Enlarged, dilated veins in the pampiniform plexus — the network of small veins in the spermatic cord that drains blood out of the testicle. When the one-way valves in those veins don't work well, blood pools and the veins dilate, producing that soft, worm-like feel above and around the testicle. It's the same underlying process as varicose veins in the leg — different location, similar mechanism.
The AUA/ASRM Best Practice Policy cites varicocele in 15% of the general male population. That number climbs sharply in specific clinical populations: about 35–40% of men presenting with primary infertility (never fathered a child), and 45–80% of men with secondary infertility (previously fertile, now struggling to conceive). So while the base rate is common, the enrichment in infertile populations is real — which is why varicocele gets so much clinical attention despite being asymptomatic in most men.
AUA/ASRM Best Practice Policy; Korean Society for Sexual Medicine and Andrology guidelines (2025); Arif et al. review 2018.
This one has a satisfying anatomic explanation. The vein draining your right testicle empties at a gentle angle into the inferior vena cava — the big central vein. The vein draining your left testicle takes a sharper path, joining the left renal vein at roughly a 90-degree angle. That geometry means higher hydrostatic pressure on the left venous system, and the small one-way valves in the pampiniform plexus are more likely to fail on that side over time.
So a left-sided varicocele is anatomically expected. A right-sided varicocele in isolation — especially if it appears suddenly in adulthood or doesn't decompress when you lie down — is less expected and warrants imaging, because it can occasionally signal something upstream compressing the vein (like a retroperitoneal mass on the right side).
A new, isolated right-sided varicocele, or a varicocele that appears suddenly in an adult, is uncommon enough that most urologists will want abdominal imaging to rule out an upstream cause. This isn't panic-worthy but it is worth flagging — mention timing and side clearly when you see the doctor.
The overwhelming majority of varicoceles produce no symptoms at all. They're found incidentally on a routine physical, during a fertility workup, or noticed by the person themselves — often after a hot shower, when the veins are most dilated. When they do produce symptoms, the classic ones are:
Chronic testicular pain from varicocele affects an estimated 2–10% of people who have them. That's low, but it's not zero, and if you're in that group the pain can be genuinely bothersome without being an emergency.
The Dubin-Amelar grading system, still standard, ranks palpable varicoceles by physical exam findings:
| Grade | Physical exam finding | Clinical relevance |
|---|---|---|
| Subclinical | Not palpable; only seen on Doppler ultrasound | Not recommended for treatment (AUA/ASRM & EAU) |
| Grade 1 | Palpable only with Valsalva maneuver (bearing down) | Clinical varicocele; treatment decided by symptoms & fertility context |
| Grade 2 | Palpable at rest, no Valsalva needed | Clinical varicocele; same criteria for treatment |
| Grade 3 | Visible through the scrotal skin; the classic "bag of worms" | Clinical varicocele; same criteria — grade alone doesn't dictate treatment |
Diagnosis is primarily by physical exam. Ultrasound is reserved for equivocal cases (AUA/ASRM). Note: a bigger varicocele isn't automatically a worse varicocele in terms of what to do about it.
The mechanism linking varicocele to reduced fertility is fairly well established even if not every detail is settled: dilated pampiniform veins lose their normal counter-current heat exchange function, testicular temperature rises slightly (usually 1–2°C above normal), and warm testicles produce lower-quality sperm. Add oxidative stress from venous stasis, possible reflux of adrenal metabolites, and pressure effects on the testicular tissue, and you have a plausible pathway to impaired spermatogenesis.
The complication is that plenty of men with grade 3 varicoceles have completely normal sperm and completely normal fertility, and plenty of men without any varicocele have infertility. Varicocele is a risk factor for impaired semen parameters — not a guarantee of them. This is why current guidelines don't recommend prophylactic treatment of asymptomatic men with normal semen analyses, no matter how impressive the varicocele looks on exam.
The 2021 AUA/ASRM male infertility guidelines recommend that surgical varicocelectomy should be considered in men who are (1) attempting to conceive, (2) have a palpable clinical varicocele, AND (3) have abnormal semen parameters — with the exception of azoospermic men, where the evidence is weaker.
Same guidelines explicitly recommend against varicocelectomy for men with nonpalpable varicoceles detected only by imaging. In other words: no palpable finding on exam, no surgery, regardless of what the ultrasound shows.
AUA/ASRM Diagnosis and Treatment of Infertility in Men Guideline, Part II.If you're a parent (or a teen reading this yourself) who just heard "varicocele" from a school physical or a urology consult, the important thing to know is that adolescent varicocele is genuinely common and often self-resolves without any intervention. About 15% of adolescent boys have one, most often after puberty starts.
The historical concern was that adolescent varicocele could cause testicular growth arrest — the affected testicle staying smaller than the other. Persistent testicular asymmetry (typically defined as >15–20% volume difference on ultrasound) was the traditional threshold for considering surgery. But newer longitudinal data has substantially changed the picture:
Kolon et al., cited in Glassberg's clinical review (Translational Andrology and Urology). Nearly three-quarters of adolescents with >15% asymmetry recover to <15% asymmetry without any surgery.
That doesn't mean adolescent varicocele is always harmless — it means the default management for most cases is careful monitoring with periodic testicular volume measurement, not immediate surgery. Surgery in adolescence is generally reserved for cases with persistent significant asymmetry that isn't catching up, abnormal semen parameters (in older adolescents where a sample is appropriate), significant pain, or a very large grade 3 varicocele in someone with clear evidence of testicular dysfunction. This is a shared-decision conversation between the family, the adolescent, and a pediatric urologist — not an automatic yes.
Several approaches exist, each with tradeoffs. The main ones:
What the varicocele actually is doesn't change. What changes is the delivery mechanism for interrupting the dilated venous drainage.
Semen parameters improve in a majority of appropriately-selected patients after varicocelectomy, but paternity rates improve by a smaller margin — one review cited semen improvement in about two-thirds of operated infertile men, with paternity following in around 40%. Those are meaningful odds, but they're not a guarantee, and they're conditional on genuinely being in the group the guidelines identify (palpable varicocele + abnormal semen + trying to conceive). Operating on the wrong patient — a normal semen analysis, no fertility goal, no significant pain — doesn't create benefit and does create surgical risk.