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.
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.
A large number of different disease processes can eventually lead to CRF including:-
CRF is, therefore, the end-stage of a number of different disease processes rather than a specific condition in its own right.
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.
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.
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.
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:
It is important that fresh water is available at all times, as cats with renal failure tend to dehydrate rapidly.
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.
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.