Abdominal ACNES: anterior cutaneous nerve entrapment syndrome and trigger point injections in the ED

Abdominal ACNES: anterior cutaneous nerve entrapment syndrome and trigger point injections in the ED

Resident Clinical Pearl (RCP) March 2019

Devon Webster – PGY1 FMEM Dalhousie University, Saint John NB

Reviewed and edited by Renee Amiro and  Dr. David Lewis.


 

Case:

A 32 year old woman with a history of chronic abdominal pain has been sitting in RAZ, presenting with, predictably, lower abdominal pain. She has been investigated multiple times over, with comprehensive labs, ultrasounds, pelvic exams and a previous CT, all of which have been normal. She carries with her a myriad of diagnoses; chronic abdominal and pelvic pain, IBS, fibromyalgia, depression and anxiety.

On history she reports near constant, left lower quadrant pain over the past 4 months. It is worse when sitting up and lying on her left side. The pain is sharp and she is able to localize the pain with a single fingertip. On history, you elicit no red flags for an intra-abdominal source of her pain. You ask her to lay down on the examination bed and hold your finger over the area of maximal pain. You feel no mass or abdominal wall defects. You apply light pressure, which triggers the pain, and ask her to lift her legs up. She yelps in pain, noting significant worsening to the site after tensing her abdominal muscles.

While you think of your differential for abdominal wall pain, you are highly suspicious of anterior cutaneous nerve entrapment syndrome (ACNES)…

What is ACNES?

  • Anterior cutaneous nerve entrapment syndrome (ACNES) is one of the most frequent causes of chronic abdominal wall pain and often goes undiagnosed. It is caused by entrapment of the anterior cutaneous abdominal nerves as they pass through the fibrous abdominal fascia.
  • This common condition can be treated rapidly and effectively by local trigger point injection of lidocaine and long acting steroid in the emergency department.

Pathophysiology:

  • The cutaneous branches of the sensory nerves arising from T7-T12 must make two 90* turns, traversing through channels within the abdominal fascia at the linea semilunaris (lateral border of the rectus muscles) in order to innervate the cutaneous surface of the abdomen.
  • While the neurovascular bundle should be protected from impingement by fat, it is susceptible to entrapment due to the tight passageway through the fibrous channels and sharp angulation.

Risk factors:

  • There are multiple risk factors for entrapment, and subsequent pain: tight clothing or belts, intra or extra-abdominal pressure, scarring and obesity. Pregnant women and those taking OCPs may also be at higher risk.
  • 4x more common in women, particularly those between ages 30-50 years of age.

 

 Clinical features on history:

  • Patients may describe chronic abdominal pain with maximal tenderness over a small area of the abdomen, typically <2cm
  • Pain is typically at the lateral edge of the rectus abdominis muscles and has a predilection for the right side although, the pain may be anywhere over the abdomen and may be in multiple locations.
  • Pain tends to be sharp in nature, positional and aggravated by activities that tense the abdominal muscles. Pain is generally better supine and worse when sitting or lying on the side.
  • There should be no red flags associated with the history suggestive of a more nefarious source of pain (e.g. GI bleeding, change in bowel function).

 

Physical exam:

  • Use a Q-tip to apply pressure as you move along the abdomen and try to locate the area of maximal tenderness. In most ACNES patients, you will find an area of allodynia or hyperalgesia corresponding to the area of nerve entrapment.
  • Look for a positive Carnett’s sign:
    • Ask the patient to either lift the head and shoulders or alternatively, lift their legs off of the bed while lying flat while you apply pressure over the area of pain on the abdomen.
    • Tightening of the rectus muscles should protect intra-abdominal pathology and pain will be reduced. In the case of abdominal wall pathology, including ACNES, pain will remain the same or be increased.
  • Understanding extra vs intra-abdominal pain:
    • There are 2 types of pain receptors: A-delta and C fibers.
      • A-delta: These fibers mediate sharp, sudden pain and innervate skin and muscles. Patient’s can localize this pain with a fingertip and this corresponds well with extra-abdominal wall pain, such as in ACNES
      • C fibers: Mediate dull ‘visceral’ pain that is often difficult to localize and results in pain over larger areas of the abdomen. These fibers innervate the viscera and parietal peritoneum.

