A case of asymptomatic colonic anisakiasis incidentally diagnosed during colonoscopy

A 42-year-old-woman who had being undergoing periodic colonoscopy since 2008 as follow-up for a colonic polyp, underwent colonoscopy at our hospital in June 2013. Although she had no abdominal symptoms, the endoscopic examination revealed Anisakis larva penetrating the mucosa of the ascending colon, which was removed with biopsy forceps. She had consumed raw mackerel in sushi 2 days prior to the colonoscopy. Colonic anisakiasis (similar to gastric anisakiasis) is treated by early colonoscopic removal of Anisakis larvae. In patients presenting with acute abdominal pain, tumor-like lesions on imaging or localized peritonitis, colonic anisakiasis must be included in the differential diagnosis, and it is important to obtain a thorough medical history, including information concerning the ingestion of raw fish. Early colonoscopic diagnosis is useful in such cases to prevent unnecessary tests and surgery.