Epididymitis typically looks like a swollen, red, and warm scrotum, usually on one side. The affected side may appear noticeably larger than the other, and the skin can take on a pink-to-deep-red discoloration as inflammation builds. These visible changes develop gradually over hours to days, which is one of the key ways it differs from other causes of scrotal swelling.
What You’ll See and Feel
The hallmark appearance is one-sided scrotal swelling. The inflammation starts at the back of the testicle, in a coiled tube called the epididymis, then can spread to involve the entire testicle. Early on, you might feel a firm, tender area behind the testicle before any visible swelling appears. As it progresses, the whole side of the scrotum can become enlarged, discolored, and warm to the touch.
Redness of the scrotal skin ranges from mild pinkness to obvious redness resembling a skin infection. In more advanced cases, the skin can look tight and shiny from the swelling underneath. A reactive hydrocele, which is a buildup of fluid around the testicle, is common in later stages and makes the affected side look even more swollen and smooth.
Pain usually comes on gradually and worsens over one to three days. It tends to radiate into the lower abdomen or groin on the same side. Other signs that often accompany the visible changes include:
- Painful urination or a frequent, urgent need to go
- Penile discharge, which can be clear, white, or yellowish, particularly when the cause is a sexually transmitted infection
- Blood in the semen
- Low-grade fever, though this is less common than the local scrotal symptoms
Acute vs. Chronic Appearance
Acute epididymitis lasts less than six weeks and produces the dramatic swelling, redness, and warmth most people picture. This is the version that sends people to urgent care because the visual change is hard to ignore.
Chronic epididymitis, defined as symptoms lasting six weeks or longer, looks quite different. The scrotum may not be visibly red or swollen at all. Instead, you might feel a persistent firm or slightly thickened area behind the testicle. The discomfort is more of a dull ache than acute pain, and symptoms tend to come and go. Someone with chronic epididymitis could look completely normal on the outside while still experiencing significant discomfort.
How It Looks Different From Testicular Torsion
This is the distinction that matters most, because testicular torsion is a surgical emergency. Both conditions can cause a swollen, red, painful scrotum, and even doctors sometimes struggle to tell them apart on visual exam alone.
The biggest clue is speed of onset. Torsion pain hits suddenly and severely, often within minutes. Epididymitis builds over hours or days. With torsion, the testicle may sit higher in the scrotum or hang at an unusual angle because the spermatic cord has twisted.
There’s also a simple physical test: gently lifting the affected testicle. With epididymitis, elevation often reduces the pain because it takes the weight off the inflamed epididymis. With torsion, lifting the testicle makes the pain worse. This is called Prehn’s sign, though it’s not reliable enough on its own to rule out torsion. Any sudden, severe scrotal pain with swelling needs imaging, typically an ultrasound, to confirm what’s happening.
How It Spreads Within the Scrotum
Inflammation and swelling usually start in the tail of the epididymis, the lower portion that sits behind the bottom of the testicle. At this stage, you can sometimes feel a distinct tender lump or thickening in that specific spot while the rest of the testicle feels normal.
Left untreated, the inflammation spreads upward through the body and head of the epididymis. Eventually it can involve the testicle itself, a condition called epididymo-orchitis. At that point, the entire side of the scrotum becomes uniformly swollen and tender, and it becomes difficult to feel where the epididymis ends and the testicle begins. The skin may develop mild cellulitis, appearing red and slightly puffy beyond just the area over the testicle.
What an Ultrasound Shows
If you end up getting a scrotal ultrasound, the images reveal details you can’t see from the outside. The epididymis appears enlarged compared to the unaffected side, sometimes dramatically so. The most telling finding is increased blood flow to the area. On a color Doppler ultrasound, the inflamed epididymis lights up with red and blue signals showing the extra blood rushing to the site of infection or inflammation. In some cases, the testicle itself also shows increased blood flow, indicating the inflammation has spread.
Ultrasound can also identify complications like a hydrocele (fluid collection) or, more rarely, an abscess forming within the scrotum. An abscess appears as a walled-off pocket of fluid that looks distinct from the surrounding tissue.
What Causes the Visible Changes
In men under 35, epididymitis is most commonly caused by sexually transmitted bacteria, particularly chlamydia and gonorrhea. Urethral discharge is a strong clue pointing to this cause. In men over 35, urinary tract bacteria are the more typical culprit, often linked to urinary tract infections, recent catheter use, or prostate issues.
Non-infectious causes also exist. Trauma, certain medications, and autoimmune reactions can produce the same swollen, red appearance without a bacterial infection. Regardless of the trigger, the visible result is the same: your immune system floods the epididymis with blood and inflammatory cells, producing the swelling, heat, and redness you can see from the outside.
The good news is that bacterial epididymitis responds well to antibiotics. Swelling and redness typically start improving within a few days of starting treatment, though complete resolution can take several weeks. Supportive measures like scrotal elevation and ice packs help reduce the visible swelling while the underlying cause clears.