Kidney problems in cats

What does kidney failure in cats mean?

Kidney problems, also known as kidney failure, are unfortunately very common in cats. Especially in older cats we see (chronic) kidney problems very often. If your cat has kidney failure, it means that the kidneys can no longer do their job properly. The kidneys are vital organs, and therefore very important for the proper functioning of your cat. In kidney failure, the kidneys swell and are painful.

What do the kidneys do?

The kidneys play a very important role in the body. First, they filter the blood, which allows toxic waste to leave the body through urine and important substances (such as salts) to be present in the blood in the right amounts. In addition, they regulate the fluid balance in the body. They indicate how much a cat should drink and urinate.

Fortunately, kidneys have a large reserve capacity. Only when 70% of kidney function is lost, the kidneys no longer function properly and increased kidney values will show in the blood. A healthy cat could lose one kidney without becoming ill.

What causes kidney problems?

There are two types of renal failure: chronic and acute renal failure.

Chronic renal failure means that the kidneys have been working poorly for a long time (longer than 2-3 months). Often, chronic inflammation in the kidneys has led to the formation of scar tissue. This scar tissue contracts and causes the kidneys to become smaller. This is also called “shrunken kidneys”.

In acute renal failure, a large part of the kidney function is lost in a very short time. There are several possible causes for this.

• poisonings: lilies, antifreezes, heavy metals, certain medications
• bacterial infections of the renal pelvis
• infections with viruses
• cancer/tumors (including lymphoma)
• high blood pressure
• trauma
• immune-mediated disorders
• congenital/hereditary disorders (e.g. PKD (polycystic kidney disease) in Persians and amyloidosis in Abyssinians)

Unfortunately, sometimes it is not possible to determine the exact cause.

What are the symptoms of a kidney problem?

The most common symptoms cats with kidney failure have are:

• eating poorly, feeling nauseous and vomiting
• drinking and urinating a lot (especially in chronic renal failure)
• lethargic
• sleeping a lot
• weight loss (especially in chronic renal failure)
• poor, plucky fur

Cats with acute renal failure have become ill in a short period of time, and were perfectly healthy not so long ago. They often do not look ill at all. Cats with renal failure that has been going on for a long time have been losing weight for a long time and often have a plucky coat. It is also possible that cats with acute renal failure suddenly stop urinating.

How do we diagnose kidney problems?

The diagnosis of kidney problems can be made by a blood test, urine test, ultrasound/X-ray and/or blood pressure measurement.

Blood test

With the blood test we look at creatinine and urea. If the creatinine is above the normal value we know that 75% of the kidney function has already been lost. The phosphate and salts in the blood are also important. Sometimes we see anemia in cats that have had kidney failure for a longer period of time. A new blood test has recently been introduced on the market, this test can determine the level of SDMA in the blood. SDMA can already rise in the blood if 25-40% of the kidney function has been lost. So we can detect kidney failure much earlier! However, the creatinine can also rise in the blood if there is no kidney failure. The SDMA only rises if there is reduced kidney function.

Urine test

A urine test can tell us if your cat drinks a lot and pees a lot, because then its urine is poorly concentrated. We also look for blood and proteins (protein/creatinine ratio) in the urine.

Echo/X-ray

With the help of an ultrasound examination we can visualize the kidneys. In this way we can sometimes determine a cause of the kidney failure.

Blood pressure measurement

We often see high blood pressure in cats with kidney failure. This high blood pressure can also cause damage to other organs in the body (eyes, brain) in the long term.

How does kidney failure develop?

There are three categories of renal failure that we distinguish:

• Pre-renal renal failure: the kidneys do not receive sufficient blood supply; this can be seen, for example, in dehydration and heart failure
• Renal failure: the kidneys themselves have been damaged, either chronically or acutely
• Post-renal renal failure: this is when urine drainage has stopped, usually in tomcats due to bladder grit or a stone in the ureter between the kidneys and the bladder

What is the severity of the damage?

In acute renal failure, kidney values can be very high, but full recovery can occur! The height of the kidney values in this case says nothing about the prognosis.

In chronic renal failure, the values do provide an indication of a prognosis. Cats with chronic renal failure are now divided into IRIS stages. These IRIS stages (1-4) have been established internationally. In addition to the kidney values, blood pressure and the amount of protein in the urine also play a role in the classification into the different stages. The lower the stage, the better the prognosis.

The average life expectancy associated with the different IRIS stages are:

• IRIS 1 – no azotemia, normal creatinine: no shortened lifespan

• IRIS 2 – mild azotemia, slightly elevated creatinine: 3 years

• IRIS 3 – moderate azotemia, elevated creatinine: 2 years

• IRIS 4 – severe azotemia, very high creatinine: 1 month

What is the treatment for kidney failure?

The goal of treatment is to ensure that your cat has as few symptoms as possible. This means that your cat will probably receive an IV and medication for the nausea. It is also important to treat the cause if necessary. Main resources are:

• renal diet (Hill’s k/d, Royal Canin renal)
• fluid infusion (into a blood vessel or under the skin; may also be given at home)
• anti-nausea medication (eg cerenia)
• stomach protector (e.g. ranitidine)
• appetite stimulant (mirtazipine)
• pain relief in lesions of the oral mucosa
• ACE inhibitor (reduces protein excretion via the kidneys)
• telmisartan (Semintra®) (also reduces protein excretion via the kidneys, but also has an appetite-stimulating effect)
• phosphate binder (e.g. Renalzin/Ipakitine, captures antioxidants as well as phosphate)
• potassium supplement (e.g. tumil K)
• antibiotic if bacteria are found in the urine

Treatment plan based on IRIS classification

Based on multiple factors (kidney values, protein loss in the urine, phosphate levels in the blood and blood pressure), kidney patients are classified into different stages. These stages have been drawn up by the IRIS , an international organization that deals with kidney problems in dogs and cats.

If you have any questions, please feel free to contact us!