Kidney Disease in Cats

What is kidney disease?

Kidney disease is a common disorder in cats which can be congenital or acquired. When kidneys malfunction, wastes build up in the blood.

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. When nephrons die the remaining ones have to work harder to maintain function. Kidney disease becomes apparent when 70% of the kidney function has been lost.

As cats age, their chances of developing chronic kidney disease increase.

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.

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 kidney disease in cats?

There are many causes of kidney disease in cats. Because the kidneys filter the blood, other diseases & infections can damage the kidneys. You will notice that some causes are seen in both acute & chronic kidney failure.

Acute Kidney Failure (Acute Renal Failure or ARF):

Acute kidney failure is brought about by a sudden decline in kidney function.

• Poisoning (ingestion of a toxic substance such as anti-freeze or poisonous plants)

• Heatstroke

• Blockage

• Infection

• Some medications

• Dehydration

• Cancer

Chronic Renal Failure:

Slow & progressive.

• Diabetes

• Infection

• Hypertension

• Dental disease

• Polycystic kidney disease

• Infections

• Congenital defects

• Cancer of the kidneys

What are the symptoms of kidney disease in cats?

• Weight loss

• Depression

• Vomiting

• Polyuria (excessive urination)

• Polydipsia (excessive thirst)

• Lethargy

• Enlarged kidneys

• Bad breath

• Weakness

• Loss of coordination

How is kidney disease in cats diagnosed?

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. 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 kidney disease in cats treated?

• 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. 

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