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Kidney Disease in Cats


Is your older cat drinking lots and leaving big puddles in the litter box? One possible explanation is kidney disease. As the saying goes: ‘Common things are common,’ and this is certainly true of kidney trouble in cats.

Think of kidney disease as a: Good news, bad news diagnosis.

The good news is in the early stages treatment slows its progression, whilst the bad news is it can’t be cured.

Far from being all doom and gloom, there are ways of supporting ailing kidneys, especially with an early diagnosis. If treatment starts when the problem is mild, it protects the kidney and makes a real difference to your four-legged’s life expectancy. And when the condition is more advanced, you can help your fur-friend by keeping her comfortable and monitoring her quality of life.


Why Do Kidneys Matter?

Kidneys work all day, every day and never take a rest, but often we don’t appreciate their hard work until it’s too late.

Kidneys have many vital roles in the body including:

  • Cleaning natural toxins from the blood
  • Getting rid of waste products in urine
  • Recycling water by reclaiming it from blood
  • Controlling levels of vital electrolytes (salts)
  • Producing hormones that control blood pressure and red blood cell production

Fascinating things, kidneys! We’re born with two, but get along fine with one (which is why we can donate a kidney without ill effects to ourselves). Those clever kidneys are efficient at their job, and we’re born with a spare!

So how does kidney damage happen?

Causes of Kidney Disease

After years of hard work, the kidneys start to wear out. Active nephrons (filtering units) become damaged and are replaced by scar tissue. Over the course of a cat’s lifetime the amount of active working kidney tissue dwindles, leading to symptoms such as thirst, weight loss, and a poor appetite.

Old age degeneration (often referred to as chronic kidney disease or CKD) is common, but damage also happens for other reasons, including:

  • Kidney infections
  • Trauma
  • Congenital problems such as cysts in the kidney
  • Damage by toxins or drugs
  • Kidney inflammation
  • Cancer


What are the Signs of Kidney Disease?

Without the kidneys working at full capacity, carefully controlled salt and water levels start to go cock-eyed. Toxins levels rise and anemia develops. But this doesn’t happen overnight because kidney disease is a slowly progressive disease. The body does it’s best to cope and this is where the symptoms creep in.

For example, a leaky kidney is not great at recycling water and the cat produces dilute urine. The body needs to replace this lost water, so the cat drinks more. Get the idea?

Other signs to be alert for include:

  • Increased thirst: You may spot this indirectly by noticing larger puddles in the litter box
  • Weight loss: The kidney tends to leak protein which is lost in urine, leading to a general loss of body condition.
  • Poor appetite: Levels of naturally occurring toxins rise. These are linked to feelings of nausea which puts the cat off her food.
  • Vomiting: The stomach lining becomes inflamed and the cat struggles to keep food down
  • Lack of energy: The cat sleeps more
  • Poor coat: The fur tends to lose its gleam and luster, as the cat’s grooming habit falters
  • Bad breath: Those toxins make for smelly breath and inflamed gums


There are other effects which may not be obvious to a pet parent, including high blood pressure and anemia.

However, all these signs are quite general so what’s most important is to recognize there’s a problem and get the cat checked by a vet.


How is Kidney Disease Diagnosed?

The vet takes a history and performs a physical exam. This is to rule out certain problems and guide the vet as to the best tests to run. Typically these start with general blood tests, to get the big picture. One complication is that older cats may have more than one problem, so the vet will want to know what’s what before starting therapy.

But kidney disease isn’t an all-or-nothing condition, and ranges from mild to severe. In fact, the vet may well want to run additional tests to work out how far along the line the kidneys are. This may then influence the choice of treatment and how the case is managed.

Your vet may want to run one or all of the following tests:

  • SDMA: This test is the new kid on the block. It’s a super sensitive way of detecting the earliest hint of kidney disease and acts as a warning the cat needs monitoring
  • Screening Blood Tests: These check general organ function, along with red cells and white cells. This important information tells the vet if it’s kidney disease alone or if other problems are present.
  • BUN, Creatinine, Phosphate: Often used as a monitoring test once the problem has been diagnosed.
  • Urine Analysis: Measuring how dilute or concentrated urine is an important measure of kidney function
  • UPC Ratio: This stands for Urine Protein: Creatinine ratio, and is a measure of how much protein leaks through the kidney.
  • Urine Culture: Low grade infection is common but often the cat doesn’t show signs. Culturing the urine lets the vet know if antibiotics would be beneficial
  • Blood Pressure Measurement: A common complication of kidney disease is high blood pressure. This can cause further damage, along with strokes, so monitoring blood pressure is a wise precaution.
  • Ultrasound Scan: If a cystic kidneys or cancer is suspected, imaging helps complete the picture.


