Pyelonephritis in Dogs: Symptoms, Diagnosis, Treatment

Pyelonephritis in dogs (i.e. kidney infection in dogs) can be a concerning diagnosis for your sweet companion. Integrative veterinarian Dr. Julie Buzby explains the symptoms, diagnosis, treatment, and prognosis for pyelonephritis. Plus, she gives some practical tips to help prevent kidney infections. With this information, you will be able to better help and care for your dog should he or she be diagnosed with pyelonephritis.

You are probably aware of the fact that dogs and cats can develop urinary tract infections (UTIs) just like people can. Most of the time a UTI in dogs is caused by bacteria that come from outside the body. Those bacteria then move up the urethra to infect the urinary bladder. When the bladder is inflamed because of bacteria, it is called bacterial cystitis (i.e. a lower urinary tract infection).

Bacterial cystitis is a fairly common condition in dogs. While it is certainly uncomfortable, it doesn’t tend to be life-threatening if caught early. It can however, cause long-lasting problems, or occasionally even death, if it goes undetected or untreated.

You see, sometimes the bacteria don’t stop at the bladder. Instead, they also move up the ureters (i.e. tubes that connect the bladder to the kidneys) and infect the kidneys. Or, very rarely, bacteria can spread from the bloodstream to the kidneys. Both of these situations cause a condition known as pyelonephritis (i.e. an upper urinary tract infection).

What is pyelonephritis in dogs?

Pyelonephritis in dogs is the medical term for inflammation of the kidneys. Often, this condition is the result of a bacterial infection. Left untreated, a dog with pyelonephritis could develop chronic kidney disease and even kidney atrophy (i.e. wasting away or shriveling of the kidneys).

In order to better understand them, I like to break complicated medical terms down into their roots. In this case, “pyelo” refers to the renal pelvis—the part of the kidney that collects urine and funnels it into the ureters. “Nephr” refers to the kidneys, and “itis” means inflammation. So putting these all together, pyelonephritis is inflammation of the kidneys and renal pelvis.

Types of pyelonephritis in dogs

Pyelonephritis in dogs can be acute or chronic. When acute pyelonephritis happens, inflammatory mediators (chemicals that drive an inflammatory response) call immune system cells into the kidney tissue. Sometimes, this chain of events can lead to acute kidney injury, and even possibly kidney failure.

What are the causes of pyelonephritis?

Bacterial infections are the most common causes of pyelonephritis in dogs. Generally when you hear the phrase “urinary tract infection (UTI),” you think of a bacterial infection affecting the lower urinary tract, especially the bladder. Sometimes those bacteria can travel up the ureters and affect the kidneys themselves, causing pyelonephritis. Kidney infections can be considered an upper urinary tract infection.

The types of bacteria that most often are the culprits for kidney infections are:

• Escherichia coli (E. coli) — responsible for 30% to 50% of all UTIs overall
• Streptococcus
• Staphylococcus
• Klebsiella
• Pseudomonas
• Bacillus
• Proteus
• Enterobacter

This is not an exhaustive list; UTIs and pyelonephritis can be caused by a host of aerobic and anaerobic bacteria. Any of these bacteria may initially infect the lower urinary tract and then eventually progress to the upper urinary tract, causing pyelonephritis.

What factors may make pyelonephritis more likely to occur?

There are no breed or age predispositions for pyelonephritis in dogs. However, it may be more common in females than in males. Females have a shorter urethra, so bacteria don’t have far to travel from the outside in order to infect the bladder. From there, the bacteria could then progress to infect the kidneys.

Some other factors may increase the risk of pyelonephritis. These include:

• Ectopic ureters (a congenital condition where ureters don’t insert into the correct place on the bladder)
• Polycystic kidneys (i.e. an abnormality where the kidney’s tissue contains multiple cavities)
• Recessed vulva in dogs
• Bladder stones
• Urinary incontinence in dogs
• Prostate disease
• Kidney scarring
• Pre-existing kidney disease
• Treatment with immunosuppressive drugs such as prednisone for dogs
• Cancer
• Diabetes in dogs
• Hypothyroidism in dogs
• Cushing’s disease in dogs

What are the symptoms of pyelonephritis in dogs?

