What you should know about kidney disease in cats
November 17, 2013
Chances are if you have a cat or know someone with a cat, you have encountered feline kidney disease. Kidney disease is one of the most common problems in cats.
Cats older than 7 are most at risk, and nearly 30 percent of cats older than 10 are affected. This is a concern because proper kidney function is vital to life. These incredible organs do more than just filter blood to form urine and eliminate metabolic waste. They also play an important role in blood pressure regulation, vitamin D activation, blood electrolyte and acid-base regulation and fluid balance, and they produce a hormone signal that is critical for red blood cell production and prevention of anemia.
These functions are continuously performed by a pair of kidneys that are normally only 2-1/2 inches long in the cat. Despite their small size at only 0.5 percent of the total body weight, they receive 25 percent of the blood pumped by the heart. At the microscopic level, it is the nearly 200,000 nephrons that are responsible for important functions of the kidney, and it is the loss of functioning nephrons that results in kidney failure.
There are many causes of kidney failure in cats. Some damaging insults cause sudden kidney failure (also known as acute renal failure or ARF). These insults include antifreeze poisoning, urinary obstruction, plant toxins, certain drugs like the non-steroidal anti-inflammatory drugs (NSAID) or certain antibiotics, heart failure, and bacterial infections of the kidney. Generally, if these problems are appropriately treated, kidney function can be restored.
Chronic kidney disease (CKD), on the other hand, generally evolves over time. Diseases that contribute to CKD include bacterial infections of the kidneys, ongoing inflammatory conditions, cancer, immune disorders and exposure to toxins and certain drugs. Since CKD is typically a slowly progressing problem and the kidney has tremendous ability to compensate and continue to perform its vital tasks, affected cats generally don't show illness until the disease is advanced. Underscoring this point is the recognition that the ability of the kidney to concentrate urine does not start to decline until 2/3 of kidney function has been lost, and the creatinine blood value does not rise until approximately 3/4 of kidney function has been compromised.
Diagnosis of kidney failure is made by blood tests measuring the blood urea nitrogen (BUN) and creatinine. Analysis of urine and other evaluations like abdominal X-rays and ultrasound can provide valuable information. Early indications of kidney problems can be subtle and may only be seen as increased water drinking and increased urination. As the kidney function continues to decline and the cat becomes increasingly unable to effectively detoxify, they can become depressed, lose their appetite, experience vomiting, and if the toxicity is severe enough, ulcers in the mouth may develop. Since the kidney has many more functions than just detoxification, the cat may also experience high blood pressure that can contribute to injury to the retinas of the eye, become anemic, become continuously dehydrated, and have problems regulating potassium and phosphorus.
Once kidney disease is diagnosed and contributing causes identified, treatment can be initiated. For ARF, the main goals are to restore hydration, work to flush out the toxins, address contributing factors, control any nausea and vomiting, and maintain food consumption. For CKD, treatments are based on the stage of severity. Generally for cats that are ill, efforts are focused on stabilizing the cat, slowing progression of the deterioration of the kidney, and maintaining quality of life. Unfortunately, in most cases of CKD it is not possible to return the kidney to normal function. Treatment and supportive approaches depend on severity and may include fluid injections, special diets, phosphorus binders, blood pressure medications, stomach acid blockers, and steps to combat anemia. Affected cats are monitored carefully for progression and support therapy modified accordingly. The integrative approach may include the addition of acupuncture, omega-3 fatty acids, herbs and supplements. While specific studies are not always available for every supportive approach, numerous clinical observations indicate that these supportive methods can be beneficial for the long-term care and comfort of affected cats.
Contact your veterinarian if you suspect your feline companion is showing any signs of kidney problems. It is always best to start supportive care early.
Ron Carsten, DVM, PhD, CVA was one of the first veterinarians in Colorado to use the integrative approach, has lectured widely to veterinarians, and has been a pioneer in the therapeutic use of food concentrates to manage clinical problems. In addition to his Doctor of Veterinary Medicine, he holds a PhD in Cell and Molecular Biology and is a Certified Veterinary Acupuncturist. He practices integrative veterinary medicine in Glenwood Springs.