Enlarged Prostate in Dogs: 3 Causes

An enlarged prostate in dogs is fairly common in male senior dogs. But how big a deal is it? Integrative veterinarian Dr. Julie Buzby shares why an enlarged prostate typically points to one of three conditions, which have variable outlooks. Learn about these conditions as well as the symptoms and treatments.

Did you know that routine prostate exams aren’t just for older men? They can be a good idea for male dogs too! You see, dogs do have prostates. And intact or castrated male dogs are prone to several conditions that lead to prostatomegaly (i.e. an enlarged prostate). Some are a big deal for your dog (no pun intended) while others may or may not ever cause noticeable issues.

I promise I will fill you in on the details of the top three causes of prostatic enlargement in dogs. But first, let me set the stage by explaining a bit more about the prostate.

What is the prostate?

Like male humans, male dogs also have a prostate gland. This oval-shaped structure has two lobes and sort of looks like a walnut. It is responsible for producing prostatic fluid, which contains nutrients that enhance the metabolism of sperm cells. This fluid also helps sperm survive when they move through a female dog’s reproductive tract after breeding.

Conveniently, the prostate surrounds a portion of the urethra and has multiple ducts that deposit prostatic fluid into the urethra. Plus, the vas deferens (i.e. tube that carries sperm cells from the testicle to the urethra) travels through the prostate before opening up in the urethra. This anatomical arrangement allows the sperm cells to mix with the prostatic fluid during ejaculation.

However, as you will soon discover, there are some aspects of prostate anatomy that become less ideal once the prostate enlarges. Normally, the prostate wraps around the portion of the urethra that first exits the bladder. It is boxed in by the bladder in front of it, rectum above, pelvic bones below, and abdominal wall on either side.

With a normal-sized prostate, these physical boundaries aren’t a problem. However, as you can imagine, when the prostate begins to grow in size, it doesn’t have a lot of places to go. This helps explain some of the clinical signs you might see if your dog has an enlarged prostate.

What are the symptoms of an enlarged prostate in dogs?

Since the enlarged prostate sometimes compresses the urethra or the rectum, affected dogs may show signs that relate to those body systems. For example, they may strain to urinate or defecate and remain in the respective posture for a prolonged period of time. Or they may only pass a small amount of urine or feces. This understandably can make a dog parent worried their dog is constipated or can’t urinate.

Also, dogs with an enlarged prostate may show signs that resemble those of a urinary tract infection (UTI in dogs), pyelonephritis in dogs (i.e. kidney infection), or other urinary issues such as:

• Increased frequency of urination
• Difficulty urinating
• Changes in urine volume
• Blood in the urine
• Urinary incontinence

However, the exact symptoms can vary greatly depending on the dog, disease, and severity of the condition. Some dogs may be asymptomatic while others are gravely ill.

How will my vet find the reason for my dog’s enlarged prostate?

If your dog is showing any of the signs we just discussed, it is best to make an appointment with your vet. During that visit, or if your vet is evaluating your dog’s prostate at a wellness visit, he or she will probably start by performing a digital rectal exam to assess the size and shape of the prostate. This is a quick and easy way to confirm prostatic enlargement for many dogs. However, it is a bit trickier for large and giant breeds since their size means the prostate is further away from the anus.

If the vet needs to gather more information about the prostate, he or she may recommend some imaging. This may involve an X-ray to confirm prostate enlargement, look at the overall shape of the prostate, and screen for cancer spread. Or the vet may suggest an abdominal ultrasound, which is especially useful for detecting prostatic abscesses, cysts, or tumors.

The vet may also want to run blood tests to look for increased white blood cells (a sign of infection), or perform urine tests. Additionally, he or she may recommend cytology or a biopsy of the prostate to look for signs of infection or cancer.

The vet will then use all of this information to try to pinpoint the cause of your dog’s enlarged prostate.

