Dynamic magnetic resonance imaging of the female pelvis: radio-anatomy and pathologic applications. Preliminary results

Dynamic MRI of the pelvis was performed in 16 young nulliparous, normally continent women. The examinations were performed in the dorsal decubitus position. Using Turbo-Flash scans (acquisition time: 2.1 sec), sagittal images were obtained at rest and with maximal pelvic straining. The sacral promontory-subpubic (PSP) and the subpubic-subsacral axes (SPSS) measured respectively 80.5 degrees and 30 degrees in relation to the horizontal plane, without a statistically significant difference between rest and straining. A marked deformation of the posterior wall of the bladder was observed in 13 cases and the bladder neck was frontally deformed in 10 cases. With straining, the base of the bladder did not descend beyond 15 mm below the SPSS, and the cervix stayed at least 14 mm above the SPSS. These were established as the normal criteria for pelvic assessment. 20 multiparous patients (mean age 65 years), referred for urinary stress incontinence and/or prolapse, were investigated using the criteria previously established. The PSP, SPSS, and vaginal angle measured 80.95 degrees, 30.57 degrees, and 69.69 degrees respectively in relation to the horizontal. No statistically significant difference was detected between straining and rest conditions. The angle of the uterus in relation to the horizontal was 57.36 degrees at rest and 65.90 degrees in straining with a difference that was statistically significant. In six patients, the base of the bladder descended more than 1.5 cm while straining and in seven patients the cervix descended at least 1.4 cm below the SPSS while straining, both statistically significant differences. Overall, between our control and study populations, there were no significant differences between PSP and SPSS measured on straining and at rest. However, differences were detected in the vaginal angle, bladder-base position, and cervical position. These results suggest the potential substitution of MRI for colpocystography.