Pet insurance companies call it a pre-existing condition. I call it glomerulonephritis.

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Feline Glomerulonephritis

Glomeruli are tiny blood vessels in the kidneys that do the first step of filtering blood to form urine. They filter out toxins and leave proteins.

Glomerulonephritis is a disease when the glomeruli become inflamed. This causes protein loss, and is one of the main causes of kidney failure.


A few things can cause inflammation:

  • Infections: bacterial or viral
  • Autoimmune diseases (the immune system attacks the body)
  • Dental disease
  • Cancer
  • Genetic disposition

In most cases, the underlying cause is not found.


The most common sign of glomerulonephritis is blood in the urine.

Othersigns may include:

  • Lethargy
  • Vomiting
  • Loss of appetite and weight loss
  • Increased thirst and urination

If you notice any of the above signs, bring your cat to the veterinarian immediately. Glomerulonephritis can lead to nephorotic syndrome where their damaged kidneys leak protein from the blood into the urine.

Cats with nephorotic syndrome will have:

  • Swollen legs
  • High blood pressure
  • Abnormal blood clotting


If there is a lot of protein on a urinalysis, your veterinarian will perform other tests to diagnose glomerulonephritis, including:

  • Urine tests: to rule out bladder infection, and to check the amount of protein loss
  • Blood tests: to check for underlying conditions, and for protein and cholesterol in the blood
  • Blood pressure test: to check for high blood pressure
  • Radiographs or ultrasound of the kidneys: to look for tumors and study kidney shape and size
  • Kidney biopsy: the most important test in diagnosing glomerulonephritis


The best method is to treat the underlying cause. However, in most cases, no underlying cause is determined. In those cases, some treatment options will include:

  • Medications: to control high blood pressure and to avoid tissue injury
  • Prescription diet: low protein, low sodium, omega-3 fatty acid supplements


Most cases of glomerulonephritis are idiopathic (no known cause), and therefore there is no way to prevent it.

It is also difficult to prevent because of the infectious, inflammatory, and cancerous diseases that lead to it.

You should bring your cat for annual exams with your veterinarian to ensure that it remains healthy and free of such diseases.


Glomerulonephritis is a serious condition, requiring extensive treatments and management.

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