Preservation of the inferior mesenteric artery (IMA) and consequential blood flow to the rectum would reduce the risk of leakage of a colorectal anastomosis. One hundred and sixty-three patients undergoing left colectomy for complicated diverticular disease of the colon were randomly placed into two groups: A, n = 86; and B, n = 77. In group A, the integrity of the IMA was preserved by artery skeletization (IMAS); in group B, the IMA was divided at its origin. Variables recorded included duration of the surgical procedure, need for blood transfusion, length of hospital stay, operative mortality and morbidity, staple-ring disruption, and radiologic and clinical leakage. Anastomotic stenosis and recurrence of diverticular disease were noted. Surgical time was superior in the IMAS group. Radiologic and clinical leakages were significantly higher in group B (P = 0.02, P = 0.03, respectively). In group A a significant lower number of staple-ring disruptions was observed, evolving into clinical dehiscence. Preserving the natural blood supply to the rectum and the ensuing use of a healthy well-nourished rectal stump are suggested as the main aspects of IMAS in preventing and healing leakage of colorectal anastomosis.