Epididymitis is inflammation of the epididymis, a tightly coiled tube that sits behind each testicle and plays a critical role in storing and maturing sperm. It affects roughly 600,000 men per year in the United States, most commonly between ages 20 and 39. The condition typically causes pain on one side of the scrotum that builds gradually over hours or days, and it’s usually treatable with antibiotics when caught early.
What the Epididymis Does
The epididymis is a crescent-shaped structure about 3.8 centimeters long. Despite its small size, it contains a single, heavily coiled tube that connects the testicle to the vas deferens (the duct that carries sperm during ejaculation). Sperm leave the testicle immature and essentially immobile. As they travel through the epididymis, they gain the ability to swim and acquire the molecular tools needed to fertilize an egg. At any given time, 50 to 80 percent of sperm in the epididymis are sitting in the tail end, waiting in storage until ejaculation. When this structure becomes inflamed, it can swell, become painful, and temporarily disrupt normal reproductive function.
Common Causes by Age Group
The bacteria behind epididymitis tend to differ depending on your age. In men under 35, sexually transmitted infections are the most frequent cause. Chlamydia and gonorrhea together account for about half of cases in this age group. The bacteria travel from the urethra backward through the reproductive tract to reach the epididymis.
In men over 35, the typical culprit is E. coli or similar bacteria normally found in the gut. These infections usually result from urine flowing backward along the ejaculatory tract into the epididymis, which can happen more often in men with urinary tract issues, recent catheter use, or prostate problems.
Not all epididymitis is caused by bacteria. Certain medications, including amiodarone (a heart rhythm drug), can trigger a non-infectious form. This happens because the drug and its byproducts accumulate in epididymal tissue and cause inflammation directly. Depending on the dose and duration of use, this affects between 3 and 11 percent of men taking the medication.
Symptoms to Recognize
The hallmark of epididymitis is testicular pain and tenderness, usually on one side, that comes on gradually rather than all at once. Other common symptoms include:
- A swollen, warm, or discolored scrotum
- Pain or burning during urination
- An urgent or frequent need to urinate
- Discharge from the penis
- Pain or discomfort in the lower abdomen or pelvic area
- Blood in the semen
- Fever (less common)
Inflammation typically starts in the tail of the epididymis but can spread to the rest of the structure and into the testicle itself. When both the epididymis and testicle are inflamed, the condition is called epididymo-orchitis. The spermatic cord, which runs above the testicle, often becomes tender and swollen as well.
Acute vs. Chronic Epididymitis
Most cases are acute, meaning symptoms develop over a few days and resolve with treatment. Chronic epididymitis refers to scrotal pain lasting six weeks or longer. It can develop after an acute episode that doesn’t fully resolve, or it may appear gradually without a clear infectious trigger. Chronic cases are harder to treat and sometimes require a longer, more nuanced approach that goes beyond antibiotics alone.
How It’s Different From Testicular Torsion
Sudden scrotal pain always raises the question of testicular torsion, a condition where the testicle twists on its blood supply and requires emergency surgery. The two can look similar, but there are important differences. Torsion pain typically hits suddenly and severely, while epididymitis pain tends to build over hours or days. In torsion, the affected testicle often rides higher than normal and sits in an abnormal horizontal position. The cremasteric reflex (where the testicle retracts when the inner thigh is stroked) is usually absent in torsion but intact in epididymitis. Nausea and vomiting are more common with torsion.
One classic bedside test involves gently lifting the affected testicle. In epididymitis, this often relieves pain (a positive Prehn’s sign), while in torsion it does not. These signs are useful but not definitive on their own, which is why imaging is usually the next step when there’s any doubt.
How It’s Diagnosed
A physical exam is the starting point. Your doctor will check for tenderness, swelling, and warmth in the scrotum. Urine tests and urethral swabs help identify the specific bacteria involved, which guides antibiotic choice.
When the diagnosis isn’t clear from the exam alone, a scrotal ultrasound is the standard imaging test. It can show an enlarged epididymis with increased blood flow, a signature of inflammation that appears as “hyperemia” on Doppler imaging. The ultrasound also helps rule out torsion, abscesses, and other causes of scrotal pain.
Treatment and Recovery Timeline
Bacterial epididymitis is treated with antibiotics. The specific regimen depends on the likely cause: STI-related cases call for antibiotics targeting chlamydia and gonorrhea, while cases linked to urinary bacteria require different coverage. You should start feeling noticeably better within two to three days of starting antibiotics, but full resolution of pain and swelling can take several weeks.
Supportive care makes a real difference during recovery. Lying down with the scrotum elevated, applying cold packs, wearing an athletic supporter, and taking over-the-counter pain relievers all help manage discomfort. Avoid heavy lifting and sexual contact until the infection has cleared, both for your own recovery and to prevent transmitting an STI to a partner.
Severe cases with high fever, intense pain, or signs of abscess formation may require hospitalization. Men with diabetes or significantly elevated inflammatory markers are at higher risk for more complicated disease.
Potential Complications
Most cases of epididymitis resolve without lasting problems when treated promptly. Left untreated or inadequately treated, the infection can lead to a scrotal abscess (a walled-off pocket of pus), which may need to be drained. In rare cases, the blood supply to the testicle can be compromised, leading to testicular infarction.
Fertility is a common concern. Because the epididymis is where sperm mature and are stored, severe or repeated infections can cause scarring that blocks sperm transport. Bilateral involvement (both sides affected) poses the greatest risk to fertility, though this is uncommon. A single, well-treated episode is unlikely to cause permanent reproductive harm.