A Rare Cause of Gastrointestinal Bleeding: Taeniasis in a Roux-en-Y Gastric Bypass Patient.

Taenia infection is a globally distributed parasitic disease that is uncommon in developed countries. Taeniasis typically presents with mild or no symptoms, and anemia is not a usual feature. We report the case of a 50-year-old woman with a history of Roux-en-Y gastric bypass who presented with a history of abdominal pain, asthenia, and melena. Blood tests revealed severe anemia, prompting endoscopic evaluation. EGD showed only postsurgical changes, and lower endoscopy revealed no bleeding source. Video capsule endoscopy demonstrated blood near the Roux-en-Y anastomosis and in the ileum. Enteroscopy subsequently identified a duodenal ulcer with recent bleeding and a tapeworm in the afferent limb. Hemostasis was achieved with hemostatic powder, and the patient was treated with praziquantel. At follow-up, she was asymptomatic, and her hemoglobin levels had normalized. Taeniasis is a rare cause of gastrointestinal bleeding, with only a few cases described in the literature. In this patient, the parasite was detected in the excluded limb of the gastric bypass. Mucosal injury caused by parasite attachment or movement may explain the bleeding. This case highlights the importance of considering parasitic infections in the differential diagnosis of melena, even in patients from non-endemic regions and without typical risk factors. Increased awareness of this rare presentation is essential to ensure timely diagnosis and treatment.