Bacterial Infection of the Kidneys (Pyelonephritis) in Dogs

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Key takeaways

Pyelonephritis is a urinary tract infection that affects the kidneys.

  • The infection is most usually caused by a bacteria (usually E. coli) that moves up the urinary tract from the bladder into the kidneys
  • Symptoms of pyelonephritis include vomiting, lower back pain, bloody urine, and straining to urinate
  • Middle-aged and older dogs are more likely to develop recurring kidney infections
  • The majority of dogs diagnosed with pyelonephritis suffer from underlying medical conditions that increase the possibility of infection
  • Diagnosis involves physical examination, urinalysis, urine culture, and diagnostic imaging to identify the kidney infection and any predisposing factors
  • The treatment for pyelonephritis is a long term antibiotic course (4-8 weeks)
  • The prognosis for acute pyelonephritis is good with appropriate treatment
  • In cases of chronic or recurring kidney infections, the prognosis is guarded
  • If left untreated, pyelonephritis can lead to kidney failure
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A closer look: Bacterial Infection of the Kidneys (Pyelonephritis) in Dogs

Pyelonephritis is an uncommon condition in dogs, but when left untreated it can lead to kidney failure or life-threatening septicemia.

Kidney infections must be treated as an emergency. Dogs showing symptoms of kidney infection require immediate veterinary attention.

Pyelonephritis can be either acute or chronic. Older dogs suffering from other conditions are more likely to develop chronic and recurring kidney infections.

Many dogs with pyelonephritis show no symptoms or very subtle symptoms until the infection is severe. In the case of chronic pyelonephritis, many cases show few symptoms until the dog has entered renal failure

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Risk factors

There are a number of risk factors which increase the likelihood of kidney infection.

Possible causes

Pyelonephritis is usually caused by an ascending infection in which bacteria originating from outside the surface of the body reach the kidneys via the urinary tract.

In rare occasions, the bacteria that cause pyelonephritis can be carried into the kidney via the bloodstream.

The most common kind of bacteria involved in pyelonephritis is Escherichia coli.

Main symptoms

Testing and diagnosis

Diagnosing pyelonephritis is not easy as its symptoms are common to a number of different conditions.

Diagnostic tools include:

  • Physical examination
  • Urinalysis and urine culture
  • Blood tests
  • Diagnostic imaging
  • Special testing for bacterial agents such as leptospirosis

Steps to Recovery

Pyelonephritis is treated with long-term antibiotics (4-8 weeks). If the infection is severe, the dog may require hospitalization for intensive and supportive care, including treatments such as IV fluids and anti-inflammatory medication. In some cases of chronic pyelonephritis, surgical removal of the affected kidney may be required.

During and after treatment, monitoring of the animal's urine, including repeated urine cultures, is necessary to ensure complete recovery.

The prognosis for pyelonephritis varies depending on the severity of the infection. Dogs with no underlying medical conditions generally respond well to treatment.

Dogs suffering from recurrent kidney infections present a more guarded prognosis. Repeated urinary tract infections may cause permanent kidney damage that in turn can cause kidney failure. Dogs with severe pyelonephritis may develop septicemia, a life-threatening condition where bacteria are spread through the bloodstream to other organs.


Pyelonephritis is not contagious.

The majority of dogs diagnosed with pyelonephritis also suffer from other conditions that increase the likelihood of infection. If the animal is known to have a predisposing condition, regular veterinary monitoring can increase the likelihood of early detection of the infection, improving the dog's prognosis.

Is Bacterial Infection of the Kidneys (Pyelonephritis) in Dogs common?

Pyelonephritis is an uncommon condition in dogs. Middle-aged and older dogs are more prone to pyelonephritis.

Typical Treatment



Joanna White and Reidun Heiene - Writing for International Renal Interest Society
Becky Lundgren, DVM - Writing for Veterinary Partner
Scott A. Brown, , VMD, PhD, DACVIM - Writing for Merck Veterinary Manual
Scott A. Brown, VMD, PhD, DACVIM - Writing for Merck Veterinary Manual
Dr. Aly Cohen - Writing for Cornell University College of Veterinary Medicine

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