In the clinic, we often encounter patients who ask about a small lump next to the “balls” that is not painful or itchy, and wonder what it is. Does it need to be removed surgically? Will it affect fertility? With these questions, let’s take a look in detail. 1.What is an epididymal cyst? Epididymal cyst is a cystic mass in the epididymis, which is also called semen cyst because its fluid often contains sperm. It occurs in young adults, generally aged 20 to 40 years old. The common site of the cyst is the head of the epididymis, while the body and tail rarely occur. It originates from the epithelial cells of the tubules of the testicular reticulum and is a few millimeters to a few centimeters in diameter, and the larger ones can reach about 10 cm. Most of the patients have no obvious symptoms, and a few may have scrotal swelling and discomfort or slight pain. 2.How do epididymal cysts form? The cause of epididymal cyst is still unknown. It may be related to sexual stimulation, chronic infection of the testes and epididymis or partial obstruction of the ducts that transport sperm. It may also be related to local injury or infection from sexually transmitted diseases. It has been suggested that the epididymal ducts at the head of the epididymis flex, turn or form diverticula, and with the passage of time and continuous accumulation of sperm, the diverticular tubules increase in size, thus forming seminal cysts. When the epididymis is blocked or scarred due to inflammation or trauma, seminal cysts may also occur. 3.How is epididymal cyst diagnosed? (1) Generally asymptomatic, sometimes there is discomfort in the scrotum or a feeling of falling. (3) Positive transillumination test. The cyst puncture fluid is milky white and opaque, and microscopic examination shows inactive spermatozoa and fatty vesicles. After being left at room temperature for a short time, the previously inactive sperm in the fluid will become active. (4) Ultrasound may reveal dark areas of fluid in the testes or epididymis. 4.What are the diseases that can be easily confused? (1) Chronic epididymitis: usually the whole epididymis is enlarged or only the caudal part has small nodules with hard texture, sometimes thickened vas deferens can be palpated. (2) Spermatic cord effusion: it is a cystic mass in the scrotum, oval or pike shaped, located in the spermatic cord. (3) Yong syndrome: The head of both epididymis is enlarged or cystic, mostly limited to 1-1.5 cm proximal to the head of the epididymis, with no abnormality in the body caudal part and vas deferens. (4) Epididymal tuberculosis: There is usually a primary tuberculosis lesion and there are bead-like nodules on palpation of the epididymis. 5.How should epididymal cyst be treated? Does it necessarily require surgery? For small and asymptomatic epididymal cysts, treatment is not necessary. Epididymal cyst excision surgery is for those patients with large cysts, with a diameter of 2cm or more, and whose symptoms are obvious or affect their life. The free cyst is revealed through a scrotal incision, the narrow neck is clamped and removed completely, and the neck stump is ligated with intestinal thread. It is best to perform testicular sheath reversal at the same time to prevent the occurrence of syringomyelia. However, the operation may destroy the epididymal duct and thus affect the fertility, so unmarried patients should be cautious. 6.How to prevent and regulate? (1) When the cyst is large and the pain is obvious, the scrotum can be lifted up with a scrotum support to reduce the pain; (2) Pay attention to rest, keep personal cleanliness and prevent infection; (3) Actively treat inflammation of the genitourinary system and sexual dysfunction to reduce the triggering factors of the disease; (4) Be relaxed, take regular rest and rest, eat regularly, have regular intercourse and combine work and rest.