The Truth About Chronic Kidney Disease in Cats

By Sarah Griffiths, DCH

According to Cornell University, in 2025, it’s estimated that 40% of cats over the age of 10 and 80% of cats over the age of 15 years will develop chronic kidney disease. So what’s driving these concerning numbers? Keep reading to find out!

Cats are still defined as a semi-domesticated species. This means that cats can revert to wild living and survive by huntingprey without issue. Despite their cute, playful and fluffy appearance, we love cats because they are predators. Felines large and small have a unique biology that has been largely ignored in the last 100 years. As is true with everything, we need to explore feline health from their point of view: from their ancestry.

CATS ARE OBLIGATE CARNIVORES… AND THEY NEED TO GO OUTSIDE

For over 100 years, medical veterinary science has been compiling clinical data on feline disease. While there have been significant advances in medical science and care for animals in recent years, heads are buried in the sand when it comes to ethical husbandry of cats. There’s a giant elephant in the room.

The truth: cats are NOT house pets and they can’t be well cared for by way of today’s conventional human protocols. Felines are a totally unique species with specialized needs:

They need a prey-based diet and to stay mobile and athletic to flourish. These two factors alone account for many of the modern diseases we see in domestic cats… including chronic kidney disease.

FELINE KIDNEY METABOLISM

If you want to understand your cat from a species-specific point of view, consider that they are a desert species. Like the fennec fox and other desert-evolved carnivores, they have incredibly efficient kidney metabolism, a genetic survival mutation allowing them to stay hydrated in extreme hot and dry environmental conditions. Facts about feline kidney function:

1. Cat kidneys produce hyperosmotic urine, meaning it contains a high amount of matter (solutes) relative to water (you know that super strong cat-pee smell? That’s why!)

2. Cats have a lower basal metabolic rate and a reduced rate of non-renal water loss, meaning they lose less water through sweat, saliva the GI tract and breathing.

3. They have a low thirst drive, meaning they only get thirsty when they are critically dehydrated (so if you see your kitty drinking water frequently, it’s a red flag!)

   
   

What does this all mean for cats? They become easily dehydrated under the wrong conditions. Chronic dehydration leads to kidney damage.

FELINE DIGESTION & KIDNEY HEALTH

Another common issue that cats face in domestic life is digestive disease including chronic constipation, vomiting, irritable bowel disease, liver disease and pancreatitis. While digestive disease might seem unrelated to kidney health, it is linked via two important digestive processes: hydrolysis and protein waste excretion (the kidneys filter protein waste). Hydrolysis is the process in which complex food molecules are broken down into absorbable forms using water. Food is the main source of water for cats– NOT drinking. They require moisture in their food to avoid withdrawing vital water deposits from body tissues (gut, liver, gall bladder, pancreas) to aid in digestion. In other words, food moisture is essential to kidney health because it maintains systemic cell hydration. Cats cannot afford to withdraw water from their tissues to digest food.

This is why DRY KIBBLE IS NEVER APPROPRIATE FOR CATS. Dry food forces the body into dehydration on a daily basis and causes chronic digestive & kidney stress.

THE KIDNEYS FILTER PROTEIN WASTE

Since cats REQUIRE a high protein diet, it means that the kidneys need to be in top form to filter and excrete protein waste (urea). Urea is a waste product created by the liver during the breakdown of dietary protein. It is transported into the bloodstream and then filtered by the kidneys where it is excreted in the urine.

The more protein that is ingested, the more efficient the kidneys need to be. That means the body needs to maintain water homeostasis at all times to efficiently excrete urea (via urine). It’s ESPECIALLY true for cats who need high protein diets to stay healthy. Human urine is roughly 95% water where cats can concentrate urine at a 92-94% water content. This means they can excrete more protein waste upon urination than we humans but this requires precise cellular hydration or the whole body suffers. Hydration is a key element in feline longevity. Can you see the puzzle pieces fitting together?

CATS ARE COMMONLY MISDIAGNOSED WITH CHRONIC KIDNEY DISEASE

If your cat has been diagnosed with kidney disease, you may want to consider the following. Cats can appear to have kidney disease if:

-dietary protein is high

-dietary protein is of poor quality

-dietary water content is low

-your cat’s digestive system is struggling (eg.chronic constipation, vomiting, IBS, etc.)

-your cat is too sedintary

-your cat has an underlying health issue

Consider deciphering your cat’s bloodwork and clinical symptoms with an alternative animal health practitioner who understands the difference between the prey-based feeding model and the kibble-fed model. A “high” BUN (blood urea nitrogen) is relative to dietary protein. If your cat eats raw, they will naturally have a higher BUN than a dry-fed cat. If your cat is displaying kidney stress (eg. increased drinking and peeing), they may simply need a food change and support to recover from dehydration & digestive insult.

Conventionally, “normal’ kidney values are largely based on dry-fed animals, not prey-fed cats. Young cats are often vital enough to keep up with the demands of a dry food diet until they can’t. The timeline is different for every cat.

WHY LOW PROTEIN DIETS ARE DANGEROUS

Low protein diets are often prescribed for kidney disease in cats. The logic behind it is that by reducing dietary protein, we reduce kidney stress. However, the world seems to have forgotten that water is as vital as protein in a cat’s diet. If your cat has been prescribed a dry, low-protein diet, you risk harming your cat in the following ways:

• Cats require high protein diets to acquire essential nutrients that their bodies can’t make (essential amino acids) – by lowering protein, you risk nutritional deficiency.

• Low protein dry diets make absolutely no sense for cats since water is an ESSENTIAL requirement in a cat’s nutrition program . A dry diet will dehydrate your cat and put extreme stress of the kidneys.

• Muscle wasting and “sticky” fur are often attributed to the progression of kidney disease but a low-protein/low-moisture diet contributes to both issues in a big way.

• While end stage kidney disease may require reduced dietary protein, it should always be in a moist food format

  
  

If you have a cat that’s struggling with kidney health, please share your story with us!