Colon and rectum cancer. Patterns of spread and implications for workup.

The preoperative evaluation of patients diagnosed as having colon or rectum cancer is influenced by the anatomic location of the primary tumors; the knowledge that 10-25% of patients harbor detectable metastases at time of initial diagnosis; the observation that as many as one-third of patients with isolated metastases may achieve significant survival benefit by aggressive surgery; and the need to accurately stage low rectum cancers to permit selection of appropriate surgery. Patients are evaluated by colonoscopy, air-contrast barium enema when required, computed tomography, and serum carcinoembryonic antigen. Magnetic resonance imaging, especially of the pelvis, may be useful, and endorectal ultrasound has an important role in staging low rectum cancer. A thorough preoperative evaluation is essential in selecting appropriate operative therapy and for sequencing surgery with available adjuvant treatments.