Objectives. To describe the pelvic floor musculature and bony pelvic anatomy in a case of naturally occurring classic bladder exstrophy in a rhesus monkey, the first reported case in the animal population since 1832, and compare the results to exstrophy seen in human newborns.

Methods. A 7-day-old male rhesus monkey with classic bladder exstrophy was examined by a pediatric urologist and primate veterinarian before being killed. A multidetector row computed tomography study with three-dimensional reconstruction was obtained, and a comparison computed tomography study of a 17-day-old male human with exstrophy was also reconstructed three dimensionally. The bony pelvis and pelvic floor muscular anatomy of both subjects were then examined and compared.

Results. On gross examination, a similar appearance of classic bladder exstrophy in the rhesus monkey and human newborn were noted, including an open exposed bladder, associated penile epispadias, and widely separated pubic bones. The evaluation of the three-dimensional models showed a similar orientation of the bony pelvis in both the rhesus and the human newborn. The iliac wings were significantly rotated outward, and the sacroiliac joint was 10° wider than that seen in normal children. The exstrophy pelvic floor in both the rhesus and the newborn was markedly flattened, with approximately 33% of the muscle located anterior to the rectum to support the pelvic structures (normal children have 50% of their levator ani anterior to the rectum).

Conclusions. By using advancements in imaging modalities, this study illustrated that naturally occurring classic bladder exstrophy in the human newborn and rhesus monkey were identical in both external appearance and internal anatomy.