Sperm are produced in the testicles. They then travel through the efferent ductules to reach the epididymis, a long tube located in each testicle, where they are stored until being transferred into the urinary tract and excreted. A cyst, called a spermatocele, can form in the epididymis or one of the other sperm ducts. This type of cyst is an accumulation of sperm cells that hardens and blocks the duct. Sperm can no longer travel easily through the duct and often spreads into the surrounding tissue to cause an inflamed area called sperm granuloma. This occurs most commonly in older, male dogs. It is frequently the result of an injury that creates scar tissue in the testicles, but it can also be related to complications and errors during vasectomy. Other contributing factors may be conditions that cause excessive estrogen and any congenital problem that creates blockage in the sperm duct. If a cyst occurs in only one sperm duct, there will often be no symptoms; however when ducts in both testicles become blocked, dogs develop azoospermia, a low number of viable sperm in the semen. Most spermatoceles are diagnosed because of infertility. The chronic, low level inflammation associated with sperm granuloma frequently doesn’t cause pain or other symptoms, but some dogs may also have hard palpable masses on the scrotum. Blockage that is close to the head of the epididymis causes sperm backup into the testicles and is more likely to damage the inner tubules where sperm is produced. There is no effective cure for sperm duct cysts, and most dogs with blockage in both testicles will remain infertile.

Cysts can block the sperm ducts of male dogs leading to low sperm count and infertility. Sperm duct cysts are called spermatoceles. Spermatoceles often cause sperm back-up and create areas of low-level inflammation which are referred to as sperm granuloma. Both of these conditions may make a dog less fertile.

These are the symptoms you might see in a dog with sperm duct cysts.

There are two types of conditions related to sperm duct cysts.

These factors will make it more likely for your dog to develop spermatocele or sperm granuloma.

Many dogs with spermatocele and sperm granuloma come to see the veterinarian because their owners have trouble breeding them. A few also have pain and inflammation in the scrotum. If the condition is bilateral, a sperm test will show azoospermia. Blood and urine tests will also be taken to help rule out other conditions, especially retrograde ejaculation.

Spermatoceles will be visible on a sonogram of the scrotum. Biopsies of the testicles usually reveal normal sperm genesis, unless the blockage is located close to the testicles and tubular degeneration has taken place. Biopsies of the epididymis may also be taken to evaluate the level of sperm granuloma. These are both minor surgical procedures that will require anesthesia.

Sperm duct cysts in dogs don’t have a history of successful treatment. If the condition is unilateral, only located in one testicle, and azoospermia is mild, it may still be possible to breed the dog with good breeding techniques and careful timing. This is rarely the case with bilateral conditions. Surgical procedures could remove or bypass the blockage, but the microscopic nature of the ducts makes this difficult and the procedure is rarely done in dogs. If your dog has pain or inflammation of the scrotum, the veterinarian may prescribe drugs or creams. These secondary symptoms are rare, so it is likely your dog won’t need any further treatment.

Dogs rarely recover from sperm duct cysts, however the condition usually doesn’t present symptoms other than infertility. Breeding may not be possible, at least with bilateral conditions, so it would be advisable to find another dog for this purpose. Unilateral conditions may be manageable in terms of breeding, but you may need to put more effort into ensuring that females are bred at the ideal time to compensate for low sperm count and lack of motility in the male dog’s semen. Sperm duct cysts don’t typically interfere with a dog’s lifestyle, other than in relation to breeding, so dogs that aren’t kept for this purpose can still live fulfilling lives.