Varicoceles are enlarged, dysfunctional veins that drain blood from the testicles, and they're present in about 15% of all men and roughly 40% of men evaluated for infertility. They can cause a dull ache, testicular atrophy, and declining semen quality, making them one of the most common correctable causes of male infertility.
Let's start with a number that might surprise you: varicoceles are present in about 15% of all men. Among men evaluated for infertility, that number jumps to roughly 40%. This is not a rare condition. It's one of the most common correctable causes of male infertility, yet most men have never heard of it until a doctor mentions it.
A varicocele is essentially varicose veins in your scrotum. The veins that drain blood from your testicles—the pampiniform plexus—become enlarged and dysfunctional. Blood pools instead of flowing out. That pooling creates heat, pressure, and oxidative stress. Your testicles are sensitive to all three.
What Does a Varicocele Feel Like?
Most men with a varicocele have no symptoms at all. They find out during a routine physical or a fertility workup. But when symptoms do appear, they tend to show up in specific ways.
A dull ache or heaviness. This is the most common complaint. It usually feels like a dragging sensation in the scrotum, often on the left side. The ache may worsen after standing for long periods, after physical activity, or toward the end of the day. Lying on your back often relieves it because gravity stops pulling on those veins.
A visible or palpable mass. Some men describe it as feeling like a "bag of worms" above the testicle. That's not an exaggeration. When the veins are significantly enlarged, you can feel them—soft, twisted, and distinct from the testicle itself.
Testicular atrophy. This is the one that matters most for fertility. The affected testicle may be smaller than the other. You might not notice this yourself, but your doctor will measure it during an exam. The size difference can be subtle or significant.
Discomfort during or after exercise. Some men notice that heavy lifting, running, or prolonged sitting triggers the ache. The mechanism is the same: increased abdominal pressure pushes blood backward into the scrotum.
No symptoms at all. This is worth repeating. Many men with varicoceles never feel a thing. They discover it only when blood tests show low sperm count or when a physical exam catches it.
Why the Left Side Is Almost Always the One Affected
About 85 to 90 percent of varicoceles occur on the left side. The anatomy explains why. The left testicular vein drains into the left renal vein at a right angle, which creates higher pressure and less efficient drainage compared to the right side, which drains directly into the vena cava. Bilateral varicoceles happen in about 10 percent of cases. Isolated right-side varicoceles are rare and sometimes warrant additional investigation to rule out abdominal masses compressing the vein.
How Varicocele Affects Fertility
The connection between varicoceles and infertility is well-documented, but the exact mechanism is still being studied. Here's what researchers know.
Heat is the primary problem. Your testicles sit outside your body for a reason. Sperm production, or spermatogenesis, requires a temperature about 2 to 4 degrees Celsius lower than core body temperature. The pooled blood in a varicocele raises scrotal temperature by roughly 0.5 to 1 degree Celsius. That might sound small, but it's enough to impair sperm production and function. Studies using scrotal thermography consistently show higher temperatures on the affected side.
Oxidative stress damages sperm DNA. The stagnant blood in varicocele veins creates an environment of oxidative stress. Reactive oxygen species accumulate and attack the DNA inside sperm cells. This fragmentation reduces the sperm's ability to fertilize an egg and increases the risk of early pregnancy loss. A 2016 meta-analysis in Andrology found that men with varicoceles had significantly higher sperm DNA fragmentation compared to fertile controls.
Hormonal disruption. The heat and oxidative stress can affect Leydig cells, which produce testosterone. Some studies show that men with varicoceles have lower testosterone levels than men without them, and that surgical repair can increase testosterone in some cases. The effect is not universal, but it's worth noting that varicoceles don't just affect sperm—they may affect hormone production too.
What the semen analysis shows. The classic pattern is a decline in sperm count, motility (movement), and morphology (shape). Not every parameter drops equally. Some men show a steep decline in count with normal motility. Others show poor motility with decent count. The pattern varies, but the overall trend is that varicocele worsens semen quality over time. This is why varicoceles are considered a progressive condition. The damage doesn't necessarily stay the same—it can get worse with age.
Who Should Be Screened
Not every man with a varicocele needs treatment. The condition is common, and many men with varicoceles have normal fertility and normal semen parameters. The decision to treat depends on three factors:
- Fertility status. Are you actively trying to conceive and having difficulty? If yes, a varicocele becomes relevant.
- Semen analysis results. If your semen parameters are abnormal and a varicocele is present, the varicocele is likely a contributing factor.
