Causes for Epididymitis and Orchitis
The most common cause for acute epididymitis and epididymo-orchitis is a bacterial infection that spreads from another area, usually the urinary tract (e.g., urethra, bladder). Sometimes, pain in the testicular area is the first sign of infection.
According to the CDC, approximately two-thirds of acute epididymitis cases in men under age 35 are complications of gonorrhea or chlamydia/NGU, which are sexually transmitted infections (also called as STIs or STDs).
Gonorrhea and chlamydia, which often occur together, may cause symptomatic urethral infections (urethritis). In some cases, the first symptom of gonorrhea or chlamydia infection is epididymitis.
Other than sexually transmitted infection, the most common cause for epididymitis is another type of bacteria, such as E. coli. Rare causes include systemic tuberculosis (TB), sarcoidosis, brucellosis (a rare bacterial infection), fungal infection, and infected hydrocele (an abnormal fluid-filled sac around the testicles). Systemic TB usually only occurs in people who have a compromised immunity, such as with AIDS, or in communities where TB is widespread.
Inflammation of the epididymes and testicles also may have noninfectious causes, such as trauma, recent urinary catheterization, or reflux (backwards flow) of urine caused by a bladder outlet obstruction (e.g., a result of enlarged prostate or urinary tract abnormalities). The drug amiodarone (Cordarone®), used to treat severe cases of irregular heart rhythms, also can cause inflammation of the epididymis.
Chronic epididymitis and epididymo-orchitis also can develop as a result of multiple episodes of acute cases. In some chronic cases, the cause is unknown.