Primary hypothesis: Side-to-end anastomosis is non-inferior to colon J pouch for reconstruction after low anterior resection for rectal cancer in fecal incontinence (Wexner score).

Research questions: Are there differences between side-to-end anastomosis and colon J pouch in

• bowel function (fecal incontinence, frequency of bowel movements, rectal urgency, incomplete evacuation)
• quality of life
• sexual function
• urinary function
• postoperative complications
• operation time/ institutional costs

Experimental intervention: Low anterior resection for rectal cancer < 12 cm from the anal verge with total mesorectal excision (TME), ligation of the inferior mesenteric artery close to the aorta, mobilization of the splenic flexure, radical lymph node dissection and side-to-end colorectal/ coloanal anastomosis (STE). The blind end of the descending colon (3-5 cm long) is closed with a linear stapler. Stapling of the anastomosis is done by introducing the stapler from the anus by the assistant surgeon while the surgeon is holding the descending colon in the correct position. The anastomosis is performed on the antimesenteric aspect of the descending colon. The length of the blind end is measured and the integrity of the anastomosis is tested intraoperatively. The intended minimal distal clearance margin from the tumor is 2 cm. A protective loop ileostomy will be performed regularly which is intended to be closed 3 months postoperatively.

Control intervention: Low anterior resection for rectal cancer with total mesorectal excision (TME), ligation of the inferior mesenteric artery close to the aorta, mobilization of the splenic flexure, radical lymph node dissection and colon J pouch rectal/colon J pouch anal anastomosis (CJP). The colon J Pouch is formed by the descending colon by stapling with a defined pouch limb length of 5-6 cm, which is measured intraoperatively. The stapling is done by introducing the stapler from the anus by the assistant surgeon while the surgeon is holding the descending colon in the correct position. The integrity of the anastomosis is tested intraoperatively. The intended minimal distal clearance margin from the tumor is 2 cm. A protective loop ileostomy will be performed regularly which is intended to be closed 3 months postoperatively.

Follow-up per patient: 24 months postoperatively

Inclusion Criteria:

• patients with histological proven middle to low rectal cancer (< 12 cm from the anal verge) requiring low anterior resection with TME
• with or without (neo)-adjuvant radiochemotherapy
• age ≥18 years
• normal preoperative sphincter status (Wexner score = 0)

Exclusion Criteria:

• synchronous metastasis
• age > 80 years
• previous colon resection
• inflammatory bowel disease
• previous pelvic malignant tumor
• no anterior resection/ TME possible
• synchronous other malignant disease
• emergency operation
• local excision by colonoscopy possible
• unability to complete or comprehend the preoperative questionnaire