What you need to know about kidney disease in cats

Cats and Dogs
March 24, 2021

What you need to know about kidney disease in cats

What is Chronic Kidney Disease (CKD)?

Chronic kidney disease (CKD) is the persistent loss of kidney function over time. Healthy kidneys perform many important functions, most notably filtering the blood and making urine, so problems with kidney function can result in a variety of health problems for a cat.

CKD is one of the most common conditions affecting older cats, and in most cases is progressive over time so that there is a gradual decline and worsening of the disease. The rate of decline varies considerably between individual cats.

Although CKD is not a curable or reversible disease, appropriate support and treatment can both increase the quality of life and prolong life by slowing down the progression of the disease.

Diet plays a role in kidney disease, urinary problems such as stones and crystals, Feline Lower Urinary Tract Disease and gastrointestinal problems such as IBD.

What is the function of the kidneys?

The kidneys regulate the water and salt balance in the body, maintaining hydration, electrolyte levels, and regulating blood pressure. As proteins are metabolized by the body for energy, by-products are produced and circulated in the blood. It’s the kidney’s job to remove these toxic substances.

Waste products such as urea nitrogen, creatinine, and phosphorus, as well as certain drug metabolites, are all filtered from the blood and excreted in the urine. These are what are measured in the blood to detect declining kidney function

High levels mean that the kidneys aren’t working normally.

As much as 75% of kidney function must be lost before abnormally high blood values can be detected for these substances. Sometimes we see increased thirst and urination before the blood values rise above normal, as the kidneys become less able to conserve water, but not always. Since so much kidney function is lost by the time disease is usually detected, we need to do everything we can to help our cats maintain good kidney health in the first place.

Like all mammals, cats have two kidneys located in the abdomen, which perform a wide variety of important roles, including :

  • Removing toxins from the blood
  • Maintaining water balance
  • Maintaining salt balance (and other electrolytes)
  • Maintaining the acid balance of the body
  • Maintaining normal blood pressure
  • Producing hormones
Chronic Kidney Disease in Cats

How common is Chronic Kidney Disease?

CKD can be seen in cats of any age but is most commonly seen in middle to old-aged cats (those over 7 years), and it becomes increasingly common with age. It has been estimated that around 20-50% of cats over 15 years of age will have some degree of CKD present. CKD is seen about three times more frequently in cats than in dogs.

What are the causes of Kidney disease?

  • Decreased blood or urine flow to the kidneys
  • High blood pressure 
  • Cancer
  • Obstructions such as kidney stones 
  • Ingestion of toxic substances, such as antifreeze, pesticides, medications, and cleaning chemicals
  • Advanced dental disease 
  • Some long-haired breeds (such as Persians and Angoras) have a genetic predisposition to the disease 
  • Age older than seven years

What are the signs my cat has kidney disease?

  • Weight loss
  • Poor appetite
  • Lethargy
  • Increased thirst (polydipsia)
  • Increased urination (polyuria)

Other signs may include:

  • Poor coat
  • Hypertension (high blood pressure)
  • Vomiting
  • Bad-smelling breath (halitosis)
  • Weakness
  • Anemia
Our 14 year old cat that we found crying under a neighbors truck when he  was 10 years old. He was chipped, but unfortunately his owner had died.  Theo is the sweetest

What should I feed my cat with kidney disease?

The type of diet you feed your cat can directly affect your cat’s kidneys. Dehydration in cats causes the kidneys to concentrate urine to try to maintain the body’s water balance. Concentrating urine predisposes a cat to renal injury. The chronic, mild dehydration that cats experience when fed dry foods exclusively can cause increased stress on the kidneys, leading ultimately to decreased kidney function. Also, the low magnesium content in diets designed to decrease urinary stone and crystal formation may adversely affect the kidneys over time.

