Low-osmolar contrast tagging in minimally cathartic CT colonography for colorectal cancer screening: an observational study.

Abstract

Objectives: Adequate bowel preparation and tagging are critical in optimizing CTC performance. Iohexol has a higher safety profile than other available tagging agents. This study aims to determine if iohexol serves as an adequate fluid and stool tagging agent in conjunction with minimally cathartic bowel preparation.

Methods: In this prospective observational study, 50 participants ingested 50 mL of oral iohexol for tagging and 10 oz magnesium citrate for bowel preparation prior to CTC. Written informed consent was obtained. CTC was performed in all participants in at least two of the standard four positions (supine, prone, right decubitus, and left decubitus). Two board-certified abdominal radiologists independently scored the 6 colonic segments of participants who underwent successful CTC. The amount of residual fluid and solid stool, attenuation of tagged fluid, and efficacy of fluid and stool tagging were recorded in each segment. Statistical analyses were performed with R-4.4.0.

Results: 47 participants (mean age 66.39 ± 8.65 years; 39 female) underwent successful CTC. Of 1252 total colonic segments, 14.8% had no residual fluid and 59.5% had < 25% residual fluid. 73.6% of segments with residual fluid demonstrated good tagging. The mean fluid tagging efficacy ratio for all segments was 0.737 (95% CI: 0.700-0.775) with mean attenuation of 467 HU. Fluid tagging efficacy decreased from the cecum (0.934) to rectum (0.493). 92.8% of segments had no residual solid stool. Of the 7.2% of segments containing solid stool, 4.7% of segments had submerged stool ≤ 5 mm, 0.8% had 1-3 pieces of retained stool between 6 and 9 mm, and 1.8% had > 3 pieces 6-9 mm or single pieces > 1 cm.

Conclusion: Low-volume (50 mL) iohexol is an effective fluid and fecal tagging agent for CTC with a minimally cathartic bowel preparation. This provides an easy option to label residual material and cleanse the bowel for patients undergoing CTC.