What type of nerve entrapment is consistent with abdominal pain in a patient with a history of fatty liver disease and obesity?

Abdominal Cutaneous Nerve Entrapment Syndrome (ACNES)

In a patient with fatty liver disease and obesity presenting with localized abdominal pain, the most likely nerve entrapment is Anterior Cutaneous Nerve Entrapment Syndrome (ACNES), caused by entrapment of the cutaneous branches of the lower thoracoabdominal intercostal nerves at the lateral border of the rectus abdominis muscle. 1, 2

Clinical Recognition

ACNES is a commonly underdiagnosed cause of chronic abdominal pain with an estimated incidence of 13%-30% in the adult population. 3 The diagnosis is reached through history and physical examination alone, without need for imaging or laboratory studies. 1

Key Diagnostic Features

• Localized, severe abdominal wall pain that is constant and often refractory to standard treatments 2
• Pain at a specific trigger point along the lateral border of the rectus abdominis muscle 2, 3
• Positive Carnett's sign: Pain increases (rather than decreases) when the patient tenses the abdominal wall by lifting their head while supine 1, 4
• Small area of maximal tenderness (typically <2.5 cm diameter) that can be localized with one fingertip 2
• Pain may be unilateral or bilateral 3

Why This Diagnosis Fits Your Patient

Obesity is a relevant risk factor because increased abdominal wall tension and altered fascial anatomy can predispose to nerve entrapment at the lateral rectus sheath. 4 The fatty liver disease itself does not cause ACNES, but both conditions commonly coexist in patients with metabolic syndrome.

Diagnostic Approach

The diagnosis is clinical and does not require imaging. 1 Perform the following examination:

• Identify the point of maximal tenderness with one finger 2
• Perform Carnett's sign: Have patient lift head/shoulders while you palpate the tender point—pain that increases confirms abdominal wall origin 1, 4
• Diagnostic trigger point injection with local anesthetic (1% lidocaine) at the point of maximal tenderness provides immediate pain relief and confirms the diagnosis 2, 5

Treatment Algorithm

First-Line: Trigger Point Injections

Begin with trigger point injections (TPI) using local anesthetic, as 86% of patients show successful response, with 76% maintaining relief at long-term follow-up. 5

• Inject 5-10 mL of 1% lidocaine (with or without corticosteroid) at the point of maximal tenderness 2, 5
• May repeat injections up to 2-3 times if initial response is partial 2
• Ultrasound guidance can improve accuracy but is not mandatory 2

Second-Line: Surgical Neurectomy

If conservative treatment with injections fails after 2-3 attempts, surgical anterior neurectomy is indicated, with 73% of patients demonstrating successful pain response compared to 18% in sham surgery groups. 5

• Surgical approach involves anterior neurectomy of the intercostal nerve with closure of its fascial foramen 3
• Long-term satisfaction rates are 61-69% at 18-32 months follow-up 5
• Surgery should be performed by surgeons experienced with this technique 3

Emerging Therapies

• Radiofrequency ablation and neuromodulation are emerging options for refractory cases 2
• Chemical neurolysis with phenol or alcohol can be considered before proceeding to surgery 2

Critical Pitfalls to Avoid

• Do not order extensive imaging or laboratory studies for localized abdominal wall pain with positive Carnett's sign—this delays diagnosis and increases costs unnecessarily 1, 4
• Do not assume visceral pathology when pain is clearly localized to the abdominal wall and increases with muscle tensing 1
• Do not use systemic opioids as primary treatment—they are ineffective for neuropathic pain and risk dependence 6
• Recognize that negative imaging does not rule out ACNES—this is a clinical diagnosis that imaging cannot detect 1, 4

Distinguishing from Other Causes

This presentation differs from:

• Median arcuate ligament syndrome: Causes postprandial pain, weight loss, and involves celiac artery compression—not localized abdominal wall tenderness 7
• Chronic mesenteric ischemia: Presents with postprandial pain, sitophobia, and weight loss—requires vascular imaging 7
• Functional abdominal pain/IBS: Pain improves with defecation, associated with bowel habit changes, and lacks focal trigger points 6

The key distinguishing feature is the focal trigger point with positive Carnett's sign, which is pathognomonic for ACNES and absent in visceral pain syndromes. 1, 2