Objective volumetric comparison of room air versus carbon dioxide for colonic distention at screening CT colonography.

PURPOSE: To objectively compare colonic distention at CT colonography (CTC) achieved with manual room air vs. automated low-pressure carbon dioxide (CO2) using a novel automated volumetric quality assessment tool.
METHODS: Volumetric analysis was retrospectively performed on CTC studies in 300 asymptomatic adults using an automated quality assessment tool (V3D Colon [beta version], Viatronix). Colonic distention was achieved with room air self-administered to tolerance via hand-held pump (mean number of pumps, 39 ± 32) in 150 individuals (mean age, 59 years; 98 men, 51 women) and via continuous low-pressure automated infusion of CO2 in 150 individuals (mean age, 57 years; 89 men, 61 women). CTC studies in supine and prone position were assessed to determine total colonic volume (luminal gas and fluid). The colonic length along the automated centerline was also recorded to enable calculation of length-adjusted colonic volumes.
RESULTS: The mean total colonic volume (±SD) for individuals receiving room air and CO2 distention was 1809 ± 514 and 2223 ± 686 mL, respectively (p < 0.01). The prone position was better distended in 78.7% (118/150) of cases using room air; whereas, the supine was better in 66.0% (99/150) of CO2 cases (p < 0.01). Using a volume threshold of 2000 mL, 49 (32.7%) of room air cases and 92 (61.3%) of CO2 cases were above this cut-off. The mean length-adjusted colonic volume (mL/cm) for the room air and CO2 techniques was 9.9 ± 2.4 and 11.6 ± 2.6 mL/cm (p < 0.01).
CONCLUSIONS: Using automated volumetry allowed quantitative analyses of colonic volumes and objectively confirmed that continuous low-pressure CO2 provides greater overall colonic distention than the manual room air technique at CTC. The supine position demonstrated better distention with CO2, whereas the prone position was better distended with the room air technique.