Background and study aims: Because of the rarity of cap polyposis of the colon and rectum, the endoscopic features of this condition have not been specified to date. The aim of this study is to characterize the endoscopic features of cap polyposis. Patients and methods: The diagnosis of cap polyposis was established by histologic findings in specimens obtained endoscopically or surgically from four patients. Colonoscopic findings in the four patients were retrospectively reviewed. Results: The endoscopic features were divided into semipedunculated type (three patients) and flat-topped protruding type (one patient). In the semipedunculated type, the polyps were characterized by reddish protrusions of various configurations with eroded surface in the rectosigmoid colon. In the remaining patient, all the lesions were flat protrusions with a reddish central depression. The polyps of both types became smaller in size and fewer in number at the proximal part of the sigmoid colon. Multiple white specks were observed in the intervening mucosa in all four patients. Conclusions: The prominence of the polyps at the distal part of the colon and rectum and multiple white specks in the intervening mucosa seem to be the additional endoscopic features suggestive of cap polyposis.
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