You may have been told to feed your kidney-compromised cat a diet that has a reduced protein content. Should you do it? Recent research demonstrates that diets high in protein have no detrimental effect on the kidneys, and animals with mildly decreased kidney function do not benefit from reduced protein diets. There is evidence that restricting protein may actually slow down the filtering action of the kidneys.  It is important that cats receive good quality protein in appropriate amounts without excessive levels of phosphorous to help maintain kidney function. This means that the protein source should be from actual meat and NOT a meat meal. 

Meat meals can consist of mostly ground-up connective tissue and bones. Usable muscle meat is removed before rendering, and so meat meals may contain high levels of calcium and phosphorous, which can harm the kidneys.

Lean beef, lamb, wild game, or poultry, seafood or other fish are low in phosphorus.

Chronic Kidney Disease in Cats

Rather than restricting the protein that cats depend upon for their energy requirements, reducing phosphorus in the diet can help many cats with kidney disease.

Phosphorous restriction is important in order to prevent the development of renal secondary hyperparathyroidism, a condition where excess phosphorous leads to an altered calcium/phosphorous balance. The end result of this imbalance causes calcium to be drawn from the cat’s bones and deposited into the tissues and organs, including the kidneys, further impairing their function.

Phosphorous limitation can be accomplished through the substitution of cooked egg whites for a portion of the meat in the diet, which dilutes the overall amount of phosphorus in the serving. Cooked egg whites are high in protein and very low in phosphorus.

Egg White Omelet
Cooked Egg White

Phosphorus Binders

Phosphorous binders can also be used. Binders are added to the food to prevent phosphorus from being absorbed into the body and bloodstream.  A blood test is required to determine blood phosphorus levels, so you will need to work with your veterinarian to choose the best course. It is best to try to keep the phosphorous level in the blood to within the normal range or only slightly above. 

Phosphate binders are medications used to reduce the absorption of dietary phosphate.


Good hydration is a key element in helping cats with kidney disease.

  • Making sure a good supply of fresh water is always available, and cats should be encouraged to drink by offering water from different bowls, etc.
  • Using flavoured waters (chicken broth or tuna, for example) or water fountains to encourage drinking
  • Adding further water to the food (if tolerated without affecting the appetite)
  • Using intermittent intravenous fluid therapy at your vet clinic
  • Using intermittent subcutaneous fluid therapy which can be given at your vet clinic or sometime in the home environment

We add water to their meat/bone/organ dinner to make a “tasty soup” as they are designed to get water from their food.

From reading this blog you might have gathered that feeding dry kibble to your cat is a NO-NO. Kibble does not contain much water which is needed for good kidney function. This also includes expensive prescription diets often recommended by vets.

How is CKD diagnosed?

A diagnosis of CKD is usually made by collection of blood sample and a urine sample at the same time for analysis.

Traditionally, two substances in the blood – urea, and creatinine – are commonly analyzed, as these are by-products of metabolism that are normally excreted by the kidneys.

Early diagnosis of CKD

Because CKD is such a common disease in cats, routine screening of all mature and older cats can help early diagnosis, which in turn may prolong a good quality of life. Yearly or twice-yearly routine veterinary check-ups are important, and as your cat begins to get older it is important that urine samples, and body weight, are monitored at each visit. A declining urine concentration or bodyweight may be early signs that CKD is developing and that further investigations should be done. Blood tests (measuring urea, creatinine, and/or SDMA may also allow early detection of CKD, especially when changes are monitored over time.

How can I transition my cat to a raw meat diet?

  • Always make a change in diet gradual – over several days at least and sometimes over a few weeks if your cat is quite fussy
  • Start by mixing a very small amount of the new food with your cats old food, and make sure it is well mixed
  • Only increase the amount of the new food slowly, once your cat is happy to eat the old mixture. Make each step where you replace old food with a greater amount of new food slow
  • Warming the food to body temperature (around 30C) may help increase the palatability
  • If necessary, talk to your vet about using drugs to increase the appetite to make the transition easier

In most cases with sufficient care and time, cats can be very successfully transitioned to a new diet, and as this is such an important part of managing CKD it is worth taking the time to do this properly.

Beverley Saunders – The Cats & Dogs Dinner Company