Noncathartic CT colonography with stool tagging: Performance with and without electronic stool subtraction

OBJECTIVE. The purpose of our study was to evaluate the performance of noncathartic, dietary unrestricted CT colonography, without and with the aid of electronic stool subtraction, for detecting colorectal neoplasia in a high-prevalence referral population. MATERIALS AND METHODS. Patients with known or suspected colorectal neoplasms were potentially eligible for participation, regardless of the presence or absence of gastrointestinal symptoms. Subjects ingested 21.6 g of barium in nine divided doses. CT colonography was performed in the standard fashion. Data sets were randomly evaluated by two of three experienced radiologists, with subsequent reanalysis of each data set after electronic stool subtraction at least 6 weeks later. Optical colonoscopy was performed after purgation and served as the reference standard. RESULTS. One hundred thirty-one adenomatous neoplasms were identified among 114 subjects. On a per subject basis, the sensitivity for detecting adenomas 6-9 or > 10 mm in diameter ranged from 53% to 88% and 84% to 93% without stool subtraction, respectively. By including stool subtraction, these sensitivity estimates improved to 68% to 92% and 93% to 94%, respectively. Specificity ranged from 71% to 91% and 88% to 100% for lesions 6-9 and > 10 mm in size, respectively. Double reading resulted in detection of 27 (87%) of 31 and 65 (96%) of 68 patients with 6-9 and > 10 mm adenomas, respectively. With double reading, the area under the receiver operating characteristic curve for large adenomas was 0.97. CONCLUSION. In this increased-risk referral population, CT colonography in the non-cathartic-tagged colon without dietary restrictions compared favorably with optical colonoscopy.