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If you're an adult male, you may have heard that getting mumps may affect your fertility. The reason is viral orchitis, an inflammation of one or both testicles, most commonly associated with the virus that causes mumps. About one-third of males who contract mumps after puberty develop orchitis.

Fortunately, infertility as a result of mumps-related orchitis is rare. And in those countries where use of the mumps vaccine is widespread, such as in the United States, your risk of contracting mumps is small.

Other causes of orchitis usually are bacterial, including sexually transmitted diseases (STDs). The best way to prevent orchitis is to prevent mumps and to avoid behaviors that may result in STDs.

The signs and symptoms of orchitis usually have an abrupt onset. They may include:

• Testicular swelling on one or both sides
• Pain ranging from mild to severe
• Tenderness in one or both testicles
• Nausea and vomiting
• Fever
• Discharge from penis
• Prostate enlargement and tenderness

The terms "testicle pain" and "groin pain" are sometimes used interchangeably. But groin pain occurs in the fold of skin between the thigh and abdomen — not in the testicle. Causes of groin pain are different from causes of testicle pain.

A number of bacterial and viral organisms can lead to orchitis.

Bacterial orchitis
Most often, bacterial orchitis is the result of epididymitis, an inflammation of the coiled tube (epididymis) that connects the vas deferens and the testicle. The vas deferens carries sperm from your testicles. When inflammation in the epididymis spreads to the testicle, the resulting condition is known as epididymo-orchitis. Bacterial orchitis is rare without epididymitis.

Epididymitis usually is caused by an infection of the urethra or bladder that spreads to the epididymis. Often the cause of the infection is an STD, particularly gonorrhea or chlamydia. The highest incidence of sexually transmitted epididymo-orchitis occurs in men ages 19 to 35. Non-sexually transmitted forms of the infection may be related to anatomical abnormalities in the urinary tract or having had a catheter or medical instruments inserted into the penis.

Viral orchitis
Most cases of viral orchitis are the result of mumps. About one-third of males who contract the mumps after puberty develop orchitis during the course of the mumps, usually four to six days after onset. The mumps virus can spread from the salivary glands to other parts of the body, including the testicles.

Several factors may contribute to developing orchitis. For non-sexually transmitted orchitis, they include:

• Not being immunized against mumps
• Being older than 45
• Recurring urinary tract infections
• Surgery that involves the genitals or urinary tract, because of the risk of infection
• Malformations in the urinary tract present at birth (congenital)

High-risk sexual behaviors that can lead to STDs also put you at risk of sexually transmitted orchitis. They include having:

• Multiple sexual partners
• Sex with a partner who has an STD
• Sex without a condom
• A personal history of an STD

If you experience pain or swelling in your scrotum, especially if the pain comes on suddenly, contact your doctor. A number of conditions can cause testicular pain, and some of the conditions require immediate treatment. One such condition involves twisting of the spermatic cord (testicular torsion), which may cause pain similar to that caused by orchitis. Your doctor can administer diagnostic tests to determine which condition is causing your pain.

Your doctor will conduct a physical exam, which may reveal enlarged lymph nodes in your groin and an enlarged testicle on the affected side; both may be tender to the touch. Your doctor also may do a rectal examination to check for prostate enlargement or tenderness and order blood and urine tests to check for infection and other abnormalities.

Other tests your doctor might order to determine the presence of an STD and to rule out the possibility of testicular torsion, which requires immediate treatment, include:

• STD screening. This involves obtaining a sample of discharge from your urethra. Your doctor may insert a narrow swab into the end of your penis to obtain the sample, which will be viewed under a microscope to check for gonorrhea and chlamydia.
• Ultrasound imaging. This test, which uses high-frequency sound waves to create precise images of structures inside your body, may be used to rule out twisting of the spermatic cord (testicular torsion) and determine increased blood flow to your testicle, which helps confirm the diagnosis of orchitis.
• Nuclear scan of the testicles. Also used to rule out testicular torsion, this test involves injecting trace amounts of radioactive material into your bloodstream. Special cameras then can detect areas in your testicles that receive less blood flow, indicating torsion, or more blood flow, confirming the diagnosis of orchitis.

Orchitis may cause the affected testicle to shrink (atrophy). It also can cause scrotal abscess, in which the infected tissue fills with pus, or lead to recurrent episodes of epididymitis. In rare cases, orchitis can impair fertility; however, if orchitis affects only one testicle, sterility is rare.

Treatment depends on the cause of orchitis.

Treating viral orchitis
Treatment for viral orchitis, the type associated with mumps, is aimed at relieving symptoms. Your doctor may prescribe pain medication, nonsteroidal anti-inflammatory drugs, such as ibuprofen (Motrin, Advil, others) or naproxen (Aleve, Anaprox, others) and recommend bed rest, elevating your scrotum and applying cold packs.

In addition to measures to relieve discomfort, bacterial orchitis and epididymo-orchitis require antibiotic treatment. If the cause of the infection is an STD, your sexual partner also may need treatment.

Treating bacterial orchitis
Antibiotic drugs most commonly used to treat bacterial orchitis include ceftriaxone (Ceftin), ciprofloxacin (Cipro), doxycycline (Vibramycin, Doryx), azithromycin (Zithromax), and trimethoprim and sulfamethoxazole combined (Bactrim, Septra). Make sure your doctor is aware of any other medications you're taking or any allergies you have. This information, as well as whether your infection is sexually transmitted and what type of STD you have, will help your doctor select the best treatment.

Be sure to take the entire course of antibiotics recommended by your doctor. Even if your symptoms clear up sooner, complete the course to ensure that the infection has been eradicated.

Getting immunized against mumps is your best protection against viral, mumps-related orchitis. Having sex with just one partner and using a condom helps protect against STDs.

To ease your discomfort, try these suggestions:

• Rest in bed.
• Lie down so that your scrotum is elevated.
• Apply cold packs to your scrotum as tolerated.