Glomerulonephritis is inflammation of the glomerulus (filters of the kidney), which is a part of the kidney. It is usually caused by immune complexes within the walls of the glomerulus.

Clinical signs may be non-specific, such as weight loss and lethargy.

The only way to definitively diagnosis glomerulonephritis is with a biopsy of the kidney.

The most important treatment for glomerulonephritis is the identification and treatment of any causative underlying disease.

What is it?

• Glomerulonephritis is inflammation of the glomerulus (first part of the kidney filtering unit), which is a part of the kidney.
• It is usually caused by the deposition of immune complexes within the walls of the glomerulus. An immune complex is an antibody (which is usually used to fight infection) unit that has united with an antigen (from an infection, medications that the pet may be receiving, or from a tumor in the body). Sometimes the source of the antigen cannot be
• Various diseases are associated with immune complex formation and subsequent glomerulonephritis. They may be infectious in origin (feline leukemia virus, heartworm, chronic bacterial infections), cancerous, inflammatory (pancreatitis, lupus, other immune-mediated disease), or the cause may be unknown.
• After the immune complexes form in the kidney, the glomerulus continues to become damaged. Once it becomes damaged the glomerulus becomes nonfunctional and is replaced by scar tissue. Protein loss in the urine (proteinuria), kidney failure, increased blood pressure, and pulmonary thromboembolism (blood clots in the lung) may result. Glomerulonephritis is thought to be one of the major causes of chronic kidney insufficiency or kidney failure in dogs.

Anatomy

• Each kidney in the cat or dog contains about 1 million nephrons, the functional unit of the kidney. Each nephron contains a tuft of capillaries called the glomerulus, through which large amounts of fluid are filtered from the blood to form urine. The glomerulus is encased in Bowman’s capsule. Fluid filtered from the glomerular capillaries flows into Bowman’s capsule and then into other parts of the kidney.

Clinical Signs

• The presenting complaint in dogs and cats with glomerulonephritis is variable and depends on the severity and duration of urine protein loss as well as the presence or absence of kidney failure and complications.
• Clinical signs associated with mild to moderate proteinuria may be non-specific, such as weight loss and lethargy. With severe protein loss, fluid accumulation in the abdomen and in other areas of the body may occur, although this is uncommon. If the glomerular disease is extensive, kidney failure and resultant vomiting, inappetance increased drinking and urination, bad breath, and nausea may occur. Occasionally, signs associated with an underlying infectious, inflammatory, or cancerous disease may be the reason the owner seeks veterinary care.

Diagnosis

• Persistent, severe elevations in protein in the urine with an otherwise normal urinalysis are the hallmark of glomerular disease.
• Other laboratory tests such as a urine protein : creatinine ratio and blood work can be used to help confirm the diagnosis. The only way to definitively diagnosis glomerulonephritis is with a biopsy of the kidney.
• Dogs with protein in their urine should be thoroughly evaluated for underlying infectious, inflammatory, or cancerous conditions. Testing may include blood tests for regional infectious diseases, urinalysis, x-rays of the chest, abdominal x-rays or ultrasound.

Treatment

• The most important treatment for glomerulonephritis is the identification and treatment of any underlying disease. The dog or cat should be subsequently evaluated for resolving protein in the urine.
• It is believed that uncontrolled proteinuria leads to progressive kidney damage. Angiotensin-converting enzyme inhibitors (ACEI) are a type of medication often used to help reduce protein levels in the urine. If high blood pressure is present, additional medications may be needed to help lower it.
• Low doses of aspirin are often given to prevent blood clots and further glomerular damage.
• Immunosuppressive medications such as prednisone may be used in some cases.
• Dietary protein restriction may be useful in the management of glomerulonephritis.

Potential Complications

• Increased blood pressure with resultant retinal detachment or hemorrhage may occur. Acute blindness due to retinal detachment may be the first complaint of dogs with glomerulonephritis.
• Increased coagulability of the blood with resultant blood clots are another complication associated with glomerulonephritis. The lungs are the most common location for a blood clot to lodge, and may result in severe respiratory illness that is difficult to treat.

Aftercare and Follow-Up

• Urinalysis and blood work should be evaluated monthly whenever modifications in the treatment plan are being made or every 3-6 months if the dog’s clinical signs are stable and therapeutic changes are not being made.
• Blood pressure should be measured at least every 3-6 months and more frequently if high blood pressure is being regulated with medications. Some dogs may require urine culture once every 6 months.

Prognosis

• The prognosis for dogs and cats with immune complex glomerulonephritis is fair to guarded unless the causative underlying disease can be identified and eliminated.
• A reduction in proteinuria with no increase in blood renal values indicates improvement or response to therapy.
• In cats with glomerulonephritis, there may be slow or rapid progression of kidney disease, prolonged remissions, or complete recovery.

References

• Ettinger SJ, Feldman EC: Glomerular disease. In Textbook of Veterinary Internal Medicine: 5th ed. Philadelphia: WB Saunders Co, 2000.
  
• Guyton AC, Hall JE: Urine formation by the kidneys: I. glomerular filtration, renal blood flow, and their control. In Textbook of Medical Physiology: 10th ed. Philadelphia: WB Saunders Co, 2000.
  
• Nelson RW, Couto CG: Glomerulonephropathies. In Small Animal Internal Medicine: 2nd ed. St. Louis: Mosby , Inc, 1998.
  
• Vaden SL: Glomerulopathy in Dogs. ACVIM 2003.