Glomerulonephritis in Cats

Overview of Feline Glomerulonephritis

The kidneys consist of many thousand microscopic filtering units called glomeruli that filter water and small substances from the bloodstream. The tubules of the kidney then reabsorb vital substances such as glucose and electrolytes from the filtered fluid leaving unneeded substances and a small amount of water in the urine.

Below is an overview on Glomerulonephritis in Cats followed by in-depth detailed information about the diagnosis and treatment of this condition.

Glomerulonephritis is inflammation of these microscopic filtering units of the kidneys that develops when immune complexes (complexes of antibodies and antigens) become trapped in the glomeruli, leading to activation of the body’s inflammatory defense system, which, in turn, damages the glomeruli. The immune complexes often form as a consequence of some other disease process such as infection or cancer. However, in many cats with glomerulonephritis, the inciting cause cannot be found and the problem is said to be idiopathic.

Glomerulonephritis results in excessive loss of protein into the urine (proteinuria). The finding of protein in the urine on urinalysis may be the first indication that your pet has glomerulonephritis. Untreated, the disease can lead to chronic kidney failure.

Cats of any age, breed or gender can develop glomerulonephritis. In many pets, there may be no obvious symptoms of glomerulonephritis.

What to Watch For

Diagnosis of Glomerulonephritis in Cats

Diagnostic tests are needed to identify acute glomerulonephritis and exclude other diseases. These may include:

Treatment of Glomerulonephritis in Cats

Home Care and Prevention

Administer as directed any medications prescribed by your veterinarian. Follow any dietary recommendations and schedule regular follow-up visits with your veterinarian to monitor your pet’s progress.

Observation is important. Make sure your pet’s activity level, appetite and attitude remain normal. Watch for difficulty breathing or limb weakness that may indicate development of thromboembolism. Observe your pet for loss of vision that could indicate complications of hypertension. Look for swelling of the paws, hocks or face that could indicate development of subcutaneous edema and for swelling of the abdomen that could indicate fluid accumulation.

Glomerulonephritis is difficult to prevent. Certain infectious, inflammatory and cancerous diseases can lead to development of glomerulonephritis and regular annual examinations by your veterinarian are advised to be certain your pet remains healthy and free of such diseases.

In-depth Information on Feline Glomerulonephritis

The kidneys filter water and small molecules from the bloodstream and into the renal tubules. Water and essential molecules are reabsorbed from the tubules and the remaining waste products and a small amount of water are excreted as urine. The microscopic filters of the kidney are called glomeruli (singular, glomerulus), which are small tufts of capillary blood vessels that act as a sieve, allowing small substances to pass through while keeping larger substances such as proteins and blood cells in the bloodstream.

Glomeruli can be damaged by inflammation and become leaky. This is called glomerulonephritis. Very large things, such as red and white blood cells, still are not filtered but some substances not normally filtered like proteins leak through the inflamed glomeruli into the urine. The excessive loss of protein in the urine is called proteinuria, and this condition can adversely affect your pet’s health.

Glomerulonephritis occurs when large numbers of immune complexes – these are antigen-antibody complexes – circulating in the bloodstream become trapped in the glomeruli as they attempt to pass into the urine. Deposition of immune complexes triggers an inflammatory reaction that damages the glomeruli and results in proteinuria. The antigens bound to the antibodies in the immune complexes arise as a result of some chronic infectious, inflammatory or cancerous disease process. Several diseases have the potential to result in glomerulonephritis.

The clinical symptoms of glomerulonephritis are quite variable.

Causes of Glomerulonephritis in Cats

Non-infectious inflammatory diseases that have been associated with glomerulonephritis include:

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 cats 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

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

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:

Follow-up Care for Cats with Glomerulonephritis

Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up can be crucial. Administer as directed any medications prescribed by your veterinarian and contact your veterinarian promptly if you have difficulty treating your pet.

Follow dietary recommendations for your pet made by your veterinarian. Pets with glomerulonephritis often are placed on a low-protein, low-sodium diet and omega-3 fatty acid supplementation may be recommended.

Observe your pet’s activity level and appetite and watch for signs of complications including swelling of the limbs or abdomen indicating subcutaneous edema or ascites, sudden loss of vision indicating possible retinal hemorrhage or detachment secondary to hypertension, or sudden onset of difficulty breathing or loss of use of the rear limbs potentially indicating thromboembolism.

Actual prescribed follow-up depends on the severity of your pet’s disease, response to therapy and your veterinarian’s recommendations. Your veterinarian will monitor protein loss in the urine by periodically evaluating your pet’s urine protein/creatinine ratio. Your veterinarian will monitor serum biochemistry on your pet to determine if blood proteins, including albumin, are increasing, cholesterol is decreasing, and to be sure that renal function (creatinine, blood urea nitrogen, phosphorus) remains stable.

Systemic blood pressure should be monitored in pets with glomerulonephritis, especially if your pet is being treated with an ACE inhibitor such as enalapril.

Close monitoring of pets with glomerulonephritis is crucial because the outcome is very variable. Pets with this disorder follow one of three clinical courses: