Injecting the Source: A Case of Abdominal Pain Resolved with Anterior Cutaneous Nerve Steroid Injection

Case Diagnosis: Anterior cutaneous nerve entrapment syndrome (ACNES).

Case Description or Program Description: A 58-year-old male with history of cholecystectomy 14 years ago and known to our service for low back pain presents to follow up with concerns of abdominal pain without a specific inciting event. Patient reported burning sensation and cramping in his right upper quadrant, particularly when performing sudden movements, reaching to the side, or forcefully contracting his abdomen.

Setting: Secondary care

Assessment/Results: Physical examination revealed right upper quadrant tenderness, reproducible to palpation at the lateral border of the rectus abdominis muscle. Pain was 7/10 in intensity on the Visual Analogue Scale (VAS) during the Carnett’s sign. CT and MRI ruled out intra-abdominal pathologies. An ultrasound-guided anterior cutaneous nerve block with lidocaine and dexamethasone was performed, providing immediate resolution of symptoms, with a reduction of pain to 0/10 on the VAS, confirming the diagnosis of ACNES.

Discussion (relevance): Abdominal pain may be a common, non-specific symptom with a broad differential diagnosis. Nonetheless, a debilitating factor in patients with chronic abdominal pain. ACNES, caused by intercostal nerve cutaneous branches entrapment, is often underdiagnosed with a higher prevalence in young females. In this middle-aged male with history of surgery and negative work up, ACNES was a consideration. An anterior cutaneous nerve block resulted in symptoms resolution and ultimately improved the patient’s quality of life.

Conclusions: This case highlights the importance of considering ACNES as a differential diagnosis in patients presenting with localized abdominal pain reproducible upon palpation, especially after ruling out other conditions. The successful treatment with anterior cutaneous nerve steroid injection emphasizes the benefits of this intervention in alleviating symptoms, highlighting the effectiveness of non-invasive interventions such as nerve blocks, and offering a therapeutic alternative to more invasive procedures.