Swollen Testicles in Dogs

Jamie Lovejoy, DVM
By Jamie Lovejoy, DVM on Mar. 21, 2024
A dog runs through a field.

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What Are Swollen Testicles in Dogs?

Dog testicles are the male reproductive organs responsible for producing sperm and the hormone testosterone in pups. Testicular changes in dogs are not only of concern in breeding dogs; the testicles of all unneutered male dogs should be monitored carefully for signs of disease. Testicles should be symmetrical in size and their appearance should not change abruptly.

Swollen testicles in dogs (either one or both) can result from issues with the reproductive organ itself or be due to swelling of the scrotum, the skin around the testicles. Infection, trauma, and cancer are the most common causes of scrotal swelling in dogs.

Any change in size or appearance should be evaluated promptly by a veterinarian, as causes of this syndrome can’t be treated at home. Swollen testicles in dogs are not always painful, but if your dog suddenly seems to be experiencing pain in this area, it may require an emergency vet visit.

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Symptoms of Swollen Testicles in Dogs

Symptoms of swollen testicles in dogs include:

  • Testicular asymmetry (one testicle is bigger than the other)

  • Testicle feels hard or is shaped differently

  • Red, irritated scrotum

  • Frequent licking of the area

  • Change in gait or sitting position

  • Decreased appetite

My Dog Has Swollen Testicles. What Should I Do?

If you notice that one or both of your dog’s testicles appears swollen or irritated, set up an appointment with your veterinarian for an exam and additional testing. If your dog experiences extreme pain in this area, it could indicate a testicular torsion, or twisting, which is an emergency due to the severity of pain.

If your dog is in a breeding program, it’s important not to let them breed if their testicles appear to be abnormal. There are some transmissible diseases that could affect their partner that should be ruled out by your veterinarian.

Causes of Swollen Testicles in Dogs

Swollen testicles in dogs can occur in any age or breed of unneutered male dog.

Possible causes include:


Infection of the testicle may be due to a bite wound, other penetrating trauma, or a contagious infection like brucellosis. It can also be secondary to infection elsewhere in the body, such as the prostate or bladder. Though these conditions are most commonly bacterial in nature, fungal and viral infections of the testicle can also occur.

Testicular Cancer

Testicular cancer usually arises from cells that make and develop sperm or testosterone. These cancers can be malignant but are usually very localized and unlikely to spread if caught and treated early.

Testicular Torsion

Testicular torsion is a condition where the spermatic cord, the structure connecting the testicles to the abdominal cavity, twists, sometimes along with the vessels that attach the testicles to the body. This twisting can occur due to trauma or the presence of other masses or abnormalities within the testicles that alter theirweight or shape. In severe cases, the blood supply to the testicles can be compromised, resulting in a very painful condition that requires urgent care.  

Scrotal Hernia

A scrotal hernia is where abdominal contents, such as fat and organs, fall into the scrotum due to a weakness or other defect in the body wall. In these cases, although the testicle itself usually remains a normal size, the scrotum will be significantly distended and feel irregular.

Testicular Degeneration

As dogs age, changing hormones can lead to a decrease in size and function of one or both testicles. In this case the “swollen” testicle is actually the normal one. Breeding dogs may receive hormone therapy to improve their testicular function, but treatment is not usually recommended for companion dogs.

How Veterinarians Diagnose Swollen Testicles in Dogs

A diagnosis of swollen testicles in dogs is usually made with a physical exam. Pain on testicular palpation raises suspicion for infection, trauma, or torsion. Non-painful testicles are more commonly associated with cancer or testicular degeneration.

A complete blood count (CBC), blood chemistry, and urinalysis can help identify any infection elsewhere in the body that could lead to testicular infection. A blood test can also often diagnose brucellosis, a highly contagious bacterial infection. A semen culture may be necessary for certain bacterial or fungal infections to ensure the appropriate medication is administered.

X-rays may be recommended to check for the spread of cancer; however, ultrasound of the abdomen and testicles is usually more helpful for diagnosis in most cases.

Aspiration or partial biopsy may be considered to get a diagnosis in male breeding animals whose pet parents are hoping to keep them unneutered. However, neutering is highly recommended if either cancer or torsion is suspected, as it serves to both diagnose and treat the problem.

Treatment of Swollen Testicles in Dogs

Treatment of swollen testicles in dogs depends largely on the cause of clinical signs and the goals for treatment. Bacterial, viral, and fungal infections often respond well to appropriate medications, although severe infection may permanently affect the fertility of breeding dogs.

For non-infectious causes of swollen testicles, surgery is usually needed. Removal of both testicles is recommended in most cases, though in dogs that breed, removal of only the affected testicle can be considered. Testicular torsions and scrotal hernias can be surgically treated without neutering.

In rare cases, testicular cancer can spread into the lymph nodes, bladder, or prostate, and chemotherapy may be necessary following surgery.

Recovery and Management of Swollen Testicles in Dogs

Neutered dogs usually improve quickly after surgery, with a two-week rest period and close monitoring of the surgical incision. Frequent follow-up visits with your veterinarian, including blood work and abdominal ultrasound, may be necessary for some dogs after the removal of cancerous testicles.

Neutering following trauma or torsion usually does not require long-term follow-up.

Dogs with infections that are not contagious often respond well to antibiotic therapy. They may also require pain medications and anti-inflammatory medications to be comfortable as they heal.

If neutering is not performed, recovery time will vary depending on the disease and its severity. More extensive nursing care and frequent follow-up visits with your veterinarian to monitor healing will likely be needed.

Brucellosis can never be eliminated from a dog, even with antibiotic therapy. Therefore, neutering is recommended for these dogs, and they should never be used for breeding purposes. Because brucellosis is zoonotic—meaning it can be spread from animals to humans—care should be taken to avoid exposure to their blood, urine, and other secretions, and any contaminated areas should be quickly and thoroughly cleaned and disinfected.

Prevention of Swollen Testicles in Dogs

The easiest way to prevent swollen testicles in dogs is to have them neutered at an appropriate age. This age differs among breeds and should be discussed with your veterinarian.

For breeding dogs, vaccination, parasite testing, and prevention are recommended, as well as brucellosis testing every three to six months. Monitor the size of your dog’s testicles at home routinely to catch problems early.

Swollen Testicles in Dogs FAQ

What do infected dog testicles look like?

Infection often results in a painful, swollen testicle that is typically warm to the touch.

If the infection affects the scrotum (the skin around the testicle), redness and drainage may be noted on the surface, but infection of the testicle or the epididymis (a coiled tube behind each testicle within the scrotum) is not usually visible.

Jamie Lovejoy, DVM


Jamie Lovejoy, DVM


Dr. Jamie Lovejoy graduated from Tufts Cummings School of Veterinary Medicine in 2012 after an undergraduate degree in Marine Biology. ...

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