Glomerulonephritis in Cats

Glomerulonephritis in Cats

By: Dr. Arnold Plotnick

Section: Veterinary Care In-depth

Veterinary care should include diagnostic tests and subsequent treatment recommendations.

Diagnosis In-depth

Diagnostic tests are needed to recognize mast cell tumors and exclude other diseases that may cause similar symptoms. These may include:

  • A complete medical history and thorough physical examination of your pet

  • A complete blood count (CBC or hemogram) to evaluate for anemia, inflammation, infection or low platelet count. A low platelet count would prompt suspicion of rickettsial diseases such as Ehrlichiosis and Rocky Mountain Spotted Fever. A low blood protein concentration also may be identified on the blood count.

  • A serum biochemical profile to evaluate for the presence of low serum albumin concentration (hypoalbuminemia) and high serum cholesterol concentration. Albumin is one of the most important proteins in blood and the first to be affected by protein loss in the urine in pets with glomerulonephritis.
    These biochemistry findings are very common in cats with glomerular disease. Other tests on the biochemical profile, such as creatinine, blood urea nitrogen and phosphorus, allow your veterinarian to assess your pet's kidney function. Finally, other tests on the serum biochemical profile allow your veterinarian to assess the general health of your pet and the possible effects of glomerulonephritis on other body systems.

  • Urinalysis to identify proteinuria and evaluate your pet's kidney function. Hyaline casts may be found in the urine of pets with glomerulonephritis.

  • Urine protein/creatinine ratio to quantitate excessive protein loss in the urine and to determine if your cat's proteinuria is severe enough to justify suspicion of glomerulonephritis. The severity of protein loss with glomerulonephritis is exceedingly variable, and it is possible for an animal to have glomerulonephritis without having a markedly increased urine protein/creatinine ratio. Also, if kidney filtration function worsens with progression of disease in some patients, the urine protein/creatinine ratio will decrease making it less useful as a diagnostic tool. On the other hand, if kidney filtration function remains relatively normal, a decrease in the urine protein/creatinine ratio is a favorable sign indicating clinical improvement.

  • A special test called serum antithrombin III concentration to assess the risk of thromboembolism or blood clot in cats with glomerulonephritis. Cats with low serum antithrombin III concentration are at increased risk of thromboembolism.

  • A heartworm test and other serum antigen or antibody tests such as borrelia and ehrlichia to search for underlying infectious diseases that may be causing glomerulonephritis.

  • Immune function tests such as antinuclear antibody (ANA) or LE prep tests if systemic lupus erythematosus is suspected.

  • Needle aspiration of a joint and microscopic analysis of obtained fluid in immune-mediated polyarthritis is suspected.

  • X-rays of the chest and abdomen to screen your pet for underlying infectious, inflammatory or neoplastic diseases.

  • Abdominal ultrasound examination to evaluate kidney structure and to evaluate other internal organs like the liver and spleen.

  • Ultimately, definitive diagnosis of glomerulonephritis requires kidney biopsy which can be performed under ultrasound guidance to minimize risk of complications and ensure an adequate tissue sample. Ideally, one kidney biopsy should be taken for routine light microscopic examination and additional samples should be taken to identify immune complexes using fluorescence and electron microscopy. The latter are very specialized tests that require special sample handing and processing by specialized diagnostic laboratories.

    Treatment In-depth

    Treatment of glomerulonephritis must be individualized based on the severity of your pet's condition and other factors that must be analyzed by your veterinarian.

    The most effective and specific treatment for glomerulonephritis is elimination of the offending antigens whether they be infectious agents or tumor antigens. Unfortunately, the underlying disease process or antigen source is identified in only 15 to 25 percent of pets with glomerulonephritis and, even if identified, the antigen may be impossible to eliminate, as in the case of lupus erythematosus and some tumor antigens. If the underlying antigen cannot be identified, treatment for idiopathic glomerulonephritis may include:

  • Immunosuppressive drugs to suppress antibody formation and production of antigen-antibody complexes. Immunosuppressive drugs aren't always effective in pets with glomerulonephritis but often are tried. Drugs commonly employed are prednisone (a cortisone-like drug). Other immunosuppressive drugs that have been tried include cyclosporine and cyclophosphamide.

  • A very low dosage of aspirin (0.5 to 5 milligrams per kilogram of body weight) has been recommended to reduce the inflammation and blood clotting in the glomeruli. Treatment with aspirin also may reduce the risk of thromboembolism, but this beneficial effect has not been proven in cats with glomerulonephritis.

  • Dietary changes. At one time, it was believed that protein lost in the urine should be replaced with an equivalent amount of protein in the diet. Unfortunately, this approach merely leads to aggravation of the proteinuria. Providing a diet slightly reduced in protein will substantially reduce the magnitude of proteinuria. Dietary sodium restriction also is recommended due to the tendency of cats with glomerulonephritis to retain sodium and develop hypertension. Lastly, omega-3 fatty acid supplementation may reduce glomerular inflammation and proteinuria. Fish oil is rich in omega-3 fatty acids and some commercial pet foods, designed for medical management of specific diseases, are supplemented with omega-3 fatty acids. Consult your veterinarian for dietary recommendations for glomerulonephritis.

  • Angiotensin converting enzyme (ACE) inhibitors. The hormone angiotensin II causes contraction of specific glomerular blood vessels such that proteinuria is worsened. The increased movement of protein across the glomerular blood vessels contributes to progression of disease by promoting scarring of the glomeruli (glomerular sclerosis). ACE inhibitors reduce the production of angiotensin II thereby reducing the blood pressure within the glomeruli. Treatment with ACE inhibitors reduces the amount of protein lost in the urine and may slow the progression of disease. Enalapril is the ACE inhibitor most commonly used for this purpose.

  • Anti-hypertensive drugs. If systemic hypertension is present and persists despite dietary sodium restriction and treatment with enalapril, other anti-hypertensive medications may need to be employed.

  • Diuretics. Pets that develop severe ascites or subcutaneous edema may require treatment with diuretic drugs to facilitate mobilization and excretion of salt and water in the urine. Furosemide is the diuretic most commonly recommended in this situation. Caution should be used to be certain that the animal does not become dehydrated while being treated with furosemide.

     
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