PoCUS Fellow Pearl
Dr. Rawan Alrashed
Pediatric Emergency Physician
Dalhousie 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:
12 years old female, previously healthy, presented to the ED with 1 day history of abdominal pain persistent, mainly in the lower abdomen, nauseated, with loss of appetite, no vomiting, no bowel motion, low grade fever, by exam she was distress in pain with tachycardia abdominal exam showed periumbilical and RLQ tenderness. Labs requested.
Awaiting the results, thinking of differential diagnosis and best imaging study….
Would POCUS help in the diagnostic process??
Background:
In children, acute appendicitis constitutes 1-8% of the abdominal pain diagnosis and is the most common condition requiring emergency surgery. The potential for morbidity and mortality from perforation of the appendix necessitates prompt diagnosis. Although a variety of clinical scoring systems have been developed, there is still no consensus on clinical, laboratory, and imaging criteria for diagnosing appendicitis, which poses a dilemma for the emergency clinician (1). The clinical presentation of children with appendicitis varies from that of adults which makes it more difficult to diagnose it. Multiple scoring systems (Pediatric Appendicitis score, Alvarado score, Pediatric Appendicitis risk calculator) were developed and externally validated with varying degree of sensitivity and specificity (2).
Anatomy:
The appendix is a blind-ended tubular structure that arises from the posteromedial aspect of the cecum, proximal to the ileocecal valve. The average length of the appendix varies from neonates to adults, ranging from 4.5 mm to 9.5 mm. The orientation of the appendix can be retrocecal, subcecal, preileal, retroileal, or in a pelvic site (1).
Pathology:
Appendicitis is a result of obstruction of the appendiceal lumen. Obstruction can occur secondary to stones, fecaliths, or other processes that inflame the lymphoid tissue.
Diagnostic Imaging
Imaging Study |
Sensitivity |
Specificity |
|
US |
88% |
94% |
|
CT |
94% |
95% |
|
MRI |
96% |
96% |
(Benabbas, 2017 (2))
PoCUS Anatomy
Cecum (C) is the most lateral structure in the RLQ, it’s a gas-fecal filled (dirty shadow) identified by following the haustra on the ascending colon caudally
Terminal ileum (TI) is a smooth wall that is fluid filled showing peristaltic movement and demonstrates valvulae conniventes.
(Ref – 9,12)
Normal 5 layers of the Appendix
a) echogenic mucosa
b) hypoechoic muscularis mucosa
c) echogenic submucosa
d) hypoechoic muscularis propria
e) echogenic serosa
PoCUS Technique
Use the LINEAR Probe (Curvilinear might be needed in large habitus people)
- Analgesia First – Start with controlling the PAIN before starting the scan
- Start by scanning the Maximum point of tenderness at the RLQ
- Use the GRADED COMPRESSION as a technique to remove bowel gas
- Scan in both planes (Longitudinal and Transverse) the entire length of appendix
- Utilize the psoas muscle, iliac vessels and caecum as landmarks by:
- Identify the iliac vessels
- Identify the ileum above them then ileocecal junction
- Scan inferiorly to the base of the caecum (appendix should be seen here)
If appendix is not visualized use the systematic approach (suggested by Sivitiz et al)
- Move the probe laterally, until identify the ascending colon and lateral abdominal wall
- Move the transducer on the lateral border of the cecum.
- Then, move the transducer medially, across the psoas and iliac vessels.
- With the psoas muscle and iliac vessels kept in view, move the transducer down into the pelvis and towards the umbilicus at the border of the cecum.
- If the appendix is not yet visualized, put the probe in the sagittal position, identifying the cecum in the long axis and move the transducer (sweep medially) compressing the cecum against the psoas muscle.
(Ref – 3,5,8)
Adaptations
Retrocecal Appendix
Consider applying pressure dorsally on the patient RLQ from the back. Scan while the patient on left posterior oblique position and scan parasagittal through the right flank in a coronal plane parallel to long axis of the psoas muscle; the appendix will appear anterior to the psoas muscle.
Pelvic Appendix
Consider using curvilinear transducer. Scan deeper and use the bladder as a window
(Ref 5)
Core Ultrasound – 5 Min Sono – Appendicitis
PoCUS Findings
Normal Appendix |
Primary signs of Appendicitis |
Secondary signs |
|
Tubular blind ended structure arising from base of the Caecum |
a non compressible appendix (Target sign) |
free Fluid in the right lower quadrant |
|
No peristalsis |
appendix wall diameter > 3 mm |
echogenic edematous mesenteric fat stranding |
|
Anteroposterior diameter |
overall appendiceal diameter > 6 mm (some reported 7mm) |
appendiceal wall hyperemia (ring of fire) |
|
Compressible target sign |
ultrasound McBurney’s sign |
abnormal lymph nodes |
|
|
presence of appendicolith |
abnormal adjacent bowel, and bowel wall edema |
(Ref 4,11)
Normal Appendix
Primary Signs of Appendicitis
Secondary Signs of Appendicitis
PoCUS Appendicitis – Evidence
- A systematic review by Benabbas et al concluded that ED POCUS had 86% sensitivity and 91% specificity which was similar to RUS with sensitivity of 88% and specificity of 94%. POCUS reported as having a positive likelihood ratio of 9.24% and a negative likelihood ratio of 0.17. (2)
- The American College of Radiology issued appropriateness criteria for imaging in RLQ pain recommending ultrasound as the first line option in children. (4)
- The utilization of staged imaging approach has led to reduction of CT by 55-63% in different studies considering US (POCUS+ RUS) as first line image and CT used in equivocal cases or non visualized appendix. (6)
- Elikashvili et al. demonstrated a significantly decreased length of stay for patients with disposition by POCUS compared to radiology (154–288 min) without any cases of missed appendicitis. (14)
- Abnormal echogenicity or so-called infiltration of peri appendiceal fat has been found to be a particularly useful sign of appendicitis on US. Trout et al. found it to be the only independent statistically significant parameter to predict appendicitis, with a positive odds ratio of greater than 60. (3)
Limitations and Pitfalls
- Operator dependent (level of experience with POCUS determines test acuracy).
