Inverted Diverticulum

Colonoscopy revealed diverticulosis in a 47-year-old man who had presented with rectal bleeding. A polypoid lesion was noted in the sigmoid colon (A). The mucosa of this lesion—unlike that of a hyperplastic or adenomatous polyp—appeared normal and was similar to the surrounding mucosa. The thin walls easily dimpled with light pressure from the closed biopsy forceps (B). This finding excludes a true polyp and confirms the diagnosis of an inverted diverticulum. The differential diagnosis includes other submucosal lesions, such as leiomyomas (lipomas), which typically have a yellowish hue.

Recognition is important because biopsy of an inverted diverticulum would result in iatrogenic colonic perforation.