A comparison between dynamic pelvic magnetic resonance imaging and videoproctography in patients with constipation

PURPOSE: This study attempts to compare the diagnostic efficacy of dynamic pelvic magnetic resonance imaging with that of videoproctography for the pr esence of rectocele, sigmoidocele, and intussusception as well as the measu rement of anorectal angle and perineal descent in constipated patients. MET HODS: Patients volunteering for the study and fulfilling the criteria for v ideoproctography to evaluate constipation were also scheduled for dynamic p elvic magnetic resonance imaging. Patients undergoing videoproctography wer e placed in the left lateral decubitus position, after which 50 ml of liqui d barium paste was introduced into the rectum. After this, approximately 10 0 mi of thick barium paste similar to stool in consistency was injected int o the rectum, and the patient was instructed to defecate while video images were taken. For dynamic pelvic magnetic resonance imaging, air, to be used as contrast, was allowed to accumulate in the rectum via examination with the patient in the prone position. A capsule was taped to the perineal skin immediately posterior to the anal orifice for marking. Sagittal and axial T1 images were obtained through the pelvis at 8-mm intervals with dynamic b reath-hold sagittal images of the anorectal region obtained at rest and dur ing strain and squeeze maneuvers. Total acquisition time per maneuver was a pproximately 19 seconds. The tests were performed by different examiners bl inded to the result of the other evaluation. The investigations were indepe ndently interpreted, findings compared, and patients questioned regarding t heir impression of dynamic pelvic magnetic resonance imaging and videoproct ography. RESULTS: From June 1996 to April 1997, 22 patients (15 females) wi th a mean age of 68 (range, 21-85) years underwent both videoproctography a nd dynamic pelvic magnetic resonance imaging. Dynamic pelvic magnetic reson ance imaging was only able to detect 1 of 12 (8.3 percent) anterior rectoce les and one of two (50 percent) posterior rectoceles identified by videopro ctography. It failed to recognize any of the rectoanal intussusception (zer o of four) but did show 9 of 12 (75 percent) sigmoidoceles. Significant dis crepancy of measurement of the anorectal angle and perineal descent exists between the two studies, and dynamic pelvic magnetic resonance imaging was not able to detect any (0 of 11) of the patients with increased fixed perin eal descent and only half (one of two) of the patients with increased dynam ic perineal descent noted on videoproctography. All 22 patients preferred d ynamic pelvic magnetic resonance imaging over videoproctography because of greater comfort. CONCLUSION: Occasionally, the increased cost of new techno logy can be justified by the enhanced diagnostic yield. The ability to avoi d unnecessary surgery or, conversely, to continue to search for otherwise o ccult pathology that can be surgically corrected justifies routine applicat ion of these new tools. However, this study has shown that, despite a cost of approximately ten times more for dynamic pelvic magnetic resonance imagi ng than for videoproctography, no clinical changes were made. Thus, on the basis of this study, we cannot endorse the routine application of dynamic p elvic magnetic resonance imaging for the evaluation of constipated patients . In certain selected individuals, it may play a role, but further study is necessary to clarify its exact role.