CT colonography for synchronous colorectal lesions in patients with colorectal cancer: initial experience

Aim

To assess accuracy of CT colonography (CTC) in identifying synchronous lesions in patients with colorectal carcinoma.

Methods

This study included 174 consecutive patients undergoing CTC as part of staging or primary investigation where a colorectal cancer was diagnosed between 2004 and 2007. Prone unenhanced and portal phase enhanced supine series with air or CO₂ distension were acquired using 4- or 16-slice CT (Toshiba) and read by 2D ± 3D formats. Synchronous lesions were classified according to American College of Radiology’s (ACR) polyp classification. Segmental gold standard was flexible sigmoidoscopy/colonoscopy within 1 year and/or histology of colonic resection supplemented by follow-up. Nine patients without gold standard were excluded. Sensitivity, specificity and accuracy were calculated on a per polyp, per patient and per segment basis and discrepancies analysed.

Results

Direct comparable data were available for 764/990 colonic segments from 165 patients. Of 41 (C2–C4) synchronous lesions on “gold standard”, 33 were correctly identified on virtual colonoscopy (VC), overall per polyp sensitivity was 80.5%, with detection rates of 20/24 C3 (83.3%) and 3/3 C4 (100%) with per patient and per segment specificity of 95.4% and 99.2%, respectively.

Conclusion

CTC is an accurate technique to assess for significant synchronous lesions in patients with colorectal cancer and is applicable for total pre-operative colonic visualisation.