A varicocele is a swelling of the veins inside the scrotum, similar to a varicose vein you might see on someone’s leg. These enlarged veins form in a network called the pampiniform plexus, which carries blood away from the testicles. About 15% of all men have one, making it one of the most common conditions affecting the male reproductive system.
Why They Almost Always Appear on the Left
Between 80% and 90% of varicoceles occur on the left side, and the reason comes down to plumbing. The vein draining the left testicle connects to the left kidney vein, which operates at relatively high pressure. The right side, by contrast, empties directly into the body’s largest vein (the inferior vena cava), where pressure is much lower. That pressure difference on the left makes it harder for blood to flow upward and out of the scrotum, so the veins are more likely to swell.
When the small valves inside these veins weaken or fail, blood flows backward and pools. Over time, this pooling stretches the veins and creates the characteristic soft, lumpy mass that doctors sometimes describe as feeling like a “bag of worms” above the testicle.
What a Varicocele Feels Like
Most varicoceles cause no symptoms at all. Many men discover them only during a routine physical or a fertility workup. When symptoms do occur, only about 2% to 10% of men report pain.
The typical sensation is a dull, aching, or throbbing feeling in the testicle, scrotum, or groin. Some men describe it more as heaviness than actual pain. These feelings tend to worsen after standing for long periods, exercising, or straining, and they often ease when you lie down. Sharp or stabbing pain is possible but uncommon.
Visually, a larger varicocele may be noticeable through the skin as a lumpy, swollen area above the testicle. Smaller ones aren’t visible and can only be detected by touch or imaging.
How Varicoceles Are Graded
Doctors classify varicoceles into three grades based on how easily they can be detected during a physical exam:
- Grade 1: Only felt when you bear down (the Valsalva maneuver, similar to the pressure during a bowel movement).
- Grade 2: Felt while standing at rest, without needing to bear down.
- Grade 3: Visible through the scrotal skin without any special maneuver.
A subclinical varicocele, sometimes called grade 0, is one that can’t be felt at all and only shows up on ultrasound. These are generally not considered clinically significant.
Diagnosis: Exam and Ultrasound
A varicocele is usually diagnosed through a combination of visual inspection and touch. You’ll typically be examined both lying down and standing up. While standing, your doctor may ask you to take a deep breath, hold it, and bear down. This increases pressure in the abdomen and makes the swollen veins easier to feel.
If the physical exam is inconclusive, or if the doctor wants to confirm the size and rule out other causes, a scrotal ultrasound can provide a clearer picture. Ultrasound is also useful for detecting anything blocking blood flow, such as a mass or lesion, which is especially important if a varicocele appears suddenly on the right side or in an older man.
How Varicoceles Affect Fertility
Varicoceles are found in about 35% of men with primary infertility (those who have never been able to conceive) and in up to 80% of men with secondary infertility (those who previously fathered children but can no longer do so). That doesn’t mean a varicocele will necessarily make you infertile, since the majority of men with varicoceles can still father children. But the link is strong enough that a varicocele is often the first thing investigated during a male fertility evaluation.
The damage comes from several overlapping problems. Pooled blood raises the temperature around the testicle, and sperm production is highly sensitive to heat. The sluggish blood flow also reduces oxygen delivery and allows waste products, including substances from the adrenal gland, to flow backward into the testicular area. Together, these changes create an environment that produces excessive free radicals, which are unstable molecules that damage cells. Those free radicals can break down the membranes of sperm cells, fragment their DNA, and disrupt the enzymes needed for healthy sperm development. Sperm DNA fragmentation is now recognized as an important marker of male fertility problems.
Testicular Shrinkage Over Time
Left untreated, a varicocele can cause the affected testicle to gradually shrink. Research confirms that men with left-sided varicoceles show significantly more size difference between their two testicles compared to men without varicoceles. In one study, the average volume difference was about 3 mL in men with varicoceles versus 1.6 mL in men without. This shrinkage, called testicular atrophy, is one reason doctors sometimes recommend treatment in adolescents, even before fertility becomes a concern. The good news is that some of this lost volume can recover after repair, particularly in younger patients.
Treatment: Surgery vs. Embolization
Not every varicocele needs treatment. If yours isn’t causing pain and you’re not trying to conceive (or your fertility is fine), monitoring it over time is a reasonable approach. Treatment is typically considered when a varicocele is causing persistent discomfort, when sperm quality is affected, or when there’s noticeable testicular shrinkage.
The two main treatment options are surgical repair and embolization.
Surgical Repair
Surgery involves tying off or sealing the swollen veins so blood reroutes through healthy ones. The microsurgical technique, performed through a small incision near the groin with the aid of a surgical microscope, has the lowest failure rate at just over 1%. Other surgical approaches have slightly higher recurrence rates but still remain under 5% overall. Recovery typically takes one to two weeks. One potential side effect is hydrocele, a fluid buildup around the testicle, which occurs in about 8% of surgical cases.
Embolization
Embolization is a less invasive alternative. A radiologist threads a thin catheter through a vein in the groin or neck, guides it to the problematic vein, and blocks it with tiny coils or a special solution. There’s no surgical incision in the scrotum, and recovery is faster, typically 48 to 72 hours. For left-sided varicoceles, embolization and surgery have comparable success rates (about 3% failure for each). Embolization also carries no risk of hydrocele and avoids the small chance of accidental injury to the testicular artery.
For bilateral varicoceles (both sides), microsurgery tends to be the better choice, since embolization failure rates climb when treating the right side. For a straightforward left-sided varicocele, embolization offers a quicker recovery with similar effectiveness, making it a strong option for many men.
What Improves After Treatment
Repair can improve total sperm count, sperm movement, and the percentage of normally shaped sperm compared to leaving the varicocele untreated. A recent meta-analysis confirmed these improvements across multiple studies. Not every man sees the same benefit, though. Researchers have developed prediction models that combine clinical findings, lab work, and sperm measurements to estimate who is most likely to improve, achieving about 87% accuracy in identifying men who will benefit. Your doctor can help you weigh the likelihood of meaningful improvement based on your specific situation.