Evaluation of Pelvic Floor Muscular Redistribution After Primary Closure of Classic Bladder Exstrophy by 3-Dimensional Magnetic Resonance Imaging

Abstract

We used 3-dimensional magnetic resonance imaging reconstruction to generate models of the pelvic floor musculature in classic bladder exstrophy, allowing for statistical analysis of changes seen in the anatomy after primary closure. Patients with classic bladder exstrophy underwent pelvic magnetic resonance imaging before and after primary closure. Contours of the levator ani were mapped and measured in 3-dimensional space. In addition, 2-dimensional angles and measurements were used to make a quantitative and qualitative analysis of the pelvic floor before and after closure. A total of 19 cases of classic bladder exstrophy were included in the study, with 12 closed as newborns without osteotomy and 7 closed later with osteotomy. In both groups the pre-closure exstrophy pelvic floor in the axial plane was box-like and after closure it had a more inward rotation. The steepness and angulation of the levator ani muscle remained relatively unchanged in both groups. The levator ani muscle group, with and without osteotomy, was redistributed into the anterior compartment of the pelvis after closure. Postoperatively a successfully closed exstrophy had the bladder positioned deeply within the pelvis. After closure the levator ani muscle regained the expected smooth contoured shape. Primary closure of bladder exstrophy 1) reshapes the pelvis from a box-like configuration to a more inwardly rotated hammock, 2) redistributes a significant portion of the levator ani muscle into the anterior compartment and 3) facilitates a smooth uniform contouring to the pelvic floor. Closing the bony pelvic ring by pubic reapproximation in the newborn or by osteotomy in an infant produces similar changes in the pelvic floor.