Pyelonephritis in dogs (i.e. a kidney infection) 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 and 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?
If you break the word “pyelonephritis” down, you get “pyelo” which refers to the renal pelvis (i.e. the area of the kidney that collects the urine and funnels it down into the ureters), “nephr” which is the medical term for kidneys, and “itis” which means inflammation. So, pyelonephritis, in the simplest sense, is inflammation of the kidneys and renal pelvis. Usually, that inflammation is the result of an infection.
Pyelonephritis can be acute or chronic. When acute (i.e. sudden) pyelonephritis happens, inflammatory mediators (i.e. chemicals that drive an inflammatory response) call immune system cells into the kidney tissue. Sometimes, this chain of events can lead to kidney injury and acute kidney failure.
If left untreated, acute or chronic pyelonephritis can also lead to scarring of the kidneys. Eventually, the dog could develop chronic kidney disease and kidney atrophy (i.e. wasting away or shriveling of the kidneys).
What are the causes of pyelonephritis?
There are several factors that can contribute to overall kidney inflammation. However, the most common cause of pyelonephritis, as discussed above, is bacterial infection.
The bacteria Escherichia coli (E. coli) and Staphylococcus species are the most frequent causes of kidney infections, with E. coli being responsible for 33% to 50% of all UTIs overall. Because E. coli can alter the urine concentrating ability of the kidneys, the urine may become more dilute. This sometimes translates to increased thirst in dogs and increased urination.
Other common types of invading bacteria include Proteus, Streptococcus, Klebsiella, Enterobacter, and Pseudomonas species. Anaerobic bacteria (i.e. those that don’t need oxygen to survive) can also make themselves at home inside of the kidneys because the environment is not oxygen-rich. All these bacteria may initially infect the lower urinary tract and then eventually progress to the upper urinary tract where they cause 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. This is because females have a shorter urethra. As a result, bacteria don’t have far to travel from the outside in order to infect the bladder. From there, the bacteria could then potentially infect the kidneys.
Some other factors may increase the risk of pyelonephritis. These include:
- Ectopic ureters (i.e. ones that 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
- Bladder stones
- Urinary incontinence in dogs
- Prostate disease
- Kidney scarring
- Pre-existing kidney disease
- Treatment with immunosuppressive drugs such as prednisone for dogs
- Diabetes mellitus
- Hypothyroidism in dogs
- Cushing’s disease in dogs
What are the symptoms of pyelonephritis in dogs?
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.
A dog’s symptoms may start out resembling those of a lower urinary tract infection such as:
- Frequent, small volume urination (i.e. pollakiuria)
- Blood in the urine (i.e. hematuria)
- Difficult or painful urination (i.e. dysuria)
Additional signs of pyelonephritis include:
- Painful abdomen due to pain radiating out from kidneys
- Increased urinary output (i.e. polyuria)
- Increased drinking (i.e. polydipsia)
- A lethargic dog
- Poor appetite
- Weight loss
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.
Your vet will probably start with blood and urine testing. In cases of pyelonephritis, the 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 show up on the urinalysis. However, those findings are also present in dogs with a bladder infection so 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. This allows the veterinary laboratory to determine which species of bacteria is growing in the urine. It also gives a list of antibiotics that may work best to treat that particular bacteria.
It would be ideal to collect a urine sample straight from the kidneys because that would be more definitive. But this approach can be technically difficult. As a result, the vet will usually submit a sample of urine from the bladder obtained by 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. And while it might sound a bit scary, most dogs are unfazed by it.
Since urine collection is usually more accurate than tissue sampling, dogs with suspected pyelonephritis rarely need a renal biopsy (i.e. kidney biopsy) for diagnosis. However, there may be other kidney issues where a renal biopsy is indicated.
In addition to the laboratory testing, your vet may recommend some 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 architecture 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 catheter. Then the veterinary team will take X-rays when the contrast fluid has made its way to the kidneys. If the contrast spends a long time at the center of the kidneys or if the renal pelvis appears dilated, this is suspicious for kidney disease.
In general, abdominal ultrasound and excretory urography are some of the best ways to determine if an infection is affecting the upper or lower urinary tract.
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?
If your vet believes your dog has pyelonephritis based on the diagnostic testing and physical exam, he or she will 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 given a knowledge of the bacteria that typically cause pyelonephritis. It is much 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 don’t stop the antibiotics early. 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 for Uncooperative Pooches 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. This is to 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.
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.
The vet may also administer anti-nausea medications and antacids. 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 there is one. For example, if your sweet pup has bladder stones, the vet may need to surgically remove them. Or, if your dog has an illnesses like diabetes mellitus or Cushing’s disease, the 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 infections deep in the center of the kidneys 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, while it isn’t common, some dogs do not survive pyelonephritis.
Are there ways to prevent pyelonephritis?
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 the urinary bladders of dogs become full, feedback signals from the stretching bladder wall tell 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 thriving. Additionally, the bladder contains special proteins, antibodies (i.e. immune system defense proteins), 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 access the kidneys. Ureters also contain one-way valves to help prevent the backflow of urine and therefore decrease the chances of bacteria moving toward the kidneys. Finally, at the level of the kidneys, there is no oxygen in the tissues for aerobic (i.e. oxygen-dependent) bacteria to utilize.
Practical prevention steps
While you can’t prevent pyelonephritis entirely, there are some things you can do to help assist the bladder’s natural defense mechanisms:
- Address urinary signs ASAP. The sooner a bladder infection, bladder stones, or other urinary issue is treated, the less likely it is to have time to turn 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 underling 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 probably just had a run-of-the-mill bladder infection or you didn’t see any warning signs before kidney failure struck, it can be especially difficult. But don’t lose hope. Once your dog gets handed a pyelonephritis diagnosis, the best thing you can do is work closely with your veterinarian.
Follow all of your vets instructions carefully and ensure your dog gets 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 attitude or behavior to your vet. It is also very important to complete any follow-up testing your vet recommends.
Hopefully, with good nursing care and lots of snuggles for good measure, your dog will be soon on the road to recovery. Finally, 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).
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