Pelvic floor anatomy in classic bladder exstrophy using 3-dimensional computerized tomography: initial insights

We present the pelvic floor anatomy of the major pelvic floor musculature in classic bladder exstrophy, including the levator ani, obturator internus and obturator externus. By improving our knowledge of pelvic floor anatomy we hope to understand better the relationship of the pelvic floor to the bony anatomy as well as the role of osteotomy in changing pelvic floor anatomy to enhance urinary control after surgery.

3-Dimensional computerized tomography was done in 6 boys and 1 girl, including 5 patients 2 days to 5 months old (mean age 7 months) undergoing primary closure and 2 who were 4 and 8 years old undergoing repeat closure. The pelvic floor musculature, including the levator ani, obturator internus and obturator externus, in these cases was compared to that in 26 age and sex matched controls.

The levator ani musculature encompasses a significantly wider area of 9.5 cm.2 in patients with classic bladder exstrophy than in controls. The anterior segment of the levator ani was shorter (1.2 cm.) and the posterior segment of the levator ani was longer (2.5 cm.) than in controls. The degree of divergence of the levator ani in classic exstrophy was significantly more outwardly rotated (38.8 degrees) than controls. In addition, the transverse diameter of the levator hiatus was 2-fold that in our control group and in that of published controls, while the length of the hiatus was 1.3-fold that in normal controls. There was also significant flattening, involving a 31.7 degree decrease in steepness between the right and left halves of the levator ani, of the puborectal sling in classic bladder exstrophy versus controls. Because of these findings, there is more anterior superior rotation in the pelvic floor in exstrophy cases. The obturator internus was more outwardly rotated (15.1 degrees) in exstrophy and the obturator externus also showed more outward rotation (16.9 degrees) than in controls.

This study provides better understanding of the pelvic floor anatomy in classic bladder exstrophy. Significant differences have been documented in the pelvic floor in classic bladder exstrophy cases and controls. Hopefully these differences may have a pivotal role in providing new insight into long-term issues, such as urinary and fecal incontinence, and pelvic organ prolapse, in classic bladder exstrophy.