Comparison of the anterior pelvis and levator ani muscle on MRI in women with and without anterior pelvic organ prolapse

Introduction and hypothesis The objective was to compare the differences in pelvic and levator ani muscle diameters in women with and without anterior pelvic organ prolapse. Methods Three groups were included, including 50 nulliparous women (nulliparous group), 50 women with stage III–IV anterior vaginal prolapse (prolapse group), and 50 women of the same age as the prolapse group but without prolapse (nonprolapse control group). The ischial interspinous diameter (ISD), anterior pelvic area (APA), levator defect score (LDS), levator ani hiatus width (LH-W), H-line, M-line, levator ani plate length, levator ani plate angle, and cervix length (CL) were measured. Results There were no significant differences in ISD (10.6±0.8 vs 10.6±0.9 cm), LH-W (3.0±0.4 vs 3.3±0.4 cm), or CL (2.9±0.6 vs 3.0±0.5 cm) between the nulliparous group and the nonprolapse control group ( p >0.05). However, there were significant differences between them and the prolapsed group (11.2±0.6 cm, 3.6±0.4 cm, 4.2±1.5 cm; p <0.05). There were no significant differences in LDS (0.70±0.61 vs 0.70±0.65) or APA (58.4±8.4 vs 60.1±7.4 cm 2 ) between the nonprolapse control group and the prolapse group ( p >0.05), but they were significantly different from those of the nulliparous group (0.08±0.34, 55.1±6.0 cm 2 ) ( p <0.05). The area under the receiver-operating characteristic curve for the ISD of nonprolapse control and prolapse groups was 0.713, and the cutoff value was 10.95 cm. Conclusions The levator ani hiatus width and cervix length were larger in patients with anterior vaginal prolapse than in those without prolapse. An ischial ISD greater than 10.95 cm was associated with prolapse.