Abdominal wall pain, ACNES and pudendal neuralgia

Think of the abdominal wall when chronic abdominal pain is focal and worse with muscle tensing: a positive Carnett sign plus relief from a local anesthetic injection supports ACNES, and pudendal neuralgia is diagnosed clinically with the Nantes criteria.

1. The wall is often overlooked. Abdominal wall pain accounts for up to 30% of chronic abdominal pain, and ACNES is its most common cause ¹².
2. ACNES is intercostal nerve entrapment. Anterior cutaneous branches of lower intercostal nerves are irritated where they pass through the rectus abdominis, giving focal pain, usually lateral to the periumbilical region, with altered sensation ¹.
3. Carnett's test separates wall from viscera. Locate the maximal tender point, then have the patient lift head and legs; pain that is the same or worse indicates an abdominal wall source ¹.
4. Local anesthetic confirms the mechanism. In a randomized trial of 48 patients, 13 of 24 responded to 10 mL 1% lidocaine at the tender point versus 4 of 24 to saline, supporting an anesthetic, not placebo, effect ³.
5. Treatment is stepwise. Scheltinga describes a three-step protocol of abdominal wall injections followed by localized removal of terminal intercostal nerve branches; neurectomy relieves about 70–90% of selected refractory patients ²¹.
6. Pudendal neuralgia has five essential criteria. Pain in the pudendal territory, worse sitting, not waking the patient at night, no objective sensory loss, and a positive anesthetic pudendal block ⁴.

Nantes exclusion criteria include purely coccygeal, gluteal or hypogastric pain, exclusively paroxysmal pain, isolated pruritus, and imaging abnormalities that could explain the symptoms ⁴.

• ACNES pain worsens with maneuvers that stress the abdominal muscles, such as coughing, stretching and bowel movements ¹.
• Prior abdominal trauma or surgery is a significant risk factor for ACNES ¹.
• About 2% of emergency department patients with acute abdominal pain in one Dutch study had ACNES ¹.
• A response to a rectus sheath or tender-point block of more than 50% pain reduction supports the diagnosis ¹.
• Other interventions include rectus sheath blocks with or without steroid, pulsed radiofrequency and botulinum toxin, with variable results ¹.
• In the lidocaine trial, success was at least a 50% fall on the visual analogue scale or 2 points on a verbal scale, 15–20 minutes after injection ³.
• Pudendal neuralgia from entrapment is a clinical diagnosis; there are no pathognomonic signs or tests ⁴.

• Pursuing repeated visceral imaging despite a positive Carnett sign ¹.
• Dismissing ACNES relief after injection as placebo ³.
• Diagnosing pudendal neuralgia when pain wakes the patient or sensory loss is objective ⁴.