Orchitis (or-KIE-tis) is an inflammation of one or both testicles. Bacterial or viral infections can cause orchitis, or the cause can be unknown. Orchitis is most often the result of a bacterial infection, such as a sexually transmitted infection (STI). In some cases, the mumps virus can cause orchitis.

Bacterial orchitis might be associated with epididymitis — an inflammation of the coiled tube (epididymis) at the back of the testicle that stores and carries sperm. In that case, it's called epididymo-orchitis.

Orchitis causes pain and can affect fertility. Medication can treat the causes of bacterial orchitis and can ease some signs and symptoms of viral orchitis. But it can take several weeks for scrotal tenderness to disappear.

Orchitis signs and symptoms usually develop suddenly and can include:

• Swelling in one or both testicles
• Pain ranging from mild to severe
• Fever
• Nausea and vomiting
• General feeling of unwellness (malaise)

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. The causes of groin pain are different from the causes of testicle pain.

When to see a doctor

If you have pain or swelling in your scrotum, especially if the pain occurs suddenly, see your doctor right away.

A number of conditions can cause testicle pain, and some require immediate treatment. One such condition involves twisting of the spermatic cord (testicular torsion), which might cause pain similar to that caused by orchitis. Your doctor can perform tests to determine which condition is causing your pain.

Risk factors for nonsexually transmitted orchitis include:

• Not being immunized against mumps
• Having recurring urinary tract infections
• Having surgery that involves the genitals or urinary tract
• Being born with an abnormality in the urinary tract

Sexual behaviors that can lead to STIs put you at risk of sexually transmitted orchitis. Those behaviors include having:

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

Complications of orchitis may include:

• Testicular atrophy. Orchitis can eventually cause the affected testicle to shrink.
• Scrotal abscess. The infected tissue fills with pus.
• Infertility. Occasionally, orchitis can cause infertility or inadequate testosterone production (hypogonadism). But these are less likely if orchitis affects only one testicle.

To prevent orchitis:

• Get immunized against mumps, the most common cause of viral orchitis
• Practice safe sex, to help protect against STIs that can cause bacterial orchitis

Your doctor is likely to start with your medical history and a physical exam to check for enlarged lymph nodes in your groin and an enlarged testicle on the affected side. Your doctor might also do a rectal examination to check for prostate enlargement or tenderness.

Your doctor might recommend:

• STI screen. If you have discharge from your urethra, a narrow swab is inserted into the end of your penis to obtain a sample of the discharge. The sample is checked in the laboratory for gonorrhea and chlamydia. Some STI screens are done with a urine test.
• Urine test. A sample of your urine is analyzed to see if anything's abnormal.
• Ultrasound. This imaging test is the one most commonly used to assess testicular pain. Ultrasound with color Doppler can determine if the blood flow to your testicles is lower than normal — indicating torsion — or higher than normal, which helps confirm the diagnosis of orchitis.

Treatment depends on the cause of orchitis.

Treating bacterial orchitis

Antibiotics are needed to treat bacterial orchitis and epididymo-orchitis. If the cause of the bacterial infection is an STI, your sexual partner also needs treatment.

Take the entire course of antibiotics prescribed by your doctor, even if your symptoms ease sooner, to ensure that the infection is gone.

It may take several weeks for the tenderness to disappear. Resting, supporting the scrotum with an athletic strap, applying ice packs and taking pain medication can help relieve discomfort.

Treating viral orchitis

Treatment is aimed at relieving symptoms. Your doctor might recommend:

• Nonsteroidal anti-inflammatory drugs, such as ibuprofen (Advil, Motrin IB, others) or naproxen sodium (Aleve)
• Bed rest and elevating your scrotum
• Cold packs

Most people with viral orchitis start to feel better in three to 10 days, although it can take several weeks for the scrotal tenderness to disappear.

To ease discomfort:

• Rest in bed
• Lie down so that your scrotum is elevated
• Apply cold packs to your scrotum as tolerated
• Avoid lifting heavy objects

You might be referred to a doctor who specializes in urinary issues (urologist). Here's some information to help you prepare for your appointment.

What you can do

Make a list of:

• Your symptoms and when they began
• Your childhood illnesses and immunizations, and any recent illnesses, especially STIs or mumps
• All medications, vitamins or other supplements you take, including doses
• Questions to ask your doctor

For orchitis, basic questions to ask your doctor include:

• What's the most likely cause of my symptoms?
• Are there any other possible causes?
• What tests do I need?
• What treatments are available?
• How long will it take before I start to feel better?
• Will this affect my ability to have children?
• Do I need to restrict my sexual activity?

Don't hesitate to ask other questions.

What to expect from your doctor

Your doctor is likely to ask you a number of questions, including:

• How severe are your symptoms?
• What treatments have you tried?
• What, if anything, seems to improve your symptoms?
• What, if anything, appears to worsen your symptoms?
• Do you practice safer sex, such as using a condom?