Abdominal wall defects and cryptorchidism: an animal model.

Intra-abdominal pressure has been implicated in the mechanism of testicular descent. Boys born with abdominal wall defects reportedly have an increased incidence of cryptorchidism. To examine this relationship further a rat model was developed. The rat testis normally descends postnatally on or about day 21. In this study newborn male rats underwent surgical excision of all anterior abdominal musculature from the umbilicus to the xiphoid, while a control group had a sham procedure. In both groups steel wire was inserted into both testes as radiological markers to monitor descent. Animals were explored on day 28 to confirm the position of the testes. A total of 36 animals survived all sections of the protocol. Eight animals had adhesions and were dropped from the study. The results of 17 rats in the experimental group and 11 in the control group revealed that the surgically created abdominal wall defect did not result in cryptorchidism. This finding suggests that an intact anterior abdominal wall is not a prerequisite for testicular descent in the rat.