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15-05-2012 | Surgery | Article

Laxative-free bowel examination feasible


Free abstract

MedWire News: Laxative-free computed tomographic colonography (CTC) is as effective for detection of polyps of 10 mm in size or larger as conventional imaging techniques, research suggests.

Recognizing that colon cleansing before optical colonography (OC) and standard CTC is considered unpleasant and discourages patients from undergoing colorectal cancer screening, the team investigated the efficacy of electronic cleansing software and computer-aided detection.

"Laxative-free CTC addresses an important barrier to screening, and its potential effect on screening merits further investigation," say Michael Zalis (Massachusetts General Hospital, Boston, USA) and co-authors.

As reported in the Annals of Internal Medicine, 605 patients aged 50 to 85 years with a moderate risk for colon cancer underwent laxative-free CTC after ingesting contrast material that tags feces, allowing electronic removal of the material from the images. The same patients were then screened using standard OC with preparative laxative.

Per-patient analysis showed that for adenomas of 10 mm or larger, per-patient sensitivity (0.91 vs 0.95) and specificity (0.85 vs 0.89) did not significantly differ between laxative-free CTC and OC.

However, laxative-free CTC was significantly less sensitive than OC for detection of adenomas 8 mm or larger (0.70 vs 0.88) and 6 mm or larger (0.59 vs 0.76). Specificity was also significantly lower with CTC than OC at both the 8 mm (0.88 vs 0.91), and 6-mm (0.76 vs 0.94) thresholds.

Patients reported that laxative-free CTC was associated with less discomfort, smaller changes in bowel movement, and greater ease of preparation than OC.

While acknowledging that polyps 10 mm and smaller can be clinically significant, the team notes that around 90% of polyps with important histologic features, such as high-grade dysplasia, villous features, or invasive malignancy, are larger than 10 mm.

"Our results suggest a role for CTC as an alternate screening method to OC with which participants would experience improved preparation and examination comfort - factors that could contribute positively to overall screening participation," Zalis et al conclude.

By Lynda Williams

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