 


Approach and Differential Diagnosis for Abdominal Wall Pain:

  • Look for ‘red flags’ (e.g. GI bleeding, abnormal labs, malnourished appearance) and rule out intra-abdominal sources of pain.
  • Once this has been ruled out, consider your differential for extra-abdominal wall pain which may include the following…

 

 

Diagnosis:

  • ACNES can be diagnosed on the basis of 3 criteria:

 1) Well localized abdominal pain

 2) Positive Carnett’s sign

 3) Response to trigger point injection of local anesthetic and steroid

 

 Treatment

  • Trigger point injections:
    • Act as both a source of treatment and diagnosis.
    • Provides immediate relief of symptoms to 83-91% of patients.
    • Injections can be repeated q-monthly.
    • Works through immediate anesthetization of the nerve, steroidal thinning of surrounding connective tissue and hydrodissection.
  • If the pain returns after trigger point injections, after considering other diagnoses, patient’s can be referred for chemical neurolysis (alcohol injections) or in some instances, surgical neurectomy.
  • Conservative treatment may include activity modification (e.g. avoid stomach crunches) and physical therapy

 

Technique for trigger point injections:

  1. Mark the site of maximal tenderness
  2. Inject 1-3 mL of 1% lidocaine and 1 mL of a long acting steroid using a 1.5 inch 26 gauge needle. Insert the needle until the tender area is reached (pt will let you know)
  3. Pain should resolve within 5 minutes.

 

  • US guidance may be useful for increasing the precision of the injection and can be used to visualize the passage of the nerve through the abdominal fascia.

Video guided review of ACNES:

https://www.youtube.com/watch?v=bDyX3myA0Gw&t=163s

 


References:

  1. Meyer, G, et al. “Anterior cutaneous nerve entrapment syndrome.” Uptodate. Accessed March 8, 2019. URL: https://www.uptodate.com/contents/anterior-cutaneous-nerve-entrapment-syndrome
  2. Suleiman, S, Johnston, D. “The Abdominal Wall: An Overlooked Source of Pain” American Family Physician. August 2001.
  3. Kanakarajan, S., et al. “Chronic Abdominal Wall Pain and Ultrasound-Guided Abdominal Cutaneous Nerve Infiltration: A Case Series.” Pain Medicine, volume 12, Issue 3, 1 March 2011, Pages 382-386.
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EM Reflections – April 2018

Thanks to Dr. Joanna Middleton for leading the discussions this month

Edited by Dr David Lewis 

 


 

Top tips from this month’s rounds:

 

Ondansetron (Zofran) and QTi

Globe Rupture

Ovarian Torsion

 


 

Ondansetron (Zofran) and QTi

  • Ondansetron prolongs QTi in a dose-dependent manner
  • Patient is most at risk for an arrhythmia when peak serum levels are reached
    • Largest difference in QTi was found at 15 minutes (IV), but has seen to persist up to 120 min in heart failure patients.
  • Arrhythmia after a single dose is EXCEEDINGLY RARE
    • No reports of arrhythmia after a single dose of oral ondansetron.
    • Consider ECG monitoring (or use another anti-emetic agent) in patients who are receiving IV ondansetron with other arrhythmogenic factors such as QTi prolonging agents or electrolyte abnormalities

Ondansetron and QTc Prolongation: Clinical Significance in the ED

 


 

Globe Rupture

  • When should you suspect?
    • Mechanism – severe blunt, penetrating, metal-on-metal
  • Signs of open globe include:
    • penetrating lid injury,
    • bullous subconjunctival hemorrhage
    • shallow anterior chamber
    • blood in the anterior chamber (hyphema),
    • peaked pupil
    • iris disinsertion (iridodialysis)
    • lens dislocation, and
    • vitreous hemorrhage. Loss of red reflex can indicate vitreous hemorrhage or retinal detachment.

The EyeRounds.org website has some useful tutorials.

 

Management 

  • Stop Examination
  • NO PATCH – Use Eyes Shield
  • Consult Ophthalmology immediately
  • NPO, Tetanus, IV Antibiotics, analgesia and antiemetics

Download (PDF, 181KB)

 


 

Ovarian Torsion

  • Uptodate:  It is one of the most common gynecologic emergencies and may affect females of all ages
  • Most common ages 20-50 years
  • Acute onset pain with adnexal mass
  • As size of mass increases, risk of torsion increases
    • #1 RF is ovarian mass >5 cm
    • benign > malignant
  • Increased risk during pregnancy, fertility treatments
  • U/S test of choice, although normal doppler does not rule out torsion
  • CT not diagnostic, although if you had a CT that didn’t show an ovarian mass of >5cm, unlikely it was torsion…
  • 86-95% of patients with torsion have a mass (exception – pediatric population – more likely to have torsion with normal ovaries)
  • Pediatric patients – early surgical detorsion more likely to be successful
  • >36 hours – non-viable

