Noticeably large or swollen testicles usually result from fluid buildup, enlarged veins, or a cyst rather than a problem with the testicles themselves. Normal adult testicles measure roughly 3 to 5 cm in length with a volume of 15 to 25 mL each, so there’s a wide range of “normal.” But if your scrotum looks or feels bigger than usual, or one side is clearly larger than the other, something specific is almost always causing it.
Hydrocele: Fluid Around the Testicle
The most common reason for a noticeably large scrotum is a hydrocele, which is a pocket of fluid that collects around the testicle. During fetal development, a thin membrane normally seals shut after the testicles descend into the scrotum. If that seal doesn’t fully form (a communicating hydrocele), fluid from the abdominal cavity can flow into the scrotum. This type may change in size throughout the day, often appearing larger after standing and smaller in the morning.
In other cases, the seal closes but extra fluid remains trapped around the testicle (a noncommunicating hydrocele). This type tends to stay the same size or grow very slowly over months or years. Hydroceles can also develop later in life after a scrotal injury or infection. The main symptom is painless swelling, though larger ones can cause a dragging discomfort or heaviness. Hydroceles are not dangerous, but large ones that bother you can be drained or surgically repaired.
Varicocele: Enlarged Veins in the Scrotum
A varicocele is a cluster of swollen veins inside the scrotum, similar to varicose veins in the legs. They’re graded on a scale from 0 to III. At the lowest grade, they only show up on ultrasound. At Grade III, they visibly change the shape of the scrotum and can be felt as a soft, lumpy mass often described as a “bag of worms.” Varicoceles occur on the left side in the vast majority of cases because of how the veins drain on that side.
Most varicoceles don’t cause symptoms beyond the visible or palpable swelling, but some produce a dull ache that worsens with standing or physical activity. They’re worth knowing about because larger varicoceles can affect sperm production and are one of the most treatable causes of male infertility.
Spermatocele: A Cyst Near the Testicle
A spermatocele is a fluid-filled cyst that develops in the epididymis, the small coiled tube sitting on top of and behind each testicle. These cysts are benign and typically painless. You might feel one as a small, smooth lump above or behind the testicle. Most spermatoceles stay small and go unnoticed, but larger ones can create a feeling of fullness or make one side of the scrotum noticeably bigger. They rarely need treatment unless they become uncomfortable.
Inguinal Hernia Pushing Into the Scrotum
Sometimes what looks like a large testicle is actually a loop of intestine that has slipped through a weak spot in the abdominal wall and pushed down into the scrotum. This is an inguinal hernia. The key giveaway is a bulge near the groin or pubic bone that becomes more obvious when you stand up, cough, or strain. Large hernias can extend well into the scrotum, causing both swelling and pain. Unlike a hydrocele, a hernia bulge often changes size with position and activity, and you may be able to push it back in while lying down. Hernias don’t resolve on their own and typically require surgical repair.
Infection and Inflammation
A rapid increase in scrotal size, especially with pain, warmth, or redness, points toward infection. Epididymitis is an inflammation of the epididymis that causes swelling that usually starts on one side and builds over a few days. It’s often caused by a urinary tract infection or a sexually transmitted infection. When the inflammation spreads to the testicle itself, it’s called epididymo-orchitis. Along with swelling, you’ll typically notice tenderness in the testicle, a swollen spermatic cord (the rope-like structure above the testicle), and sometimes a secondary hydrocele that forms in response to the inflammation. Antibiotics resolve most cases, and the swelling gradually goes down over a few weeks.
Testicular Torsion: A Time-Sensitive Emergency
Testicular torsion happens when the spermatic cord twists, cutting off blood flow to the testicle. It causes sudden, severe pain and rapid swelling on one side. This is a surgical emergency. The survival rate for the affected testicle is 97% if blood flow is restored within 6 hours, but drops to 79% between 7 and 12 hours and only 42% between 19 and 24 hours. If you have sudden, intense scrotal pain with swelling, go to an emergency room immediately.
When Swelling Could Be Cancer
Testicular cancer is far less common than the other causes on this list, but it’s the one that matters most to catch early. The first sign is usually a hard lump or mass on the testicle itself, not general swelling of the whole scrotum. The lump is typically painless, though some men notice a dull ache or heaviness. One testicle may feel firmer or heavier than the other, or the scrotum may swell suddenly.
Any solid mass found on a testicle during a physical exam or ultrasound is treated as potentially cancerous until proven otherwise. The standard evaluation includes a scrotal ultrasound with Doppler imaging and blood tests for specific tumor markers. Testicular cancer has very high cure rates when caught early, which is why paying attention to changes matters.
How To Check Yourself
A monthly self-exam is the simplest way to notice changes early. The best time is during or right after a warm shower, when the scrotal skin is relaxed. Hold your scrotum in the palm of one hand, then use the other hand to gently roll each testicle between your thumb and fingers. You’re feeling for any hard lumps, areas of unusual firmness, or changes in size compared to last time. The epididymis runs along the back of each testicle and normally feels like a soft, slightly bumpy ridge, so don’t mistake it for something abnormal.
If you notice new swelling, a lump, persistent heaviness, or a size difference that wasn’t there before, an ultrasound is the first-line imaging tool for figuring out what’s going on. It’s painless, takes about 15 minutes, and can distinguish between fluid, cysts, enlarged veins, and solid masses with high accuracy.