Chronic Renal Failure In Cats

What do my cat’s kidneys do?

Kidneys have many functions, they principally act to remove nitrogenous waste products from the bloodstream, maintain essential nutrients e.g. potassium at the correct level, maintain hydration and produce urine.

What is chronic renal failure?

The kidneys have a large amount of spare capacity to perform their various functions so at least 70% of the kidneys need to be dysfunctional before clinical signs are seen. In many cases, this means that the damage to the kidneys has been occurring over a number of months or years (chronic) before failure is evident. As chronic renal failure (CRF) is most commonly seen in old cats, early signs of disease such as weight loss and poor coat quality are often put down to normal ageing. In the initial stages of the disease the kidneys cope with their inability to concentrate waste products by excreting them at a lower concentration over a larger volume (compensated renal failure), at some point this is no longer possible resulting in a relatively rapid rise in waste products in the bloodstream and an apparent sudden onset of severe disease.

What are the causes of CRF?

A large number of different disease processes can eventually lead to CRF including:-

1. Congenital malformations of the kidneys – e.g. polycystic kidneys in long-haired cats.
2. Bacterial infections (pyelonephritis).
3. Glomerulonephritis – damage to the filtration membrane.
4. Neoplasia – various tumours of the kidney are seen, most commonly lymphosarcoma.
5. Amyloidosis – this is the build-up of unusual material in the kidney which prevents the kidney from functioning normally.
6. Viral infections e.g. feline immunodeficiency virus or feline infectious peritonitis virus.

CRF is, therefore, the end-stage of a number of different disease processes rather than a specific condition in its own right.

How is the disease diagnosed?

Renal failure is usually diagnosed by looking at the level of two waste products in the bloodstream, blood urea and creatinine. Tests to measure the blood levels of other substances e.g. potassium, phosphorus and calcium, as well as the red and white blood cell counts, can also be important in order to determine the best course of treatment.

Could the renal failure have been diagnosed earlier?

Unfortunately, this is very difficult as neither clinical signs of renal failure nor rises in BUN and creatinine are evident until significant loss of kidney function has occurred. In earlier stages of the disease there are no clinical signs to indicate that sophisticated renal function tests, which can pick up early renal damage, are required.

How does CRF affect my cat?

Because the kidneys perform a variety of different functions, the clinical signs of renal failure can be somewhat variable. The most common changes seen are weight loss, poor hair quality, halitosis (bad breath), a variable appetite which may be associated with mouth ulcers, lethargy and depression. Less commonly cats are seen to drink and urinate more and some will have vomiting and diarrhoea. Rarely renal failure is seen as sudden onset blindness.

What treatments are available?

Depending on the result of blood tests your veterinary surgeon may be faced with several problems which require different treatments.  Don’t worry if the list below seems so long that you will never be able to administer all the medication.  The majority of cats can be effectively managed with diet change including supplementation of one or two other treatments:

1. Lowering the level of waste products in the bloodstream can be achieved by low protein and low phosphorus diets.  These are readily available from your veterinary practice. The palatability of reduced protein diets is usually not as high as normal cat food, so you may have to persevere for a while before your cat will eat it.
2. Phosphate binders – despite low phosphate in the diet, blood phosphate levels remain above normal in some cats.  Reducing blood phosphorus can have a major effect on improving your cat’s wellbeing and slowing disease progression.  Phosphate binders eg. Ipakitine is given by mouth to further lower the amount of phosphorus absorbed through the gut wall.
3. Fortekor- this is a drug that reduces protein loss in urine and lowers the systemic blood pressure and the blood pressure within the kidneys to be able to maintain as much of the kidney function as possible.  It increases your cat’s quality of life.  Some cats might have quite high blood pressure and other drugs can be used to lower that pressure.
4. Laurabolin – regular administration of an anabolic steroid improves wellbeing.  It has no influence on the kidney function, but it maintains the body condition, maintains weight and increases appetite. It can be given by monthly injection.
5. Chronic renal failure almost always leads to decreased appetite and weight loss.  Appetite stimulants may be helpful.  The increased levels of toxins can lead to nausea.  They can either act directly on the brain, causing vomiting or they act on the wall of the stomach or gut, causing ulcers.  There are drugs available that can help to stop the vomiting and/or improve the ulcers.
6. Fluids-since cats with kidney failure have a lot of circulating toxins that make them feel sick, the aim is to reduce them.  Some cats may need intravenous fluids or fluids under their skin to make them feel better

It is important that fresh water is available at all times, as cats with renal failure tend to dehydrate rapidly.

What is the cost of treatment?

Treatment costs will vary somewhat with each individual case. In the majority of cases, long term management is unlikely to cost more than a few dollars a week.

How long can I expect my cat to live?

Unfortunately, once damaged the kidneys have a very limited ability to recover but the progress of the disease may be very slow so, with treatment, your cat may have several years of good quality, active life ahead.