What’s ACNES (anterior cutaneous nerve entrapment syndrome)?

 As the name implies, this is an abdominal pain syndrome thought to be due to the entrapment of cutaneous branches of an intercostal nerve at the level of the rectus abdominis muscle (1,2).   It may be acute or chronic.

Up to a third of patients with chronic abdominal pain may have ACNES with the source of pain attributed to the abdominal wall, not the viscera (1,3).  Unfortunately, a third of patients with ACNES experience pain for >1 year and about 10% for > 5 years before diagnosis of ACNES is made.

In about one-half of cases, ACNES begins spontaneously, with the remainder developing after abdominal surgery or pregnancy, or is associated with “sports”, “job” or “unusual activity” (4).   Females outnumber males by a 4:1 margin with an average age of 37  y (2).  Carnett’s sign on physical exam may be a clue (2,5) with a sensitivity of 78% and specificity of 88% for abdominal wall pain (6) .

Identification of abdominal wall trigger points and their infiltration with lidocaine may relieve the pain instantaneously and can serve as a diagnostic test.  Surgical neurectomy may be effective in those with only temporary or partial response to repeated lidocaine injections (1).

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1. Boelens OBA, Scheltinga MR, Houterman S, et al. Randomized clinical trial of trigger point infiltration with lidocaine to diagnose anterior cutaneous nerve entrapment syndrome. Br J Surg 2013;100:217-221. https://www.ncbi.nlm.nih.gov/pubmed/23180371

2. van Assen T, Brouns JAGM, Scheltinga MR, et al. Incidence of abdominal pain due to anterior cutaneous nerve entrapment syndrome in an emergency department. Scand J Trauma Resusc Emerg Med 2015;23:19. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4327965  

3. van Assen T, de Jager-Kievit JW, Scheltinga MR, et al. Chronic abdominal wall pain misdiagnosed as functional abdominal pain. J Am Board Fam Med 2013;26:738-44. https://www.ncbi.nlm.nih.gov/pubmed/24204070

4. Boelens OB, Scheltinga MR, Houterman S, et al. Management of anterior cutaneous nerve entrapment syndrome in a cohort of 139 patients. Management of anterior cutaneous nerve entrapment syndrome in a cohort of 129 patients. Ann Surg 2011;254:1054-1058.  https://www.ncbi.nlm.nih.gov/pubmed/21881494

5. Pearls4Peers.  https://pearls4peers.com/2016/12/20/in-my-patient-with-abdominal-pain-what-physical-exam-finding-can-help-differentiate-abdominal-wall-from-intra-abdominal-sources-of-pain

6. Sweetser S. Abdominal wall pain: a common clinical problem. Mayo Clin Proc 2019;94:347-355. https://www.mayoclinicproceedings.org/article/S0025-6196(18)30671-2/fulltext

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What’s ACNES (anterior cutaneous nerve entrapment syndrome)?