CT colonography: positioning order and intracolonic pressure.

OBJECTIVE: The purpose of this study was to prospectively evaluate the effect of the order of positions on sustained rectal pressure and factors affecting pain perceived by patients during air-insufflated CT colonography. SUBJECTS AND METHODS: Rectal pressure was measured in the supine and prone positions for CT colonography of 379 patients in two groups. One hundred seventy-seven patients underwent imaging supine and then prone, and 202 patients were prone and then supine. Insufflation and patient pain parameters were based on patient self-report and investigator visualization of observable indicators. Colonic distention, residual feces or fluid, and diverticulosis were evaluated with a semiquantitative scoring system. Fisher's exact, Student's t, and chi-square tests as well as multivariate logistic regression analysis were performed.
RESULTS: Pressure was higher in the prone than in the supine position in both groups (p < 0.001). The measured pressure in the initial position did not differ between groups (p = 0.88). Pressure increased from 38.3 to 40.07 mm Hg in the second position in the supine-first group and decreased from 38.3 to 32.25 mm Hg in the second position in the prone-first group (p < 0.001). The percentage of patients with pain in the second position was 40% in the supine-first group compared with 18% in the prone-first group (p < 0.003). Distention did not differ between the groups. Pain was associated with increased pressure and diverticulosis (p < 0.001) but not with retained feces or fluid.
CONCLUSION: Sustained pressure in the air-insufflated colon was higher in the prone than in the supine position. Imaging in the prone position first results in a significant decrease in pressure in the latter phase and less pain. Pain was associated with pressure and diverticulosis.