What Is It?

Epididymitis is a swelling (inflammation) of the epididymis, the coiled tube located at the back of the testicle. In most cases, an infection causes this inflammation. The infection spreads to the epididymis from the organs and ducts involved with urination and reproduction.

Orchitis is an infection of the testicle. It is much less common than epididymitis. Orchitis usually spreads to the testicle through the bloodstream. Viruses commonly cause the infection. About 20% of males over age 14 who have the mumps get orchitis.

When epididymitis spreads to the testicle, the condition is called epididymo-orchitis, which is an inflammation of both the epididymis and the testicle.

Infections that cause epididymitis usually are related to age, medical history and sexual activity:

• Before puberty - Intestinal bacteria, such as E. coli, most often cause epididymitis, when they travel from an infection in the bladder or some other site in the urinary tract. In many cases, a birth-related abnormality affects the urinary tract's structure or function. For example, a boy may be born with a structural abnormality involving the tube that carries urine from the kidney to the bladder, or he may experience a backward flow of urine from the bladder toward the kidney. These abnormalities increase the boy's risk for urinary tract infections, which eventually spread to the epididymis.

• In sexually active men - The most common cause of epididymitis is a sexually transmitted disease (STD), usually chlamydia, gonorrhea or both. Although the initial site of infection is the tube-like passageway (urethra) that carries urine and semen out of the penis, eventually bacteria spread backward through the reproductive tract to attack the epididymis. It may take several months after the sexual encounter that causes the STD for epididymitis to appear. In some cases, the man first has symptoms of an infected urethra, such as an abnormal discharge from the penis or a burning sensation when urinating. In other cases, symptoms of epididymitis are the first and only signs of an STD. Among men who have anal intercourse, epididymitis usually is caused by intestinal bacteria from the anus. These bacteria enter the urethra through the penis, and then travel backward through the reproductive tract to the epididymis.

• In adults with a high risk medical history - In men with a history of urinary tract infections or prostate infections, epididymitis usually is caused by intestinal bacteria that have spread from the infected site. This is the most common form of epididymitis in men over age 40.

• After surgery, testing or catheterization - Epididymitis may develop after surgery or a diagnostic test that involves the bladder or urethra, or after a catheter has been inserted to collect urine. In these cases, the infection usually is caused by intestinal bacteria that have entered the urethra or bladder, either during the procedure or through the catheter.

• Other forms (all age groups) - Rarely, epididymitis can occur when a systemic (whole-body) infection spreads through the bloodstream and moves to the epididymis. Also, a noninfectious form of epididymitis can develop in men who take amiodarone (Cordarone, Pacerone), a heart medication that seems to build up in the epididymis. Some cases have been blamed on intense exercise, especially heavy lifting. The strain of heavy lifting may force urine from the bladder into the epididymis, where it causes a form of chemical irritation that triggers epididymitis.

• Of unknown origin - Noninfectious epididymitis (epididymitis with no medical evidence of an infection) is fairly common, but its cause is not clear.