A varicocele is a cluster of enlarged, swollen veins inside the scrotum, similar to varicose veins that form in the legs. About 15% of all men have one, and most develop during puberty. They’re the most common reversible cause of male infertility, but many varicoceles cause no symptoms and never need treatment.
How a Varicocele Forms
Inside the scrotum, a network of small veins called the pampiniform plexus drains blood away from each testicle. These veins contain one-way valves that keep blood flowing upward toward the abdomen. When those valves are weak or missing entirely, blood flows backward and pools in the veins, stretching them out over time. The result is a tangle of dilated, sometimes visible veins along the spermatic cord.
This happens far more often on the left side, and the anatomy explains why. The left testicular vein is 8 to 10 centimeters longer than the right, runs straight up vertically, and connects to the left kidney vein at a sharp right angle. That creates a taller column of blood pressing downward when you stand, which puts more strain on the valves. The right testicular vein drains at an oblique angle into a larger vessel, making reflux less likely. Bilateral varicoceles occur, but an isolated right-sided varicocele is uncommon enough that doctors will sometimes investigate for an underlying cause like a mass or blood clot blocking venous drainage.
What a Varicocele Feels Like
Many men never know they have a varicocele. When symptoms do appear, they typically include a dull, aching heaviness in the affected testicle that worsens after standing for long periods, exercising, or spending time in heat. The discomfort usually eases when you lie down, because gravity stops pulling blood into the dilated veins. Some men notice a visible lump or describe the feel of a “bag of worms” above the testicle.
Varicoceles don’t appear suddenly. They develop gradually, often during adolescence when the testicles are growing rapidly and blood flow to the area increases. Because they tend to progress slowly and silently, many are discovered incidentally during a fertility evaluation or routine physical exam.
Grading: Mild to Severe
Doctors grade varicoceles on a three-point scale based on a standing physical exam:
- Grade 1: Can only be felt when the patient bears down (the Valsalva maneuver, like straining during a bowel movement).
- Grade 2: Can be felt at rest while standing, without any straining.
- Grade 3: Large enough to be seen through the scrotal skin.
If the physical exam is inconclusive, an ultrasound with Doppler imaging can confirm the diagnosis. A vein diameter of 3 millimeters or more, measured while the patient stands and bears down, is the standard threshold for diagnosis. The Doppler also detects backward blood flow in the veins, which confirms that the valves aren’t functioning properly.
Effects on Fertility and Sperm Quality
Varicoceles show up in about 35% of men with primary infertility (couples who have never achieved a pregnancy) and up to 80% of men with secondary infertility (those who previously fathered a child but can no longer conceive). The connection comes down to heat and oxidative stress.
The pampiniform plexus normally acts as a cooling system, keeping the testicles a few degrees below core body temperature. When warm abdominal blood pools in dilated veins instead of draining efficiently, scrotal temperature rises. That elevated temperature impairs sperm production and increases oxidative damage to sperm DNA. The practical effects are lower sperm counts, reduced motility (how well sperm swim), and higher rates of DNA fragmentation, which makes each individual sperm less capable of fertilizing an egg even through assisted reproduction.
The encouraging part is that these changes are often reversible. A large meta-analysis found that surgical repair improved sperm concentration by roughly 9.6 million sperm per milliliter, boosted progressive motility by about 8.7 percentage points, and significantly reduced DNA fragmentation levels.
Effects on Testosterone
Varicoceles can also lower testosterone production. The cells in the testicle responsible for making testosterone (Leydig cells) depend on a protein that transports cholesterol into the cell’s energy centers, where it gets converted into the hormone. Varicoceles suppress production of that transport protein, and over time this compromises testosterone output. Animal studies show significantly reduced testosterone levels within the affected testicle, and in humans, surgical repair has been shown to increase serum testosterone along with improvements in sperm count and motility. This suggests the hormonal damage is reversible rather than permanent.
When Treatment Is Recommended
Not every varicocele needs to be fixed. A small, painless varicocele in a man who isn’t trying to conceive can simply be monitored. Treatment is typically recommended when one or more of the following applies: documented infertility or declining semen quality, persistent pain that doesn’t respond to over-the-counter pain relievers and supportive underwear, or noticeable shrinkage of the affected testicle.
In adolescents, the decision is more nuanced. Doctors track the size difference between the two testicles over time. A volume difference of 15 to 20% or more, especially if the smaller testicle isn’t catching up during follow-up visits, is generally the threshold for recommending repair. Persistent abnormal semen parameters, if the teen is old enough for testing, also tip the scale toward treatment.
Treatment Options
There are two main approaches: surgery and embolization.
Microsurgical Varicocelectomy
This is the gold standard. A surgeon makes a small incision in the groin area and, using a high-powered microscope, identifies and ties off the swollen veins while preserving the artery, lymphatic vessels, and the vas deferens. The microsurgical approach performed through the lower groin (subinguinal) has the lowest recurrence rate of all techniques, ranking highest in a large network meta-analysis comparing nine different surgical methods. It also carries a low risk of hydrocele, a complication where fluid accumulates around the testicle after surgery.
Recovery is straightforward. Most people return to work or school within three days. You’ll need to avoid lifting anything over 10 pounds for at least two weeks and hold off on sexual activity for about a week.
Percutaneous Embolization
This is a minimally invasive alternative performed by an interventional radiologist. A thin catheter is threaded through a vein in the groin or neck and guided to the testicular vein, where tiny coils or a sclerosing agent are placed to block blood flow through the dilated veins. There’s no surgical incision in the scrotum, and recovery is often faster. Embolization ranks as the best approach for avoiding hydrocele formation, though it does have a higher recurrence rate than microsurgery.
Varicoceles in Teenagers
Varicoceles first appear during puberty in most cases, and roughly 15% of adolescent boys are affected. The challenge with teenagers is that fertility can’t always be assessed directly, so doctors rely on physical measurements instead. Serial ultrasounds track whether both testicles are growing at the same rate. If the affected testicle falls behind by 15 to 20% in volume and shows no signs of catching up over several visits, repair is recommended to protect future fertility. Painful varicoceles and those with very high-velocity reflux on Doppler imaging (above 38 centimeters per second) are also candidates for earlier intervention.
For adolescents whose varicocele is small and both testicles are developing symmetrically, watchful waiting with periodic check-ups is a safe and common approach.
Secondary Varicoceles
The vast majority of varicoceles are idiopathic, meaning they develop on their own due to the normal anatomical vulnerability of the testicular veins. In rare cases, a varicocele forms because something is compressing or blocking venous drainage higher up. One recognized cause is nutcracker syndrome, where the left renal vein gets pinched between the aorta and another major artery, creating back pressure that forces blood into the testicular vein. Kidney tumors can also obstruct venous outflow by extending into the renal vein. Doctors consider these secondary causes when a varicocele appears suddenly in an older adult, occurs in isolation on the right side, doesn’t drain when the patient lies down, or is accompanied by blood in the urine.