An Unexpected Finding of Diphyllobothrium nihonkaiense in a Patient with Inflammatory Bowel Disease

The patient in this case was a 52-year-old man with a known history of ulcerative colitis. His inflammatory bowel disease was asymptomatic; he presented for an outpatient endoscopy for routine surveillance of his condition. He underwent lower endoscopy to exclude colonic dysplasia; he was taking no medications at the time of his procedure. The patient had experienced no diarrhea or blood loss from the rectum and reported no symptoms that would suggest changes in his condition since his most recent previous colonoscopy 27 months previously. The patient had no known allergies. We did not discuss with the patient whether he might have ingested raw or undercooked fish. Results of a digital rectal examination were normal. ### Endoscopic Findings On lower endoscopic examination, we discovered mild inflammation characterized by friability, granularity, linear erosions, and loss of vascularity in a continuous and circumferential pattern from the anus through the rectum. Compared with the results of previous examinations, the findings were unchanged and were believed by the gastroenterologist to be consistent with the patient’s known ulcerative colitis. A benign-appearing sessile polyp was also noted in the rectum; this entity was biopsied and sent to the pathology department. The remainder of the colon and the terminal ileum had an unremarkable appearance. An incidental parasitic tapeworm was discovered in the ascending colon (Image 1). The tapeworm was extracted from the ascending …