A useful recent review can be viewed here

CoreEM provides another useful summary (as well as a huge amount of other EM Topics)

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EM Reflections – September 2017

Thanks to Dr Paul Page for leading the discussion

Edited by Dr David Lewis

Top tips from this month’s rounds:

  1. Non-specific Abdo pain – Appendicitis is always high on the differential 

  2. Intoxicated patients are at high risk for Head Injury

  3. Acute Heart Failure has a higher mortality than acute NSTEMI

  4. Enhancing Morbidity and Mortality Rounds Quality


Non-specific Abdo pain – Appendicitis is always high on the differential 

Does a normal white count exclude appendicitis?No – Clinicians should be wary of reliance on either elevated temperature or total WBC count as an indicator of the presence of appendicitis. The ROC curve suggests there is no value of total WBC count or temperature that has sufficient sensitivity and specificity to be of clinical value in the diagnosis of appendicitis. Acad Emerg Med. 2004 Oct;11(10):1021-7.Clinical value of the total white blood cell count and temperature in the evaluation of patients with suspected appendicitis.

Does a normal CRP exclude appendicitis?No – Acad Emerg Med. 2015 Sep;22(9):1015-24. doi: 10.1111/acem.12746. Epub 2015 Aug 20. Accuracy of White Blood Cell Count and C-reactive Protein Levels Related to Duration of Symptoms in Patients Suspected of Acute Appendicitis.

 

A useful review on the diagnosis of appendicitis – JAMA. 2007 Jul 25; 298(4): 438–451. Does This Child Have Appendicitis?

 

Summary of Accuracy of Symptoms

Download (PDF, 124KB)

Summary of Accuracy of Signs

Download (PDF, 117KB)

 

 

Finally – Don’t forget Emergency Physicians can learn how to use Point of Care Ultrasound (PoCUS – ?Appendicitis) which can significantly improve diagnostic accuracy in experienced hands. Experience comes with practice.

J Med Radiat Sci. 2016 Mar; 63(1): 59–66. Published online 2016 Jan 20. doi:  10.1002/jmrs.154
Ultrasound of paediatric appendicitis and its secondary sonographic signs: providing a more meaningful finding

See SJRHEM PoCUS Quick Reference

PoCUS – Measurements and Quick Reference

 


Intoxicated patients are at high risk for Head Injury

Intoxicated patients with minor head injury are at significant risk for intracranial injury, with 8% of intoxicated patients in our cohort suffering clinically important intracranial injuries. The Canadian CT Head Rule and National Emergency X-Radiography Utilization Study criteria did not have adequate sensitivity for detecting clinically significant intracranial injuries in a cohort of intoxicated patients.

ACADEMIC EMERGENCY MEDICINE 2013; 20:754–760. Traumatic Intracranial Injury in Intoxicated Patients With Minor Head Trauma

Canadian CT Head Rule not applicable to intoxicated patients (GCS<13)

Download (PDF, 76KB)

 

 

CMPA provide useful guidance on the duties expected in the management of intoxicated ED patients.

 

All intoxicated patients, even the so called ‘frequent fliers’ require a full assessment, including history (from 3rd parties if available), full examination (especially neurological), blood glucose level, neurological observations, and this assessment should be carefully documented.

 

Can we defer CT imaging for intoxicated patients presenting with possible brain injury?

This study suggests that deferring CT imaging while monitoring improving clinical status in alcohol-intoxicated patients with AMS and possible ICH is a safe ED practice. This practice follows the individual emergency physician’s comfort in waiting and will vary from one physician to another.

http://www.sciencedirect.com/science/article/pii/S0735675716306805

 

Download (PDF, 172KB)

 

 


Acute Heart Failure has a higher mortality than acute NSTEMI

Cardiac markers are routinely used to exclude NSTEMI in patient presenting with chest pain. However the diagnosis of acute heart failure (AHF) is mainly clinical, including CXR, ECG, PoCUS.

