1.  Introduction

How bad is it? This is probably the first question people ask themselves after diagnosis. This page attempts to help you understand a bit more about what the test results mean, and to explain why it is not as bad as it sounds when your vet says your cat has lost a certain percentage of his/her kidney function.

If your vet has told you there is no hope for your cat, and has recommended euthanasia, I urge you to:

1. read this page;

2. check out the Index of Symptoms and Treatments page to see which symptoms your cat has; and

3. ask your vet about trying some of the treatments outlined on the Treatments page to treat any of the symptoms you are seeing and any imbalances indicated by your cat's test results

before making the irrevocable decision to put your cat to sleep.

2. How Bad Are These Numbers?

There are a number of ways in which the vet can determine how advanced your cat's case is. Most vets will start with bloodwork, and many will also analyse your cat's urine (urinalysis).

Bloodwork

Bloodwork tells vets quite a lot about how a cat's kidneys are functioning. BUN (urea) and creatinine are the two main measures of kidney function in bloodwork. Many vets now use the categorisation system proposed by the International Renal Interest Society which divides CRF into four stages:

*It is normal not to be able to detect CRF until at least 66% of function has been lost, because before that there are usually no symptoms, see below. Therefore for cats in Stage 1, kidney problems would normally only be suspected if an anatomical or functional abnormality had been detected.

In all cases, two readings in a stable cat, ideally after fasting (though that is not always the best choice for a CRF cat), are required before making a firm diagnosis of CRF.

Urine Specific Gravity (USG)

Because of their desert heritage, healthy cats have concentrated urine. The normal range is 1.008 to 1.060 but a cat with a more dilute USG, below 1.040, is generally considered to have a problem of some kind. A CRF cat will probably have a USG between 1.008 and 1.012. 

Other possible causes of dilute urine include liver disease, diabetes, hyperactive thyroid or use of corticosteroids. Cats with pyelonephritis (kidney infection) may have low USG.

Once a cat is receiving regular fluid therapy, this test can be rather unreliable. 

The International Renal Interest Society has information on the significance of USG in cats.

Proteinuria

The International Renal Interest Society (pages 3 and 4 for cats) also mentions the importance of proteinuria when deciding how advanced a cat's CRF is.

Healthy cats only have tiny amounts of protein in their urine because their kidneys do not allow the protein to leak through. In CRF cats, this mechanism can be faulty and excess levels of protein in the urine, known as proteinuria but sometimes referred to as microalbuminuria, may occur. The main proteins which leak through are albumin and globulin. 

See the Methods of Early Detection, What Do All Those Test Results Mean? and Treatments pages for more information on proteinuria.

Renal Insufficiency versus Renal Failure

Many people are shocked by the use of the word "failure" but the word to focus on is "chronic": CRF is an ongoing disease which can often be managed. Some vets therefore use the word "insufficiency" for early stage cases instead. In Progression of chronic kidney disease: can it be altered by treatment? (2003) Proceedings of the 27th Waltham OSU Symposium, Dr Scott Brown divides kidney problems into renal disease, renal insufficiency and renal failure. I have put these stages into a table and added my own estimates as to the approximate percentage of kidney function lost at each stage:

Percentage of Function Lost 

You may well panic if your vet tells you that your cat has lost two thirds or more of his/her kidney function. I regularly hear from people who say "my vet told me my cat has lost 75% of kidney function and it's looking really bad". However, it may help you to know that it is actually normal for CRF not to be diagnosed until a cat has lost at least 66% of kidney function. The What is CRF? page has more information on why this is the case.

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 help your cat manage with whatever function remains for as long as possible.

What Does All This Mean in Practical Terms?

It is all very well being told which stage your cat falls into, but that doesn't really tell you much about what you are facing on a practical level. Generally speaking, for cats in lower stages, the cat will usually be acting better and will probably need fewer treatments. For cats in all stages, you should monitor for hypertension (high blood pressure), anaemia, high phosphorus levels, low potassium levels and metabolic acidosis, so you can nip these problems in the bud if they are present. The International Renal Interest Society has some suggestions on what to watch for and be prepared to treat at each stage, including what to do if proteinuria or hypertension are present.

Whatever stage your cat is at, most people find the treatments only take about 20 minutes out of their day, including the time needed to give sub-cutaneous fluids.

Here are some tips on what you may be facing:

Cat in IRIS Stage 1, Stage 2 or the Lower End of Stage 3

If your cat seems to fall into IRIS Stage 1, 2 or the lower end of Stage 3, it is early stage and with proper care and a little luck on your side, your cat could live for years. Most cats in these Stages (creatinine below 3.5-4.0 in US values) will not need sub-cutaneous fluids and can easily be managed with just a few treatments tailored to the individual cat's needs, e.g. treatment for stomach acid to prevent vomiting, constipation remedies and/or control of elevated phosphorus levels. In all cases, it is essential that your cat eats!

