CT Colonography in 546 Patients with Incomplete Colonoscopy1

Abstract

To retrospectively evaluate the positive predictive value (PPV) of computed tomographic (CT) colonography performed in patients who were referred for further examination after incomplete colonoscopy. This HIPAA-compliant retrospective study was approved by the institutional review board; informed consent was waived. We identified 546 consecutive patients (mean age, 64.1 years; 401 [73.4%] women) who underwent CT colonography after incomplete colonoscopy between November 1999 and December 2002. A retrospective chart review was performed if CT colonography depicted endoscopically nonvisualized lesions 6 mm or greater in diameter. Repeat colonoscopy rate, endoluminal findings, and PPV of CT colonography were determined. Subsequent colonoscopic findings were used as the reference standard. In 72 (13.2%) patients, CT colonography depicted 88 endoscopically nonvisualized lesions 6 mm or greater. Of 11 patients reported to have 12 masses (> or =20 mm), at subsequent colonoscopy, one patient had no mass. Eighteen patients had 23 large (10-19-mm) polyps that they were suspected of having, and 47 patients had 53 medium (6-9-mm) polyps that they were suspected of having. At a median follow-up of 31 months (range, 6-42 months), 45 (63%) of 72 patients underwent follow-up colonoscopy because of their CT colonographic findings. Rates of repeat colonoscopy for masses, large polyps, and medium polyps were 100%, 94%, and 45%, respectively. Per-patient and per-lesion PPVs of CT colonography for masses, large polyps, and medium polyps were 90.9% and 91.7%, 64.7% and 70%, and 33.3% and 30.4%, respectively. CT colonography has the potential to become an accepted technique for evaluation of the nonvisualized part of the colon after incomplete colonoscopy, and it can increase the diagnostic yield of masses and clinically important polyps in this part of the colon.