Understanding Feline Chronic Renal Failure (CRF) in cats
Chronic Renal Failure (CRF) is the term used to describe a long term deterioration of the kidneys. Approximately 200,000 tiny structures (nephrons) in the kidneys eliminate waste products and regulate electrolytes in the body. If these nephrons begin to die off, waste products and electrolytes can no longer be processed effectively. The waste then accumulates in the cat's body, causing the cat to become unwell. Electrolyte imbalances, anaemia and blood pressure problems may also occur as the kidneys continue to deteriorate.
The kidneys have five primary functions:
Filtering waste products from the body (primarily urea and creatinine, which are by-products of protein breakdown).
Regulating electrolytes (potassium, calcium, phosphorus and sodium).
The production of erythropoietin, which helps to stimulate the bone marrow to produce red blood cells.
The production of renin, an enzyme that controls blood pressure.
Production and concentration of urine
Only 30% of kidney capacity is needed for normal functioning, therefore, no symptoms will be seen until approximately 70% of renal function is lost. It is important to begin treatment as soon as the first symptoms appear. Screening tests can help pick up a problem even before symptoms are seen, which is why it is wise to have your vet to check for CRF during each annual exam if your cat is over 7 years old, with a blood test, urinalysis and blood pressure measurement.
Symptoms can be vague and similar to those seen with other illnesses, therefore CRF can only be accurately diagnosed with clinical tests. You should always have your cat seen by a vet and tested if you notice increased thirst (polydipsia) and excessive urination (polyuria). As the disease progresses, other common symptoms include: loss of appetite, nausea and vomiting, weight loss, dehydration, constipation, poor coat condition, anaemia, oral ulcers and bad breath, muscle wasting/emaciation and lethargy.
Your veterinarian will need to perform some clinical tests to accurately diagnose your cat’s condition. Analysis of the urine will be done to determine if the cat's urine is dilute; this indicates that the kidneys are not able to concentrate the urine properly and are not passing waste materials. Blood tests will determine the levels of creatinine and blood urea nitrogen (BUN) (which are normally excreted by the kidneys) as well as other components of the blood. An elevated creatinine level is the most certain sign of loss of kidney function. A blood pressure test may be also be done, as high blood pressure can be a complication of kidney disease
Chronic vs. Acute Renal Failure
Renal failure may be either chronic or acute. Chronic Renal Failure in cats is a progressive, irreversible deterioration of kidney function. Because cats hide their illnesses and the very early signs of CRF are subtle, this disease may only be recognized when the patient reaches the 70% deterioration level and more dramatic symptoms are observable. The seemingly sudden onset may appear to be an acute condition but is most often a crisis point of CRF.
CRF may have one or more causes. The common contributing factors are age, genetics (e.g. inherited conditions such as Polycystic Kidney Disease), environment/toxins, disease (e.g. tumours or infection), and dental disease (due to bacteria entering the bloodstream and ending up in the kidneys). One of these factors that can be controlled is dental disease – it is important to keep an eye on your cat’s dental health and have regular dental cleaning at your veterinary clinic.
By comparison, Acute Renal Failure (ARF) is characterized by an abrupt shutdown of kidney function, most often accompanied by reduced urine production. The primary causes of ARF in cats are: urinary obstructions, infectious diseases, trauma, and the ingestion of toxins - the most common two being ethylene glycol which is contained in antifreeze, and eating lilies. ARF is extremely serious and can quickly become fatal. Immediate veterinary treatment is imperative. Though the prognosis is usually poor, if damage has not been too severe and medical treatment is aggressive, it may be possible for normal kidney function to be restored.
There is no cure for CRF but the condition may be managed for a time. The cornerstone of CRF management is to control the amount of waste products that are sent through the kidneys. Since the remaining nephrons are limited in their ability to process waste, the idea is to reduce the amount of waste to a level that the nephrons can accommodate. This is done through a combination of diet (renal specific foods such as Hills k/d, Royal Canin Renal diet or Eukanuba Renal diet), medication, and hydration therapy (trying to increase fluid intake by using flowing water fountains, adding water to food etc, or IV/subcutaneous fluids). Electrolyte supplements can be given if needed. Dietary additives can be used for general renal support, or to “bind” phosphates, which means that phosphates that would normally be excreted by the kidneys can be excreted by the gastrointestinal system instead.
ACE inhibitors and calcium channel blockers can be used to target and slow the progression of CRF. These medications dilate the blood vessels thereby decreasing blood pressure while facilitating a non-damaging increase in blood flow that doesn't tax the kidneys.
CRF is a terminal disease. The only questions are how long and how well the patient will live until the end. With proper treatment, the cat may have from months to years of relatively high-quality life. As CRF progresses and toxin levels rise, cats become more uncomfortable with an overall sensation of feeling unwell. The owner is usually the best placed to make the final decision for their pet.
This article is intended as a guide only. Always seek advice from your veterinary surgeon prior to changing your cat’s diet or introducing any supplements.