Cat in Stage 4 or the Upper End of Stage 3

If your cat seems to fall into Stage 4 or the top end of Stage 3, don't panic! If your cat is dehydrated at diagnosis, particularly if s/he has crashed, the numbers you are seeing won't be an accurate representation of true kidney function. You need to treat your cat, particularly any dehydration, before you can know the true status of the kidneys.

Even if your cat proves to be at the top of Stage 3 or in Stage 4 following stabilisation, don't give up hope: some cats do seem to manage very well on very little kidney function, and it is possible that your cat might be one such cat. You will probably need to be more proactive and your cat will probably need more treatments than cats with lower bloodwork values, but it is certainly worth trying to help.

These cats will usually need the same treatments as cats in lower stages for whatever problems may be present, e.g. for stomach acid, high phosphorus levels, constipation etc. In addition, they will usually need regular fluid therapy in the form of sub-cutaneous fluids in order to avoid dehydration.

Cats in IRIS Stage 4 will often have anaemia, and will need treatment for that - untreated severe anaemia can be very dangerous and can kill a CRF cat before the CRF does. Fortunately, many effective treatments for anaemia are available, meaning no CRF cat need die of anaemia. See the Anaemia page for more information.

How Long Have We Got?

The short, though annoying, answer to this question is, how long is a piece of string? It is impossible to say how long an individual cat has, or how long a cat will take to move from one IRIS stage to the next.

In Prolonging the life of the renal failure patient (2000), Waltham Focus 10 (3), Dr Jonathan Elliott states that "in a retrospective study, the correlation between plasma creatinine and survival in cats who presented with signs of stable CRF was very poor, with only 5% of the variation in survival time being predicted by the initial plasma creatinine concentration". However, Survival in cats with naturally occurring chronic kidney disease (2000-2002) (2008) Boyd LM, Langston C, Thompson K, Zivin K & Imanishi M Journal of Veterinary Internal Medicine 22(5) pp1111-7 found that "median survival for cats in IRIS stage IIb at the time of diagnosis was 1151 days (range 2-3107), and was longer than survival in stage III (median 778, range 22-2100) or stage IV (median 103, range 1-1920)." But the median is a halfway point i.e. 50% of cats lived less than the median, and 50% lived longer than the median. So sadly 50% of the cats in Stage 4 at diagnosis lived less than four months, but that means that 50% of Stage 4 cats lived for longer than four months. What I find interesting is that at least one cat in Stage 4 lived for 1920 days after diagnosis, or more than five years!

If I had to generalise, I would say that cats who are diagnosed early with low numbers have the best chance. Many of them live for years. But as the Success Stories page shows, some cats with high numbers also live for years.

The longest surviving CRF cat I know of lived for sixteen years after diagnosis, having been diagnosed at six months of age. The next longest surviving lived for twelve years, having been diagnosed at three years old.

So Is There Any Hope?

Yes! The numbers only tell part of the story. Much depends upon your particular cat, how sick s/he is at diagnosis, how much s/he wants to fight, how well s/he copes with being handled, and how good the veterinary care is that s/he receives. Some vets seem to recommend euthanasia almost immediately, but CRF is not generally considered to be a painful disease (dehydration feels a bit like a hangover, uncomfortable but not agonising), so there is no need to rush into an irrevocable decision.

I do not understand vets who say things such as "if s/he's not better by tomorrow/within three days/whatever period the vet mentions, you have to put to sleep", or "well, your cat's numbers have not fallen far enough, so we have to put to sleep". These statements are bizarre, because they are using totally arbitrary criteria to decide whether a cat lives or dies. In the vast majority of cases, you need to treat your cat properly for at least two weeks before you can make an informed decision. Plus deciding on euthanasia is your decision, not the vet's, and you have to live with the feelings of guilt and loss which often follow. So do not be talked into euthanasia on the day of diagnosis or if your cat's numbers do not improve after a day or two on IV fluids,  because in many cases there is room for hope; the cat just needs some time to stabilise with proper treatments tailored to his or her particular needs. 

This section covers the following scenarios:

• cat who is not in crisis

• cat who is in crisis (perhaps on intravenous fluids (IV or a drip)

• if bloodwork worsens after a period of stability

• if bloodwork worsens suddenly

• if a cat with low bloodwork values acts sick

Cat Not in Crisis

If your cat has been diagnosed early and/or is stable, you are fortunate in many ways because with careful monitoring and a proactive approach, your cat may stay relatively well for months or years. For cats who are stable but who have relatively high bloodwork values, perhaps at the top end of Stage 2 (see above), there is still hope: the values may fall with treatment, but even if they do not, there is a possibility your cat may remain at this level for some time (see below). If your cat is stable despite having numbers in Stage 3 (see above), your cat clearly copes well with CRF, which is usually a good sign, although treatments should still be begun as soon as possible, including possibly a session on IV. 

