Colorectal cancer: Role of CT colonography in preoperative evaluation after incomplete colonoscopy

PURPOSE: To evaluate computed tomographic (CT) colonography in patients with clinical suspicion of colorectal cancer and in whom colonoscopy was incomplete. MATERIALS AND METHODS: After incomplete colonoscopy, 34 patients underwent CT colonography before and after intravenous injection of iodinated contrast agent, in supine and prone positions. Twenty patients with no evidence of colon cancer after complete colonoscopy were included as a control group. Sensitivity and specificity of CT colonography were determined for detection of cancers, polyps, and metastases to liver. RESULTS: In 29 patients, surgery revealed 30 colorectal cancers (three synchronous cancers) and two ischemic lesions of the descending colon. Colonoscopy missed 10 colorectal cancers and three synchronous cancers; all were detected with CT colonography. Sensitivity and specificity for detection of colorectal cancer were 56% and 92%, respectively, for incomplete colonoscopy and 100% and 96%, respectively, for CT colonography (P <.01). Sensitivity and specificity of CT colonography in detection of polyps were 86% and 70%, respectively, for diameters of 5 mm or less; 100% and 80%, respectively, for 5-10-mm diameters; and 100% for diameters greater than 10 mm. Spiral CT of the liver revealed four metastases (2-5 cm); sensitivity and specificity were 100% and 43% for nonenhanced scans and 100% for contrast-enhanced scans (P <.01). CONCLUSION: In this selected group of patients, CT colonography provided complete information to properly address surgery of colorectal cancer and treatment of liver metastases. (C) RSNA, 2002.