Division of Pediatric Gastroenterology, British Columbia Children's Hospital, Vancouver, Canada.
An adolescent had marked systemic features suggestive of inflammatory bowel disease. Giardia lamblia trophozoites were present in endoscopic biopsy specimens from the terminal ileum and from the duodenum. His illness rapidly and completely resolved after metronidazole therapy. Giardiasis must be included in the differential diagnosis of inflammatory bowel disease in children.