A 58 year-old man with stipsis and a rectosigmoid stenosis at 15 cm from anal verge not passable by the colonoscope. CT showed a 10cm stenosing mass in continuity with sigmoid colon and rectum, infiltrating the bladder wall, and diverticular disease of the remaining sigmoid colon. Endoscopic biopsies at the level of the stenosis showed a moderate dysplasia. The patient, hospitalized on emergency for symptoms worsening and bowel obstruction, underwent surgery with high suspicion of a locally advanced malignant lesion. Adhesions are partially divided accessing the Retzius space. An infra-mesocolic window is created with such maneuvers, and the dissection is furthered posteriorly and downward reaching the avascular holy plane. Inferior mesenteric artery is dissected and divided. Descending mesocolon is opened and bowel divided by endostapler. Inferior mesenteric vein is dissected free and divided. The mass is freed from its attachment to the descending colon and the mesentery upstream of it. Left ureter is searched for and followed downward till the mass. Sharp dissection is carried on carefully and frozen section taken from tissue suspected for tumor infiltration. The ureter is encircled by tape and dissected free till the merging into the trigonus. The mid rectum downstream from the mass is now dissected free and stapled. Bladder wall is incised all around the area of suspected ab-extrinsic infiltration. The last attachments with the left ureter are then divided. The specimen is withdrawn through a mini-laparotomy with abdominal wall protection. Double layer bladder closure is accomplished by deeper interrupted sutures and a running suture to close the overlying peritoneum. A double stapled colorectal anastomosis is carried out. Histology showed no malignancy but a fistulized sigmoid diverticulitis.