Aug 186 min read

Diet and Chronic Kidney Disease

Updated: Aug 25

We all know how stressful it can be when our pets need to eat a diet formulated to their needs but decide they won't eat it. In this article we explain what is required of a scientifically formulated renal diet and a few hints and tips about managing Chronic Kidney Disease (CKD).

Chronic kidney disease (CKD) is unfortunately common in cats and is estimated to affect 30 per cent over the age of 12.1 Diet changes are important to maintain quality of life, slow down disease progression and increase longevity.2 The veterinary team will often recommend a specially adapted “renal diet” for cats with CKD.

When to start a renal diet

Early diagnosis is important for all aspects of CKD management. It is now especially important when considering dietary modifications, because the International Renal Interest Society recommend that some cats should be started on a renal diet as early as stage 1 (such as those with FGF23 values of >400pg/ml in the absence of hypercalcaemia, anaemia or marked inflammatory disease and those with persistent proteinuria).7 It is recommended that other cats are transitioned to a renal diet in IRIS stage 2 CKD.3

Figure 1: Comparison of mortality in cats with chronic kidney disease fed a renal food or maintenance food over a 2-year period. Adapted from Ross et al (2006).4

Nutritional modifications for the feline renal patient

Phosphate restriction is thought to be the most important influencer of survival in cats with CKD.5 Restricting phosphate slows the progression of chronic kidney disease by reducing morphological damage to the kidneys.

Phosphorus restriction reduces plasma parathyroid hormone (PTH) levels and minimises the risk of secondary renal hyperparathyroidism. If left untreated, secondary renal hyperparathyroidism will progress, and is associated with reduced survival times.6 High levels of parathyroid hormone may contribute to the uraemic state by acting as a uraemic toxin. Increased parathyroid hormone concentrations can also contribute to renal damage as this can result in increased calcium influx into renal tubular cells and precipitation of calcium phosphate in the lumen of the renal tubules. As CKD progresses, serum phosphate may rise above IRIS’s targets and these cats may require a phosphate binder in addition to a phosphate restricted diet.

Protein levels are typically lower in renal diets. Though protein is not thought to be a key influencer of survival time, it has an important impact on quality of life. Restricting protein can help to minimise the levels of nitrogenous waste, as well as the formation of uraemic toxins, which can contribute to nausea and inappetence. Reducing dietary protein may also help to reduce proteinuria. While proteinuria is less common in cats with CKD compared to dogs, where present, elevated urine protein:creatinine (UPC) in feline CKD patients has been demonstrated to be a negative prognostic factor.8

Protein levels vary between different commercially available renal diets, and there is a range of suggestions about the degree of protein restriction required at different stages of renal disease. Whilst protein restriction in the later stages of CKD is helpful to minimise uraemic toxin production, protein plays a key role in supporting lean body mass and body weight – known to be important factors correlating with survival in both healthy cats and cats with CKD.9

Increasing dietary potassium aims to compensate for excessive urinary loss in CKD and helps to reduce – although not completely remove – the risk of hypokalaemia, which can contribute to ongoing renal damage in addition to inappetence and lethargy. Renal diets also contain increased levels of water-soluble vitamins, such as B vitamins because of higher urinary losses.

Other features of renal diets include careful formulation to be non-acidifying because of the risk of metabolic acidosis in these patients. They often contain additional omega-3 polyunsaturated fatty acids and antioxidants due to the proinflammatory environment and oxidative stress that develops in cats with CKD.10

Which diet should I feed?

Because of the special requirements of cats with CKD, a commercially produced veterinary renal diet is usually most appropriate. While a wet diet may be preferable to help maintain hydration, dry options should also be available for cats that prefer them. It’s important to try and maintain the appetite of cats with CKD due to the negative prognostic implications of a loss of lean body mass.

A staged approach is recommended, since patients in the early and later stages of CKD have differing nutritional requirements – particularly with respect to protein requirements. Many renal diets now reflect this, with nutrient profiles formulated to better support either the ‘earlier’ or ‘later’ stages of CKD.

Cats can be fussy and slow to accept a new food. This is especially true if they are feeling unwell. Some top tips to improve acceptance.

It can take months for a cat to accept a new food, so don’t expect it to happen in days. It doesn’t mean the new food isn’t tasty, or that the cat won’t come to enjoy it, given time
If possible, don’t make diet changes when your cat is stressed or unwell and avoid feeding the new diet at the same time as medications. These can all cause aversion to the food.
Choose the right diet. Your vet practice should recommend a high quality, science-based diet that is tested for palatability and available in wet and dry formats to suit all preferences.
Smell is important to cats. Let the food reach room temperature before serving or gently warm a small amount to body temperature to increase the aroma.
Sometimes tasty toppings can be added to your cat’s diet. You must check with your veterinary team before adding anything. They may recommend a palatability enhancer that is formulated to be safe in cats with kidney disease or even a probiotic such as FortiFlora as a great palatability enhancer suitable for cats with renal disease. Cats with CKD frequently have a dysbiosis so this can help both palatability and support intestinal health and microflora balance
Slowly substitute the old food for the new one over at least one week. Try putting the foods in separate bowls if your cat doesn’t like them mixed.

Furthermore, getting a cat to drink more is also fundamental to management but can be tricky.

In this article, we help explain how to encourage a cat to drink more at home, which is an essential conversation to have with clients who have cats diagnosed with renal impairment.

Diet and Chronic Kidney Disease

We all know how stressful it can be when our pets need to eat a diet formulated to their needs but decide they won't eat it. In this article we explain what is required of a scientifically formulated renal diet and a few hints and tips about managing Chronic Kidney Disease (CKD).

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