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Anisakiasis of the Anorectum.

A 51-year-old man was evaluated due to a 1-month history of right upper quadrant pain. The findings on laboratory data, abdominal X-ray, and esophagogastroduodenoscopy were unremarkable. On colonoscopy, living Anisakis larvae was found in the anorectum without penetration (Picture 1, 2), although the total colon and terminal ileum were normal. The larvae were successfully removed using straight grasping forceps (Picture 3). Anisakiasis is a parasitic disease of the gastrointestinal tract, and most cases occur in the stomach and intestines (1). Colonic anisakiasis is rare, with half of the cases occurring in the ascending colon (1, 2). The mechanism by which living larvae reach the anorectum remains unclear. In the present case, the larvae may have been washed out from the gastrointestinal tract to the anorectum during pretreatment for colonoscopy or could have reached the anorectum through gastrointestinal movement without invasion of the gastrointestinal wall. Asymptomatic anisakiasis of the anorectum is extremely rare and could be diagnosed by colonoscopy in the present case.