Description
A 54-year-old Japanese woman visited the emergency room with a gradual onset of severe sharp right lower abdominal pain over the last 48 hours. The pain was repeatedly triggered by coughing, sneezing, standing, walking, anteflexion positioning or right rotation of the trunk. She denied any other symptoms. Her vital signs showed no abnormality. Then, blood tests and contrast-enhanced CT of the abdomen were performed, but these revealed no abnormality. A repeat careful physical examination revealed that a localised tender point was elicited with one finger and the area of maximal tenderness was in accordance with right Th10 intercostal nerve along the right edge of the rectus abdominis muscle (video 1). The pain was also congruent with the abdominal wall tenderness test (Carnett’s sign positive) (video 2). Thus, we diagnosed her with anterior cutaneous nerve entrapment syndrome (ACNES). After the administration of 5 mL of 1% lidocaine solution at the tender point, her abdominal pain did not recur after 2 weeks and up to 2 months of follow-up.
Video 1.
Video 2.
The prevalence of patients with ACNES in the emergency room of teaching hospitals is approximately 2%; thus, it is more common than previously thought.1 The age at peak incidence is between 30 and 50 years, but it can be identified at any age. The pain is mostly localised to the abdominal wall dermatomes between Th9 and Th12 (88%), and approximately half of the pain in the right lower quadrant. Carnett’s sign is typically positive (87%); however, this sign is not specific to ACNES and still unclear about the test characteristics for the diagnosis. Furthermore, 80% of the patients have somatosensory disturbances of the skin overlying the maximal pain point, which is also very often positive after pinching the skin, and 42% of the patients have complete pain remission after the injection of a local anaesthetic agent on the abdominal wall.2 It is important for the correct diagnosis of ACNES that the patient’s history of pain is carefully assessed and that the localised maximal pain point (<2 cm in diameter) between the midline and lateral edge of the rectus abdominis muscle is identified.3
Learning points.
Anterior cutaneous nerve entrapment syndrome (ACNES) is caused by irritated intercostal nerves, which lead to severe abdominal pain that is often not diagnosed correctly.
The combination of typical findings from the medical history and physical examination, together with a modified rectus sheath block, may lead to the correct diagnosis of ACNES in patients with abdominal pain.
Acknowledgments
The authors are extremely grateful to Professor Kazumichi Onigata, Dean of Faculty of Medicine of the Shimane University, for his valuable help with the technical details of this work.
Footnotes
Contributors: TW took care of the patient and made these videos, and TW and YT wrote the manuscript.
Funding: The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests: None declared.
Patient consent for publication: Obtained.
Provenance and peer review: Not commissioned; externally peer reviewed.
References
- 1. van Assen T, Brouns JAGM, Scheltinga MR, et al. Incidence of abdominal pain due to the anterior cutaneous nerve entrapment syndrome in an emergency department. Scand J Trauma Resusc Emerg Med 2015;23:19 10.1186/s13049-015-0096-0 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2. FMU M, Maatman RC, De Joode L, et al. Characteristics of 1116 consecutive patients diagnosed with anterior cutaneous nerve entrapment syndrome (acnes). Ann Surg 2019. [DOI] [PubMed] [Google Scholar]
- 3. Scheltinga MR, Roumen RM. Anterior cutaneous nerve entrapment syndrome (acnes). Hernia 2018;22:507–16. 10.1007/s10029-017-1710-z [DOI] [PubMed] [Google Scholar]