Ante-natal testicular torsion: only one cause of the testicular regression syndrome?

It has been suggested that the most likely cause of the Testicular Regression Syndrome (TRS) is ante-natal torsion of the testis. As testicular torsion is twice as common on the left this theory cannot explain the incidence of right sided or bilateral cases. From a 5-year retrospective surgical and pathological review, we confirmed that the left testis was the most commonly affected, that boys with TRS tended to be delivered closer to term, and that frequently both testes were present at birth, but one or both subsequently vanished. We also found that direct trauma can produce histological findings indistinguishable from TRS. Close to term, fetal testes are liable to be intrascrotal and therefore susceptible to direct trauma. As the left testis descends into the scrotum at an earlier stage than the right, it is therefore at greater risk of injury. Since the findings of TRS can be produced by direct trauma, we suggest that intra-partum trauma may predispose to the TRS.