A cross-sectional study of anterior cutaneous nerve entrapment syndrome at a Japanese emergency department.

Background: Anterior cutaneous nerve entrapment syndrome (ACNES) is the most common cause of abdominal wall pain. This study aimed to clarify the proportion of ACNES cases among those of abdominal pain and the clinical characteristics and prognosis of the disease in an emergency department (ED) of a Japanese general hospital. Methods: The medical records of patients from January 2014 to December 2023 were reviewed, and patients aged 15 years or older with abdominal pain with positivity for Carnett's sign, a good response to trigger point injection (TPI), and an ACNES diagnosis were included. The proportion of ACNES cases among the complaints related to abdominal pain in the ED between 2020 and 2023 was then determined. The recurrence rate was also determined using data from the medical records and telephone follow-ups. Results: Twenty-one patients were included. Their median age was 50 years (range: 16-83 years), 13 (62%) were female, and 11 (52%) had acute-onset pain. Follow-up data were available for 11 patients (52%), seven (64%) of whom had recurrent pain for a median period of 1 week after the index visit. The proportion of ACNES cases among those of abdominal pain was 0.11%. Conclusion: ACNES might be uncommon among patients with abdominal pain in the ED setting although underdiagnosis of this condition might have led to an underestimation of the proportion of cases. Moreover, given the high recurrence rate of abdominal pain associated with ACNES, following up these patients is very important.