Top 3 causes of enlarged prostate in dogs

The three main causes of prostatic enlargement in male dogs (intact or castrated) that your vet will be looking for include:

#1: Benign prostatic hyperplasia

As intact male dogs become middle-aged or older, their hormones can cause the prostate to grow larger. This natural process is called benign prostatic hyperplasia (BPH) and it affects roughly 80% of non-neutered older male dogs. As such, BPH is the most common cause of an enlarged prostate in dogs.

Here’s how it happens. In intact male dogs, the hormone testosterone (made primarily by the testes) is converted to dihydrotestosterone (DHT). The role of DHT is to control the size of the prostate by binding to DHT receptors. As dogs age, a higher percentage of the testosterone is converted to DHT and number of DHT receptors is also increased. As a result, the number of cells in the prostate increases (i.e. hyperplasia) and the cells get bigger too. These hormonal and cellular changes translate to enlargement of the prostate.

Symptoms

Thankfully, the majority of dogs with BPH can stay asymptomatic and healthy for many years. Some dogs with BPH, however, can have the following complications:

• Urinary signs or constipation
• Increased risk of prostate infection or inflammation (i.e. prostatitis) because prostatic fluid is a good medium for the growth of bacteria
• Increased risk of the formation of prostatic cysts (i.e. pockets of fluid in the prostate)
• Decreased motility and integrity of sperm in breeding males, which can lead to infertility

Treatment

Although it often doesn’t require treatment, BPH is arguably the simplest prostatic disorder to manage. All you need to do is schedule a neuter surgery for your canine companion. Removing the testicles (and therefore the source of testosterone), will cause an enlarged prostate to start to shrink down.

Typically, the prostate will shrink by 50% by three weeks post-neuter and by over 70% by nine weeks post-neuter. If for some reason it doesn’t, then one of the other processes we are about to discuss may be at play as well.

Alternatively, there are some medication options which may also help shrink the prostate if a dog is symptomatic. One such medication, Finasteride (Proscar®), is useful for breeding dogs because it blocks the conversion of testosterone to DHT but does not decrease testosterone levels. It is worth noting, though, that clinical signs tend to reoccur after stopping the medication.

#2: Prostatitis

In unneutered male dogs, prostatitis (i.e. inflammation of the prostate gland) is the second most common cause of an enlarged prostate. It tends to affect intact male dogs or recently neutered dogs. And it is most common in dogs over three years of age. However, this prostatic disease is rare in neutered male dogs.

Typically, prostatitis occurs when bacteria migrate up the urinary tract and enter the prostate gland. This may happen in conjunction with BPH because of the changes in the prostate anatomy and the fact that prostatic fluid is a good bacterial growth medium.

However, it can also happen independent of BPH. Any disorder that predisposes a dog to developing a urinary tract infection can also cause prostatitis. Examples of these disorders include:

• Bladder stones and urethral stones
• Urethral stricture (i.e. narrowing of the urethra)
• Any trauma or injury affecting the urogenital tract
• Bladder cancer in dogs (e.g., transitional cell carcinoma or TCC)

The most common bacteria implicated in cases of prostatitis is E. coli. However, several other bacteria can also cause prostatic infections, as can some fungal agents.

Symptoms

Prostatic infections can be acute or chronic in nature, with chronic bacterial prostatitis being more common.

When there is an acute onset of prostate infection you may see the general symptoms of an enlarged or swollen prostate that we discussed earlier, plus:

• Fever
• A lethargic dog
• Decreased appetite
• Vomiting
• Abdominal pain or lower spinal pain
• Trouble holding their urine
• Blood and discharge that can be observed coming from the penis

On the other hand, dogs with a chronic infection may not have any symptoms. Or they may appear to have a UTI or constipation.

Unfortunately, some acute or chronic prostatic infections can also result in the formation of a large prostatic abscess. If the abscess ruptures or goes untreated it can cause a significant body-wide infection (i.e. sepsis). Sepsis can be very difficult to treat and may be life-threatening.

Treatment

The vet will use a four to six week (or longer) course antibiotics to treat a prostatic bacterial infection. Often the vet will base antibiotic selection on the results of a culture and sensitivity.

