Oral contrast adherence to polyps on CT colonography

Although oral contrast agents are known to improve the accuracy of CT colonography (CTC) by tagging fluid and stool, it is not well recognized that oral contrast also adheres to the surface of polyps. The authors' objective was to quantitate the frequency of contrast adhering to polyps. Three hundred thirty-eight optical colonoscopy-proven polyps were identified on CTC of all of the 216 patients with polyps in a larger cohort of screening patients. CT scans of polyps were analyzed for adherent contrast (ie, a thin coat/adherent drops) in at least one view (prone/supine). Forty-six percent of the 312 polyps not touching a contrast pool had adherent contrast. Polyps with villous histology were significantly more likely to have adherent contrast (77% [20/26] vs. 43% [124/286], P<0.001). Oral contrast agents often tag polyp surfaces in a pattern that is distinct from internal tagging of adherent stool, which must be recognized during CTC interpretation. Polyps with villous histology show a higher rate of contrast adherence than nonvillous polyps.