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How to Recognize Kidney Disease in Your Cat

Updated On April 13th, 2016

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Reviewed By Christie Long, DVM

Chronic kidney failure, meaning loss of function of the kidneys that is slowly progressive, is one of the most common diseases of aging that we see in cats. There is no cure for it, but when we recognize the disease earlier, we can make changes in how we take care of the cat that increase its lifespan and quality of life in general.

Read on to discover some ways you can recognize developing problems in your cat’s kidneys at home.

Urinating more

It’s difficult to say what is most commonly the first clinical sign seen – that means a change we can see with our eyes, not just detect on lab testing – when a cat’s kidneys start to fail. Studies tell us that by the time we can detect a change on lab work – which is usually loss of ability to make a concentrated urine – cats have lost 75% of the function in their kidneys.

But probably the most often recognized change in cats at home by owners that suggests loss of kidney capacity is an increase in urination, or “polyuria”. While this can mean more frequent trips to the litter box, more often we’ll notice that the urine clumps in the box are getting larger. So the cat is actually producing larger volumes of urine, but not necessarily “going” more frequently. Polyuria is detected on a urine sample by measuring specific gravity. To the naked eye, the urine actually looks almost like water, because it mostly is water.

This is often counterintuitive to people. Owners will often say things to their vets like, “Well, I know his kidneys are working well, because he urinates A LOT”. Turns out that when the kidneys aren’t functioning as they should be, it takes more water for them to do their job. Which leads to the next most commonly observed sign of chronic kidney failure in cats…

Increased consumption of water

I don’t know how they do it, but sometimes it seems like cats actually never drink any water. So owners tend to notice when they start visiting the water bowl more frequently. Sometimes they’ll even seem to hang out there, like it’s a kind of kitty Cheers or something.

Increased water consumption, or “polydipsia”, occurs in kidney failure secondary to the increased production of urine. Because the kidneys are demanding more water, the brain is driving the cat to drink more to satisfy those requirements.

Dehydration

In the earlier stages of chronic kidney failure, the cat is able to effectively increase its water consumption to the point of satisfying the kidney’s demands. In the later stages, those demands cannot be met by simply drinking more water, and that’s when we see dehydration set in. Visible signs of dehydration include a dull hair coat, sunken eyes, and loss of elasticity in the skin. If you pick up the skin on the back of a normally hydrated cat, it should quickly regain its correct position. The skin of a dehydrated cat will return to position much more slowly, sort of sinking back in. You can also feel the gums with the tip of your finger – they should be nice and moist normally. Dry, sticky gums indicate dehydration.

Bad breath

On blood work we can measure two products called “blood urea nitrogen” and “creatinine”. These are waste products that are created when protein is metabolized, and it’s the kidneys’ job to filter them out of the blood and make urine out of them, so that they can be excreted from the body.

When then kidneys stop effectively filtering these products, a situation called “uremia” sets in. Uremia literally means, “urine in the blood”. Yuck, right? Because of uremia, in advanced cases of renal failure you can actually detect a change in the smell of an animal’s breath. These uremic waste products are high in acidity, and they are especially irritating to the mucous membranes of the mouth, often producing oral ulcers.

Intermittent vomiting

Cats vomit with a number of diseases, and to complicate manners, normal cats vomit up hairballs routinely. But the uremia caused by kidney failure causes gastritis (inflammation of the stomach lining) in the same way that it causes oral ulcers, and the irritation it causes leads to intermittent vomiting.

It’s that same stuff – that “urine in the blood” – that causes a decreased appetite, and ultimately weight loss. People who have kidney failure describe the feeling as one of being perpetually hung over – which doesn’t sound very pleasant.

Litter box mishaps

Cats with chronic renal failure have kidneys that could be compared to raisins. They get smaller and smaller, and become misshapen, the longer the disease progresses. Sometimes we can feel this on physical exam.

This misshapenness seems to predispose them to developing infection in the kidneys – a condition known as pyelonephritis. Sometimes they get very sick from this, and often we’ll see them start to urinate outside the litter box, like they will when they have a bladder infection. Very often, in fact, they have an infection in both places.

Weakness

Cats with kidney disease can become weak for a couple of reasons. They become weak due to anemia, because the kidneys produce the hormone erythropoietin (known as “e-po” in the cycling world and sometimes abused by athletes), which stimulates the bone marrow to produce red blood cells. When the kidneys fail, less erythropoietin is produced, and the cat subsequently becomes anemic. Cats with anemia are in a chronic low-oxygen state, and that makes them weak.

Kidney failure depletes the body of potassium. Muscles need potassium in proper quantities to function. This causes a condition called “hypokalemic myopathy”, and the most common manifestation of this that you can see is a posture that’s often compared to bowing their head to pray. Cats that are low on potassium have difficulty lifting their heads due to weakness, and thus their necks are bowed downwards.

Dilated pupils or blindness

Kidney failure can cause an increase in blood pressure. Left untreated, high blood pressure can cause the retinas, or optic nerves, to detach from their anchor on the back of the eye, leading to blindness. The eye’s response to this is to dilate the pupil fully in order to increase the amount of light that enters. Any cat that appears to be suddenly blind, or has consistently dilated pupils even in bright light (when the pupils should be small) should be checked for high blood pressure and kidney disease.
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