An experimental model of neonatal testicular torsion: evidence against an exclusively extravaginal etiology.

The present study was designed to determine whether extravaginal torsion of the spermatic cord (EVT) can be distinguished from intravaginal torsion (IVT) on the basis of gross and histologic examination of the testis. It is traditionally believed that EVT, postulated to occur only in neonates, can be grossly distinguished from IVT, which occurs in older patients, on the basis of adherence between testis and tunica vaginalis. Such adherence is felt to be present in EVT but not IVT. This concept that the two types of torsion can be distinguished in the operating room has important clinical ramifications. In cases of EVT, contralateral orchidopexy theoretically need not be performed, since adhesions develop between tunica vaginalis and dartos by a few weeks of age. This is in contrast to IVT, in which contralateral orchidopexy is necessary due to the bilateral nature of the bell clapper deformity. Using a rat model, we first demonstrated that IVT could produce adherence of the tunica vaginalis to testis. Then, eight rats were operated on, producing right IVT and left EVT. Animals were then sacrificed at intervals of up to one month. Gross and histologic examination showed involvement of the tunica vaginalis in an ischemic and inflammatory response in a majority of testes, regardless of the type of torsion. Attempts to distinguish EVT from IVT on the basis of grossly evident adhesions between tunica vaginalis and testis are of questionable validity. Early contralateral orchidopexy is therefore recommended in all cases of neonatal torsion.