- The duration since the onset of symptoms (around 48 hours was found to be the optimal time to diagnose appendicitis by POCUS)
- Misidentification of small bowel as the appendix (confirm a blind ended structure to prevent this)
- Visualization of only the normal portion of a diseased appendix, where inflammation is isolated to the tip (false negative) scan the entire appendix.
- Misdiagnosing a normal appendix as inflamed secondary to other intra-abdominal processes, such as Crohn’s disease or pelvic inflammatory disease (false positive).
- Misdiagnosing acute appendicitis based on a diameter greater than 6 mm in an ovoid appearing compressible appendix and/or without any secondary signs of inflammation.
- It can be difficult to visualize a perforated appendix due to the inability to perform a graded compression exam on a patient with peritonitis. (7)
Case Conclusion
PoCUS was performed. The images strongly suggested a diagnosis of appendicitis. A consultative ultrasound was performed in Diagnostic Imaging which confirmed our findings. After surgical consultation the child had an appendectomy and discharged the next day.
Bottom Line
- Follow a Bayesian approach when using PoCUS to support your diagnosis of appendicitis. Pre-test probability will influence your staged approach to a child with RLQ pain.
- Utilize PoCUS and consultative DI Ultrasound to minimize radiation exposure with CT.
- Review the proposed algorithm as an approach to suspected pediatric appendicitis.
- Always consider appendicitis mimics in pediatrics (intussusception, IBD, ovarian torsion etc..) – don’t miss these!
References
1) Becker C, Kharbanda A. Acute appendicitis in pediatric patients: an evidence-based review. Pediatr Emerg Med Pract. 2019;16(9):1-20.
2) Benabbas, R., Hanna, M., Shah, J., & Sinert, R. (2017). Diagnostic Accuracy of History, Physical Examination, Laboratory Tests, and Point-of-care Ultrasound for Pediatric Acute Appendicitis in the Emergency Department: A Systematic Review and Meta-analysis. Academic Emergency Medicine, 24(5), 523–551.
3) Swenson DW, Ayyala RS, Sams C, Lee EY. Practical Imaging Strategies for Acute Appendicitis in Children. AJR Am J Roentgenol. 2018;211(4):901-909.
4) Lawton B, Goldstein H, Davis T, Tagg A. Diagnosis of appendicitis in the paediatric emergency department: an update. Curr Opin Pediatr. 2019;31(3):312-316.
5) Berghea-Neamţu, C. T. (2019). The Ultrasonographic Exam for Acute Appendicitis at Patient’s Bed. Acta Medica Transilvanica, 24(4), 48–50.
6) Doniger SJ, Kornblith A. Point-of-Care Ultrasound Integrated Into a Staged Diagnostic Algorithm for Pediatric Appendicitis. Pediatr Emerg Care. 2018;34(2):109-115.
7) Marin JR, Abo AM, Arroyo AC, et al. Pediatric emergency medicine point-of-care ultrasound: summary of the evidence [published correction appears in Crit Ultrasound J. 2017 Dec;9(1):3]. Crit Ultrasound J. 2016;8(1):16.
8) Sivitz AB, Cohen SG, Tejani C. Evaluation of acute appendicitis by pediatric emergency physician sonography. Ann Emerg Med. 2014;64(4):358-364.
9) “US of the GI Tract – Normal Anatomy.” The Radiology Assistant : US of the GI Tract – Normal Anatomy, https://radiologyassistant.nl/abdomen/ultrasound/lk-jg-1-1.
10) Riscinti, Matthew. “Bedside Ultrasound for Acute Appendicitis – Featuring Colorized Images.” TPA, TPA, 10 Jan. 2021, https://www.thepocusatlas.com/new-blog/appendicitis.
11) Gongidi P, Bellah RD. Ultrasound of the pediatric appendix. Pediatr Radiol. 2017;47(9):1091-1100.
12) Jeffrey RB, Wentland AL, Olcott EW. Sonography of the Cecum: Gateway to the Right Lower Quadrant. Ultrasound Q. 2018;34(3):133-140.
13) US probe: Ultrasound for small bowel obstruction. emDOCs.net – Emergency Medicine Education. (2018, March 27), http://www.emdocs.net/us-probe-ultrasound-for-small-bowel-obstruction.
14) Elikashvili I, Tay ET, Tsung JW. The effect of point-of-care ultrasonography on emergency department length of stay and computed tomography utilization in children with suspected appendicitis. Acad Emerg Med. 2014 Feb;21(2):163-70.
