Feline Chronic Renal Insufficiency (kidney failure) (CRI)

The function of the kidneys is to filter the blood, removing harmful waste products from the blood whilst retaining water, protein and electrolytes. The kidneys also have a secondary function of helping to control blood pressure.4336912 low

We may become suspicious of kidney failure if an older cat starts to drink and or urinate more than usual, is loosing weight or has elevated blood pressure.


There are many causes of kidney failure including loss of functional kidney tissue with age, polycystic kidney disease, (which can be inherited in some breeds of cat), progression from acute renal failure and infection.

Acute renal failure is almost always caused by exposure to toxins that affect the kidneys, sometimes even with rapid treatment the kidneys do not recover and the damage results in chronic renal insufficiency.


The diagnosis of kidney failure is made by a combined investigation of blood and urine. In general cats tolerate the process of collecting blood very well and no sedation is required.

The blood test will show an elevation of urea and creatinine - two bi-products of metabolism that are normally excreted by the kidneys. The urine will be dilute as the kidneys have lost the ability to concentrate urine normally.

It is important to run a full blood profile (including thyroid hormone levels) to help rule out concurrent illness, as these may affect our diagnosis and treatment.

It may be necessary to repeat the blood test during treatment, in particular the urea and creatinine levels to help us to monitor the course of the disease.


1. Diet

Dietary management is an extremely important aspect of managing cats with kidney failure.

There are several excellent prescription diets available in both wet and dry forms. These diets contain smaller amounts of high quality protein and less phosphorus than normal cat food. The body is able to use this high quality protein very efficiently hence reducing the amounts of waste products from protein digestion that the kidneys need to excrete. Kidney failure also causes a buildup of phosphorus in the blood which in turn hastens the progression of the kidney disease. These diets work best if fed exclusively.

There have been some good studies to show that cats on these diets not only live longer but are happier than cats with kidney failure eating normal cat food. This is thought to be because it is the build up of these waste products in the blood that leads to cats with CRI feeling nauseous and lethargic.

Cats are creatures of habit and sometimes need some time of gradual introduction to get used to their new food but it is well worth the effort. Liver sprinkles, or mixing the new food with their very favourite food are sometimes a good way to help in this process.

2. Blood Pressure

A high proportion of cats with kidney failure will either have or develop high blood pressure. We routinely measure the blood pressure of our older feline patients to monitor for this. Measuring blood pressure is not invasive or painful we use similar equipment to that used to measure human blood pressure.

It is important to treat high blood pressure as it can lead to severe damage to the heart, eyes, brain, kidneys and blood vessels.

The medication used to treat high blood pressure is generally given once daily in tablet form. These tablets are tiny and are usually easily administered in food. It may be necessary to measure the blood pressure every 3mths in these cats.

3. Protein Loss Through Urine

Sometimes the damage can cause the kidneys to leak protein. This can be identified by a specific test run at our 4425482_lowpathology laboratory called a urine protein: creatinine ratio. The urine used to run this test is collected by cystocentesis. This involves carefully placing a needle into the bladder through the abdominal wall. This is a relatively quick and painless procedure carries a very small risk of infection or urine leakage.

If the kidneys are leaking protein then it is appropriate to treat with a medication to try to change the way blood flows in the kidney, to help slow the progression of the kidney disease, help your cat feel better for longer and slow the protein loss from the body.. This medication is given in tablet form once daily.

4. Urinary Tract Infection

Some cats with kidney failure will develop a subclinical urinary tract infection, as bacteria grow better in dilute urine than when it is very concentrated. A urinary tract infection may cause increased frequency of urination and discomfort during the passing of urine. However some urinary tract infections, especially kidney infections, may not produce any clinical signs.

An untreated infection may worsen the kidney failure and will lead to your cat feeling discomfort and perhaps ill.

We can use the urine sample collected by cystocentisis to obtain a culture of any bacteria present in the urine.

A course of antibiotics should clear this infection. A second urine sample should be collected to confirm the infection has cleared.

5. Potassium Loss Through Urine

3878453 lowAs the kidneys loose the ability to function normally they may leak excess potassium into the urine. Normal potassium levels within the body are essential for normal muscle function and even when levels are slightly low affected cats can have muscle soreness. This can cause cats to become grumpy.

A combined blood and urine test called the fractional excretion of potassium can be used to determine this.

Low potassium levels are readily treated with potassium supplement. Potassium supplement must only be given if testing indicates this is required. A repeat blood test is required to confirm that the right dose of potassium is being given.


Whilst it is distressing to have your cat diagnosed with kidney failure, with appropriate treatment and ongoing monitoring and management, the prognosis has improved greatly over the last few years.

We believe that we should do our best to make sure that we are not only ensuring that your cat's physical wellbeing is optimised but that they are happy. If at any stage you feel any procedures or medications are causing your cat distress, please talk to us about your concerns.

In cases where medication is required if tablets are difficult to administer we can arrange for compounding pharmacists to make these medications into tasty treats or paste.

None of these treatments provide a cure but when used appropriately your cat will feel better and almost certainly live longer.