Think you know all there is to know about nutritional management of cats and dogs with chronic kidney disease (CKD)? It might be time for a refresh. While nutrition remains the cornerstone of therapy for this disease—it is, in fact, the only intervention shown to slow progression of CKD^1-3—there have been innovations in nutrient bioavailability, palatability, and, most importantly, improved outcomes of which you may not be aware.

Together, these advances can give your patients a brighter future than ever before.

Let’s take a look at what we have learned about improving the lives of affected pets and the pet parents who care about them and where the field is headed next.

Early CKD intervention is essential

While both cats and dogs experience kidney disease, the condition is highly prevalent in cats, with 50 percent of cats of all ages, and as many as 81 percent of cats 15 years and older, diagnosed with CKD.⁴ Cats also tend to live longer with the disease.⁵ All of this means you are more likely to see a cat than a dog with CKD in your clinic.

One of the most challenging aspects of managing this condition for many practitioners is knowing when to implement a food change. While diagnostic advances have helped us detect, and even predict, onset of kidney disease earlier than ever, there is still often a question of when to switch patients to a therapeutic food.

Fortunately, we now have evidence that earlier is better.^6-7 CKD cannot be reversed or halted, but it can be slowed through nutritional intervention, specifically a diet lower in phosphorus and higher in omega-3 fatty acids.^5,8 Earlier intervention can help lessen kidney damage and clinical signs associated with kidney disease.

We also know that age is a risk factor for CKD.^4,9-10 Therefore, it makes sense to screen patients carefully as they age. Once you have confirmed kidney disease based on guidelines from the International Renal Interest Society (IRIS),¹¹ it is time to start the patient on a therapeutic food.

One reason it is important to start a therapeutic kidney food early is to maintain and protect the CKD patient’s lean body mass and body weight, which is key to protecting overall health.^6,12,13 The danger of waiting until the “skinny CKD cat” stage is once muscle is gone, it is very difficult to get back.

The great protein debate

Let’s talk about protein. The role of this macronutrient in CKD has been controversial in veterinary circles for a number of years,^5,8,14,15 and knowing exactly when to limit dietary protein is still debated. We do know it may not be the most important thing to do if a patient is not experiencing proteinuria.^11,16

On one hand, is the objective to do everything possible to ensure we do not accelerate muscle loss in these already sick animals—this could lead one to argue against reducing protein. On the other hand, we know that in advanced CKD, the kidneys cannot process dietary protein. This results in proteinuria, which leads to further kidney damage. Although it may seem counterintuitive, reducing dietary protein intake is one of the most important nutritional interventions for patients with protein-losing nephropathy.

Given these important considerations, an ideal therapeutic diet will have enhanced levels of essential amino acids—after all, that is what animals really need from the protein they ingest. This allows for the overall protein level to be lower than a typical maintenance food. What’s more, the protein should be formulated to be as highly digestible and bioavailable as possible.

Studies have validated this approach, showing the right balance of protein in a renal therapeutic diet not only maintained, but also improved lean body mass.⁶ As a result, researchers were able to feed these patients less protein, which we know is important for the kidneys, particularly in later stages of CKD, while still providing everything the pet needs for maintenance of muscle mass.⁶

A taste for palatability

An important discovery was confirming that reduced food intake, not dietary protein, leads to CKD-associated cachexia. It is especially important for cats with CKD to continue eating because they can live a long time with the disease and, therefore, are more likely to experience reduced body mass.^6,17,18 However, as every practitioner and pet parent who has dealt with kidney disease knows, getting these patients to eat enough is a major challenge.

We know when people have kidney disease, their taste preferences change,¹⁹ so we assume this to be true for companion animals as well. The ideal therapeutic diet will address taste for pets with kidney disease and their altered taste.

However, not all therapeutic renal diets are created equal. In a study of 20 cats with early-stage CKD,⁶ researchers compared two therapeutic diets to manage kidney function over six months. Cats on the control food experienced significant weight (13 percent) and muscle (11.1 percent) loss. Cats on the test food—which provided more calories and essential nutrients per serving—gained weight (5.8 percent), maintained muscle, and had stable kidney function markers. The cats eating the test food consumed about 23 percent more calories compared to those eating the control food. An extrapolation of these findings was they enjoyed the test food’s taste more.⁶

Looking back—and ahead

In conclusion, managing CKD in cats and dogs requires a comprehensive approach that includes early intervention, appropriate nutritional strategies, and consideration of the microbiome. Advances in the understanding of CKD have shed light on the importance of timely dietary changes and the role of protein in kidney health. Starting a therapeutic kidney food early can help maintain lean body mass and mitigate the progression of CKD. Further, palatability plays a crucial role in ensuring that cats and dogs with CKD consume enough food to prevent weight and muscle loss.

While the science continues to advance, one thing remains the same: the power of nutrition to enrich and lengthen the special relationships between people and their pets.

ALL ROADS LEAD TO THE MICROBIOME

This is a whole new way to think about the microbiome. We know about the gut-brain axis; now we have the gut-kidney axis. The microbiome lies at the intersection of an untold number of physiological systems, and we are only beginning to unlock its potential. Leveraging the microbiome to further slow the progression of kidney disease is an important milestone in this journey. A new innovation, launching this year, targets the microbiome, specifically activating the gut microbiome to reduce the production of gut-derived uremic toxins, which have been shown to harm kidney function.20 Prebiotic fiber blends have been found to reduce the production of gut-derived uremic toxins in cats and dogs with CKD.21,22 This results in reduced circulating levels of uremic toxins, thus reducing their potential to impact kidney function. This is unique in the veterinary nutrition arena in that the diet uses microbiome technology to promote therapeutic effects outside the gastrointestinal tract.

Karen Shenoy, DVM, is chief veterinary officer for Hill’s U.S., where she has worked since 2008 in a number of professional, cross-functional and leadership roles of increasing responsibility. Catherine Ruggiero, DVM, DACVIM (Nutrition), is manager, scientific communications for Hill’s Pet Nutrition.

References

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2. Jacob F, Polzin DJ, Osborne CA, et al. Clinical evaluation of dietary modification for treatment of spontaneous chronic renal failure in dogs. J Am Vet Med Assoc. 2002;220(8):1163-1170. https://pubmed.ncbi.nlm.nih.gov/11990962/
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