Epididymitis, orchitis, and related conditions.

Epididymitis is the most common intrascrotal inflammation. Retrograde ascent of pathogens is the usual route of infection. Nonspecific bacterial epididymitis is caused by various aerobic bacteria, is frequently associated with anatomic abnormalities, and represents the most common type of epididymitis in older men. Sexually transmitted epididymitis is usually caused by Chlamydia trachomatis or Neisseria gonorrhoeae and represents the most frequent cause of acute scrotal swelling in men younger than 35 years of age. Underlying urologic abnormalities are uncommon in patients with sexually transmitted epididymitis. Systemic infections and trauma are unusual causes of epididymitis. Orchitis is less common than epididymitis. Blood-borne dissemination is the major route of testicular infection. With the exception of viral diseases, genitourinary tract infections seldom involve the testis primarily. Mumps is the most frequent cause of viral orchitis. Pyogenic orchitis usually results from an inflammatory process in the epididymis. Systemic dissemination of granulomatous infections may occasionally cause orchitis.