239: When the Scar Hurts: Postoperative Anterior Cutaneous Nerve Entrapment Syndrome

Topic: Clinical Science
Subtopic: Pain category (ICD-11), Chronic postsurgical pain, Treatment/management

Background and Aims: Chronic abdominal wall pain is frequently misdiagnosed as visceral pathology, resulting in unnecessary investigations and prolonged morbidity. Anterior cutaneous nerve entrapment syndrome (ACNES) is the most common cause of abdominal wall pain and may occur following abdominal surgery due to scar-related nerve entrapment. Diagnosis is clinical, supported by a positive Carnett’s sign and response to local anaesthetic injection. We present a case of postoperative ACNES to highlight key diagnostic features and the therapeutic role of ultrasound-guided rectus sheath block with hydrodissection.

Methods: A 58-year-old woman presented with severe localised lower abdominal pain (NRS 8/10) over a previous appendectomy and incisional hernia repair scar. Pain was sharp, episodic, and functionally limiting. Extensive laboratory and imaging investigations were non-diagnostic. Physical examination revealed focal scar tenderness and positive Carnett’s sign. Ultrasound imaging demonstrated adhesion-like changes along the posterior rectus sheath. A diagnostic trigger-point injection produced temporary relief. Subsequently, an ultrasound-guided rectus sheath block using 1% lidocaine (20 mL) with hydrodissection was performed.

Results: The patient experienced immediate pain relief following the block. Post-procedure, pain frequency reduced to 0–1 brief episodes per month with significant improvement in daily functioning. No complications occurred. The clinicoradiological findings and response to hydrodissection confirmed postoperative anterior cutaneous nerve entrapment as the pain source.

Conclusions: ACNES should be suspected in patients with localised postoperative abdominal pain and negative visceral work-up. Careful clinical examination, especially Carnett’s test, remains critical for diagnosis. Ultrasound-guided rectus sheath block with hydrodissection serves both diagnostic and therapeutic roles and may release scar-related nerve entrapment. Early recognition by pain physicians can prevent unnecessary investigations and improve quality of life.

References: 1. Scheltinga MR, Roumen RM. Anterior cutaneous nerve entrapment syndrome (ACNES). Hernia. 2018;22(3):507–516. PMID 29270882. DOI: 10.1007/s10029-017-1710-z
2. Boelens OB, Scheltinga MR, Houterman S, Roumen RM. Randomized clinical trial of trigger point infiltration with lidocaine to diagnose anterior cutaneous nerve entrapment syndrome. Br J Surg. 2013;100(2):217–221. PMID 23180371. DOI: 10.1002/bjs.8958.
3. Boelens OB, Scheltinga MR, Houterman S, Roumen RM. Management of anterior cutaneous nerve entrapment syndrome in a cohort of 139 patients. Ann Surg. 2011;254(6):1054–1058. PMID 21881494. DOI: 10.1097/SLA.0b013e31822d78b8.
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Identifier: PMID 31920313 | DOI: 10.2147/JPR.S233191.

Presenting Author: Vindu Yadav
Submitting Author: Vindu Yadav

Senior Author: Vindu Yadav

IASP 2026 Global Year theme of Neuropathic Pain: Yes