A. Orchitis
Inflammation of testis tissue is most commonly due to bacterial infection, termed epididymo-orchitis. Viral infections also occur in the testis in the form of mumps orchitis. Orchitis is observed in approximately 30% of postpubertal males who contract parotitis. Testis atrophy is a significant and frequent result of viral orchitis but is less common with bacterial infections.

B. Torsion
Ischemic injury to the testis secondary to twisting of the testis on the spermatic cord pedicle is not uncommon in prepubertal and early postpubertal boys. When diagnosed and corrected surgically within 6 h of occurrence, the testis can usually be saved. Torsion may result in inoculation of the immune system with testis antigens that may predispose to later immunological infertility. It recognized that the “normal” contralateral mate of a torsed testis could also exhibit histologic abnormalities. It has not been clearly demonstrated whether this is related to the actual torsion or to an underlying abnormality in testes predisposed to torsion.

C. Trauma
Because of the peculiar immunologic status of the testis in the body (ie, it is an immunologically privileged site), trauma to the testis can invoke an abnormal immune response in addition to atrophy resulting from injury. Both may contribute to infertility. Trauma to the testis that results in fracture of the testis tunica albugineal layer should be surgically explored and repaired to minimize exposure of testis tissue to the body.