CT colonography after incomplete colonoscopy in subjects with positive faecal occult blood test

AIM: To report our experience with computed tomog-raphy colonography (CTC) systematically performed in subjects with positive faecal occult blood test (FOBT) and an incomplete colonoscopy in the setting of a population-based screening for colorectal cancer (CRC).METHODS: From April 2006 to April 2007, 43290 indi-viduals (age range 50-70) who adhered to the regionalscreening program for the prevention of CRC under-went immunochemical FOBT. FOBT was positive in 1882 subjects (4.3%). 1463 (77.7%) of these subjects underwent colonoscopy, 903 performed in a single center. Of 903 colonoscopies 65 (7.2%) were incom-plete. Forty-two of these subjects underwent CTC. CTC was performed with a 16-MDCT scanner after standard bowel prep (polyethyleneglycole) in both supine and prone position. Subjects whose CTC showed polyps or masses were referred to the endoscopist for repeat colonoscopy under sedation or underwent surgery. Per-lesion and per-segment positive predictive values (PPV) were calculated.RESULTS: Twenty-one (50%) of 42 CTCs showed pol-yps or masses. Fifty-five of these subjects underwent a repeat colonoscopy, whereas 2 subjects underwent surgery for colonic masses of indeterminate nature.Four subjects refused further examinations. CTC cor-rectly identified 2 colonic masses and 20 polyps. PPV for masses or polyps greater than 9 mm was of 87.5%.Per-lesion and per-segment PPV were, respectively,83.3% and 83.3% for polyps greater or equal to 10 mm, and 77.8% and 85.7% for polyps of 6-9 mm.CONCLUSION: In the context of a screening program for CRC based on FOBT, CTC shows high per-segment and per-lesion PPV for colonic masses and polyps greater than 9 mm. Therefore, CTC has the potential to become a useful technique for evaluation of the non visualized part of the colon after incomplete colonos-copy.