An elusive cause of perianal pain in a patient with Hirschsprung's disease.

A 23-year-old woman presented to the outpatients department with symptoms of acute onset perianal pain of 2 weeks' duration and constipation. She was a known case of Hirschsprung's disease and was operated on in infancy. Rectal examination ruled out acute fissure or perianal sepsis, and subsequent colonoscopy was normal.