PURPOSE: To determine whether intravenous contrast material given during CT colonography improves (1) reader confidence for visualizing the bowel wall in patients with suboptimal bowel preparation, and (2) the sensitivity for detection of colorectal polyps and cancers.
METHOD AND MATERIALS: We performed 152 CT colonography (CTC) examinations in both the supine and prone positions. Eighty-four patients had CTC performed following an incomplete colonoscopy, and 68 patients had CTC performed for colorectal cancer screening with complete colonoscopic correlation. Reader confidence for visualizing the bowel wall was graded using a 5 point scale: 1 = no confidence; 5 = great confidence. Using helically-acquired magnified axial images, each colon visualized at CTC was divided into 10 segments, yielding a total of 1520 colonic segments. Suboptimal bowel preparation was graded per segment using a 5 point scale: 1= lumen full of fluid or stool; 5 = no luminal fluid or stool. Seventy-seven patients received intravenous (IV) contrast (150 cc Optiray; 4cc/sec;45 seconds delay. In those patients with complete colonoscopic correlation (n=68), we compared the diagnostic accuracy in patients who received IV contrast (n=37) with that of patients who did not receive IV contrast (n=31). In addition we blindly compared axial images in patients who received IV contrast viewed at windows sensitive and insensitive to contrast enhancement.
RESULTS: 22% of patients had ideal bowel preparation (grade 5), while significantly more bowel segments were ideally visualized with intravenous contrast than without (690/770 (90%) vs 540/750 (72%); p10mm) in patients who received intravenous contrast, were not visualized without IV contrast due to the presence of adjacent pooled fluid. The diagnostic accuracy for large polyp detection was significantly improved with intravenous contrast (100% vs 40%; p
CONCLUSIONS: Intravenous contrast significantly enhances diagnostic accuracy for large polyps (>10mm) and significantly improves reader confidence for the detection of polyps and bowel wall visualization, particularly in suboptimally prepared colons.
