“In my patient with abdominal pain, what physical exam finding can help differentiate abdominal wall from intra-abdominal sources of pain?”

Carnett’s sign (described by a surgeon, J.B. Carnett, in 1926) is a physical exam finding that helps differentiate abdominal wall or psychogenic pain from intra-abdominal sources of pain.

The test is considered positive when, upon locating the tender abdominal spot, the patient’s pain worsens on tensing of the abdominal wall muscles by lifting the head and shoulders from the bed or by raising both legs with straight knees. Conversely, if the pain decreases with this maneuver, an intra-abdominal source is more likely1,2. Sensitivity of ~80%, specificity of ~90%, positive likelihood ratio of 2.6 and negative likelihood ratio of 0.2 have been reported in various studies. 3,4,5

A positive Carnett’s sign should broaden the differential of abdominal pain to include: hernias, irritation of intercostal nerve roots, rectus sheath hematomas, myofascial pain, anterior cutaneous nerve entrapment or ACNES (also see another P4P pearl 6) and psychogenic pain. In the appropriate clinical setting,  local corticosteroids or anesthetic injections, or the application of hot or cold packs may be therapeutic. 2,7

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 References

  1. Carnett JB. Intercostal neuralgia as a cause of abdominal pain and tenderness. J Surg Gynecol Obstet 1926; 42:625-632.
  2. Bundrick JB, Litin SC. Clinical pearls in general internal medicine.  Mayo Clin Proceedings 2011;86: 70–74.  https://mayoclinic.pure.elsevier.com/en/publications/clinical-pearls-in-general-internal-medicine-2.
  3. Takada T, Ikusaka M, Ohira Y, et al. Diagnostic usefulness of Carnett’s test in psychogenic abdominal pain. Intern Med 2011;50:213-17. https://www.jstage.jst.go.jp/article/internalmedicine/50/3/50_3_213/_article
  4. Kamboj Ak, Hoverten P, Oxentenko AS. Chronic abdominal wall pain: a common yet overlooked etiology of chronic abdominal pain. Mayo Clin Proc 2019;94:139-44. https://www.mayoclinicproceedings.org/article/S0025-6196(18)30852-8/pdf
  5. Sweetser S. Abdominal wall pain: a common clinical problem. Mayo Clin Proc 2019;94:347-335.https://www.mayoclinicproceedings.org/article/S0025-6196(18)30671-2/fulltext  
  6. https://pearls4peers.com/2015/11/18/whats-acnes-anterior-cutaneous-nerve-entrapment-syndrome/
  7. Suleiman S , Johnston DE.  The abdominal wall: an overlooked source of pain. Am Fam Physician 2001; 64: 431-8. https://www.ncbi.nlm.nih.gov/pubmed/11515832

Contributed in part by Brad Lander MD, Mass General Hospital, Boston, MA.

 

“In my patient with abdominal pain, what physical exam finding can help differentiate abdominal wall from intra-abdominal sources of pain?”

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).

 

References

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

 

 

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