Varicocele: The Most Common Correctable Cause of Male Infertility

A varicocele is a set of dilated veins in the scrotum, it is present in about one man in seven, and it is the most common correctable cause of male infertility. It is also routinely oversold. Repair reliably improves semen parameters; whether it produces more babies is a genuinely open question, and the honest version of this subject holds both of those facts at once.

What it is, and how common

The pampiniform plexus is a network of small veins draining the testicle. When the valves in that system fail, blood pools and the veins dilate, in much the same way varicose veins form in the leg. The result is a varicocele.

Secondary infertility here means a man who has previously fathered a child and is now unable to. The high prevalence in that group is the strongest circumstantial evidence that varicoceles cause progressive damage over time rather than being incidental.

The corollary is worth stating plainly because it cuts the other way: most men with a varicocele are fertile. Only about 20 percent of men with a documented varicocele have fertility difficulties. Finding one on an examination does not, on its own, explain anything.

Why it is almost always the left side

On clinical examination, roughly 85 to 90 percent of varicoceles are left-sided, about 10 percent are bilateral, and isolated right-sided varicoceles are well under 1 percent.

The reason is plumbing. The left internal spermatic vein ascends and drains into the left renal vein, joining it at approximately a right angle. The right internal spermatic vein drains directly and obliquely into the inferior vena cava, a lower-pressure vessel, at a shallower angle. The left venous column is also longer, so it transmits a greater hydrostatic pressure downward. There is a further contribution from the nutcracker phenomenon, in which the left renal vein is compressed between the superior mesenteric artery and the aorta, raising pressure upstream.

Two refinements matter. First, systematic imaging finds bilateral involvement far more often than examination does, in anywhere from about a third to the large majority of cases depending on the modality. A varicocele that feels left-sided is frequently bilateral on ultrasound.

Second, the received wisdom about isolated right varicoceles deserves qualifying. The teaching is that a right-sided varicocele in isolation should prompt a search for a retroperitoneal mass obstructing venous drainage, and that remains sound advice, particularly for a new-onset varicocele that does not decompress when lying down, or one in an older man. But the malignancy yield is lower than the folklore implies. In a series of patients with right-sided varicocele on ultrasound, non-malignant causes explained 29.1 percent, and malignancy was found in 3.6 percent, in both cases alongside other signs of metastatic disease. It is a reason for a scan, not a reason to panic.

How it is graded

The grading system is purely clinical and takes about fifteen seconds to apply.

On ultrasound, the accepted thresholds for a clinically significant varicocele are a maximum venous diameter above 3 mm measured standing during Valsalva, together with venous reflux lasting more than two seconds.

The distinction between clinical and subclinical is not academic. It determines whether anyone should operate, and both major guidelines are unusually blunt about it. The AUA and ASRM make it a strong recommendation that clinicians should not recommend varicocelectomy for men with non-palpable varicoceles detected solely by imaging. The European guideline says the same. A systematic review found no demonstrable pregnancy benefit or meaningful semen improvement from treating subclinical varicoceles.

How it damages sperm

Four mechanisms are proposed, and they are not mutually exclusive: raised testicular temperature, hypoxia from venous stasis, reflux of metabolites from the renal and adrenal veins, and oxidative stress causing sperm DNA damage.

The temperature evidence is the most concrete. In a study of 119 men, testicular surface temperature on the affected side averaged around 34.0 to 34.4 degrees Celsius against roughly 32.9 to 33.0 in controls, a difference of a little over one degree. After varicocelectomy, temperatures fell to match the control range.

The DNA evidence is more recent and arguably more important, because it explains outcomes that conventional semen parameters do not. Men with varicocele have a sperm DNA fragmentation index a mean of 15.34 points higher than controls (95% CI 9.74 to 20.9). After repair, fragmentation falls by a mean of 6.86 points (minus 10.04 to minus 3.69), with improvement measurable within three months.

This is why the European guideline carries a specific recommendation, graded weak, that varicocelectomy may be considered in men with raised DNA fragmentation and otherwise unexplained infertility, or after failed assisted reproduction. Standard semen parameters can look acceptable while fragmentation is high, and fragmentation is what predicts miscarriage and failed fertilisation.

Does repair work

This splits into two questions with two different answers.

