A varicocele is a cluster of swollen veins inside the scrotum, while a hydrocele is a pocket of fluid surrounding a testicle. Both create scrotal swelling, and both are common enough that many men will encounter one or the other at some point, but they differ in what has gone wrong, how they feel, how they are diagnosed, and what treatment looks like. The confusion between them is understandable because the symptoms can overlap on the surface, yet the underlying problems and their consequences are quite different.
What Each Condition Actually Is
A varicocele is essentially a varicose vein, but instead of occurring in the leg, it develops in the network of veins that drain blood away from the testicle. When the valves inside those veins stop working properly, blood pools and the veins stretch out. The result is a tangle of dilated vessels you can sometimes feel through the skin, often described as a “bag of worms.” Varicoceles are far more common on the left side because of the way the left testicular vein connects to the renal vein at a steep angle, which makes it harder for blood to flow upward against gravity.
A hydrocele is a completely different problem. It occurs when fluid accumulates in the thin sac that normally surrounds each testicle. A small amount of fluid in this space is normal and acts as a lubricant, but when production outpaces absorption, the sac swells. A hydrocele has been defined as a pathological buildup of serous fluid in the pelvis and groin, with causes ranging from injury to infection to no identifiable trigger at all.1PubMed Central. Classifying Hydroceles of the Pelvis and Groin: An Overview of Etiology, Secondary Complications, Evaluation, and Management The swelling is typically smooth, painless, and can grow quite large before a man seeks medical attention.
How They Feel and Look
The physical sensation of a varicocele is often described as a dull ache or heaviness in the scrotum, particularly after standing for long periods or exercising. The ache tends to ease when you lie down because gravity is no longer working against the sluggish blood flow. When you examine the scrotum while standing, the affected side may feel lumpy and irregular because of the engorged veins underneath. Smaller varicoceles produce no symptoms at all and are only discovered during a fertility workup or a routine physical.
A hydrocele, by contrast, presents as a smooth, rounded swelling that can feel taut or squishy depending on how much fluid has collected. Pain is unusual unless the hydrocele grows large enough to become physically cumbersome, or unless there is an underlying cause like infection or injury. The swelling tends to be uniform rather than lumpy, and it does not change much with body position the way a varicocele does. Many hydroceles are noticed because one side of the scrotum gradually looks bigger than the other over weeks or months.
How Doctors Tell Them Apart
One of the simplest and oldest bedside tests is transillumination: shining a bright light against the scrotum in a dark room. A hydrocele, being filled with clear fluid, lets light pass through and produces a characteristic red glow. A varicocele, made up of blood-filled veins and vascular tissue, blocks the light.2PubMed Central. Transillumination: shining a light from within This test is quick and free, and while it does not replace imaging, it helps a clinician narrow the possibilities in seconds.
Ultrasound with color Doppler is the standard next step when the diagnosis is unclear. For a varicocele, ultrasound can measure the diameter of the dilated veins and detect the backward flow of blood when a patient bears down (a Valsalva maneuver). For a hydrocele, ultrasound confirms that the swelling is fluid rather than something more concerning like a tumor. In many cases, ultrasound settles the question definitively and helps rule out other conditions that can cause scrotal swelling, such as inguinal hernias, epididymal cysts, or testicular masses.
Causes and Who Gets Them
Varicoceles are remarkably common, appearing in roughly 15 percent of the general male population and up to 40 percent of men being evaluated for infertility. They typically develop during puberty, when the testicles are growing rapidly and blood flow to the area increases. The left-side predominance is well established and relates to the anatomy of the venous drainage: the left testicular vein empties into the left renal vein at a nearly perpendicular angle, creating more resistance than on the right side, where the vein drains directly into the larger inferior vena cava.
Hydroceles come in two broad categories. In newborns and young children, most hydroceles are “communicating,” meaning there is a small opening between the abdominal cavity and the scrotal sac that has not yet closed. These often resolve on their own during the first year or two of life. In adults, hydroceles are usually “noncommunicating” and develop because the body produces more fluid in the scrotal sac than it absorbs. Adult hydroceles can arise after infection, injury, or surgery, though many have no obvious cause. Classification systems have identified numerous subtypes, including communicating, noncommunicating, congenital, trauma-induced, infection-related, and iatrogenic (caused by a medical procedure).1PubMed Central. Classifying Hydroceles of the Pelvis and Groin: An Overview of Etiology, Secondary Complications, Evaluation, and Management
Effects on Fertility
This is where the two conditions diverge most sharply. Varicoceles are one of the most commonly identified and treatable causes of male infertility. The pooling of warm blood around the testicle raises the local temperature and triggers oxidative stress, which damages sperm production and sperm function.3PubMed. Pathophysiology of varicocele in male infertility in the era of assisted reproductive technology Not every man with a varicocele has fertility problems, but the association is strong enough that varicoceles are found in a disproportionately large share of men at infertility clinics compared with the general population.
