Kidney Problems in Cats: Causes and Treatments

Cats’ kidneys play several important roles in keeping your pet healthy including removing toxins, maintaining their blood pressure and helping to produce hormones for new red blood cells.

With so much to do, it’s perhaps not surprising that as cats get older, it’s quite common for their kidneys to wear out after working so hard. There are a number of causes for kidney failure, from cat kidney diseases to tumors, and these problems can be acute or chronic.

Acute Kidney Failure in Cats

If your cat has acute kidney failure, it means that their kidneys are suddenly unable to function properly – this can be due to causes such as infection, or because your cat’s eaten something dangerous to them, such as antifreeze. Acute kidney damage in cats can either be permanent or reversible, depending on what the cause is.

Chronic Kidney Failure in Cats

Chronic kidney failure in cats is more gradual and usually develops over several months or even years. There are a number of reasons for chronic kidney failure in cats including infections and tumors, and unfortunately by the time it’s diagnosed, the kidney damage is sometimes irreversible.

In the early stages of kidney disease in cats, the healthy areas of the kidney compensate for any damage by increasing their already busy workload. However, as the disease progresses, the healthy areas start to shrink and eventually there simply aren’t enough remaining healthy areas for the kidneys to be able to perform as they should. By this stage your cat will be showing signs of kidney failure (see below for more information).

Chronic kidney failure in cats is a progressive illness that your vet will need to keep an eye on, but it can usually be managed with a combination of medical treatments and a special diet.

Signs of Kidney Disease in Cats

Large Amounts of Very Dilute Urine and Increased Thirst

As your cat's kidneys become less able to concentrate their urine, they will urinate more and drink more to replace the lost fluids.

Poor Appetite and Lethargy

Because the toxins that would normally pass in their pee build up in cats with kidney disease, they may feel nauseous and vomit, retch or go off their food. This can also make them seem tired and generally not very happy, and you might notice bad breath.

Do be careful before you diagnose kidney disease, as these same symptoms could also be connected to other illnesses, so see your vet for a proper diagnosis and for advice on treatment of kidney disease.

Cat Kidney Disease Diagnosis by Your Vet

As part of their investigation to see if your cat has kidney disease, your vet may want to test a sample of your cat’s pee. This will show if your cat’s urine is being concentrated, whether protein is being lost in the urine and whether there are any other problems such as underlying infections to take into account. They may also take a blood test to gain a full health profile of your cat and to see if the toxin build-up has had any effect on other organs.

How to Take a Cat Urine Sample

The best time to take a urine sample is first thing in the morning. You’ll need to keep your cat indoors and, as always, provide them with a clean bowl of fresh water. Replace your normal litter with a non-absorbent litter (your vet may be able to supply this) or any other non-absorbent material, like polystyrene packing peanuts. 

Your cat can use their litter tray as normal, and you can then collect their pee either in a sterile container provided by your vet, or a clean jar (any residue can affect the results, so do make sure the container is very clean). The fresher the sample, the more accurate the tests will be, so try not to delay in getting the cat urine sample to your vet.

Treatment of Kidney Failure in Cats

Depending on how severe your cat’s symptoms are, treatment for cats with kidney disease is usually a mix of medical and dietary interventions.

Cat Kidney Medication

There unfortunately is no medication that can cure kidney disease. However, your vet may be able to prescribe medication to help with associated conditions that cats with kidney failure may develop, such as high blood pressure and anemia.

Kidney Diet for Cats

A special diet can reduce signs of kidney failure and slow the progression of the disease. Your vet may suggest a carefully tailored prescription diet that has been formulated to meet your cat’s specific needs. The protein in cat food for kidney disease is highly digestible, so there’s not much waste for the kidneys to flush it out. It also has reduced phosphorous and essential fatty acids that work as natural anti-inflammatories to support your cat’s kidneys.

One of the downsides of a prescription diet is that they’re made to very strict recipes so aren’t as tasty as your cat’s usual food. Even if your cat turns their nose up at first, which is quite likely given their sense of taste is 200,000 times more sensitive than yours, it’s important to persevere for your cat’s sake. They will come around in the end.

When feeding cats with kidney disease, introduce their new diet very gradually, so they can slowly adapt to the blander flavors and different textures. Unless your vet says otherwise, blend the new diet thoroughly into your cat’s original diet.

Then, increase the quantity of the new diet by very small amounts every day while, at the same time, reducing the amount of their original diet. You might find that the quantities differ from your old food to the new cat food, so check the packaging or ask your vet’s advice about portion sizes.

While your cat’s getting used to their new regime, they may prefer smaller meals more regularly rather than one or two larger meals. You’ll need to avoid giving them treats when they’re on their special cat diet, so more regular feeding might help.

You can also try to make their new cat diet more palatable by warming wet food in a microwave (never hot) to release aromas and soften its texture. If your cat's new diet is dry and they’re used to wet food, try soaking it briefly in warm water to soften it slightly.

The changeover process can take anywhere from two to six weeks to complete, but it’s worth all the effort to keep your cat as fit and healthy as possible. Both you and your cat should then be able to enjoy a healthy and happy life together without any worries.

For more tips from Purina experts on cat health, explore our other cat symptoms articles.