Symptoms of pyelonephritis include:

• Blood in the urine (i.e. hematuria)—inflammation and infection irritate the sensitive lining of the urinary tract, all the way from the kidneys to the urethra. When the lining is irritated it sometimes bleeds, which is excreted in the urine.
• Frequent, small volume urination (i.e. pollakiuria)—irritation of the urinary tract can create a feeling of urgency, meaning dogs may urinate more frequently to keep the bladder empty and more comfortable.
• Difficult or painful urination (i.e. dysuria)—when the urinary tract lining is irritated, it can make urinating very painful.
• Painful abdomen—due to pain radiating out from kidneys.
• Increased urinary output (i.e. polyuria)—bacteria can alter the urine concentrating ability of the kidneys, making urine more dilute. This sometimes translates to increased urination.
• Increased thirst in dogs (i.e. polydipsia)—increased urination can make dogs drink more water.
• Dehydration—if the dog’s water intake can’t compensate for the increased urine output, dehydration may result.
• Fever—just like with other bacterial infections, pyelonephritis may cause a fever.
• Vomiting—the infection may cause systemic illness, including nausea.
• A lethargic dog—this systemic illness can make a dog feel generally unwell.
• Poor appetite—nausea and vomiting can make food less appetizing.
• Weight loss—if not treated promptly, the decreased appetite can lead to weight loss.

You may notice that some of these signs of pyelonephritis overlap with signs of lower urinary tract/bladder infections. Sometimes without more advanced testing, it can be difficult to distinguish between the two.

Interestingly, some dogs with kidney infections may appear to have no clinical signs at all. Others may be severely sick and go into acute kidney failure.

If your dog is showing some of these signs, it is important to make an appointment with your veterinarian promptly. The sooner the veterinarian can start treating the bladder or kidney infection, the better the outcome tends to be.

How is pyelonephritis diagnosed?

Unfortunately, the hard part about diagnosing pyelonephritis is that there is no one perfect diagnostic test. Instead, your vet will probably rely on many different tests. And most of the time, your dog’s diagnosis will be a presumptive one.

Laboratory testing

Your vet will probably start with blood and urine testing. In cases of pyelonephritis, a complete blood count (CBC) may show increased white blood cells, which is a sign of infection or inflammation. The blood chemistry may reveal elevated creatinine (CREA), blood urea nitrogen (BUN), and phosphorus levels, which could indicate kidney damage.

Dogs with pyelonephritis may have white blood cells, bacteria, or protein in their urinalysis. However, those findings can also be present in dogs with a bladder infections. Therefore, urinalysis alone can’t necessarily distinguish between the two conditions. Also, the urine may be very dilute, which can make it harder to find the bacteria or white blood cells.

When the vet finds bacteria in a urine sample, he or she will probably recommend a urine culture and sensitivity test. As we discussed, many different bacterial species can cause urinary tract and kidney infections. Urine cultures allow the veterinary laboratory to determine which species of bacteria is growing in the urine. They also provide a list of antibiotics that may work best to treat that particular bacteria.

Ideally, urine would be collected straight from the kidneys, because that would be more definitive. But this approach can be technically difficult. Instead, your vet may collect a urine sample via a procedure called a cystocentesis (i.e. sticking a needle in the bladder and withdrawing a sample). This sample collection method minimizes bacterial contamination from the urethra and genital region. While it might sound a bit scary, most dogs are unfazed by it.

Since urine collection is usually a more accurate way to diagnose pyelonephritis than tissue sampling, affected dogs rarely need a renal biopsy (i.e. kidney biopsy) for diagnosis. However, there may be other kidney issues where a renal biopsy is indicated.

Diagnostic imaging

In addition to the laboratory testing, your vet may recommend diagnostic imaging. Abdominal X-rays of a dog with pyelonephritis may reveal bladder or kidney stones, asymmetrical kidneys, or an enlarged prostate. An abdominal ultrasound can be very helpful for pyelonephritis diagnosis. Like an X-ray, it also can assess overall kidney size. Additionally, it can detect changes to the structure of the kidneys, such as a dilated renal pelvis, that may not be visible on an X-ray.

A specialized test called an excretory urography (EU), also can be quite beneficial. To perform the test, the vet will inject contrast (i.e. a fluid that shows up on X-rays) into a vein through an intravenous (IV) catheter. Then the veterinary team will take X-rays when the contrast fluid has made its way to the kidneys. If the contrast is delayed at the center of the kidneys or if the renal pelvis appears dilated, this is suspicious for impaired kidney function.

In general, abdominal ultrasound and excretory urography are some of the best ways to distinguish between upper and lower urinary tract infections in veterinary medicine.

For more information, a 2018 study published in the Journal of Veterinary Internal Medicine entitled Pyelonephritis in Dogs: Retrospective Study of 47 Histologically Diagnosed Cases (2005–2015) does a great job of looking at the risk factors, symptoms, diagnostic results, and more for dogs with pyelonephritis.

What is the treatment for pyelonephritis in dogs?

Because it’s typically caused by a bacterial infection, antibiotics are generally the most common and effective treatment for kidney infections in dogs.

If your vet believes your dog has pyelonephritis, he or she will likely start treatment right away. Because urine cultures can take several days for results, the vet may make an empirical antibiotic selection. This means he or she will pick one that is likely to work against the bacteria that typically cause pyelonephritis. It is usually safer to start treatment with a broad-spectrum antibiotic immediately than it is to wait for the culture results.