Hydroceles, on the other hand, do not directly impair fertility. Because the fluid sits outside the testicle rather than affecting its blood supply or temperature regulation, sperm production usually continues normally. A very large hydrocele can be uncomfortable and may compress surrounding structures, but the testicle itself is generally unaffected. The main concerns with a hydrocele tend to be cosmetic, physical discomfort from the bulk, and the occasional need to rule out an underlying cause like infection or a tumor.
The Testosterone Connection
Research over the past decade has uncovered a link between varicoceles and lower testosterone levels that goes beyond fertility. Multiple reports suggest that varicoceles are associated with low testosterone, and that repairing a varicocele can raise levels meaningfully in men who are deficient.4PubMed Central. When is a varicocele repair indicated: the dilemma of hypogonadism and erectile dysfunction? A systematic review and meta-analysis found that testosterone levels were significantly higher after varicocele repair compared with pre-treatment levels and compared with men whose varicoceles went unrepaired, with the post-repair levels statistically indistinguishable from those of healthy men without varicoceles.5PubMed Central. Effects of Varicocele Repair on Testicular Endocrine Function: A Systematic Review and Meta-Analysis
This finding matters because it offers men with both a varicocele and low testosterone a treatment that can improve hormone levels while preserving fertility. Exogenous testosterone therapy, by contrast, typically suppresses sperm production. For men who want to address low testosterone and still have the option of fathering children, varicocele repair could serve both purposes at once.6PubMed Central. Effect of Varicocele and Its Treatment on Testosterone in Hypogonadal Men with Varicocele: Review of the Literature Hydroceles have no comparable hormonal impact.
Treatment for Varicoceles
Many varicoceles need no treatment at all. If you have no symptoms and are not trying to conceive, a urologist may recommend observation. When intervention is warranted, the two main options are surgery and percutaneous embolization. Microsurgical varicocelectomy involves a small incision in the groin, through which a surgeon uses a microscope to tie off or clip the dilated veins while preserving the artery, lymphatic channels, and vas deferens. Embolization is a less invasive approach in which a radiologist threads a catheter through a vein in the neck or groin and blocks the malfunctioning veins from the inside using coils or a sclerosing agent.
Head-to-head comparisons of these two techniques have shown similar improvements in sperm quality and similar pregnancy rates afterwards, though embolization tends to come with faster recovery and less postoperative pain.7PubMed Central. Subinguinal microsurgical varicocelectomy vs. percutaneous embolization in infertile men: Prospective comparison of reproductive and functional outcomes Longer-term follow-up studies have confirmed that both approaches produce equivalent improvements in semen parameters.8Egyptian Journal of Radiology and Nuclear Medicine. Impact of percutaneous embolization versus subinguinal microsurgical ligation on semen parameters in primary varicocele patients: comparative study The choice between the two often comes down to surgeon preference, local expertise, and how quickly the patient wants to return to normal activity.
One complication worth knowing about: if the lymphatic vessels near the veins are inadvertently cut during varicocelectomy, the disrupted drainage can lead to fluid buildup around the testicle. In other words, treating a varicocele can sometimes cause a hydrocele. One study found that when lymphatic vessels were divided during repair, about a quarter of patients developed a hydrocele and nearly a third had measurable testicular swelling at one year.9PubMed. Division of lymphatic vessels at varicocelectomy leads to testicular oedema and decline in testicular function according to the LH-RH analogue stimulation test This is one reason microsurgical technique is preferred: the magnification helps the surgeon identify and spare the tiny lymphatic channels.
Treatment for Hydroceles
Small, painless hydroceles in adults often need nothing more than periodic monitoring. When treatment is needed, the gold standard is a surgical procedure called hydrocelectomy, in which the fluid-filled sac is opened, drained, and either excised or folded back so fluid cannot reaccumulate. It is performed as day surgery and is highly effective, though it involves a recovery period of a few weeks and the usual risks of any surgical procedure.
A less invasive alternative is aspiration and sclerotherapy, where a needle is used to drain the fluid and then a sclerosing agent is injected to irritate the sac lining and discourage refilling. This approach is quicker, cheaper, and involves less downtime, but comes with a significant trade-off: recurrence. A systematic review and meta-analysis found that recurrence was substantially higher with sclerotherapy compared with surgery.10PubMed. Aspiration and sclerotherapy versus hydrocelectomy for treating hydroceles: a systematic review and meta-analyses A prospective trial reported that about a third of sclerotherapy patients experienced recurrence within three months, and that all who had the procedure repeated still saw the hydrocele return. Patient satisfaction was also higher after surgery than after sclerotherapy, though the cost of surgery was roughly five times greater and required about seven times more days away from work.11PubMed. Comparison of aspiration-sclerotherapy with hydrocelectomy in the management of hydrocele: a prospective randomized study
For men who cannot tolerate surgery due to age or other medical conditions, aspiration alone (without sclerotherapy) can provide temporary relief, though the fluid almost always returns. It is best thought of as a palliative measure rather than a cure.
