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From Good Dog! Magazine The Barking Edge of Medicine™ by Rob Hilsenroth, DVM Glomerulonephritis (pronounced: glow-mare-you-low-ne-FRIGHT-us) is a severe disease of the kidneys that can lead to kidney failure and death. Specifically, glomerulonephritis means inflammation of the glomerulus, small tuft-like arrangements of the blood vessels that are essential to the blood-filtering function of the kidneys. Glomerulonephritis occurs commonly in dogs: 43% to 90% of randomly selected dogs in various studies were shown to be affected. But the cause is usually undetermined. For this reason, the disease is said to be idiopathic (of unknown cause). It's likely that many affected dogs have a mild case of glomerulonephritis that never results in clinical disease. But dogs that are more severely affected have a high probability of developing life-threatening kidney failure and possibly even dying from the disease. Glomerulonephritis starts when disease-fighting proteins called antibodies become deposited along the wall of the delicate blood vessels that comprise the glomerulus. Antibodies are made by the immune system in response to the presence of molecules (proteins, sugars, and fats) that are recognized as foreign. The exquisite sensitivity of the immune system to these foreign molecules, also called antigens, provides an effective defense against microorganisms such as bacteria and viruses that can cause disease. In some cases, however, the immune system is activated inappropriately in response to antigens that may not have potential to cause disease. The antigens may be inhaled (for example, pollen, dust mites, mold spores, skin dander), touched, or ingested. These immune hypersensitivities are called allergies. In theory, allergic patients may be predisposed to develop glomerulonephritis. Antibodies alone usually don't cause any problem, since they remain dissolved in the blood and are not deposited in the glomerulus. Yet, when antibodies encounter and bind to antigens in the circulation, they may form very large complexes that have difficulty staying dissolved in the blood. These complexes may fall out of solution in the glomerulus and become lodged in the small pores where the blood is filtered. When antigen-antibody complexes are deposited in the glomerulus, the body responds by mounting an inflammatory response to try to remove them and repair the glomerular damage. Ultimately, the inflammation can cause even more damage and impair the function of the glomerulus, leading to renal failure. Clearly, not every allergic patient will develop clinical glomerulonephritis, but some may. In dogs, allergies usually manifest themselves by causing severe itching, frequently in the nose, paws, and armpits. Allergies can be due to inhaled antigens, contact hypersensitivity (things the dog touches), or food components. In some dogs, food allergies may cause diarrhea instead of -- or in addition to -- itchiness. Dogs can be allergic to many different food components such as corn, wheat, chicken, beef, soy, or lamb, among others. Food allergies are usually diagnosed by "elimination diets," where veterinarians evaluate the response to removing the potential offending antigen or antigens. Often, the presence of the specific allergy is established by re-exposure to the antigen, leading to the reappearance of clinical signs. A relatively new test has been developed that recognizes the presence of antigen-specific antibodies in the feces. This test can be used to screen dogs for potential antigens in food that may be causing the allergic reaction, thus reducing the time required for diagnosis using traditional elimination diets. Scientists think a potential association between allergies and glomerulonephritis could then be established by comparing the presence of both diseases in the canine population at large, and the prevalence of glomerulonephritis in dogs with food allergies as compared to the prevalence in dogs with no allergies. To establish if there's any association between food allergies and the development of glomerulonephritis in dogs, Morris Animal Foundation is supporting a study entitled, "Food Antigen-Specific Fecal IgE in Dogs with Idiopathic Glomerular Disease." This study is being conducted by Dr. Shelly L. Vaden of the College of Veterinary Medicine at North Carolina State University and her colleagues at four additional veterinary institutions. For this project, Dr. Vaden and her collaborators are comparing the levels of antigen-specific fecal IgE in a group of dogs known to have glomerulonephritis, with the levels found in healthy dogs or dogs with diseases other than glomerulonephritis. This study has the potential to determine one possible cause for glomerulonephritis, and give veterinarians a means to prevent this severe disease of dogs.
Rob Hilsenroth, DVM, is Executive Director of Morris Animal Foundation. This nonprofit organization sponsors animal health studies at veterinary schools and institutions throughout the U.S. and in other parts of the world. All annual unrestricted contributions to the foundation support health programs -- not the cost of administration or fund-raising. If you'd like to make a contribution, write Morris Animal Foundation, 45 Inverness Drive East, Englewood CO 80112. For more information, call (800) 243-2345 or visit http://www.morrisanimalfoundation.org From Good Dog! Magazine Order your Good Dog! Online Subscription NOW and get 6 issues for $12!
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