Background: CT colonography (virtual colonoscopy) is a new technique being off ered to patients as a noninvasive method of imaging the colon. The aims of this study were to prospectively determine the prevalence of extracolonic findings in patients undergoing CT colonography, as well as to determine the clinical signi ficance and consequences of these findings. Methods: Two-hundred and fifty pati ents who were referred for colonoscopy for clinically indicated reasons underwen t CT colonography using low-dose radiation (50 mAs) immediately prior to conven tional colonoscopy. A single radiologist reviewed the CT images for extracolonic pathology, and findings were classified as having high, moderate, or low clinic al significance. Electronic medical records were reviewed to assess what follow up diagnostic tests, if any, were performed. Results: A total of 136 extracoloni c findings were detected in 83 (33.2%) of the 250 patients. Of these 136 findin gs, 17 (12.5%) were highly significant, 53 (38.9%) were moderately significant , and 66 (48.5%) were of low significance. The most common highly significant l esions were solitary lung nodules in 3 patients, mesenteric lymphadenopathy in 3 , adrenal masses in 2, low attenuation liver lesions consistent with metastases in 2, and bone metastases in 2 patients. Fourteen of the 17 (82.4%) highly sign ificant findings were new findings, and in 11 the extracolonic abnormalities res ulted in further diagnostic testing. None of the patients with moderate or low s ignificance lesions underwent further testing. Conclusions: Low-dose CT colonog raphy can detect highly significant extracolonic findings. Although extracolonic lesions were common, only a small proportion of patients required further diagn ostic testing. Additional studies to determine the optimal radiation dose,costef fectiveness, and legal implications of detecting extracolonic findings are warra nted.
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