If your dog has a prostatic abscess, the vet may also need to drain it to help avoid the abscess accidentally rupturing into the abdomen. There are a variety of drainage methods including intracapsular prostatic omentalization surgery and ultrasound guided drainage.

Your vet may also prescribe additional medications such as non-steroidal anti-inflammatory drugs (NSAIDs) and stool softeners to help with inflammation and constipation, respectively.

Ideally, intact dogs with chronic prostatitis (and sometimes acute prostatitis) would also be neutered. This can help shrink the prostate and decrease the chances of continued prostatitis. However, if you intend to breed your dog, there are some medications available (e.g. Finasteride) which can reduce prostatic size yet won’t affect breeding capability.

3. Prostate cancer

Like other areas of the body, it is possible for tumors to develop within the prostate gland. Overall, prostate cancer makes up about 5-7% of cases of prostatic disease in dogs. This means it is much less common than BPH and prostatitis.

The most common type of prostatic cancer is adenocarcinoma. However, other tumor types are also possible. Unfortunately, prostatic cancer is rarely benign and it tends to have high metastatic rates. This means that the tumor cells can quickly move to other parts of the body, resulting in a poor response to therapy.

Interestingly, genetics may play a role in the development of prostate cancer in dogs. Researchers have isolated a mutation in the BRAF gene which seems to occur in a majority of urogenital cancers. Luckily, there is a simple test that can look for the mutated BRAF gene in the urine sample of a dog.

The other risk factor that researchers are still exploring is reproductive status, as prostate cancer appears to be more common in neutered males. This may be because sex hormones have a protective effect on prostatic cells. However, these studies also acknowledge that neutered dogs have a longer lifespan compared to intact males. This may put them at an increased risk of cancer developing simply because they are alive for longer.

Symptoms

Prostatic cancer can cause all the typical symptoms of an enlarged prostate that we have already discussed. But painful or difficult urination (i.e. dysuria) and straining to urinate (i.e. stranguria) are more commonly seen with prostatic tumors. In the later stages, a dog may be completely unable to urinate. Or he or she may experience spinal pain, difficulty walking, or other signs of tumor spread.

Treatment

Dogs with prostatic cancers may require partial or total surgical removal of the prostate, radiation therapy, chemotherapy, or other modalities. Additionally, oral NSAIDs like piroxicam may help keep affected dogs comfortable and have some anti-tumor effects. Yet even with these treatments, sadly, the prognosis can still be guarded to poor.

Are there home remedies or natural treatments for an enlarged prostate in dogs?

After learning about the three most common reasons for an enlarged prostate and the medical treatment options for each condition, you may be wondering if there is anything else you can be doing for your dog. Typically, there isn’t a natural treatment or home remedy that is going to be as effective as what your vet can offer. However, taking a holistic approach, in addition to working with your vet, can be helpful.

For example, by keeping your pup on a complete and balanced diet, you are ensuring that his immune system will have everything he needs to fight infection and minimize inflammation. Additionally, supplements that contain glucosamine, chondroitin, omega-3 fatty acids for dogs, and vitamin C are often helpful. These ingredients naturally decrease inflammation in the body, especially throughout the urogenital tract. Plus, Vitamin C may also help decrease the chances of a bacterial infection.

Talk to your veterinarian

One of the biggest things I hope you take away from this article (and most of my articles really) is to work closely with your veterinarian when making decisions for your dog’s health. If you don’t know if or when you should neuter your dog because BPH and prostatitis are common in intact males but prostate cancer may occur in neutered males more often, talk to your veterinarian.

If you are noticing concerning symptoms and wondering if your dog has an enlarged prostate, talk to your vet. And if your dog does have an enlarged prostate—you guessed it—keep talking to your vet. Lean on his or her expertise to figure out the cause and next steps so you can get back to enjoying life with your senior dog ASAP.

And let me offer one finally word of advice—even if your dog seems totally healthy, keep up with wellness visits. That way your dog can get a much-needed routine prostate exam to check for prostate enlargement. Like everything else, early detection of prostate problems can make a difference!

Did your dog have an enlarged prostate?

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