Semen parameters: yes, clearly. The largest analysis pooled 351 articles and found large standardised improvements after repair across sperm concentration (SMD 1.590), total sperm count (1.824), progressive motility (1.845) and total motility (1.613). In absolute terms, a smaller analysis of 289 patients found sperm concentration rose by 9.59 million per mL, progressive motility by 8.66 percentage points, and normal morphology by 2.73 percentage points.

One methodological caveat applies to all of it. These are before-and-after comparisons, which cannot separate a treatment effect from regression to the mean. Men are selected for surgery when their parameters are poor, and poor measurements tend to be followed by better ones regardless of what happens in between.

Pregnancy and live birth: much less certain. A Cochrane review pooled 48 randomised trials and 5,384 men.

The live birth confidence interval spans from a 5-fold reduction to a 27-fold increase. That is not weak evidence of benefit; it is an absence of usable evidence, and it should be read that way rather than as a promising signal.

The pregnancy result is real but modest, and Cochrane’s own framing is useful: couples with no treatment or delayed treatment had roughly a 21 percent chance of pregnancy, against 22 to 48 percent after treatment. That range is wide because the trials disagree.

Both guideline bodies land in the same place. The AUA and ASRM say clinicians should consider surgical varicocelectomy in men attempting to conceive who have a palpable varicocele, infertility and abnormal semen parameters, excluding azoospermic men, at a moderate recommendation. The European guideline makes it a strong recommendation to treat infertile men with a clinical varicocele, abnormal semen parameters and otherwise unexplained infertility, and an equally strong recommendation not to treat men whose semen analysis is normal.

Which gives the practical filter: palpable varicocele, abnormal semen analysis, and infertility. All three. Any two of the three is not the indication.

Which operation

This is where the largest, most avoidable differences in outcome sit, and it is the question most worth asking a surgeon directly.

The microsurgical row is not a rounding difference. A recurrence rate of 0.4 percent against 15 to 29 percent, and a hydrocele rate of 0.44 percent against up to 43 percent, is the difference between one operation and the possibility of a second. The reason is optical: magnification allows the surgeon to identify and preserve the testicular artery and the lymphatic vessels, and it is lymphatic injury that produces hydrocele.

The European guideline states that microsurgical varicocelectomy is the most effective technique, with fewer complications and lower recurrence, while noting it requires specialised training. Randomised evidence agrees: microscopic subinguinal surgery beat other surgical approaches on pregnancy (RR 1.18, 1.02 to 1.36) and on recurrence (RR 0.48, 0.29 to 0.79), both at moderate certainty. Surgery against radiological embolisation showed no clear difference (RR 1.13, 0.75 to 1.70), at low certainty.

Testosterone, pain and adolescents

Testosterone. Repair raises testosterone in men who are hypogonadal and does essentially nothing in men who are not. Pooled across studies, mean testosterone rose by 34.3 ng/dL overall. In the hypogonadal subgroup it rose by 123 ng/dL, and against untreated controls the difference was 105.65 ng/dL. In eugonadal men there was no significant difference from control, at p = 0.36. Note also that the AUA and ASRM guideline contains no statement recommending varicocelectomy for testosterone, which is worth knowing if it is being offered to you on that basis.

Pain. A minority of varicoceles hurt, typically as a dull ache that worsens through the day and eases on lying down. Outcomes after repair done specifically for pain are good: 86 percent complete resolution in one series, 83.3 percent in a more recent series of 132 men. The predictors are informative. Dull pain resolved far better than dragging pain (OR 5.73) or sharp pain (OR 8.72), subinguinal approaches beat high ligation (OR 2.73), and microsurgical beat laparoscopic (OR 7.12). Grade of varicocele made no significant difference to pain outcome.

Adolescents. The trigger for intervention is not the varicocele but the testicle. The European guideline makes it a strong recommendation to offer surgery in adolescents when a varicocele is associated with a persistently small testis, defined as a difference of more than 2 mL or 20 percent. Catch-up growth after repair occurred in an average of 76.4 percent of boys across 14 studies and 1,475 patients, with better results in boys under 14.

This article is for information only and is not medical advice. Varicocele repair is a surgical decision that depends on your semen analysis, your partner’s fertility assessment and your own priorities. Talk to a urologist about your own situation.