Glomerulonephritis (GN) in Dogs
Causes of Glomerulonephritis in Dogs Viral infections Infectious hepatitis in dogs (canine adenovirus 1) Bacterial infections Lyme disease (borreliosis) Ehrlichiosis (an infectious disease transmitted by ticks) Rocky Mountain Spotted Fever (another disease transmitted by ticks) Brucellosis (an infectious disease) Dermatitis (infection of the skin) Gingivitis (infection of the gums) Endocarditis (infection of the heart valves) Prostatitis (infection of the prostate) Pyometra (infection of the uterus) Chronic fungal infections Heartworm disease Leishmaniasis (a protozoal infection rarely encountered in the United States and transmitted by sandflies)
Non-infectious inflammatory diseases that have been associated with glomerulonephritis include: Pancreatitis (inflammation of the pancreas) Immune-mediated polyarthritis (inflammation of the joints) Systemic lupus erythematosus (an autoimmune disorder) Neoplasia (cancer) Lymphosarcoma Mast cell tumor Other tumors
Despite the long list of infectious, inflammatory and neoplastic disease processes that can result in glomerulonephritis, in as many as 75 to 80 percent of dogs and cats with glomerulonephritis, the underlying cause cannot be identified and the disorder is referred to as “idiopathic.”
Many other medical problems can lead to symptoms similar to those encountered in pets with glomerulonephritis. It is important to exclude these conditions before establishing a definitive diagnosis.
Veterinary care should include diagnostic tests and subsequent treatment recommendations.
Diagnosis In-depth of Glomerulonephritis in Dogs
Diagnostic tests are needed to recognize mast cell tumors and exclude other diseases that may cause similar symptoms in dogs. These may include: A complete medical history and thorough physical examination of your dog. 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 dogs 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 dog’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 dog’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 bloodclot in dogs with glomerulonephritis. Dogs 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 of Glomerulonephritis in Dogs
Treatment of glomerulonephritis must be individualized based on the severity of your dog’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) and azathioprine (an anti-metabolite drug). Other immunosuppressive drugs that have been tried include cyclosporine and cyclophosphamide. Of all of these drugs, azathioprine seems to produce the best results with the fewest adverse effects. 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 dogs 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 dogs 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.