We report a unique case of a 70-year-old woman with Gardner's syndrome who had a subtotal colectomy with ileoproctostomy. Since then, she has undergone 12 uncomplicated proctoileoscopies, each time with argon plasma coagulation ablation of small polyps without any bowel preparation. However, during the most recent procedure, when we attempted to cauterize some rectal polyps, an immediate explosion occurred, leading to multiple rectal and ileal perforations that required surgical repair with a temporary end ileostomy. This event suggests that bacterial fermentation of colonic content or visible feces is not necessary for combustion because we observed a cautery-related explosion in the absence of a colon. This case shows the need for adequate bowel preparation if cautery is to be used, even in patients who have undergone a colectomy.