After removing the rectum at surgery, bowel continuity can sometimes be restored by an anastomosis between the anus and the bowel. This anastomosis is most commonly created by the use of surgical circular stapling instruments. In a retrospective pilot study the risk of developing an acute leak in the anastomosis was increased with one of the most commonly used instruments in Sweden as compared to the other brand in use. In the current study the patient is randomized to either one of the instruments after a resection of the rectum for rectal cancer.