Chronic Kidney Disease in Cats - Royal Canin

Cats - like dogs and humans - have two kidneys situated in the abdomen close to the spine and last rib. They are vital organs, continually filtering toxins and waste materials from the blood and producing urine to enable those toxins to be excreted from the body. They are very intricate and the filtration process is complicated.  Kidneys are very good at compensating when they start to wear out, working harder and harder to continue their vital work even as some of tiny tubules within them start to fail.  The resulting condition is called chronic kidney disease (CKD) and around 25% of cats over the age of 7 are affected, with the figure rising to more than a third of cats over the age of 12 years.

CKD is an insidious and progressive condition which is not curable and the only way to detect it early is with blood screening. If a cat owner waits till clinical signs of the disease are showing – symptoms such as weight loss, excessive thirst and urination, loss of appetite and poor body condition – then it’s already too late and any treatment will be palliative because the cat will likely be in the final stages of the disease, with around 85% of its kidney function lost.

Over recent years, there have been huge leaps in our ability to detect CKD much earlier than ever before and there is even an algorithm tool which was developed by Royal Canin, available free of charge to all vets in the UK, which can accurately predict whether a cat over 7 will develop CKD in the next 12 months. This is great news for cat owners since the only way to slow down the condition is to catch it early and make dietary adjustments.

Going back to the purpose of the kidney (filtration of toxins) we can see why we need to make nutritional changes. One of the things that the kidney filters is a mineral called phosphorus. This is an essential mineral and must be present in a cat’s diet. However, it also has a peculiar need to remain in a specific ratio with calcium within the body. In a scientifically formulated pet food  for healthy cats, this ratio will be exact and it’s one of the reasons you should never supplement any diet with extra calcium (found in dairy products or bone meal) or phosphorus (in abundance in raw meat).

Maintaining the ratio is so important to the body, that if that ratio is incorrect, hormones within the body make changes to redress this and rebalance the ratio. In the case of CKD, when the kidney is not working properly, this increases the circulating phosphorus which in turn causes those hormonal changes to kick in. To maintain that ratio, the body draws calcium from the bones. Unfortunately, this a flawed mechanism and causes several problems. Firstly, since calcium is responsible for bone strength, depletion of calcium results in bone weakness which causes wobbly teeth or even bone fractures. Secondly, as it redresses that calcium to phosphorus balance, it increases the calcium circulating in the blood, and when calcium and phosphorus meet in the kidney to be filtered, they cause more damage to the kidney. From there, it is a vicious cycle – the more damage to the kidneys, the more excess phosphorus there is, and the more calcium is drawn from the bones and so it goes on. The only way to slow down the progression of the disease is to break this cycle by reducing phosphorus to a very low level using either a specifically formulated Renal diet or by giving phosphate binders as prescribed by your vet.

Studies show that by reducing phosphorus intake to the very low levels found in veterinary diets specifically formulated to support pets with kidney disease, life expectancy can be doubled. Without these nutritional changes, unfortunately, the progression of this terminal disease is fast.

We recommend asking your veterinarian about senior pet blood screening to help catch CKD early and give your cat the best chance of living a longer life.