Ultrasound B Lines and Heart Failure

 

There is good evidence that BNP can be helpful in ruling out AHF – BMJ 2015;350:h910

Recommended Link – Emergency Medicine Cardiac Research and Education Group

Download (PDF, 1.32MB)

 

 

Emergency Treatment of Acute Congestive Heart Failure

Most recent recommendations from Canadian Cardiovascular Society (2012)

  • 1 – We recommend supplemental oxygen be considered for patients who are hypoxemic; titrated to an oxygen saturation > 90% (Strong Recommendation, Moderate-Quality Evidence).

Values and preferences. This recommendation places relatively higher value on the physiologic studies demonstrating potential harm with the use of excess oxygen in normoxic patients and less value on long-term clinical usage of supplemental oxygen without supportive data.

  • 2 – We recommend CPAP or BIPAP not be used routinely (Strong Recommendation, Moderate-Quality Evidence).

Values and preferences. This recommendation places high weight on RCT data with a demonstrated lack of efficacy and with safety concerns in routine use. Treatment with BIPAP/CPAP might be appropriate for patients with persistent hypoxia and pulmonary edema.

  • 3 – We recommend intravenous diuretics be given as first-line therapy for patients with congestion (Strong Recommendation, Moderate-Quality Evidence).
  • 4 – We recommend for patients requiring intravenous diuretic therapy, furosemide may be dosed intermittently (eg, twice daily) or as a continuous infusion (Strong Recommendation, Moderate-Quality Evidence).
  • 5 – We recommend the following intravenous vasodilators, titrated to systolic BP (SBP) > 100 mm Hg, for relief of dyspnea in hemodynamically stable patients (SBP > 100 mm Hg):
    • i

      Nitroglycerin (Strong Recommendation, Moderate-Quality Evidence);

    • ii

      Nesiritide (Weak Recommendation, High-Quality Evidence);

    • iii

      Nitroprusside (Weak Recommendation, Low-Quality Evidence).

Values and preferences. This recommendation places a high value on the relief of the symptom of dyspnea and less value on the lack of efficacy of vasodilators or diuretics to reduce hospitalization or mortality.

  • 6 – We recommend hemodynamically stable patients do not routinely receive inotropes like dobutamine, dopamine, or milrinone (Strong Recommendation, High-Quality Evidence).

Values and preferences. This recommendation for inotropes place high value on the potential harm demonstrated when systematically studied in clinical trials and less value on potential short term hemodynamic effects of inotropes.

  • 7 – We recommend continuation of chronic β-blocker therapy with AHF, unless the patient is symptomatic from hypotension or bradycardia (Strong Recommendation, Moderate-Quality Evidence).

Values and preferences. This recommendation places higher value on the RCT evidence of efficacy and safety to continue β-blockers, the ability of clinicians to use clinical judgement and lesser value on observational evidence for patients with AHF.

  • 8 – We recommend tolvaptan be considered for patients with symptomatic or severe hyponatremia (< 130 mmol/L) and persistent congestion despite standard therapy, to correct hyponatremia and the related symptoms (Weak Recommendation, Moderate-Quality Evidence).

Values and preferences. This recommendation places higher value on the correction of symptoms and complications related to hyponatremia and lesser value on the lack of efficacy of vasopressin antagonists to reduce HF-related hospitalizations or mortality.

 

Emergency Medicine Cases – Episode 4: Acute Congestive Heart Failure 

In Summary

  • AHF is a serious life-threatening condition in its own right, excluding NSTEMI does not change that. Appropriate management and disposition (almost always admission) is required.
  • Oxygen and intravenous Diuretics are the first-line  treatment
  • Nitrates are recommended in the relief of dyspnea in hemodynamically stable patients (SBP > 100 mm Hg)

 


Enhancing Morbidity and Mortality Rounds Quality

The Ottawa M&M Model

CalderMM-Rounds-Guide-2012

 

 

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EM Reflections – May 2017

Thanks to Dr Paul Page for his summary

Edited by Dr David Lewis

 

Top tips from this month’s rounds:

  1. DVT – Anticoagulation Bridging… when is it needed?
  2. Anticoagulated elderly patient with minor trauma. Can we rely on a recent INR?
  3. Abdominal pain in an elderly patient. Does a nonspecific exam and normal vitals exclude serious illness?

 


DVT – Anticoagulation Bridging… when is it needed?

Consider the type of anticoagulation best suited for your patient. Remember warfarin needs bridging until therapeutic INR is achieved.  Ensure that patients discharged after hours have a robust plan for follow up and enough supply until follow up occurs.