Cat in Crisis: Probably Receiving Intravenous Fluids (IV)

Since it is so hard to diagnose CRF early (see What is CRF? to understand why), your cat may be in crisis at diagnosis. Please do not be too despondent if this is the case, particularly if your cat has crashed (see Symptoms) and is on a drip, as happened to Thomas. Many cats have horrendous bloodwork at diagnosis, or may experience a sudden crisis after having CRF for a while, which is often a reflection of severe dehydration. The true bloodwork values will not be apparent until your cat is rehydrated and stabilised, either via sub-Qs for less critical cases or via IV for more severe ones. If your cat has an infection, you need to get it under control before you can tell how severe things really are; hypertension may also make bloodwork look worse than it will once the hypertension is under control.

Some cats with very high numbers will actually be suffering from acute renal failure (ARF) rather than CRF, and whilst ARF is difficult to treat, if treatment is successful the cat may actually make a complete recovery.

There are a variety of possible outcomes for a cat who has crashed and is on IV with extremely high bloodwork values:

1. the cat's numbers improve on IV and the cat looks and acts better, and continues to do well at home;

2. the cat's numbers do not improve on IV (in some cases they may even get worse), but the cat nevertheless acts better, and the numbers gradually reduce at home (usually with sub-Q therapy);

3. the cat's numbers do not improve on IV (in some cases they may even get worse) or with sub-Qs, but the cat acts better and continues to do well at home despite the high numbers;

4. the cat's numbers do not improve on IV, and the cat continues to act ill once s/he is home, and is put to sleep;

5. the cat's numbers do or do not improve on IV, but the cat crashes again once at home. 

Obviously I cannot predict to which category your cat might belong, but it is usually worth trying treatments, particularly if your cat has a kidney infection, where the numbers may improve once the infection is under control.

I am growing increasingly concerned recently at the number of vets who offer just one day on IV, tell the person their cat's numbers have not improved after that short stint, and recommend euthanasia. In most cases this is inappropriate in my opinion. Yes, not every CRF cat can be saved; but euthanasia is an irrevocable decision so you need to be very sure, and for most people that means giving their cat every chance.

For a severely ill cat, one or two days on IV are simply not going to be long enough. Thomas was on IV for four solid days and nights, and only began to eat a little on day 3. Also, Thomas's numbers did not improve at all on IV fluids. He had urea of 89 (BUN: 241) at diagnosis, and it was the same after four days and nights of IV. Some cats will actually have numbers which worsen while on IV fluids. Try not to panic! Your cat did not get this sick overnight, and s/he won't necessarily get better in only 2-3 days. In Thomas's case, my vet suspected he would fall into category 5, but in fact he was in the second category. He was acting a little better by the end of the four days on IV fluids, and with home treatments over a few weeks we eventually reduced his numbers to urea 27 (BUN: 76) and creatinine 316 (US: 3.57), where they stabilised for some months. 

So even if you are dealing with category 4, I would recommend that you make sure that your cat is given a reasonable stint on IV, and is given a reasonable chance of success at home. Being at the vet's is very stressful for most cats, and they often need a few days at home convalescing before they begin to act better.

If Bloodwork Worsens After a Period of Stability

If we take the analogy of a CRF cat falling over a precipice, what seems to happen to quite a few CRF cats is that the cat's bloodwork deteriorates in stages, like moving one step closer to the edge of the precipice; but the cat may remain stable at each step for some time. Thomas, for example, was in Stage 2 (see above) with a creatinine level of 318 (US: 3.57), nearly double what it should be, for six months; and he then moved a step closer, but managed a couple of months with creatinine of 627 (USA: over 7) and had a very good quality of life during this period. Other cats may not show such extreme changes, with gradual falls that may be a year or more apart.

If your cat already has high numbers, and these worsen, try not to be too discouraged. Creatinine is not a linear measurement, so a worsening of creatinine that is already relatively high is not as sinister as it might first appear. The What Do All Those Test Results Mean? page explains more about this.

So if your cat's bloodwork has suddenly worsened, don't give up hope - if you review your treatment programme and add new treatments as appropriate (including a period on IV if the bloodwork values are high and your vet agrees) and work closely with your vet, you may well find your cat stabilises once again, albeit at the higher bloodwork values. If your cat's phosphorus levels worsen, it is particularly important to get these under control, because high phosphorus levels may make the CRF progress faster and also make many cats feel bad.

