Kidney failure... kidney disease in the dog and cat is a common and difficult disorder to manage.
Often called CRF... Chronic Renal Failure, it is seen most often in the older dog or cat. Kidney failure has it origins in a wide variety of causes. For example, some animals are born with poorly constructed or functioning kidneys and never reach totally optimum health. Eventually, these individuals usually fall into kidney failure at an early age. Another type of kidney failure can occur after accidental ingestion of antifreeze that contains ethylene glycol.
These situations cause sudden and often irreversible renal (kidney) failure. Quite commonly, kidney failure results from low grade, long term (chronic) inflammation of kidney tissues called chronic nephritis; the damage caused by this inflammation renders permanent damage to delicate renal tissues that are not able to repair themselves or heal as some other body tissues do. Eventually, not enough normal functioning tissue remains to support the body's need for metabolic regulation and waste elimination. The dog or cat becomes UREMIC, a condition where body waste material builds up in the blood. These toxins promote vomiting, poor appetite, depression, and eventually death. Bacterial invasion of the kidneys is a common cause of chronic nephritis and kidney failure.
The kidneys receive about 20 percent of the heart's blood output and play a vital role in keeping the dog or cat in normal metabolic balance. The glomerular blood vessels have a large endothelial surface which allows for the active and passive transport of many chemicals into and out of the kidneys.
Normal kidney function involves the following responsibilities, among others:
1.) Regulating the amount of fluid in the spaces surrounding the body's cell. This is called extracellular fluid volume regulation.
2.) Regulating the amounts and types of solids in the blood in order to keep blood concentration within normal limits. This is called blood osmotic pressure regulation.
3.) Regulating the acid-base balance of the animal through retention or elimination of specific ions in the blood. Common important ions affecting the acid-base balance of dogs and cats are bicarbonate, sodium, ammonium, potassium and hydroxyl ions. This function keeps the pH (amount of acidity) of the blood and body fluids within strict normal ranges.
4.) Removing metabolic waste products such as uric acid and also molecular foreign substances detoxified by liver.
5.) Reacting to Aldosterone (ADH) produced in the adrenal glands. The major target of aldosterone is the distal tubule of the kidney, where it stimulates exchange ofThe Nephron sodium and potassium and the reabsorption of water back into the blood.
6.) Production (Erythropoetin), a chemical effecting red blood cell production.
DIAGNOSIS OF KIDNEY FAILURE
One of the first signs an animal will show when beginning to be affected by kidney failure is an increased thirst. Polydipsia is the term used for this situation where the animal needs to consume greater amounts of water than normal. Increased toxins and other metabolic waste products triggers sensors in the brain that the blood is tooPolydipsia... drinking abnormally large quantities of water. concentrated and through a series of chemical reactions the animal may have a sense of dehydration... and drinks more water to alleviate this sensation. Compounding this sense of dehydration is actual water loss through the kidneys above normal amounts due to the kidneys being inefficient in retaining water within the body.
The increased thirst/water intake (polydipsia) causes an increased urine flow... and the animal urinates more frequently and produces higher volumes of urine. Called Polyuria, the increased urine output seems unintuitive if the animal is actually affected with kidney failure. Many pet owners have been baffled when the veterinarian mentions that the patient may have early kidney failure. They often respond "How can that be, its urinating a lot more than it usually does?" What really is happening is that much more urine is being produced and eliminated however the urine is becoming more and more dilute; the urine is not bringing along all those toxins and waste products for removal from the body. And certain substances that the kidneys are supposed to be conserving and keeping in the body such as glucose and protein are inappropriately being lost in the urine. Especially protein loss, called Proteinuria, contributes to the animal's weight loss, inability to perform normal metabolic chemical processes, tissue repair and energy metabolism.
Water soluble vitamins, such as the B-vitamins are washed out of the body with this polyuria and polydipsia and the animal suffers from hypovitaminosis.
In order to make a diagnosis of renal failure the veterinarian will need to check two avenues of data gathering... a urine sample and a blood sample. Checking one without the other may render a diagnosis less accurate.
TREATMENT FOR KIDNEY FAILURE
In human medicine, dialysis and kidney transplantation are the main methods of dealing with advanced kidney failure. Expensive and time consuming, these methods are also employed in treating dogs and cats but impose heavy financial and time burdens on the pet owner and some stress on the patient who is already stressed by the disease. Unfortunately, once the diagnosis of kidney failure is made, most patients are so sick that response to treatment is unrewarding and slow. The pet's owner may need to consider euthanasia in order to prevent the long, slow, and agonizing death that comes from complete renal shutdown. In very extreme and special circumstances, a kidney transplant may be an animal's only hope of long term existence. See an article about KIDNEY TRANSPLANTS here. Kidney transplantation is a controversial topic but the science and success rate in cats and dogs has advanced greatly in recent years.
Treating kidney failure is one of the most consistently discouraging aspects of veterinary medical practice. The difficulty stems from the fact that once a dog or cat hasIntravenous fluid therapy may be temporarily helpful. lost 75% of total renal function, the ability to remove metabolic waste products is outweighed by the buildup of those toxins. The animal is simply not able to keep up with the "housecleaning" and as a result gradually becomes increasingly more toxic. Body chemistry swings more and more acidic, important chemicals and nutrients are lost from the body and the animal comes gradually closer and closer to a fatal uremic poisoning. In some cases, gradual kidney tissue loss can be present for years before the patient becomes critical and actual "renal failure" is diagnosed.
The goal of treatment is to allow the patient to live as close to a normal life as possible under the circumstances. Since the kidneys do not heal or regenerate new and functioning tissue, the remaining functional tissue carries the entire burden normally handled by two healthy kidneys. Intravenous and subcutaneous fluids can be administered for varying lengths of time to try to correct acid-base imbalances. Vomiting can be controlled. Anti-ulcer medication can be given. Bicarbonate may be administered either orally or intravenously to assist in neutralizing acid buildup. B-vitamins are provided. Antibiotics are employed if there is an infection present anywhere in the body... taking into consideration that some antibiotics will also build up in the patient if renal function is compromised. Phosphate binders and Omega Fatty acids in correct amounts and proportions may be temporarily beneficial for the Chronic Renal Failure patient. High quality, low protein diets have been proven to be helpful in lessening the metabolic tasks that must be performed by the kidneys once end stage kidney disease is present.
Contrary to popular myth, diets rich in protein ("high protein levels") do not cause kidney damage. Research done decades ago indicated that rodent kidneysHigh protein diets do not cause kidney damage. were adversely affected by diets high in protein... and misguided researchers extrapolated that data to apply to the canine. There is no evidence that feeding dogs and cats diets rich in or "high" in protein actually causes kidney damage or disease. Some day this myth will be finally be put to rest. In fact, there is ample research and well documented studies that prove that dogs and cats thrive on diets with levels of protein consistent with a meat-eater's (carnivore) natural prey selection.
The diagnosis of kidney failure is made only after...
* A thorough physical exam
* A thorough discussion with the owner about the dog or cat's relevant history
* A urinalysis is performed
* A blood chemistry analysis is performed