- Symptoms or testicular atrophy. If the varicocele causes pain or the affected testicle is shrinking, treatment is worth discussing regardless of fertility plans.
The American Urological Association recommends varicocele repair for men with a palpable varicocele, abnormal semen parameters, and documented infertility. For men who are not trying to conceive, the decision is more nuanced. Some urologists recommend monitoring with annual exams and repeat semen analysis. Others suggest repair if the testicle shows atrophy.
What Treatment Looks Like
The standard treatment is varicocelectomy—surgical ligation of the enlarged veins. The procedure redirects blood flow through normal channels. Recovery time is typically a few days to a week. Success rates are high. Most studies report improvement in semen parameters in 60 to 80 percent of men after surgery, and pregnancy rates improve accordingly. A 2021 Cochrane review found that varicocele repair improved pregnancy rates compared to no treatment in couples with male infertility.
There is also percutaneous embolization, a less invasive option where a radiologist blocks the abnormal veins using coils or a sclerosing agent. The outcomes are similar to surgery, though recurrence rates may be slightly higher.
Important note: This is a summary of what treatment involves. If you are considering varicocele repair, you need to discuss the specific risks, benefits, and alternatives with a urologist. The decision is personal and depends on your fertility goals, your symptoms, and the severity of the varicocele.
What You Can Do Right Now
If you are concerned about varicoceles or fertility, here are practical steps you can take:
- Get a physical exam. A varicocele is diagnosed by palpation. Your doctor will examine your scrotum while you are standing and lying down. If a varicocele is suspected, a scrotal ultrasound can confirm the diagnosis and measure vein diameter.
- Request a semen analysis. This is the single most useful test for assessing fertility. It's simple, noninvasive, and gives you concrete data. If you have a varicocele, a baseline semen analysis helps determine whether it's affecting your sperm.
- Monitor testicular size. If you notice that one testicle is smaller than the other, mention it to your doctor. Testicular atrophy is a sign that the varicocele is causing damage.
- Reduce scrotal heat exposure. This is not a treatment for varicocele, but it supports overall testicular health. Avoid hot baths, keep laptops off your lap, wear loose underwear, and take breaks if you sit for long periods. These habits won't fix a varicocele, but they reduce additional thermal stress on your testicles.
- Don't panic. A varicocele is common, treatable, and in many cases doesn't affect fertility at all. If it does, the outcomes of treatment are good. The key is knowing whether you have one and whether it's causing problems. That requires a conversation with a doctor and a semen analysis.
Varicoceles are one of those conditions that fly under the radar until they become relevant. Now you know what to look for, how it affects fertility, and what the path forward looks like. If any of the signs sound familiar, make an appointment. The information you have is the first step. The next one is acting on it.
Frequently asked questions
What does a varicocele feel like?
Many men feel nothing at all and only discover a varicocele during a fertility workup or routine exam. When symptoms do appear, the most common is a dull ache or dragging heaviness, usually on the left side, that tends to worsen after standing for long periods or physical activity and eases when lying down. Some men can feel the enlarged veins above the testicle, often described as a bag of worms.
How does a varicocele affect sperm and fertility?
Pooled blood in the varicocele raises scrotal temperature, and because sperm production requires a temperature lower than core body temperature, even a modest rise is enough to impair it. The stagnant blood also creates oxidative stress that can fragment sperm DNA, reducing the ability to fertilize an egg and raising the risk of early pregnancy loss. The classic semen analysis pattern is a decline in sperm count, motility, and morphology, and the damage can worsen over time.
Why do varicoceles mostly affect the left side?
About 85 to 90 percent of varicoceles occur on the left side because of how the anatomy is arranged. The left testicular vein drains into the left renal vein at a right angle, creating higher pressure and less efficient drainage than the right side, which drains directly into the vena cava. Bilateral varicoceles occur in about 10 percent of cases, while an isolated right-side varicocele is rare and can warrant further investigation.
What are the treatment options for a varicocele?
The standard treatment is varicocelectomy, a surgical procedure that ties off the enlarged veins and redirects blood flow, with recovery typically taking a few days to a week. Most studies report improvement in semen parameters in 60 to 80 percent of men after surgery, and a 2021 Cochrane review found that repair improved pregnancy rates compared to no treatment. A less invasive option called percutaneous embolization uses coils or a sclerosing agent to block the abnormal veins, with similar outcomes though potentially slightly higher recurrence rates.