Bowel preparation in MRI for detection of endometriosis: Comparison of the effect of an enema, no additional medication and intravenous butylscopolamine on image quality

Purpose: To compare the effect of three different patient preparation strategies for reducing bowel motion on image quality in pelvic MRI. Methods: Retrospective study in which 95 consecutive patients undergoing pelvic MRI were subdivided based on preparation type for reduction of bowel motion: group 1 (N = 31) fasted 4 h and applied an enema (Bisacodyl 10 mg); group 2 (N = 32) received no medication; group 3 (N = 32) received intravenous butylscopolamine (Buscopan® 50 mg). Image quality was reviewed by visual assessment of delineation (3-point-scale) of pelvic structures: uterus, adnexa, bladder, rectum, sigmoid, uterosacral ligaments, round ligaments and small bowel. As secondary endpoint the presence of rectal wall edema was evaluated. Interobserver agreement was calculated, as well as relative diagnostic odds ratios (RDOR) for the protocols to provide an outcome in the best delineation category. Results: Interobserver agreement proportions varied from 0.48 to 1.00. The rectum and sigmoid colon respectively have a 5.4 and 2.6 RDOR when butylscopolamine is applied compared to Bisacodyl (P = 0.051; P = 0.008), and a 4.2 and 5.7 times higher RDOR with Bisacodyl preparation compared to no medical preparation (P = 0.006; P < 0.01). Small bowel delineation was significantly better with butylscopolamine compared to Bisacodyl (P = 0.007). There was no significant difference in delineation of the other structures between protocols. There is a significant higher chance of observing rectal wall edema with Bisacodyl compared to the other protocols (both P < 0.001). Conclusions: Butylscopolamine provides better delineation of the small bowel and rectosigmoid compared to Bisacodyl, which in turn, provides better delineation of the rectosigmoid compared to no medication. Moreover, Bisacodyl causes rectal wall edema in the majority of cases.