What is chronic renal failure?

Each kidney has tiny filtering units called nephrons. Blood passes through the kidney & is filtered by the nephrons. They reabsorb what is needed & the waste is excreted in the urine.  The wastes come from the normal breakdown of active muscle from the food the cat eats. The body uses the food for energy & self repair. After the body has taken what it needs from the food, waste is sent to the blood & transported to the kidneys. The kidneys are an amazing organ & even with the loss of some nephrons, the remaining ones can compensate. Kidney disease becomes apparent when 70% of the kidney function has been lost. Once this happens, the kidneys are unable to remove the waste from the body & therefore these wastes build up in the cat causing poisoning.

It also causes other problems such as anaemia, high blood pressure, and bone disease in the body by impairing hormone production by the kidneys.

CRF is the progressive deterioration of the kidneys, which happens over a period of time.

CRF is one of the leading causes of death in senior cats.

What do kidneys do?

Kidneys help control blood pressure by releasing an enzyme called renin. When blood pressure drops and kidneys don’t receive enough blood, renin is released; causing blood vessels to contract (tighten). When blood vessels contract, blood pressure goes up. Acute kidney disease is a sudden decline in kidney function.

Kidneys filter waste products & excess water from the blood. The cleaned blood stays in the body & the waste products leave the body in urine.

Stimulation of red blood cell production.

They help maintain the proper balance of acid and minerals, including sodium, calcium, potassium and magnesium, in the blood.

What causes chronic renal failure?

• There are many possible causes of CRF including;
• Infections
• Hereditary or congenital abnormalities
• Kidney tumours
• Infectious diseases, especially FIP & FeLV
• Prolonged exposure to toxins
• Nephritis & nephrosis
• Polycystic kidney disease

Sometimes a cause isn't able to be determined.

What are the symptoms of chronic renal failure?

Over time, the more damage to the kidneys the more they lose their ability to filter efficiently. The kidneys are no longer able to conserve water & concentrate urine, therefore more urine is produced & the cat drinks more to make up for this extra urine output. Some symptoms include;

• Increased thirst
• Increased urination
• Urinating outside the litter tray
• Decreased appetite
• Loss of weight
• Poor coat
• Lethargy
• Vomiting
• Bad breath
• Anemia

How is chronic renal failure diagnosed in cats?

Your veterinarian will perform a thorough physical examination & take a medical history of your cat. Some tests he/she may run include;

• Complete blood count
• Biochemical profile will be taken for testing. Elevated blood urea nitrogen (BUN) and creatinine are both indicative of renal failure.
• Urinalysis will be able to provide additional information on the extent of kidney damage, urine-concentrating ability & if an infection is present in the urinary tract.
• Urine specific gravity: This test is to check to see how concentrated the urine is.
• Kidney ultrasound or X-ray
• Kidney biopsy

How is chronic renal failure in cats treated?

Most cases of CRF are irreversible & treatment is based on managing the condition With proper treatment, your cat may still have many months or years of life ahead. Reducing the level of toxins in the cat is important. Fresh drinking water, available 24/7 is extremely important as these cats need to compensate for large urine outputs.

Treatment may include:

• Fluids: Administration of fluids subcutaneously to treat dehydration & electrolyte imbalances.
• Prescription diet: Such a prescription diet contains a lower percentage of protein and less phosphorus than normal cat food. Cats need protein every day for growth, building muscles and repairing tissue. After the body uses the protein in the foods, a waste product called urea is made. Cats with kidney failure are not able to get rid of this urea normally. Damaged kidneys may not be able to remove phosphorus from the blood. This causes the level of phosphorus in the blood to become too high. A high blood phosphorus level may cause the cat to lose calcium from their bones.
• Phosphorus binders: Phosphate is an abundant mineral in the body. Together, calcium & phosphate work closely to  build & repair bones & teeth. Around 85% of phosphate is found in the bones, the remaining 15% is stored in the cells where it is responsible for energy metabolism as well as being an integral structural component of DNA & RNA. Excess phosphate is filtered by the kidneys & excreted in the urine.  As the kidneys begin to fail, they are less able to get rid of excess phosphate, and levels begin to build up. A high blood phosphorus level may cause the cat to lose calcium from their bones. Your veterinarian may recommend phosphate binders in conjunction with a phosphate restricted diet to slow the progression of kidney failure.
• High blood pressure (hypertension):  Medication which helps reduce blood pressure, these are usually calcium channel blockers, beta blockers, ACE inhibitors & diuretics.  The calcium channel blocker amlodipine is most often prescribed. Medications won't cure high blood pressure, but will assist in controlling it.
• Antacids & anti nausea medication.
• Erythropoeitine: The kidneys produce a hormone, erythropoietin, which instructs the bone marrow to produce red blood cells. Cats with kidney failure often have a low red blood cell count. Only the human form is available & some cats may eventually recognise this substance as foreign & antibodies will be created against it. 
  

Further resources:

Feline CRF Information Centre: This is an excellent & much more in depth site for more information on CRF.