Outpatient Management of Anticoagulation Therapy – American Family Physician 2013

 

For Warfarin therapy in DVT, Thrombosis Canada recommends:

Full-dose low molecular weight heparin (LMWH) overlapping with warfarin for at least 5 days and until the INR is at least 2.0 for at least 2 days.

 

Bridging is not required when prescribing a Direct Oral Anticoagulant (DOAC) e.g Apixaban or Rivaroxaban.

 

Thrombosis Canada tool to support decision making for Anticoagulation therapy in DVT

Management of DVT:

General measures:
Unless compression ultrasound (CUS) is rapidly available, patients with moderate-to-high suspicion of DVT (except those with a high risk of bleeding) should start anticoagulant therapy before the diagnosis is confirmed.  Imaging confirmation should be obtained as soon as possible.
Outpatient management is preferred over hospital-based treatment unless there is an additional indication for hospitalization.
Initial treatment should have an immediate anticoagulant effect. Therefore, warfarin monotherapy is not appropriate initially.

Treatment Regimens:

Depending on the clinical presentation, one of following regimens should be used for the initial 3 months:

  • Full-dose low molecular weight heparin (LMWH) overlapping with warfarin for at least 5 days and until the INR is at least 2.0 for at least 2 days.
  • Full-dose IV heparin overlapping with warfarin for at least 5 days and until the INR is at least 2.0 for at least 2 days.
  • Apixaban 10 mg PO BID for 1 week before reducing dose to 5 mg PO BID.
  • Rivaroxaban 15 mg PO BID for 3 weeks before reducing dose to 20 mg PO once daily.
  • Full-dose SC LMWH or IV heparin for at least 5-10 days before switching to dabigatran 150 mg PO BID or to edoxaban 60 mg PO once daily.
  • Full-dose LMWH alone without switching to an oral anticoagulant.
  • Full-dose LMWH for the 1st month or so before switching to a DOAC or warfarin.

 


Anticoagulated elderly patient with minor trauma. Can we rely on a recent INR?

 

Elderly patients on warfarin presenting with minor trauma are commonly seen in the ED.  Many will have been on warfarin for a prolonged period and will have stable INRs. However we can not rely on a previous INR level when assessing the current presentation. Consider the following rational:

  • Why did the patient fall?
  • Do they have a concomitant illness?
  • Are they compliant with their medication?
  • Have they been prescribed or are you considering prescribing new medication that may interact with warfarin?

Clinically Significant Drug Interactions

Anticoagulated patients frequently re-attend the ED with complications of bleeding after discharge following minor injury e.g enlarging hematoma, blood soaked dressings, missed internal bleeding, mobility failure. Consider whether admission for observation may be more appropriate than discharge in this group of patients. For those discharge ensure that they have close support and clear advice on when to return.

Practical tips for warfarin dosing and monitoring – Cleveland Clinic Journal

 

See this recent Medical Student Pearl on Reversal of Anticoagulation in the ED

Medical Student Clinical Pearl – Reversal of Anticoagulation in the Emergency Department

 


 

Abdominal pain in an elderly patient. Does a nonspecific exam and normal vitals exclude serious illness?

Elderly patients presenting to the ED with acute abdominal pain should be considered extremely high risk. Published series have reported mortality rates approaching 10% (https://www.ncbi.nlm.nih.gov/pubmed/7091511)

Presentations can be delayed, physical exam can be innocuous, lab results can be misleading. The risk of serious pathology is much greater and the outcome of delayed diagnosis can be significant.

Abdominal emergencies in the geriatric patient – Int J Emerg Med. 2014; 7: 43.

 

 

An excellent post from ALIEM – 10 Tips for Approaching Abdominal Pain in the Elderly

After seeing your fifth young patient of the day with chronic pelvic pain, constipation, and irritable bowel syndrome, it is easy to be lulled into the mindset that abdominal pain is nothing to worry about. Not so with the elderly. These 10 tips will help focus your approach to atraumatic abdominal pain in older adults and explain why presentations are frequently subtle and diagnoses challenging.

 

Erect CXR – Abdominal Series – Free air under diaphragm in perforated bowel

 

Bottom Line –

Elderly patients with abdominal pain are at a much greater risk of serious pathology and require an extremely thorough assessment before (if ever) discharging with a rule-out diagnosis e.g constipation, gastro, abdo pain NYD etc.

 

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