Attenuated adenomatous polyposis coli: the role of ascertainment bias through failure to dye-spray at colonoscopy.

PURPOSE: The aim of this study is to show that the diagnosis of attenuated adenomatous polyposis coli must be made with caution and certainly only after adequate colonic examination with dye-spray. METHODS: Four patients thought to have attenuated adenomatous polyposis coli on the basis of family history and the identification of fewer than 100 polyps on simple colonoscopy underwent colonoscopy with dye-spray. RESULTS: All four individuals were found to have more than 100 polyps when dye-spray was used, confirming a diagnosis of classical familial adenomatous polyposis. CONCLUSIONS: The diagnosis of familial adenomatous polyposis may be missed altogether or incorrectly assigned as attenuated adenomatous polyposis coli if dye-spray is not used at colonoscopy. Patients with a family history of familial adenomatous polyposis or colorectal cancer should be considered for dye-spray before the diagnosis of familial adenomatous polyposis is excluded or one of attenuated adenomatous polyposis coli is made.