Active Rectal Bleeding Due to Polyp Avulsion Induced by Bowel Preparation: A Case Report.

Lower gastrointestinal bleeding (LGIB) represents a significant clinical burden. While typically attributed to diverticulosis or angiodysplasia, iatrogenic mechanisms remain poorly characterized. This report describes a case of active rectal bleeding in a 32-year-old male patient following bowel preparation for colonoscopy. Endoscopy revealed massive fresh red blood and clots in the rectum, with an 8-mm mucosal protrusion showing arterial pulsatile bleeding at 8 cm from the anal verge. Characteristic chicken skin mucosa (CSM) surrounded the lesion. Based on the hemorrhagic lesion morphology and CSM features, it was postulated as a mechanical avulsion of a pedunculated (Ip-type) polyp induced by friction from hardened stool or a fiber-induced "snare-like" effect during bowel preparation, exposing vessels and causing massive hemorrhage. This case provides a novel perspective on "bowel preparation-induced polyp avulsion" as a mechanism for LGIB and highlights the potential of CSM as a marker for underlying neoplastic risk.