The vet puts the piece together like a jigsaw puzzle, to decide what stage the renal disease is at. This allows the vet to suggest the most appropriate treatment for your cat.


Managing Kidney Disease

Chronic kidney disease is controlled rather than cured. This sounds gloomy, but as mentioned earlier, a problem caught early can be well managed and the cat lead a normal life.

The backbone of treatment is diet, so let’s look at this first.

Renal Diets

One of the kidney’s most important jobs is getting rid of toxins from the body. Therefore it makes sense to give an ailing kidney as little work as possible. This is where renal foods come in.

These prescription diets contain reduced levels of high quality protein. In practical terms this means the food is ‘purer’ and once digested, there are less waste products to be excreted in urine. Thus, the kidney has less detoxing to do.

But renal diets don’t stop there. They are also low in minerals, such as phosphate, which are difficult to filter and known to encourage scar tissue. They are rich in antioxidants and essential fatty acids, to reduce inflammation and ongoing damage, plus are rich in potassium (which is lost through leaky kidneys) and B vitamins (to help appetite.)

Switching to a renal diet is the first step, but there are plenty of other therapeutic options to explore.

Phosphate Binders

For the cat that continually refuses to eat a renal diet, adding a phosphate binder to their regular food is beneficial. These supplements cling onto the phosphate in food, keeping it within the gut, rather than letting it pass into the blood stream.

Phosphate binders are simply mixed with each meal to reduce the amount of phosphate reaching the kidney.


Encourage Drinking

Water cleans the blood and flushes out the kidneys, therefore encouraging the cat to drink is a good thing. Strategies include giving wet food, providing lots of water bowls, or even a pet drinking fountain.

In the later stages of kidney disease, your vet may even teach you how to inject saline solution under the cat’s skin, to boost her hydration.


ACE inhibitors

An exciting treatment that is an investment in the long term health of the kidney is drugs called ACE inhibitors. These change the blood pressure gradient across the kidney, to help it work more efficiently.

Not all cats are suitable for ACE inhibitors, so your vet is best placed to make a judgement call on an individual basis.

Managing Blood Pressure

Cats with high blood pressure often benefit from taking medication, such as amlodipine, to bring it back to normal. Again, this call is made on an individual basis, but could help protect the cat against heart muscle damage or even a stroke.

Potassium Supplements

Potassium leaks through the kidney and can leave the cat deficient. Potassium is important for muscular strength, and a deficiency leaves the cat weak or even struggling to hold her head up.

Supplements need to be carefully monitored, as too much can cause heart complications, but your vet can advise you on the dose.

Ant-acids Medications

Kidney cats are prone to stomach ulcers, which are painful and reduce appetite. There are liquid medications available which coat the stomach lining and improve appetite, or an excellent once daily antacid tablet.

Appetite Stimulants

An ailing appetite is sadly all too common as things progress. However, your vet may be able to prescribe medications such as cyproheptadine or mirtazapine to pep up their eating. Injections of B vitamins can also help improve a faltering appetite.


When Things Get Serious

The kidneys work 24/7 and eventually, be it weeks, months or year later, all that work means the cat enters a more worrying stage where her kidneys seriously struggle. This is when her appetite is poor; she can’t keep food down, and becomes dehydrated.

Your vet may suggest intravenous fluids, to flush her body of toxins and give temporary relief. Sadly, how beneficial this is can vary hugely depending on how sick the cat is.

While no-one wants to say a final goodbye, it is vitally important to keep your cat’s best interests as the focus of attention. Be realistic about her quality of life, and keep talking to friends and family about how they perceive her.

Share any concerns with your vet, who can give you the medical perspective on her condition. However, only you know how she is at home, and the weight of the ultimate decision rests on your shoulders. But let’s hope that’s many months and years in the future.

Take heart if your cat is diagnosed with renal disease. Whilst the problem can’t be cured, there are ways of managing the condition which keep those purrs coming!

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