Bacterial Infection (Pyelonephritis) of the Kidneys in Cats

Pyelonephritis, or kidney infection, occurs when bacteria enter and infect the kidneys. Most commonly, the infection is “ascending”, or travels up the urinary tract to the kidneys.

Occasionally the infection may be “hematogenic” or arising from bacteria in the bloodstream which travel to the kidneys.

Pyelonephritis can be life-threatening and requires urgent veterinary care. It is an uncommon condition in cats, but it is more common in cats with pre-existing urinary or kidney disease.

Pyelonephritis is often asymptomatic, and may not cause obvious signs until the infection and kidney damage is advanced. Chronic pyelonephritis may result in irreversible damage to the kidneys and has a variable prognosis. Unresolved infections may cause secondary infections in other parts of the body, or sepsis. Kidney infections can be cured, but chronic renal failure may result due to irreversible organ damage.

Risk factors for pyelonephritis include old age, urinary tract obstruction, diabetes, and weakened immune systems. Young cats may be predisposed to infection if congenital abnormalities of the urinary tract or kidneys are present.

Symptoms of pyelonephritis vary depending on the acuity or severity of the infection. Some cases may be asymptomatic, or have subtle signs such as increased urination and thirst.

Symptoms such as fever, vomiting or blood in the urine indicate more severe infection. Signs and symptoms of pyelonephritis are similar to signs of other kidney and urinary problems, e.g. increased frequency of urination or urinating outside the litter box.

Any condition that obstructs or damages the kidneys or urinary tract, or alters the healthy composition and concentration of the urine may predispose a cat to developing pyelonephritis.

Chronic pyelonephritis may be asymptomatic.

Diagnosis includes:

• Physical examination
• Bloodwork
• Urinalysis including urine culture
• Diagnostic imaging (ultrasound, CT, MRI)

Treatment includes antibiotic medication, usually for 1-2 weeks. IV fluids, pain medication and anti-nausea/antiemetic medication may be prescribed to treat symptoms. Specific treatments for predisposing conditions may also be required (e.g. treatment for kidney stones, or diabetes).

Monitoring and rechecks after treatment via urinalysis and urine culture may be required to confirm that the treatment is working or has cleared the infection in the weeks following the antibiotic course. Urinalysis also allows the veterinarian to assess kidney function and recovery.

Cats with a history of urinary and renal problems may be prone to reinfection.

In cases where the kidney is severely diseased and damaged, a veterinarian may recommend surgery to remove the affected kidney (nephrectomy).

The prognosis is good in many cases, and antibiotic treatment may clear the infection and allow complete recovery of renal function.

Chronic infections may cause irreversible kidney damage and secondary infections in other parts of the body such as the heart or spine. Cats with predisposing endocrine diseases, persistent urinary problems, or kidney disease have a more guarded prognosis.

Some infections are more difficult to treat depending on the part of the kidney affected . Some cases may persist or recur, and must be managed on an ongoing basis.

Pyelonephritis can be prevented by maintaining urinary tract health and managing predisposing conditions.

Cats should have access to fresh water at all times to maintain hydration and urinary health. Urinary issues associated with higher risk of pyelonephritis such as urinary tract infections (UTIs), bladder infections, or urinary stones, must be treated promptly.

Pyelonephritis is not contagious, but very rarely, certain bacteria causing the infection can be transmitted between cats.

Pyelonephritis is an uncommon condition in cats, typically affecting those with predisposing conditions such as lower urinary tract infections, or immunosuppression. It becomes more common with age.

Antibiotics Nephrectomy Treatment for symptoms

• IV fluids
• Pain medication
• Antiemetics