Introduction

CRF is a disease of the kidneys, and as indicated by the word "failure", CRF is ultimately terminal. This is a devastating thing to hear for many people. However, it makes more sense to focus instead on the word "chronic": this means that the disease is an ongoing one, with gradual deterioration taking place as kidney function fails; and with appropriate treatments it may be possible in some cases to slow the deterioration down. 

Why Does CRF Occur?

Most cats with CRF develop CRF as a result of aging, although some younger cats may develop it for genetic reasons; occasionally infections may also cause CRF, although this is less common. The Causes of CRF page has more information about possible causes.

It is estimated that around 10% of cats over the age of ten will develop CRF, with as many as 30% of cats over the age of 15 having the disease. It is highly unlikely that anything you have done has caused your cat to develop CRF, so please don't feel guilty.

Diagnosis and medical treatment of chronic renal failure in cats (2004)

Chew DJ, DiBartola SP & Schenck PA mentions that 15-30% of cats over the age of 15 develop CRF.

Dr Katherine James mentions that up to 30% of cats aged over 15 develop CRF.

Clinical benefit of calcitriol in feline chronic renal failure (2005) is a report by the Morris Feline Foundation on a study by Dr David Polzin into the use of Calcitriol in cats with CRF. Dr Polzin mentions that 10% of cats over the age of 10 and 30% of cats over the age of 15 develop CRF.

Management of feline chronic renal failure (1998) Brown SA Waltham Focus 8 pp27-31 mentions that up to a third of geriatric cats may have CRF, and also discusses the disorders that may cause renal disease, but does mention that for many cats, the cause can not be found.

What Happens in CRF?

To answer this question, it is necessary to understand a little about the role of the kidneys. The kidneys have five main functions:

1. the regulation of fluid levels in the body;

2. the regulation, including filtering and disposal, of waste products in the body;

3. the regulation of electrolytes (salts in the body's cells which are necessary for survival) in the body;

4. stimulation of red blood cell production; and

5. production of renin, which controls blood pressure .

In cats with CRF, as the kidneys become more and more damaged (see how much function is necessary) and their ability to function declines, an imbalance can arise in any or all of these areas.  The Symptoms and What Do All Those Test Results Mean? pages explain how these functions are adversely affected by CRF; the How Bad Is It? page explains more about the different stages of CRF; and the Treatments section focuses on how to minimise the effects on your cat.

Long Beach Animal Hospital clearly explains more about the way the kidneys work.

Washington State University College of Veterinary Medicine has more information on the kidneys' functions.

University of Georgia has a student guide to CRF.

Feline Good describes how the kidneys work. 

People and pets: common diseases - kidney disease is a video from University of California at Davis which provides an overview of what happens in CRF and shows a dog receiving dialysis. It also features a human CRF patient talking about how CRF feels.

How Much Function is Necessary?

You may well panic if your vet tells you that your cat has lost two thirds or more of his/her kidney function. However, it may help you to know that it is actually normal for CRF not to be diagnosed until it is at this stage. To understand this, it helps to know a little bit about how the kidney works.

A cat’s kidneys contain around 170,000 - 190,000 functional units called nephrons, which filter the blood flowing into the kidneys. The measure of the nephrons’ function is called glomerular filtration rate (GFR). Cats have many more nephrons than they actually need in their kidneys; plus nephrons can increase their individual function to some extent when other nephrons die: this is why people can donate a kidney and still manage perfectly well with one kidney. To take the example of a kidney transplant, if you remove one kidney the GFR will immediately fall to half of what it was, but will then gradually improve as the remaining nephrons increase their function to compensate, and eventually will reach almost the same level of function as two kidneys.

Thus, in the case of a cat with kidney disease, as damaged nephrons die (they often are described as "scar tissue"), other nephrons take over their work. Eventually, however, all the remaining nephrons will be working fulltime (i.e. there will be no "renal reserve" left). It is at this point, when around 66-75% of function has gone, that you will probably start to see symptoms in your cat, as the remaining nephrons start finding it harder to cope with the workload.

So please do not feel guilty for not noticing sooner - there was probably nothing for you to notice, plus cats are very good at hiding signs of illness. There are a number of possible Methods of Early Detection, but most people don't know about CRF, so do not know about these methods; and why should they? What you need to focus on is the fact that cats with CRF can often manage quite well on limited kidney function - for some cats, things only become critical when they have lost as much as 90% of function, and there are  some cats who cope astonishingly well with even less function. So the goal is, not to worry about the function that has already been lost, but to try to retain the remaining function for as long as possible.

Is There Any Hope?

Many European vets seem to view CRF as an immediate or imminent death sentence, in contrast to vets in other countries, notably the USA and Canada, where various treatments have been developed. Although much depends upon how advanced the illness is in your cat and how well your cat responds to treatment, in many cases it may be possible to buy your cat several months or sometimes even years of quality life by using these treatments. If you find this hard to believe, you might be encouraged by the contrasting experiences of my CRF cats, Tanya and Thomas, and the many cats in the Success Stories section.

There are no guarantees with CRF because every cat is an individual, but it is worth trying treatments - even if they do not work, it can be comforting to know you have tried your best - and very importantly, even if the treatments do not prolong your cat's life, they can really help to make him or her more comfortable.

Related Diseases

CRF is often linked to three other diseases:

• hypertrophic cardiomyopathy (HCM), a form of heart disease where the heart becomes thickened; and/or  

• hyperthyroidism, where the thyroid gland, which regulates metabolism, becomes overactive; and/or

• diabetes, where not enough insulin is produced by the pancreas, or the insulin which is produced is not processed properly by the body's cells.

If your cat has one or more of these diseases as well as CRF, you must treat all of the conditions.

If your cat has been diagnosed with CRF or if you suspect he/she has CRF, visit the Index of Symptoms and Treatments,  Symptoms, What Do All Those Test Results Mean? and Treatments pages for more information.

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