If Bloodwork Worsens Suddenly

Please do not panic if your cat's bloodwork worsens suddenly. Whilst this may indicate that the CRF is progressing, there are a number of other possible causes. Infections, particularly kidney infections, may cause a spike in bloodwork, as may kidney stones. An ultrasound can help determine if these issues are present.

Many cats with uncontrolled hypertension may have worsening bloodwork, which may improve once the hypertension is brought under control.

If your cat's phosphorus levels are high, it is particularly important to get these under control, because high phosphorus levels may make the CRF progress faster and also make many cats feel bad.

If A Cat with Low Bloodwork Values Acts Sick

I would expect a cat with low bloodwork values (creatinine below 3.5, Stages 1, 2 and the lower part of Stage 3 of the IRIS classification system) not to appear too sick. These cats may have the occasional bout of vomiting or diarrhoea, and may sometimes not want to eat, but overall they should be doing quite well as long as they are not dehydrated and are eating enough.

Therefore if your low numbers cat is consistently off colour (lethargic and exhibiting general malaise) even after treatment for obvious problems, I would ask your vet about other possible causes. Many cats with hypertension feel off colour, but improve greatly once their blood pressure is back to normal. My Ollie had low kidney values (creatinine of 2.8) but had fairly regular diarrhoea. It turned out this was caused by hyperthyroidism and it disappeared once the hyperthyroidism was under control.

Some CRF cats who persistently exhibit general malaise despite treatment for obvious problems may have some kind of gastro-intestinal problem, such as inflammatory bowel disease (IBD), pancreatitis or cancer (lymphoma). It would probably be worth considering an abdominal ultrasound in order to rule out such problems. 

Treat the Cat, Not the Numbers

In Prolonging the life of the renal failure patient (2000), Waltham Focus 10 (3), Dr Jonathan Elliott states that "in a retrospective study, the correlation between plasma creatinine and survival in cats who presented with signs of stable CRF was very poor, with only 5% of the variation in survival time being predicted by the initial plasma creatinine concentration". So the bloodwork matters, but it is not the whole story.

This leads us to the mantra of the Feline CRF Information list: "treat the cat, not the numbers". Of course, it is still important to do what you can to improve the bloodwork and to treat whatever issues arise, because this will both make your cat more comfortable and increase his/her chances of survival. This mantra is simply a way of pointing out that many cats do astonishingly well despite their bloodwork results being poor. There are no guarantees and it is a fine line to tread, but it is usually worth trying treatments, although you must also consider your cat's temperament when deciding how much to fight the CRF.

Some vets consider levels in Stage 2 of Dr Brown's range above to indicate high numbers and therefore to carry a very poor prognosis; but on the Feline CRF Information list, these are actually considered to be "medium numbers", and in fact many list cats have lived three or four years or longer with Stage 2 levels. Cats with numbers in this range should really be considered as having renal insufficiency rather than kidney failure.

Dr Katherine James has mentioned that most people seem to opt for euthanasia when creatinine remains consistently in the 660-900 (US: 7.5-10) range, and the cat is doing badly. However, this is just a rough guide; cats in Stage 3, with very high numbers despite IV therapy and rehydration, may sometimes respond very well to treatment and enjoy several months of quality life, particularly if their numbers have worsened gradually over time, giving their bodies time to adjust to the reduced levels of kidney function. Even if a cat is in crisis at diagnosis, there may still be hope: Vet Info mentions a cat they treated who lived for eight years with CRF despite initially presenting in crisis (click on Kidney Failure - Daily Fluid Treatment). The Success Stories page tells the stories of some CRF cats who have managed to lead happy and in many cases, lengthy, lives at various stages of the disease, including one cat, Paris, who survived for over sixteen years.

End Stage Renal Disease (ESRD)

This expression literally means that the cat's kidneys are at the point of failure and there is no longer anything that can be done. Some vets use it in this sense, referring to a cat who is rapidly becoming unable to deal with the CRF, ceasing to respond to treatments and likely to die very soon. However, other vets use it to mean any cat with numbers in the range of Stage 2 or 3 (see above), which does not necessarily mean that death is a couple of days away - some cats can manage very well in end stage for some time.

Try to clarify what your vet means by ESRD, and if he/she merely means that your cat has high numbers, consider treating the cat; the numbers may come down with treatment, and even if they don't, your cat might be able to handle high numbers as Thomas did. Even if your vet thinks death is imminent, it may be worth treating your cat regardless to see how he or she responds; cats are real fighters and can often pull through. Obviously though, you don't want your cat to be in pain when it is a hopeless situation. It is not always easy to tell when a CRF cat has come to the end of the road - The Final Hours contains details of the symptoms you are likely to see towards the end, and making the painful decision to let go is discussed in Saying Goodbye.