Virtual colonography: Identification and differentiation of colorectal lesions using multi-detector computed tomography

Abstract

Objective. Early detection of precancerous or malignant lesions may be decisive for prognosis of patients with colorectal cancer. In this prospective feasibility study, multi-detector spiral computed tomography (CT) colonography was compared with conventional colonoscopy for the detection of colorectal polyps. Material and methods. Seventy-eight patients underwent CT colonography (standard colonoscopy preparation, distension with room air, prone and supine position) immediately before colonoscopy. Sixty-five (83%) were asymptomatic screening subjects, while the rest had symptoms suggestive of colorectal disease. Presence, location, and size of lesions were prospectively assessed. Sensitivity, specificity, and positive and negative predictive values of CT colonography were calculated using conventional colonoscopy as the reference standard. Results. Conventional colonoscopy was normal in 52 patients. In 26 patients a total of 49 polyps and 3 carcinomas were identified. All three carcinomas and 39 polyps (80%) were identified by CT colonography. Seven of 7 polyps ≥10 mm (100%), 13 of 16 polyps of 6 to 9 mm (81%), and 19 of 26 polyps ≤5 mm (73%) in diameter were identified. Fourteen false-positive findings (10 of which were ≤5 mm in diameter) were related to 8 patients (specificity at the patient level was 86%). In 10 patients, a total of 10 polyps were missed by CT colonography, 7 of which were ≤5 mm in diameter. Conclusions. In this feasibility study, multi-detector spiral CT colonography allows accurate detection of polyps>5 mm in diameter, but at the expense of low specificity in the small size range.

• Colonography
• colonoscopy
• colorectal cancer
• CT
• multi-detector CT
• polyps