When Scrotal Swelling Is a Red Flag
Most varicoceles and hydroceles are benign, but there are scenarios where either condition signals something more serious. A varicocele that appears suddenly in an older man, particularly on the right side, warrants prompt investigation. The vast majority of varicoceles develop gradually during adolescence and appear on the left. An acute varicocele, especially in a patient past his twenties, can indicate a mass in the abdomen or kidney that is compressing or invading the veins draining the testicle. In one reported case, a 68-year-old man presented with an acute left-sided varicocele that turned out to be the first sign of renal cell carcinoma.12PubMed Central. Acute left side varicocele as primary presentation of renal cell carcinoma
Right-sided varicoceles deserve special scrutiny because the anatomy of the right testicular vein makes spontaneous varicoceles less common on that side. A right-sided varicocele appearing in isolation should raise suspicion for a hidden retroperitoneal condition, particularly a renal malignancy, and should prompt imaging of the abdomen.13African Journal of Urology. A rare case of right-sided varicocele in right renal tumor in the absence of venous thrombosis and IVC compression The same principle applies to a varicocele that does not collapse when the patient lies down: the veins should empty with gravity assistance, and if they do not, something may be obstructing drainage from above.
Hydroceles can also occasionally accompany a testicular tumor, though this is uncommon. Ultrasound during the evaluation of a hydrocele routinely checks the testicle itself, which is one reason imaging is recommended rather than relying on physical examination alone when a hydrocele is large enough to obscure the testicle.
Varicoceles in Teenagers
Varicoceles frequently show up during puberty, and the question of when to intervene in an adolescent is one of the trickier problems in pediatric urology. The main concern is whether the varicocele is stunting growth of the affected testicle. Urologists track this by measuring testicular volume on both sides with ultrasound. If the testicle on the varicocele side is more than 20 percent smaller than the other, there is legitimate concern about long-term function.
Some adolescents with this size difference will experience spontaneous catch-up growth without surgery, but the likelihood of that happening depends in part on how severe the blood reflux is. Research has shown that when the peak backward flow in the varicocele veins reaches a certain threshold in combination with significant size asymmetry, spontaneous catch-up growth becomes unlikely.14PubMed. Testicular asymmetry and adolescent varicoceles managed expectantly More recent work has also looked at the maximum diameter of the dilated vein as a practical indicator. A vein diameter at or above roughly 3.5 mm appeared to identify adolescents who were more likely to benefit from surgery, while those with smaller vein diameters more often saw their asymmetry resolve on its own.15PubMed. Ultrasound maximum vein diameter contextualizes testicular asymmetry in adolescent varicocele
Because adolescents are still growing, the decision is rarely urgent, and many are followed with serial ultrasounds over months or years before any treatment decision is made. The goal is to protect future fertility without subjecting a teenager to unnecessary surgery.
Can You Have Both at the Same Time?
Yes, and the combination is not as unusual as you might expect. A varicocele and a hydrocele can coexist on the same side, and as mentioned earlier, varicocele repair itself can cause a hydrocele if the lymphatic channels are disrupted during surgery. When both are present, ultrasound can usually distinguish the two: the fluid of a hydrocele appears as a dark, echo-free space, while the varicocele shows up as a tangle of dilated vessels with detectable blood flow on Doppler.
Having both conditions simultaneously can complicate the physical exam because the fluid from the hydrocele may make the varicocele veins harder to feel. This is another situation where imaging becomes essential rather than optional. If surgery is planned, the surgeon may address both in the same procedure, draining the hydrocele and repairing the varicocele through a single incision, though this depends on the size and location of each problem.
Hydroceles in Women
Most people associate hydroceles exclusively with men, but a comparable condition exists in women. The canal of Nuck is a small pouch of tissue in the inguinal region that is the anatomical equivalent of the processus vaginalis in males. When fluid accumulates there, it forms what is sometimes called a female hydrocele or a hydrocele of the canal of Nuck. It presents as a painless lump in the groin and is classified as a subtype of hydrocele in the literature.1PubMed Central. Classifying Hydroceles of the Pelvis and Groin: An Overview of Etiology, Secondary Complications, Evaluation, and Management This condition is rare and is sometimes mistaken for an inguinal hernia, which makes imaging important for a correct diagnosis. Treatment, when needed, is surgical.