table 1: Estimated β-hCG levels in relation to gestational age.3

In the first trimester of a normal pregnancy, the serum β-hCG should increase by ≥ 53% every 48 hrs until 41 days of gestation.1,3 Serum β-hCG will then continue to rise more slowly until approximately 10 weeks after which it will begin to decline until reaching a plateau. Serum β-hCG levels are noted to raise more slowly in an ectopic pregnancy, thus a slower rate of increase, plateau, or decline in serum β-hCG in the first 41 days suggests a possible miscarriage or ectopic pregnancy.1

Note on β-hCG Discriminatory Zones

The value of discriminatory zones in the emergency management of ectopic pregnancy is low, with many considering it unreliable and potentially dangerous. In short, a low β-hCG does not exclude an ectopic. This useful post provides a good summary on ectopic rule-out in the ED:

Rule Out Ectopic in the Emergency Department

 

An intrauterine pregnancy is confirmed by visualization of a gestational sac and a yolk sac within the uterus (juxtaposed to bladder).1 A gestational sac alone is not sufficient for diagnoses of an intrauterine pregnancy as it may be a pseudogestational sac formed by hormonal stimulation from an ectopic pregnancy.5 Additionally, if an intrauterine pregnancy is visualized, a heterotopic pregnancy should also be considered.1 The risk of heterotopic pregnancy when conceived normally is estimated to be 1 in 30,000.

Figure 1: Visualization of an intrauterine pregnancy on a transvaginal ultrasound.3

 

 

Structure Transvaginal Ultrasound Transabdominal Ultrasound
Gestational Sac 4.5-5 weeks 5.5-6 weeks
Yolk Sac 5-5.5 weeks 6-6.5 weeks
Fetal Pole 5.5-6 weeks 7 weeks
Cardiac Activity 6 weeks 7 weeks
Fetal Parts 8 weeks >8 weeks

Table 2: Ultrasound findings based on gestational age.5

 

Diagnosis of Ectopic Pregnancy

An ectopic pregnancy is suspected in all women with a positive pregnancy test when no intrauterine pregnancy is visualized on ultrasonography. A low β-hCG or declining β-hCG does not exclude an ectopic. Ultrasound findings of an ectopic pregnancy may include an extrauterine gestational sac or embryonic cardiac activity outside of the uterus, a complex adnexal mass, or intraperitoneal fluid.3

From emupdates.com

 

Management of Ectopic Pregnancy

Is the patient unstable?

  • If the patient is hemodynamically unstable (tachycardia or hypotension or pale or syncopal) then commence immediate resuscitation (IV Access, CBC, type & crossmatch,  iv fluids, transfusion, etc) and stat consult to ObGyn.

In stable patients

  • Consult ObGyn
  • The gold-standard of treatment for ectopic pregnancy is surgical management however, treatment options include expectant, or medical management.6 Medical management with methotrexate, a folic acid antagonist that inhibits DNA synthesis and cell production, has a higher success rate when initiated at lower β-hCG levels. Methotraxate is initiated if β-hCG is <5000 mlU/mL and is reserved for those with reliable follow up as β-hCG levels are required to be trended until they are undetectable. Individuals with renal disease, hepatic disease, active pulmonary disease, or immunodeficiencies are not candidates for methotrexate.3,7 Individuals who do not meet the criteria for medical management, are hemodynamically unstable, have failed methotrexate, or a ruptured ectopic is suspected, will receive surgical management.6

 

Case Report Continued

The patient was hemodynamically stable on presentation. Her vital signs were normal. As part of the initial assessment, PoCUS was used to further evaluate for the presence of free fluid in the abdomen or pelvis. Free fluid was identified in the RUQ in both Morrison’s pouch and surrounding the caudal tip of the liver. Intraperitoneal fluid was also seen in the LUQ in both the subphrenic and splenorenal spaces. Free fluid was also visualized in Douglas’ pouch in the pelvic view.

RUQ

LUQ

Pelvis

 

Throughout the PoCUS examination the patient remained well appearing, however she had become hypotensive with a blood pressure of 90/53 mmHg. Her initial bloodwork had come back at this time revealing a β-hCG of 32 mlU/mL and a Hgb of 67 g/L. The patient received 1g of TXA, and a 1L bolus of normal saline while PRBC’s were ordered. She was documented to be Rh+ thus, she did not require RhoGAM (anti-D immune globulin). An urgent consultation to Obstetrics and Gynecology was made following the visualization of intraabdominal fluid and the patient underwent an exploratory laparotomy shortly after.

