Uploaded and Shared in Youtube by: NEJMvideo A 46-year-old woman presented with a history of 3 days of pruritus in the anal area and 1 day of excretion of tapelike materials. During the year before presentation, she had reported intermittent colicky abdominal pain and loose stool, which had been attributed to irritable bowel syndrome. Laboratory evaluation was unremarkable, with no evidence of anemia. Colonoscopy revealed a long, moving tapeworm, Diphyllobothrium latum, located in the terminal ileum and extending to the sigmoid colon. D. latum is a fish tapeworm that can infect humans after they consume infected undercooked or raw fish. The patient had a history of eating raw fish and recalled eating raw trout most recently 2 months before presentation. She was treated with a single dose of praziquantel. After administration, the abdominal pain resolved, but she continued to have intermittent loose stool.