A proctosigmoidectomy, Hartmann's operation or Hartmann's procedure is the surgical resection of the rectosigmoid colon with closure of the anorectal stump and formation of an end colostomy. It was used to treat colon cancer or inflammation. Currently, its use is limited to emergency surgery when immediate anastomosis is not possible, or more rarely it is used palliatively in patients with colorectal tumours.