Orchitis may be caused by numerous bacterial and viral organisms. It is usually a consequence of epididymitis, which is inflammation of the epididymis (the tube which connects the vas deferens and the testicle).

The most common viral cause of orchitis is mumps. Approximately 30 % of patients who have mumps will develop orchitis during the course of the illness. It is most common in boys past puberty, rare before the age of 10. It usually manifests 4 to 6 days after the onset of mumps. In one-third of boys who get orchitis caused by mumps, testicular atrophy (shrinking of the testicles) will result.

For the bacterial causes, please refer to the epididymitis article. Of note, brucellosis is a rare disease in which orchitis develops in 2 to 20% of men with the disease.

Orchitis may also occur in conjunction with infections of the prostate or epididymis and, like those conditions, may occur as a manifestation of sexually-transmitted diseases such as gonorrhea or chlamydia. The incidence of sexually-transmitted orchitis or epididymitis is higher in men 19 to 35 years old.

Risk factors for non-sexually-transmitted orchitis include:

• Inadequate immunization against mumps
• Older age (age greater than 45)
• Recurrent urinary tract infections
• Congenital abnormalities of the urinary tract
• Genito-urinary surgery and instrumentation
• Chronic indwelling urethral (Foley) catheter

• Multiple sexual partners
• Other high risk sexual behaviors.
• History of a sexual partner with a previously diagnosed STD
• Personal history of gonorrhea or other STD

• Scrotal swelling
• Tender, swollen, heavy feeling in the testicle
• Tender, swollen groin area on affected side
• Fever
• Discharge from penis
• Pain with urination (dysuria)
• Pain with intercourse or ejaculation
• Groin pain
• Testicle pain aggravated by bowel movement or straining
• Blood in the semen

• A urinalysis
• Urine culture (clean catch) (the provider may request several specimens, including initial stream, mid-stream, and after prostate massage.)
• Tests to screen for chlamydia and gonorrhea (urethral smear)
• A CBC (complete blood count)
• Doppler ultrasound (to rule out testicular torsion). It also can confirm the diagnosis of orchitis by demonstrating increased blood flow to the region as well as characteristic finding of hypoechogeneic texture. This study can also detect scrotal abcesses.
• Testicular scan (nuclear medicine scan) may also be obtained to rule out torsion and can confirm the diagnosis of orchitis with increased blood flow.

Orchitis may cause infertility and atrophy (diminished size) of one or both testicles.

Other potential complications include scrotal abcess, testicular infarction, cutaneous scrotal fistula and chronic epididymitis.

Acute pain in the scrotum or testicles is a surgical emergency. If you experience acute pain in the scrotum or testicles, seek immediate medical attention.