Hydrocele and spermatocele (epididymal cyst): differences and when to treat

The testicle lies within the tunica vaginalis, a thin serous membrane, between whose layers a small amount of fluid is normally present. A hydrocele forms when fluid collects in excess, most often because of an imbalance between production and absorption of the fluid. In newborns and infants a hydrocele is usually linked to a patent processus vaginalis of the peritoneum, which connects the peritoneal cavity with the scrotum. In adults it often appears with no identifiable cause (primary hydrocele), and secondarily it can accompany epididymitis, injury, a procedure in the groin area, and also a testicular tumour.

An epididymal cyst and a spermatocele are fluid-filled sacs developing in the epididymis, the thin, coiled tube lying against the back of the testicle, in which sperm mature and are stored. A spermatocele contains fluid with sperm, an epididymal cyst clear fluid without sperm; in clinical practice and on ultrasound the distinction has no major significance, and the two terms are often used interchangeably. These lesions are usually painless, grow slowly and occur most often in adults.

Two clues are useful for telling them apart yourself, but neither settles the diagnosis. First, an epididymal cyst is usually felt as a separate, round structure beside the testicle, whereas in a hydrocele the fluid surrounds the whole testicle, which is then hard to feel. Second, a lesion that changes size with position and coughing suggests a hernia or varicose veins. In addition, the doctor assesses whether the spermatic cord can be felt above the lesion (typical of a hydrocele, not of a hernia descending into the scrotum) and whether the lesion transilluminates with a torch. Only these examinations and ultrasound allow a confident distinction from lesions within the testicle.

Scrotal ultrasound is the first-choice test because it is non-invasive, quick and distinguishes fluid from solid structures well. It shows the testicle, epididymis, tunica vaginalis and the vessels of the cord: in a hydrocele fluid is seen around a normal testicle, in an epididymal cyst a round fluid-filled structure related to the epididymis, in varicose veins dilated, tortuous vessels. It is also important that ultrasound allows the testicle itself to be checked for normality, that is, a tumour hidden behind the fluid to be excluded. A hydrocele can be so tense that it makes it impossible to palpate the testicle properly; for that reason imaging, not palpation alone, is recommended before any decision on treatment.

There are situations in which ultrasound needs supplementing: the image is equivocal, a solid component or septa are seen in the lesion, a cyst grows quickly, or a neoplastic or inflammatory process is suspected. The urologist may then order a repeat ultrasound after some time, an MRI and, if a testicular tumour is suspected, tumour markers and further work-up. In a secondary hydrocele, for example after epididymitis or an injury, it is the cause that is treated first.

If the lesion does not hurt, does not interfere with daily activities and raises no suspicion on ultrasound, the standard approach is observation. Hydroceles and epididymal cysts usually neither threaten health nor damage testicular function, and size alone is not an indication for a procedure if the patient does not feel it. A procedure is considered when the lesion is large and troublesome (a feeling of weight, difficulty walking, sitting or having intercourse), causes pain, grows quickly, becomes infected or when the patient does not accept it for cosmetic reasons. In people with a large hydrocele, treatment is sometimes indicated also so that the testicle can be examined.

There are no drugs or herbs that effectively shrink a hydrocele or epididymal cyst; home methods (compresses, pressure, special underwear, supplements) have no documented effectiveness. Supportive underwear may ease symptoms but does not remove the lesion. In practice, a patient with symptoms therefore has two options: observation with symptomatic care, or a procedure.

A practical compromise follows from these data. Surgery (hydrocelectomy) has a lower recurrence rate but carries a higher risk of complications, a longer return to work and a higher cost. Aspiration with sclerotherapy is less invasive and quicker but more often has to be repeated, and recurrence is not exceptional; Low's series suggests that after one procedure the success rate was about two thirds, and after at most two about 80–85%. The evidence is of low quality (small trials, no blinding, different sclerosants), so the choice of method rests on individual preferences, operative risk and availability, not on a clear superiority of one technique.

Epididymal cysts are usually painless and grow slowly; without symptoms, observation is enough. If they cause discomfort or pain or are large, aspiration with sclerotherapy or excision (spermatocelectomy) is considered. In the Low series cited, the success rate after at most two aspirations with sclerotherapy was 85% for spermatoceles and epididymal cysts with a low complication rate, but the series covered a limited number of patients (34) and was retrospective.

The epididymis is the route by which sperm travel from the testicle to the vas deferens, so a procedure within it could in theory damage this route. For that reason, in men planning to have children urologists usually exercise caution with sclerotherapy and surgery for epididymal cysts and discuss the risk to fertility before the procedure. This approach comes from clinical practice and anatomical reasoning, not from the studies cited here, so the decision should be made with the doctor. If a couple is trying for a child, it is also worth considering a semen analysis before the procedure (we write about interpreting the result in a separate article on semen analysis).

In infants a hydrocele is usually linked to a patent processus vaginalis through which fluid from the peritoneal cavity seeps into the scrotum, and it often closes spontaneously in the first year of life; in adults this mechanism is rare, and a hydrocele does not resolve by itself as often. A hydrocele that does not resolve after the second year of life, changes size during the day or coexists with a hernia usually needs a paediatric surgical assessment; data from children must not, however, be transferred to adults. In an adult man a scrotal lesion diagnosed as 'hydrocele' needs an ultrasound, because in this age group a testicular tumour is also excluded.

Hydroceles and epididymal cysts are in most cases benign lesions that can be lived with without a procedure. The key is the first step: confirming the diagnosis by examination and ultrasound, because that is what distinguishes them from a testicular tumour and a hernia. The further decision depends on symptoms, and the choice between sclerotherapy and surgery on the patient's preference, operative risk and plans for children. The strength of the evidence is low to moderate (small trials, retrospective series), and small differences in effectiveness do not justify haste unless there are warning signs.