CT colonography with rectal iodine tagging: Feasibility and comparison with oral tagging in a colorectal cancer screening population

• In the group receiving rectal tagging, mean per-polyp sensitivity, specificity were 96.1% and 95.3%; while in the group receiving oral tagging, mean per-polyp sensitivity, specificity were 89.4% and 95.8%. The difference between the two groups was not statistically significant (p = 0.549).
• Rectal tagging can be an effective alternative to oral tagging.
• Rectal tagging allowed greater patient acceptance and lower overall examination time.

PurposeTo evaluate feasibility, diagnostic performance, patient acceptance, and overall examination time of CT colonography (CTC) performed through rectal administration of iodinated contrast material.Materials and methodsSix-hundred asymptomatic subjects (male:female = 270:330; mean 63 years) undergoing CTC for colorectal cancer screening on an individual basis were consecutively enrolled in the study. Out of them, 503 patients (group 1) underwent CTC with rectal tagging, of which 55 had a total of 77 colonic lesions. The remaining 97 patients (group 2) were randomly selected to receive CTC with oral tagging of which 15 had a total of 20 colonic lesions. CTC findings were compared with optical colonoscopy, and per-segment image quality was visually assessed using a semi-quantitative score (1 = poor, 2 = adequate, 3 = excellent). In 70/600 patients (11.7%), CTC was performed twice with both types of tagging over a 5-year follow-up cancer screening program. In this subgroup, patient acceptance was rated via phone interview two weeks after CTC using a semi-quantitative scale (1 = poor, 2 = fair, 3 = average, 4 = good, 5 = excellent).ResultsMean per-polyp sensitivity, specificity, positive and negative predictive values of CTC with rectal vs oral tagging were 96.1% (CI95% 85.4 ÷ 99.3%) vs 89.4% (CI95% 65.4 ÷ 98.1%), 95.3% (CI95% 90.7 ÷ 97.8%) vs 95.8% (CI95% 87.6 ÷ 98.9%), 86.0% (CI95% 73.6 ÷ 93.3) vs 85.0% (CI95% 61.1 ÷ 96.0%), and 98.8% (CI95% 95.3 ÷ 99.8%) vs 97.2% (CI95% 89.4 ÷ 99.5%), respectively (p > 0.05). Polyp detection rates were not statistically different between groups 1 and 2 (p > 0.05). Overall examination time was significantly shorter with rectal than with oral tagging (18.3 ± 3.5 vs 215.6 ± 10.3 minutes, respectively; p < 0.0001).ConclusionsRectal iodine tagging can be an effective alternative to oral tagging for CTC with the advantages of greater patient acceptance and lower overall examination time.