Autoamputation of a large pedunculated colon polyp.

A 49-year-old man was referred for colonoscopy after a positive fecal occult blood test. Laboratory tests and physical examination were unremarkable but colonoscopy revealed a large pedunculated polyp in the sigmoid colon (●" Fig.1). Owing to inadequate bowel cleansing, polypectomy was not carried out. On repeat colonoscopy 120 days later, bowel cleansing was excellent. The examination was performed by an expert endoscopist, under good vision with adequate colonic distension and no blind angulations. However, despite every effort, the endoscopist was unable to find the polyp.A second expert endoscopist repeated the examination in the same session, and although he reached the cecum twice, he also could not detect the polyp. Interestingly, both endoscopists observed a prolapse of the normal mucosa, with a scar on the edge, in the site where the polyp had been previously seen (●" Fig.2). On close inspection, no adenomatous tissuewas visible. We hypothesized that polyp autoamputation had occurred, with the prolapsed mucosa being the remnant of the stalk of the amputated polyp. Indeed, the patient reported having passed some bright red material and clots per rectum a fewweeks before, with no significant consequences. To our knowledge, only three cases of colonic polyp autoamputation have been reported [1,2]. Autoamputation has also been described in the stomach [3] and in theduodenum[4],mainlywith thepedunculated typesof polyp,whichare subject to higher mechanical traction and torsion of the stalk. The present case is the first with documented endoscopic images both before and after the event. Autoamputation can be asymptomatic or accompanied by abdominal pain and bleeding, eventually leading to hospitalization [4]. No fatalities have been reported. Intrinsic limitations of colonoscopy are usually the first reason mentioned for missed polyps [5]. Nevertheless, gastroenterologists should consider the possibility of autoamputation in the case of pedunculated polyps that are not found in subsequent colonoscopies.