Chronic Renal Failure


Chronic renal failure (CRF), also known as chronic kidney disease, is one of the most common conditions affecting older cats. It has been estimated that around one in five cats over 15 years old has renal failure. CRF is a progressive condition without a cure, therefore early diagnosis and supportive treatment are required to slow the progression and improve your cat’s quality of life.

CRF kidney

Causes of CRF:

CRF occurs where there is long-standing, irreversible damage to the kidneys which impairs their function. Some of the known causes include:

  • Polycystic kidney disease (an inherited condition mainly seen in Persian and Exotic cats)
  • Kidney tumours e.g. lymphoma
  • Infections e.g. pyelonephritis which is a type of bacterial infection
  • Other causes include damage to the kidneys  by toxins, birth defects, persistent  inflammation (glomerulonephritis).

If an underlying cause can be found and if this is treatable, the progression of the CRF may be halted. In most cases however a specific cause is not found and treatment is aimed at management of the disease.

Function of the kidneys:

The kidneys have a variety of functions including removing toxins from the blood and maintaining water and salt balance in the body. Blood is continually filtered through both kidneys removing the toxic waste products and urine is produced in the process. The kidneys also concentrate urine by reabsorbing water into the body, preventing dehydration.

Other important functions include maintaining the balance of important electrolytes (such as potassium, sodium, calcium and phosphate), regulating the acidity of blood and controlling blood pressure. The kidneys also release a hormone that stimulates red blood cell production by the bone marrow. 

The kidneys have a large ‘reserve capacity’ and about 70% of the functioning tissue must be lost before any signs of renal failure will develop.

cat drinking

Clinical signs of CRF:

  • Poor appetite
  • Weight loss
  • Dehydration
  • Lethargy and depression
  • Increased thirst
  • Increased urine production
  • Poor coat
  • Bad smelling breath
  • Ulceration in the mouth
  • Weakness

The signs may be mild or vague initially but with time the clinical signs tend to worsen. High blood pressure and anaemia are some of the other conditions that develop as a consequence of kidney failure.


Diagnosis is usually made following analysis of a blood and urine sample. The two main substances measured in the blood are urea and creatinine which are normally excreted by the kidneys. These substances increase in the blood when the kidneys are not functioning properly. The urine is usually poorly concentrated (normally less than 1.030 on a concentration scale).

blood sample


Treat any underlying cause if one can be found. Many cats will require initial intravenous fluids therapy to correct dehydration and flush out the toxins building up in the blood. Once stable, treatment is aimed at supporting renal function and minimising complications. Unfortunately CRF cannot be reversed and will progress over time despite appropriate therapy.


Diet and Fluids:

  • Water intake – CRF cats are dehydrated and need plenty of fluids to combat this. Cats generally gain most of their water through their food and should therefore be fed tinned/sachet foods rather than dry. Fresh water should be available in different places throughout the house. Some cats prefer to drink running water and small water fountains have now been produced for this purpose. Other cats may need flavoured water (small amount of tuna water added etc.) to encourage drinking.
  • Protein content - An ideal diet for cats with CRF should have low protein content since the toxic products which build up in the blood are formed from breakdown of proteins. Specially designed ‘renal diets’ are now available. Unfortunately low protein diets tend to be less palatable for cats therefore the new diet must be introduced very slowly (over 10-14 days). However, if a cat refuses to eat the renal diet it is better they eat their normal diet than eat too little
  • Low phosphate content – Restricting phosphate is beneficial in protecting the kidneys from further damage. Commercial diets are also phosphate restricted. If a cat is not on a renal diet, ‘phosphate binders’ can be added to the diet to reduce the amount of phosphate absorbed.
  • Potassium supplementation – some cats with CRF have low potassium and may require supplementation in the form of tablets, gel or powder.


High blood pressure – (hypertension) is common in CRF cats and can lead to other problems related to bleeding. This can be treated with medication.

Treatment of anaemia, nausea and vomiting may also be required intermittently to improve
your cat’s quality of life.

Use of ‘ACE inhibitors’ – these are a class of drugs which dilate the blood vessels and are commonly used to help manage renal failure. They appear to help maintain renal function and reduce protein loss through the kidneys.


Unfortunately the disease is usually progressive and will eventually lead to the need for euthanasia. The rate of progression however varies hugely between individuals and appropriate support and treatment can improve the quality of life and slow the progression of the disease.

If you think that your cat is showing any of these symptoms, contact the surgery now to book an appointment to get them checked out.

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