Comparative Study between Low dose Virtual Colonoscopy (CT Colonoscopy) and Conventional Colonoscopy in Colorectal Tumors and Tumor like lesions

Abstract

Purpose: to assess the role of low dose CT colonography (virtual colonoscopy) as a non-invasive imaging technique in detection and diagnosis of colonic lesions using optical colonoscopy and / or operative findings as a reference standard, as well as highlighting its advantages and possible pitfalls.

Methods: sixty-one patients were examined by low dose CT after standard bowel preparation, rectal insufflation and IV contrast injection. Imaging was performed in both supine and prone positions. Evaluation consisted of review of the transverse CT images, sagittal and coronal reformations and 3D endoluminal images. CT colonographic findings were correlated with standard conventional colonoscopic and/or operative findings.

Results: Low dose virtual colonoscopy identified over all 12 malignant colonic masses with sensitivity about 100 %, 4 polyps out of 5 polyps measured ≥10 (80 % ), 2 polyps out of 3 polyps measured 6-9 mm ( 66.6 %), 2 polyps out of 4 polyps measured 1-5 mm ( 50%). The overall sensitivity of polyp detection was 66.7 % with 5 false positive and 4 false negative polyps. The overall sensitivity and specificity of low dose virtual colonoscopy were 88.6 % and 70.5 % respectively. The positive predictive value was 88.6 %, negative predictive value was 70.5 % and accuracy was 83.6 %.

Conclusion: Low dose CT colonography has high sensitivity for the detection of clinically important polyps and cancer as well as multiple advantages over conventional colonoscopy in imaging of colorectal neoplasms.