Preoperative evaluation of patients with primary colorectal cancer.

Preoperative evaluation should focus on techniques that either preclude surgery entirely, alter the planned operation either preoperatively or intraoperatively, or suggest the need for preoperative adjuvant therapy. The presence of a synchronous colonic neoplasia should be excluded by colonoscopy or air-contrast barium enema combined with sigmoidoscopy. A preoperative carcinoembryonic antigen level provides useful prognostic information. Abdominal computed tomography (CT) or hepatic ultrasonography should be done in patients with hepatomegaly or abdominal liver function tests. Those with rectal cancer should undergo a careful digital palpation done by an experienced observer combined with rigid proctosigmoidoscopy. Intrarectal ultrasonography may provide more objective data in regard to the extent of the local disease. If preoperative radiation therapy is planned, abdominal CT is appropriate to exclude extrapelvic disease that would preclude such a strategy. The benefit of routine preoperative CT in patients with otherwise resectable colonic or rectal cancer remains unclear.