Epididymitis is diagnosed primarily through a physical exam combined with urine tests that confirm inflammation and identify the underlying infection. In most cases, a doctor can make the diagnosis during a single office or emergency room visit, though some lab results take a few days to finalize. The process also involves ruling out testicular torsion, a surgical emergency that can mimic epididymitis closely enough to require imaging.
What the Physical Exam Involves
The exam starts with palpation of the scrotum. Tenderness and hardening typically begin at the tail (lower portion) of the epididymis, the coiled tube that sits behind each testicle. In more advanced cases, the swelling spreads upward through the body and head of the epididymis, and it can extend into the spermatic cord or the testicle itself. The skin of the scrotum may be red, and fluid buildup around the testicle (a reactive hydrocele) is common when inflammation has progressed, which can make the exam harder to interpret.
Your doctor will likely perform the Prehn sign test: gently lifting the affected side of the scrotum. If the pain eases with elevation, that points toward epididymitis, because lifting takes the weight off the inflamed epididymis. If lifting makes the pain worse, torsion becomes a concern. A cremasteric reflex test, where the inner thigh is stroked to see if the testicle rises, is also checked. A normal reflex makes torsion less likely, though no single physical exam finding can definitively separate the two conditions.
About 5 to 10 percent of cases are bilateral, but the vast majority involve one side. Pain typically develops gradually over one to two days, often accompanied by fever, painful urination, blood in the urine, or urinary frequency. That gradual onset is itself a diagnostic clue, since torsion tends to strike suddenly.
Urine and Urethral Tests
Every suspected case should be evaluated with at least one point-of-care test to confirm that inflammation is actually present. The CDC guidelines specify three options that can be performed during your visit:
- Urethral swab with staining: A sample of urethral discharge is examined under a microscope. Finding two or more white blood cells per field confirms urethritis (inflammation of the urethra). This same stain can reveal gonorrhea bacteria inside the white blood cells, giving a rapid answer about one of the most common sexually transmitted causes.
- Leukocyte esterase on first-void urine: A simple dipstick test on the first portion of urine you pass. A positive result indicates white blood cells are present, signaling infection or inflammation in the urinary or reproductive tract.
- Microscopic exam of spun urine: A urine sample is centrifuged and the sediment is examined. Ten or more white blood cells per high-power field supports the diagnosis.
Beyond these rapid tests, your doctor will typically order a nucleic acid amplification test (NAAT) on a urine sample to check specifically for chlamydia and gonorrhea. NAAT results usually come back within one to three days. A standard urine culture may also be sent to identify other bacteria, particularly in older men or those with urinary tract risk factors. Culture results typically take two to three days, sometimes longer. Because these results aren’t immediate, treatment is usually started at the first visit based on the point-of-care findings and your risk profile, then adjusted once final results arrive.
When Ultrasound Is Needed
Scrotal ultrasound with color Doppler is not a routine part of the epididymitis workup when the diagnosis is clinically clear. The CDC recommends reserving it for two situations: when testicular torsion is suspected, or when the history, exam, and lab tests don’t add up to a confident diagnosis.
On ultrasound, an inflamed epididymis appears enlarged (greater than 17 mm), with increased blood flow compared to the unaffected side. That asymmetry in blood flow is the key finding, since a normal epididymis can show some blood flow on its own. Scrotal wall thickening and fluid around the testicle may also be visible. If the infection has spread to the testicle, the scan may show increased blood flow within the testicular tissue as well. In cases where an abscess has formed, it appears as a dark, blood-flow-free pocket within the epididymis.
There are important limits to what ultrasound can do here. A normal ultrasound does not rule out epididymitis and wouldn’t change the treatment plan. More critically, partial torsion of the spermatic cord can look like epididymitis on imaging, so if torsion remains a concern even after the scan, the clinical picture still takes priority. The ultrasound is most useful for what it can definitively rule in: complete torsion, which shows absent blood flow to the testicle and demands immediate surgery.
Ruling Out Testicular Torsion
Distinguishing epididymitis from torsion is the single most important diagnostic task, because torsion can permanently damage the testicle within hours. Several features help separate them. Epididymitis typically builds over a day or two and is often accompanied by urinary symptoms like burning or frequency. Torsion tends to hit suddenly and severely, often without urinary complaints. Pain localized specifically to the epididymis on palpation, rather than the testicle as a whole, favors epididymitis.
In younger patients and children, torsion of the appendix testis (a small tissue remnant on the testicle) can also mimic epididymitis. A visible blue dot on the scrotal skin, caused by the dying tissue showing through, is a hallmark of appendix torsion that helps clinicians tell the two apart. If there’s any real doubt after the exam and labs, the standard approach is urgent urology referral rather than waiting for test results.
Identifying the Cause
The diagnostic tests do more than confirm epididymitis. They also point toward the underlying cause, which determines treatment. In sexually active men under 35, chlamydia and gonorrhea are the most common culprits. NAAT testing and the urethral swab stain are designed to catch these. In men over 35, or in those with recent urinary tract procedures, bladder outlet problems, or a history of urinary infections, standard urinary bacteria are more likely, and the urine culture becomes especially important.
Not all epididymitis is infectious. Certain medications can trigger it as a side effect. Sterile urine refluxing back through the vas deferens, often due to bladder outlet obstruction, can cause chemical irritation that looks identical on exam. Underlying systemic conditions like sarcoidosis or Behçet syndrome occasionally present as epididymitis. Risk factors such as prolonged sitting, cycling, or recent trauma can also contribute. When urine cultures and STI tests come back negative and the patient doesn’t respond to antibiotics, these noninfectious causes move higher on the list.
Chronic Epididymitis
When scrotal pain persists for three months or longer, the condition is classified as chronic epididymitis. The diagnostic approach shifts somewhat. The same urine tests and physical exam apply, but additional evaluation often focuses on structural causes: imaging to check for anatomical abnormalities, assessment for chronic pelvic pain patterns, and sometimes repeated cultures to ensure an infection hasn’t been missed or incompletely treated. Chronic cases are more likely to be noninfectious, and the diagnosis often becomes one of exclusion after infectious and structural causes have been ruled out.