The kidneys are responsible for eliminating waste products produced by the body’s normal metabolism. If they fail to perform this function adequately, the body will literally poison itself.
For this reason, special attention must be directed at keeping these organs healthy, or—if a disease state already exists—at treating to prevent further functional deterioration. In cats, kidney (renal) disease is the most common disorder associated with old age.
In essence, through normal wear and tear, the kidneys become unable to perform their functions in the same way that they did when they were young. Worn-out kidney cells die and are replaced by scar tissue, which can’t filter out toxins from the blood.
When enough of these nephrons die and the buildup of toxins in the blood becomes great enough, the pet begins to exhibit signs of kidney failure.
But don’t get the idea that only older pets can suffer from kidney impairment. Young cats might have been born with inadequate kidney function, or they might suffer from other diseases (such as feline infectious peritonitis or leptospirosis) or toxic agents that kill nephrons and impair renal performance.
For example, systemic infections, heat stroke, heart disease, and autoimmune diseases are only some of the acquired conditions that can lead to kidney disease and kidney failure.
Many therapeutic drugs, such as aspirin and certain antibiotics, can be damaging to the kidneys if used indiscriminately.
Antifreeze, or ethylene glycol, is deadly to dogs and cats when ingested because of the profound damage it causes to the kidneys. Finally, periodontal disease, with its associated complications, can predispose pets, both young and old, to kidney problems in the future.
The clinical signs associated with kidney disease can be quite variable depending on the extent of damage to the kidneys. Interestingly, dogs and cats rarely show outward signs of kidney disease until at least 75 percent of the function in both kidneys is lost!
As a result, when signs do finally become apparent, it is vital that therapeutic measures be taken quickly to prevent loss of the remaining 25 percent. Sudden, acute kidney failure, the type that can result from the ingestion of a poison such as antifreeze, can lead directly into intense dehydration, shock, unconsciousness, and death without manifesting any other signs.
Chronic, more long-term kidney disease and kidney failure rarely have such a dramatic presentation, yet such conditions can eventually turn into acute kidney failure if measures aren’t instituted to prevent this progression.
Ccats with chronic renal failure will exhibit an increased thirst and an increased desire to urinate. Depression and loss of appetite might also set in. In addition, since renal disease can cause stomach ulcers, vomiting might occur.
Veterinarians can diagnose kidney disease through a series of laboratory tests performed on the blood and the urine. Two blood parameters, blood urea nitrogen (BUN) and serum creatinine, will be elevated if the kidneys are failing.
The urine specific gravity is also an important parameter that helps the veterinary practitioner determine the extent of damage to the kidneys. Under normal circumstances, the specific gravity of the urine, which measures how concentrated the urine is, should fluctuate depending on the body’s own needs for water.
Diseased kidneys, however, are unable to conserve water for the body; hence, the specific gravity of the urine in a pet with advanced kidney disease will be diluted, even if the pet is clinically dehydrated.
Cats suffering from acute renal failure must be hospitalized and placed on intravenous fluids to correct dehydration. Other medications designed to stimulate kidney function will be given as well.
If the pet survives this acute attack, support measures for chronic kidney failure must then be implemented. Stress reduction is vital in cats with chronic renal disease and/or failure. Unlimited access to clean, fresh water should be provided at all times, since water deprivation could lead into an acute kidney-failure crisis.
Special diets that are low in phosphorus and contain only high-quality protein should be fed to help reduce toxin buildup within the bloodstream. These are available from veterinarians. Vitamin supplementation should also be considered to replace those lost in the increased urine flow.
Since renal disease can alter, among other things, the blood levels of calcium and phosphorus, medications designed to keep levels of these electrolytes constant are used as well. If a pet is having trouble with vomiting, human antiulcer medications can be employed to help settle the stomach.
Finally, since kidney disease places an incredible burden on the affected pet’s immune system, all underlying disease processes and disorders (such as periodontal disease) need to be addressed.