Noncathartic CT Colonography Detects Adenomas

Noncathartic CT colonographies, or virtual colonoscopies, can detect most adenomas that are 6 mm or larger, according to an article published in the American Journal of Roentgenology.

Approximately 40 percent of older Americans avoid undergoing regular screening colonoscopies because they do now want to go through the traditional cathartic method of bowel cleansing to prepare for the examination. To address this issue, researchers from the Mayo Clinic in Rochester, Minn., undertook a prospective study to determine the quality and performance of noncathartic CTC in detecting adenomas.

A total of 564 asymptomatic patients underwent noncathartic CTC without dietary modification but with 21 g of barium with or without iodinated oral contrast material (four regimens). Among this group, 556 patients also underwent a complete colonoscopy with bowel purgation.

A gastrointestinal radiologist evaluated examinations using primary 2D search supplemented by electronic cleansing (EC) and 3D problem solving. The results of the noncathartic CTC were compared with the complete colonoscopy.

The researchers found that 37 of the 556 subjects who underwent both procedures (7 percent) had 52 adenomatous polyps that were 6 mm or larger and 16 patients (3 percent) had 20 such polyps that were 10 mm or larger. The addition of iodine significantly improved the percentage of labeled stool and specificity (80 percent versus 89–93 percent, respectively).

The overall sensitivity of noncathartic CTC for adenomatous polyps 6 mm or larger was 76 percent, which is similar to the sensitivity of the iodinated regimens with most patients (sensitivity: 231 patients, 74 percent; 229 patients, 80 percent. The negative predictive value was 98 percent (481/490) and the lone cancer was detected (0.2 percent, 1/556).

The authors concluded that among asymptomatic patients, the sensitivity of noncathartic CTC is slightly less than that of imaging with traditional colonoscopy procedures, without the stress of the prescreening bowel cleansing. The availability of this procedure may increase the number of patients who seek screening colonoscopies overall.