Syndrome of the rectus abdominis muscle mimicking the acute abdomen.

The syndrome of the rectus abdominis muscle is a disorder of unknown etiology that produces rupture or tear of the epigastric artery, and stretches the rectus cutaneous medialis nerve, producing excruciating pain. The disorder is misdiagnosed in 60% to 93% of cases. We report two cases that presented as acute abdomen. One helpful diagnostic test was the lidocaine test, accomplished by subcutaneous injection of lidocaine into the sheath of the rectus abdominis muscle near the rectus cutaneous medialis nerve; the procedure provided immediate pain relief and the patients remained asymptomatic. In addition to helping establish a diagnosis quickly the lidocaine test may spare the patient the unnecessary morbidity or mortality of more invasive procedures.