Overview 

Pyelonephritis is a bacterial infection of the kidneys, which are part of the upper urinary tract.  

Infection is more common in middle-aged or older dogs. Often pyelonephritis starts from bacteria in the bladder that spread upwards to the kidneys. This infection may cause potentially life-threatening damage (acute kidney injury) and even lead to bacteria entering the bloodstream.  For this reason, it is important to make a diagnosis and start treatment as early as possible. 

Clinical signs 

The signs of pyelonephritis can vary in severity, and some may even show little to no signs at all. The most common signs include: 

• Poor appetite   

• Increased thirst and urination 

• Painful belly 

• Fever 

• Vomiting  

• Weight loss  

• Lethargy 

• House soiling  

• Blood in urine 

• Straining to urinate 

Risk factors 

• Kidney stones 

• Recurrent UTIs (urinary tract infections) 

• Kidney disease  

• Diabetes 

• Cushing’s disease 

• Anatomic abnormalities (ex. ectopic ureters) 

• Immunosuppression 

• Cancer 

Diagnosis 

Diagnosing pyelonephritis can be difficult. Your veterinarian will likely perform blood work to assess your dog’s general health status and kidney function. A urinalysis followed by a urine culture and sensitivity will look for signs of infection, the type of bacteria and antibiotics that can be used to treat it. 

Ultrasounds and X-rays may be performed to look for changes in the kidneys. Additional tests could also include blood cultures or testing for leptospirosis, another type of bacterial infection. 

Treatment 

Pyelonephritis is treated with antibiotics. Your veterinarian will initially prescribe an antibiotic that most commonly treats kidney infections; however, this may need to be changed once the urine culture results finalize.  

If the infection is severe, some dogs may require hospitalization for treatment of acute kidney injury including IV fluids and additional supportive care. Treatment will also involve addressing any potential underlying conditions.  

Outcome 

The prognosis for pyelonephritis can vary based on severity of illness and response to treatment. 

Dogs without underlying causes generally do well with treatment. If there are underlying conditions, recurrent or resistant infections, the prognosis may be less favorable. Some may even have residual kidney damage if treatment was delayed or ineffective.  

Dogs should have a follow up appointment with their veterinarian 1-2 weeks after finishing antibiotics to recheck blood work and urinary health.