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11 A Comparison Between Dynamic Pelvic Magnetic Resonance I magmg and Videoproctography in Patients with Constipation [2001년 4월 DCR] 2011-11-12 3108
 
Hiroyoshi Matsuoka, M.D., Steven D. Wexner, M.D., Mehul B. Desai, M.D.,Tetsuro Nakamura, M.D.,Juan J. Nogueras, M.D.,* Eric G. Weiss, M.D.,Carol Adami, M.D.,t V. Lee Billotti, L.P.N.
 
From the Departments of Colorectal Surgery and tRadiology, Cleveland Clinic Florida, Fort Lauderdale, Florida
 
PURPOSE: This study attempts to compare the diagnostic efficacy of dynamic pelvic magnetic resonance imaging with that of videoproctography for the presence of rectocele, sigmoidocele, and intussusception as well as the measurement of anorectal angle and perineal descent in constipated
patients.
METHODS: Patients volunteering for the study and fulfilling the criteria for videoproctography to
evaluate constipation were also scheduled for dynamic pelvic magnetic resonance imaging. Patients undergoing videoproctography were placed in the left lateral decubitus position, after which 50 ml of liquid barium paste was introduced into the rectum. After this, approximately 100 ml of thick barium paste similar to stool in consistency was injected into 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-ram intervals with dynamic breathhold
sagittal images of the anorectal region obtained at rest and during strain and squeeze maneuvers. Total acquisition time per maneuver was approximately 19 seconds. The tests were performed by different examiners blinded to the result of the other evaluation. The investigations were independently interpreted, findings compared, and patients questioned regarding their impression of dynamic pelvic
magnetic resonance imaging and videoproctography.
RESULTS: From June 1996 to April 1997, 22 patients (15 females) with a mean age of 68 (range, 21-85) years underwent both videoproctography and dynamic pelvic magnetic resonance imaging. Dynamic pelvic magnetic resonance imaging was only able to detect 1 of 12 (8.3 percent) anterior rectoceles and one of two (50 percent) posterior rectoceles identified by videoproctography. It failed to recognize any of the rectoanal intussusception (zero of four) but did show 9 of 12 (75 percent) sigmoidoceles. Significant
discrepancy 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 t 1) of the patients with increased fixed perineal descent and only half (one of two) of the patients with increased dynamic perineal descent noted on videoproctography. All 22 patients preferred dynamic pelvic
magnetic resonance imaging over videoproctography because of greater comfort.
CONCLUSION: Occasionally, the increased cost of new technology can be justified by the enhanced diagnostic yield. The ability to avoid unnecessary surgery or, conversely, to continue to search for otherwise occult pathology that can be surgically corrected justifies routine application of these new tools. However, this study has shown that, despite a cost of approximately ten times more for dynamic pelvic magnetic resonance imaging than for videoproctography, no clinical changes were made. Thus, on the basis of this study, we cannot endorse the routine application of dynamic pelvic magnetic resonance imaging for the evaluation of constipated patients. In certain selected individuals, it may" play a role, but further study is necessary to clmqfy its exact role.
 
DISCUSSION
VP has been used to diagnose such evacuative disorders as rectocele, rectoanaI intussusception, and
sigmoidocele and increased perineal descent. However, in theory, the high-resolution capability of MRI,
combined with theoretic advantages including no radiation exposure and lack of need for intrarectal injection of contrast, makes it a potentially attractive test. The anterior rectal wall receives the force of
abdominal pressure when the patient is evacuating. Thus, a patient who has a weakened pelvic floor may be prone to developing an anterior rectal bulge (anterior rectocele)) 2 A rectocele is often only apparent during forceful evacuation when the rectum is emptying. Thus, the absence of material (barium paste) in the rectocele and the use of the rather unphysiologic prone position during maximal evacuative effort while "freezing" motion for 19 seconds may have contributed to the failure of DPMRI to detect 11 of the 12 anterior rectoceles and one of the two posterior rectoceles. We therefore concur with Delemarre et
al. 23 that DPMRI is not a useful test to detect anterior rectoceles.
 
Rectoanal intussusception is usually seen during VP at the end of evacuation. Once again, the prone position may not have allowed patients to keep pushing long enough to detect the pathology during DPMRI. Unlike rectoceles and rectoanal intussusceptions, three-fourths of sigmoidocetes were revealed by DPMRI. To distinguish sigmoidocele, the sigmoid colon was traced from the rectum. It was sometimes difficult to distinguish between the sigmoid colon and small intestine, and thin-section sagittal imaging did not traverse the entire pelvis. This may explain why one-fourth of sigmoidoceles were overlooked. Some nvestigators have suggested that urinary bladder voiding is important before DPMRI to avoid extrinsic (bladder) rectal compression. We did not request that patients void before their examination, and cystoceles were noted in seven patients. Thus, although DPMRI does not appear as sensitive as VP for detecting rectocele or rectoanal intussusception, it may be more sensitive than \@ for detecting other intrapelvic pathologies causing or associated with evacuative disorders. As Ferrante eta. suggested, there is wide interobserver variation in the measurement of the anorectal angle. Jorge et aL concluded that there were highly significant differences in the measurement of the anorectal angle between balloon proctography and cinedefecography. The interobserver variation with MRI is noted to be much less than that with defecography. Our results regarding measurements of anorectal angle and perineal descent also show a poor correlation between these two examinations.
Despite the ability of DPMRI to find cystoceles and allow urologic referral, these cystoceles were not believed to be the cause of the problem in any of these patients; nor did they result in operations performed on these patients by the urology service. Thus, allowing that the procedures enhanced the diagnostic yield of otherwise occult pathology, they did not improve the clinical course of the patient. Conversely, although DPMRI identified fewer rectoceles than did VP, these rectoceles were all small, and none of them would have been operated on even based exclusively on VP findings. Thus, once again, DPMRI did not prevent us from operating on patients who would have received operations had they only undergone VP.
Lastly, DPMRI costs approximately ten times more than VP. Thus, because of the lack of concordance in this study and the large number of lesions seen by VP but missed by DPMRI, DPMRI should not be performed initially for constipation unless other intrapelvic pathology is suspected. However, if surgical intervention is planned, DPMRI may- supply additional pelvic anatomic and functional information that cannot be provided by VP.