 

Key Points

  • Ectopic pregnancy should be considered in the differential diagnosis of any female patient, of childbearing age, presenting with abdominal pain, syncope or shock
  • An Intrauterine contraceptive device does not exclude an ectopic
  • Unless a previous ultrasound has documented the presence of an intrauterine pregnancy, an empty uterus in a patient with a positive pregnancy test should be considered to be a possible ectopic until ruled out
  • An intrauterine pregnancy on ultrasound requires the following to be confirmed:
    • A gestational sac and a yolk sac, in the uterus which is juxtaposed to the bladder
    • or a gestational sac containing a normal fetal pole, in the uterus which is juxtaposed to the bladder
  • A low β-hCG or declining β-hCG does not exclude an ectopic
  • Medical management of ectopic pregnancy with methotrexate requires close follow-up. Failure can occur. Ruptured ectopic pregnancy can still occur.

 

Further Reading

Ectopic Pregnancy and Ruptured Ectopic: Pitfalls in Diagnosis

ED Rounds – Early Pregnancy

The Pregnant ED Patient – A Compendium of Pearls

 

 

References

  1. Tulandi, T. (2020, November 2). Ectopic pregnancy: Clinical manifestations and diagnosis. Retrieved from: https://www.uptodate.com/contents/ectopic-pregnancy-clinical-manifestations-and-diagnosis?search=ectopic%20pregnancy&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1#H1
  2. Toy, E.C., Simon, B.C., Takenaka, K.Y., Liu, T.H., & Rosh, A.J. (2017). Ectopic Pregnancy. Case Files Emergency Medicine. (4th, pp. 369-376). McGraw-Hill Education.
  3. Hang, B.S. (2016). Obstetrics and Gynecology. Tintinalli’s Emergency Medicine: A Comprehensive Guide. (8th, pp. 629-633). McGraw-Hill Education.
  4. The American College of Obstetricians and Gynecologists. (2018, February). Retrieved from: https://www.acog.org/womens-health/faqs/ectopic-pregnancy
  5. Leonard, N.J. (2019, January 23). The Pregnant Pelvic POCUS. EMRounds. Retrieved from: https://emrounds.org/the-pregnant-pelvic-pocus/
  6. Tulandi, T. (2020, March 31). Ectopic pregnancy: Choosing a treatment. Retrieved from: https://www.uptodate.com/contents/ectopic-pregnancy-choosing-a-treatment?search=ectopic%20pregnancy&topicRef=5407&source=see_link#H2976630177
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Small Bowel Obstruction & PoCUS

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Small Bowel Obstruction & PoCUS – Medical Student Pearl

Patrick Rogers, Clinical Clerk (CC3)

Memorial University of Medicine Class of 2021

Reviewed by Dr. Kavish Chandra

Small bowel obstructions (SBO) are a common cause of acute abdominal pain in emergency departments across Canada. Diagnostic imaging plays a key role in the diagnosis and management of SBO as the history, clinical examination and laboratory investigations lack the sensitivity and specificity needed. Furthermore, diagnostic imaging may help differentiate SBO from other causes of abdominal pain (hernias, malignancies, intussusception, etc).

Historically, plain film abdominal radiography (AXR) has been an initial investigation in emergency departments when an SBO is suspected.  However, the current literature suggests that abdominal radiography is a relatively poor test for the diagnosis or exclusion of SBO when compared to other available modalities like US, CT, or MRI. In fact, multiple studies argue for the reduction of abdominal x-rays, especially when patients come in presenting with general abdominal tenderness. 1 Fortunately, there exists a compelling alternative: point of care ultrasound (PoCUS), and is being increasingly used as a first line investigation for SBO. 2

There are several reasons why physicians may start to choose PoCUS over traditional diagnostic modalities:

  • PoCUS avoids the radiation exposure that patients receive from cumulative plain films and abdominal CT’s. 3
  • PoCUS has been shown to reduce time to diagnosis and treatment in comparison to abdominal plain films. 3
  • PoCUS is more sensitive/specific modality when compared to abdominal plain film. 4
  • PoCUS allows for serial examination in the ED. 5
  • PoCUS may be rapidly available to centers with limited access to CT scanner. 6

The current evidence is highly favorable for the diagnostic efficacy of PoCUS in SBO. Here are the findings of peer-reviewed studies on the subject (published between 2013-2020):

