CT colonography for the detection of nonpolypoid colorectal lesions A prospective series.

To determine the diagnostic accuracy of CT-colonography (CTC) for colorectal nonpolypoid lesions.In the period 2010-2011, 51 out of 454 patients undergoing CTC received also optical colonoscopy (OC). Three human readers with high, intermediate and low expertise interpreted the images. Flat lesions were defined as 3 mm or less in height; laterally spreading type (LST) lesions were defined as nonpolypoid lesions with more than 10 mm lateral diameter.A total of 75 nonpolypoid colorectal lesions were identified in 21 patients: 43 type II-A low-grade adenomas, 2 type II-c Tis adenocarcinomas, 2 LST Tis adenocarcinomas, 24 nonadenomatous (hyperplastic) lesions and 4 LST infiltrating tumors (T1N0M0 in 2 cases and T2N0M0 in 2 cases). Per-lesion sensitivity and NPV were 44% and 80.5%, while per-patient sensitivity, specificity, PPV, NPV and accuracy were 80.9%, 93.7%, 89.5%, 88.2%, 88.7%. The readers with high and intermediate experience yielded significantly better diagnostic performances than reader with low experience (p =0.072 and p=0.030). All the infiltrating carcinomas and 75% of tis carcinomas were detected by all the readers.CTC showed a low per-lesion and an high per-patient diagnostic accuracy for all nonpolypoid colorectal lesions, but an high ability to detect nonpolypoid colorectal carcinomas. Diagnostic performances are strictly related to the reader experience.Adenoma, Colon cancer, Colonoscopy CT colonography, Non polypoid lesions, Screening.