A 77-year-old Japanese man presented with chronic mild lower abdominal pain for the past 3 years. The pain had occurred spontaneously and was exacerbated on an empty stomach and during feelings of stress, without any other accompanying symptoms. Despite the chronic abdominal pain, the patient was able to mountain climb as a hobby. The results of abdominal computed tomography and upper gastrointestinal endoscopy done at a local hospital were normal. Rebamipide and lansoprazole had been administered for abdominal pain by a local doctor, but the symptoms did not resolve. The patient had a past medical history of active pulmonary tuberculosis 2 years previously, and polypectomy of a colonic polyp 1 year previously.
Physical examination revealed that the patient’s body temperature was 36.4 °C, blood pressure was 128/60 mmHg, pulse rate was 66 beats/min, respiratory rate was 15/min, and oxygen saturation was 95% (room air). There were no remarkable abnormalities of the head, eyes, ears, nose, mouth, chest, and extremities. There was no tenderness of the abdominal region during palpation, and swab testing, alcohol testing, and skin pinching all produced negative results. Carnett’s sign was not examined at that time. All laboratory investigations showed values within normal range. Thoracic magnetic resonance imaging was performed for suspected thoracic nerve pain, but no abnormalities were detected. After this investigation, conservative therapy was started for unidentified abdominal pain likely originating from a psychiatric etiology.
At follow-up examination 7 days later, the symptoms had improved slightly, but the abdominal pain recurred 9 days later. Repeated physical examination of the abdominal region by palpation still revealed no tenderness, but we found three tender points in accordance with intercostal nerves Th10, Th11, and Th12, ranging within one finger-length along the lower left side of the rectus abdominis muscle; the pain was present only when the patient’s abdominal wall was tensed (when Carnett’s sign was examined) (Fig. 1), although local sensory disturbances were not seen. ACNES was suspected, and a diagnostic cutaneous injection of 5 ml of 1% lidocaine was administered by freehand technique without ultrasound (US) guidance at each of the upper two tender points, which had the most marked pain (Fig. 1A, B). Thirty minutes after the injections, the pain had reduced from 10/10 to 2/10 on a pain scale where 0 indicates no pain and 10 represents maximum pain.
One week later, the pain at the sites where 1% lidocaine had been injected was resolved, but the pain remained on the lower left side of the navel (Fig. 1C). Hence, we injected 10 ml of 1% lidocaine into the subfascial space at the remaining painful point under US guidance, and the pain had completely resolved to 0/10 by 30 min after the injection. Due to the above results, ACNES was diagnosed, and there has been no recurrence of symptoms in 4 months after the treatment.