Vancouver Feline Hospital - Cat Veterinary Clinic

CHRONIC RENAL INSUFFIENCY

The progressive deterioration of your cat's kidneys, and what you can do.

Sometimes this problem is called "age-appropriate" in cats. That's because so many older cats do have to deal with this progressive condition. The age at which it can be considered appropriate is debatable - some eighteen year old cats show no signs of kidney disease despite other age-related problems, yet many twelve year old cats are already diagnosed with "fading kidneys".

This is a syndrome. We can demonstrate on blood and urine tests that the kidneys are no longer functioning but in most cases, we cannot say WHY or what caused or is causing the problem. The initial cause - a parasite, bacterial infection, toxin exposure, or whatever event led to decreased blood flow to the kidneys - may have happened a long time before the diagnosis of CRI is made. There may not even be a cause, other than "age" - that syndrome of genetically programmed cellular deterioration that happens to all of us - and we all "age" differently. The rate at which the kidneys fail varies significantly from cat to cat, and many cats do live for years after the diagnosis is made.

This is a CHRONIC syndrome, that is, it takes time - months, years, to develop and progress. It is important to differentiate this diagnosis from ACUTE renal failure, pyelonephritis (kidney infection), and other kidney problems that require an entirely different therapeutic approach.

There are two kidneys. They have several very important functions for sustaining life and so have what we call a large "reserve capacity" - in other words, your cat can appear to be doing just fine on only ½ a kidney, never mind the other 1 ½ that stopped doing anything . (This is why we can donate a kidney, provided the other is healthy). About 75% of the kidneys are non-functional when blood and urine tests first indicate there is a problem. That is why the earlier we pick up the problem, the more helpful the lifestyle changes and treatments are likely to be - there is more kidney to work with. Kidneys cannot regenerate or regain function - lost kidneys are lost kidneys. All our management and treatments are aimed at conserving the remaining kidney function for as long as possible, and ensuring a comfortable life.

For this article, I am going to discuss the failing kidneys function by function - what the doctor looks for on the blood and urine tests, what is happening to your cat, and what can be done about it.

Concentration urine, maintaining hydration

Kidneys conserve the body's water by making the urine much more concentrated than the blood that is filtered. As they lose this ability, your cat will produce more dilute urine. Your cat will feel thirsty, drink more, and produce more urine. Eventually your cat cannot drink enough to compensate for the body's loss of water, and becomes dehydrated. Many cats hover on subclinical dehydration, which speeds up the rate of kidney decline. More severe dehydration can be rapidly fatal.

The veterinarian assesses "urine concentrating ability" by checking Urine Specific Gravity. During the physical exam, the veterinarian will assess oral mucus membranes, skin turgor, coat quality and overall body condition to give a subjective grade of dehydration. Dehydrated cats will show relatively increased haematocrit, total serum proteins, serum creatinine on blood tests - these values drop when the cat is rehydrated.

Early on, you can encourage your cat to drink more water **weblink***. Later on, this is not enough, and we maintain hydration by treatment with subcutaneous fluids - called SQ fluids - this is a balanced isotonic intravenous (IV) electrolyte solution that can be injected under the skin. It is absorbed over a few hours. This technique ****weblink*** is easy to learn, most cats tolerate and seem to appreciate the beneficial routine, and how often it needs to be done depends on the cat. Many people learn to do this treatment at home. If this is not possible at home, it does help to have it done weekly or as often as possible at the vet's.

Filtering Toxins

The body produces a lot of toxins during normal metabolism - these are removed from the blood by the kidneys, and excreted in the urine. As the kidneys fail, more of these toxins build up in the blood. Your cat will start to feel listless, nauseas (noticeable by becoming a finicky eater, eating less, or snubbing meals), and constipated. Weight loss, especially muscle loss from protein malnutrition, makes this worse, as nitrogen by-products build up. The toxins affect the brain (causing confusion, depression, possibly headaches, central nausea and vomition), increase gastric acid secretion causing gastritis, vomiting and stomach ulcers, and are the reason for the bad breath and oral ulcers we often see. At high levels, they cause dementia, seizures, and the whole terrible uremic syndrome.

The blood tests for kidney disease actually measure the serum (blood) concentration of two toxins - BUN (blood urea nitrogen) and CREATININE.

Body weight needs to be closely monitored.