If the culture and sensitivity testing reveals that a different antibiotic would be a better choice, the vet may switch to that antibiotic. Keep in mind that most patients with pyelonephritis will need to be on antibiotics for four to six weeks. It is important that you never stop antibiotics early without first consulting your vet.

If you are having trouble getting your dog to take the medication, check out my article Your Dog Won’t Take Pills? 5 Easy Solutions and contact your veterinarian for advice.

Your vet may recommend repeating a urinalysis and urine culture within a week of starting therapy. He or she will probably also recommend the same tests one week after completing treatment. These tests ensure that the antibiotics are working and the infection is truly gone. Failure to follow up with your veterinarian may lead to a persistent infection and chronic pyelonephritis.

Supportive care

Some dogs with pyelonephritis are critically ill and might require aggressive supportive care in addition to antibiotic therapy. The vet may decide to hospitalize the dog and start intravenous (IV) fluid therapy. This can help flush toxins from the blood stream and replenish any fluid losses from frequent urination.

The vet may also place an indwelling urinary catheter and connect it to a urine collection system. This helps the vet carefully monitor the dog’s urinary output for changes that could indicate worsening kidney problems.

Anti-nausea medications and antacids may also be indicated. These medications may help decrease the stomach upset that sometimes goes along with kidney dysfunction.

Additionally, it is important to address the underlying cause for the pyelonephritis, if one is identified. For example, if your sweet pup has bladder stones, the vet may need to surgically remove them. Or, if your dog has an illness like diabetes mellitus or Cushing’s disease in dogs, your vet may suggest some ways to get those conditions under control. This can help prevent a pyelonephritis reoccurrence.

What is the outlook for dogs with pyelonephritis?

The prognosis for pyelonephritis in dogs is variable. Most furry friends have a fair to good prognosis. However, those with more severe infections may be more difficult to treat. Long term urinary tract issues like chronic kidney disease or cancer can also make for a guarded to poor prognosis. Unfortunately, some dogs do not survive pyelonephritis.

Are there ways to prevent pyelonephritis?

While we don’t have a surefire way to completely prevent pyelonephritis from occurring, there are some ways we can make it less likely.

In order to understand how to decrease your dog’s chances of pyelonephritis, we need to briefly discuss how the urinary tract normally protects itself from infection. Then you will have a better idea of how to support those natural defense mechanisms.

When a dog’s bladder fills, the stretching bladder wall signals the dog to empty the bladder right away. Frequent urination can help flush out any bacteria that may have started to climb up the urethra or reached the bladder. This is especially the case for bacteria that aren’t very good at adhering to the urethra or bladder wall.

The pH of the urine (i.e. how acidic or how alkaline urine is) can also help prevent bacteria from growing. Additionally, the bladder contains special proteins, antibodies, and glycosaminoglycans (i.e. connective tissue building blocks) that prevent bacteria from sticking to the bladder wall.

The ureters themselves are quite long. As a result, bacteria would need to travel far in order to reach the kidneys. Ureters also contain one-way valves to help prevent the backflow of urine, making it more difficult for bacteria to move toward the kidneys. Finally, there is no oxygen in the kidneys for aerobic (i.e. oxygen-dependent) bacteria to utilize.

Practical prevention steps

While we can’t prevent pyelonephritis entirely, there are some things any dog owner can do to help assist the bladder’s natural defense mechanisms:

• Address urinary signs ASAP. The sooner a urinary issue is treated, the less likely it is to have time to progress into pyelonephritis.
• Talk to your vet about routine urine screening if your dog is at risk for UTIs.
• Give your dog a high-quality diet and unlimited access to fresh, clean water.
• Consider giving your dog some canned food to boost water intake.
• Allow your dog lots of chances to go outside and empty his or her bladder. This may mean running home over lunch break or hiring a dogwalker to give your pup a midday potty break.
• Keep your dog’s skin clean and watch closely for signs of irritation or infection around the vulva or prepuce.
• Work with your vet to manage any underlying problems that may predispose your dog to pyelonephritis.

Work with your veterinarian

I understand that pyelonephritis can be a scary diagnosis for your beloved canine. If you thought your dog just had a bladder infection or you didn’t see any warning signs before renal failure struck, it can be especially difficult. But don’t lose hope. Once your dog gets diagnosed with pyelonephritis, the best thing you can do is work closely with your veterinarian.

Follow all of your vet’s instructions carefully. Make sure your dog takes the full course of antibiotics, even if he or she seems to be feeling better. Monitor your dog closely, and promptly report any changes in his or her behavior to your vet. It is also very important to complete any follow-up testing your vet recommends.

Hopefully, with good care and lots of snuggles, your dog soon will be on the road to recovery. As you continue to make memories together, don’t forget to institute some of the changes listed above to make it less likely your dog will have pyelonephritis again (or ever).

Has your dog had pyelonephritis?

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