Magnetic resonance imaging of the pelvic floor in the postpartum patient.

Magnetic resonance imaging (MRI) was used to assess anatomical changes in the pelvic floor after childbirth. Six women underwent serial MRI examination within 30 hours and at 1 week, 2 weeks, 6 weeks and 6 months after delivery; 8 additional women were studied only within 30 hours of delivery. T-1 and T-2-weighted images of the pelvis in the transverse and sagittal planes with a 1.5-T MR imager were obtained. In the sagittal section we assessed the urethrovesical angle, urethral length, distance from the symphysis to the proximal and distal vagina, vaginal length, width and length of the sphincters, and the presence of sphincter defects. Axial sections were assessed for sphincter defects for the distance between the symphysis and midurethra, vagina and rectum. Only one parameter (distance between symphysis and distal vagina) changed significantly over time, without a clear trend in direction. Interobserver variation was reasonable (<15%) except for anal canal length, urethral length and distance between symphysis and anus. There were no significant correlations between birthweight and MRI parameters. There was a non-significant association (P = 0.09) between the sole combined sphincter defect and rectal injury, but not with episiotomy or parity. We concluded that it is feasible to determine multiple measurements on MR images to evaluate structures of the pelvic floor.