Background: CT colonography (virtual colonoscopy) is a new technique being offered 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 significance and consequences of these findings.
Methods: Two-hundred and fifty patients who were referred for colonoscopy for clinically indicated reasons underwent CT colonography using low-dose radiation (50 mAs) immediately prior to conventional colonoscopy. A single radiologist reviewed the CT images for extracolonic pathology, and findings were classified as having high, moderate, or low clinical significance. Electronic medical records were reviewed to assess what follow up diagnostic tests, if any, were performed.
Results: A total of 136 extracolonic findings were detected in 83 (33.2%) of the 250 patients. Of these 136 findings, 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 lesions 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 significant findings were new findings, and in 11 the extracolonic abnormalities resulted in further diagnostic testing. None of the patients with moderate or low significance lesions underwent further testing.
Conclusions: Low-dose CT colonography can detect highly significant extracolonic findings. Although extracolonic lesions were common, only a small proportion of patients required further diagnostic testing. Additional studies to determine the optimal radiation dose, cost-effectiveness, and legal implications of detecting extracolonic findings are warranted.