Kidney Disease, an Overview
by Anne Jones RN, BSNE
The kidneys are major organs of the body, affecting health in many ways. The kidneys function to filter waste (urine), to maintain a balance of the normal chemicals in the body, as well as regulation of blood pressure. Healthy kidney function is critical! Symptoms of kidney failure should be understood by all pet owners. Kidney disease may occur as an acute illness but at other times, it can be slow to manifest symptoms and can be quite insidious. The symptoms of kidney disease may be masked because they can be similar to (or the same as) other major diseases. Because of the interaction of the major organs, symptoms alone will not be sufficient to diagnose disease and further study is always needed, starting with urinalysis and blood chemistry.
The kidneys are located on either side of the backbone and just under the last ribs. The kidneys are a filtering organ made up of microscopic nephrons, structures that filter and reabsorb fluids passing through the kidneys. Many substances (chemicals, poisons, germs) can damage the nephrons, as can aging, trauma and disease.
Long term damage may occur over months and years until such damage reduces kidney function to as few as one quarter of the nephrons before total kidney failure occurs. In the other extreme, sudden and acute kidney failure may be sufficient to permanently destroy kidney function and may be irreversible. One such event, frequently seen in the fall and early spring, is the destruction of kidneys by the consumption of antifreeze! The sweet taste is an immediate temptation to the dog who wanders past as the radiator is drained or fluids cleared from boats that have been winterized. Be aware because you have only hours to save the dog’s life when he takes in as little as a spoonful of antifreeze!
Signs of possible kidney or bladder ailment may be any of the following: excessive drinking; excessive urination; blood in the urine; stiff legged gait and a hunched back. A dog that has a stiff legged walk, hunched back and seems to be carrying himself gingerly may well be expressing to the owner his discomfort from diseased kidneys. In Bichons, frequent urination and/or blood in the urine can be a sign of bladder infection or bladder stones. Untreated bladder infections may cause the bacteria in the bladder to back up through the ureters until the kidneys themselves become infected.
Chronic inflammation of the kidney is called pyelonephritis. This is the name given to infection which may come from other parts of the body and seat itself in the kidneys. Pyelonephritis can occur over a period of years and may begin with malformation of the kidney(s) or from infection and may be well advanced before symptoms are noted. Because of failing nephrons, the dogs produce large amounts of dilute urine due to the inability to concentrate the urine. In the earlier stages, this condition may be treated and may be somewhat reversed.
In acute pyelonephritis – kidney failure caused by disease, poisons (rat poison, antifreeze), some antibiotics and chemotherapy drugs – damage to the nephrons occurs so quickly that the surviving nephrons do not have time to compensate. Again this situation requires immediate treatment! Antifreeze (ethyleneglycol based) will usually be fatal but fast treatment may save the dog that has consumed rat baits. It is ironic that some of the very antibiotics given to treat non-kidney disease can harm the kidneys and any dog receiving those drugs known to damage the kidneys must be closely monitored during treatment.
Every dog owner must be aware that giving dogs grapes or raisins is tantamount to giving them poison! Grapes can cause acute kidney failure and must not be fed even in small amounts!
Chronic kidney failure may result in another long-term condition called glomerulonephritis, in which the immune system proteins damage the blood vessels of the nephron. Nephrosis is the scarring of tissues of the kidneys by diseases such as leptospirosis, distemper, herpes and hepatitis. Kidney cancer can also occur.
Any of the diseases of the kidneys if untreated will lead to the final kidney failure known as uremic poisoning. Signs of uremia are apathy, depression, failure to eat or drink, ammonia odor to the breath, general signs of poor health and eventually a comatose condition from which the dog will not recover.
Kidney failure is often the diagnosis in the aging dog with signs of failing health. It is imperative that a Bichon receive annual examination after age 12 that includes urinalysis and blood chemistry in order to have early warning of insipient kidney disease. Remember that kidney function is closely tied to the health of all organs of the body and must be monitored and treated early. Every Bichon, with a tendency in the breed to bladder infection, needs fresh water available at all times. Bladder infections need prompt treatment and proper diet. Be sure to see the article on Bladder Stones to understand the difference between inherited bladder problems and those that are from infection and remember that the stones must be properly assayed to determine which are from an inherited condition.
It is also a good idea to familiarize yourself with other metabolic health issues sometimes seen in Bichons because proper treatment of any of these conditions will help to prevent chronic kidney disease.
Information in this overview article on kidney disease comes from The Dog Owners Home Veterinary Handbook, Carlson DVM and Giffen MD and other publications on canine health.