1.  Introduction

Bloodwork

Scott Brown in Evaluation of Chronic Renal Disease: A Staged Approach The Compendium for Continuing Education for Practising Veterinarians, August 1999, suggests that CRF can be divided into three stages, based on the bloodwork. In a more recent paper, Progression of chronic kidney disease: can it be altered by treatment? (2003) Proceedings of the 27th Waltham OSU Symposium, Dr Brown basically uses the same stages, apart from now considering that renal insufficiency is present once creatinine is at 180 (US: 2.0) rather than at 210 (US: 2.4) as he previously stated.  

I have included the 1999 stages below and added my own estimates as to the approximate percentage of kidney function lost at each stage:

*In this instance, kidney problems would be suspected only if an anatomical or functional abnormality had been detected.

Staging and management of feline chronic kidney disease (2007) Grauer GF NAVC Clinician's Brief August 2007 pp19-22, also discusses the stages of CRF.

Proteinuria

The existence of proteinuria may also be a factor. Some vets now check the urine protein:creatinine ratio.

Relation of survival time and urinary protein excretion on cats with renal failure and/or hypertension (2004) Syme HM, found that cats with a urine protein:creatinine ratio below 0.5 survived almost three times as long as cats with a urine protein:creatinine ratio of over 0.5.

Assessment and management of proteinuria in dogs and cats: 2004 ACVIM Forum Consensus Statement (Small Animal) (2004) Lees GE, Brown SA, Elliott J, Grauer GF & Vaden SL Journal of Veterinary Internal Medicine 19 pp377-385 also has information about the severity of proteinuria and its implications for survival times.

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

Glomerular Filtration Rate

Dr Elliott also mentions that the International Renal Insufficiency Society believes that eventually GFR will be the measure by which CRF can be categorised, but it will take some time to determine appropriate reference ranges.

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 it is at this stage. 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.

Is There Any Hope?

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. 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, 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

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:

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

• the cat's numbers do not improve on IV, but the cat nevertheless acts better, and the numbers gradually reduce at home (usually with sub-Q therapy);

• the cat's numbers do not improve on IV or with sub-Qs, but the cat acts better and continues to do well at home despite the high numbers;

• 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;

• 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. Incidentally, even after Thomas began to eat, my vet suspected he would fall into category 5, but in fact he was in the second category. He had urea of 89 (BUN: 241) at diagnosis, and it did not actually improve after four days and nights of IV either. But he was acting better in himself by the end of the four days, 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. 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.

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. 

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.