  • PoCUS has high diagnostic accuracy and may also decrease time to diagnosis of SBO in comparison to other imaging modalities like CT and plain film.2
  • PoCUS has been found to have superior diagnostic accuracy for SBO in comparison to plain abdominal radiography. 4
  • PoCUS has been shown to be an accurate tool in the diagnosis of SBO with a consistently high sensitivity of 94-100% and specificity of 81-100%. 5
  • Current evidence suggests PoCUS is comparable in sensitivity and specificity to a CT scan when diagnosing SBO. 6
  • Ultrasound was found to be equivalent to CT in terms of diagnostic accuracy with a sensitivity of 92.31% (95% CI, 74.87% to 99.05%) and a specificity of 94.12% (95% CI, 71.31% to 99.85%) in the diagnosis of SBO. 7
  • In a study comparing XR, US, CT, and MRI, the abdominal x-ray was shown to be to be the least accurate imaging modality for the diagnosis of SBO. AXR’s were found to have a positive likelihood ratio of 1.64 (95% CI 1.07 to 2.52). In contrast, CT and MRI were both quite accurate in diagnosing SBO with positive likelihood ratios of 3.6 (95% CI = 2.3 to 5.4) and 6.77 (95% CI = 2.13 to 21.55). The use of ultrasound was found to have a positive likelihood ratio of 9.55 (95% CI = 2.16 to 42.21) and a negative likelihood ratio of 0.04 (95% CI = 0.01 to 0.13) for beside scans. 4

There are two major barriers identified in the literature that may prevent the effective use of PoCUS in the diagnosis of SBO. First, not every emergency physician has been trained on the use of PoCUS. Fortunately, two recent studies show that even minimally trained ED physicians can use it accurately. 8 Secondly, some surgeons have argued that PoCUS does not show the location of the obstruction accurately. This becomes a concern when the care team elects for surgical management of the patient’s SBO. However, recent evidence suggests that PoCUS may lead to quicker time to diagnosis and enteric tube insertion in conservative management. 8

Finally, how can learners use this technology? 5 Here are some specific sonographic findings to look for when evaluating a patient for SBO with US:

 

  • Dilatation of small bowel loops > 25 mm *
  • Altered intestinal peristalsis *
  • Increased thickness of the bowel wall
  • Intraperitoneal fluid accumulation

Figure 1. Dilatation of small bowel loops. Image courtesy Dr. Kavish Chandra

Figure 2. Altered intestinal peristalsis*. Image courtesy Dr. Kavish Chandra

Figure 3. – abnormal peristalsis “to and fro”9

References

  1. Denham G, Smith T, Daphne J, Sharmaine M, Evans T. 2020. Exploring the evidence-practice gap in the use of plain radiography for acute abdominal pain and intestinal obstruction: a systematic review and meta-analysis. International Journal of Evidence Based Healthcare. DOI: 10.1097/XEB.0000000000000218
  2. Guttman J, Stone M, Kimberly H, Rempell J. 2015. Point of care ultrasonography for the diagnosis of small bowel obstruction in the emergency department. CJEM. DOI: 10.2310/8000.2014.141382
  3. Flemming H, Lewis D. 2016. SBO- A New Focus for PoCUS. Saint John Regional Hospital Department of Emergency Medicine
  4. Taylor M, Lalani N. 2013. Adult small bowel obstruction. Academic Emergency Medicine. DOI: 10.1111/acem.12150
  5. Pourman A, Dimbil U, Shokoohi H. 2018. The accuracy of point of care ultrasound in detecting small bowel obstruction in emergency department. Emergency Medicine International. DOI: 10.1155/2018/3684081
  6. Gottlieb M, Peska, G, Pandurangadu A, Nakitende D, Takhar S, Seethala R. 2018. Utilization of ultrasound for the evaluation of small bowel obstruction: A systematic review and meta-analysis. The American Journal of Emergency Medicine. DOI: 10.1016/j.ajem.2017.07.085
  7. Tamburrini S, etal. 2019. Diagnostic accuracy of ultrasound in the diagnosis of small bowel obstruction. Diagnostics. DOI: 10.3390/diagnostics9030088
  8. Carpenter C. 2013. The end of X-Rays for suspected small bowel obstruction? Using evidence-based diagnostics to inform best practices in emergency medicine. Academic Emergency Medicine. https://doi.org/10.1111/acem.12143
  9. The PoCUS Atlas. https://www.thepocusatlas.com/bowel-gi

Copyedited by Dr. Mandy Peach

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