Computed tomography evaluation of colorectal carcinoma.

Knowledge of the extent of primary colorectal carcinoma at initial diagnosis is critical for proper management of disease. Currently, CT does not have a role in screening for colorectal carcinoma, though promising work on virtual colonoscopy is on the horizon. In patients with proven colorectal carcinoma, accurate prospective noninvasive assessment can identify those who may benefit from preoperative local radiotherapy, hepatic resection or cryoablation, or intra-arterial chemotherapy. CT should be considered complementary to the clinical assessment of colorectal carcinoma and to other modalities, such as barium enema, endorectal ultrasonography, MRI, and immunoscintigraphy. Although limited in evaluation of the primary tumor and local spread, CT has proven useful in assessing patients thought to harbor extensive local or metastatic disease. CT is generally the modality of choice for imaging the postoperative patient. The cross-sectional display of CT clearly depicts the operative bed, particularly after abdominoperineal resection. Baseline examinations should be obtained 2 to 4 months after surgery, with follow-up examinations every 6 to 9 months for 2 years, and yearly studies thereafter. CT-guided biopsies should be performed when findings suggest recurrent carcinoma.