Chronic kidney disease (also known as renal disease) is an irreversible and progressive loss of kidney function that ultimately results in illness and death. It is most common in older pets, but can occur at any age. Even though the disease is progressive, appropriate treatment helps many dogs live comfortably for several months to years.
In the past, even with medical treatment that consisted of controlling high blood pressure, the loss of protein through the urine, and hyperparathyroidism (resulting in an imbalance of calcium and phosphorus), dogs were likely to die shortly after diagnosis. However, numerous studies now show that feeding these patients a therapeutic renal diet is the most successful tool in managing chronic kidney disease in dogs. Kidney diets help to reduce the progression of the disease and prolong survival times.
Several nutrients are important in the dietary management of chronic kidney disease:
1) Phosphorus – a mineral that is consumed in the diet and needed for all living cells in the body. It is present mostly in the bones and teeth, less so in soft tissues and extracellular fluids. It is excreted from the body through the urine. Studies show that restriction of phosphorus in dogs with Stage 3 (out of 4) kidney disease increases survival time.
2) Protein – Two schools of thought have duked it out with regards this nutrient.
Reduced protein diets result in less nitrogenous waste that needs to be excreted by the kidneys and lower phosphorus levels (because protein contributes to increased phosphorus levels).
Increased or normal levels of good quality protein help to maintain lean body mass (and maintain strength, coordination and good immunity) and have no adverse effects on life expectancy as long as phosphorus intake is restricted. Current recommendations are to provide adequate, good quality protein and reduced phosphorus levels.
3) Omega-3 Polyunsaturated Fatty Acids – essential fatty acids that are not made in the body and need to be present in the diet. In particular, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are omega-3 fatty acids that help reduce inflammation and reduce glomerular hypertension (glomeruli are part of the kidneys), consequently improving kidney function. Omega-3 polyunsaturated fatty acids are most abundant in fish oil.
4) Antioxidants – substances that help neutralize free radicals. If not dealt with, free radicals can cause significant cellular injury and produce more free radicals. Renal diets that have both omega-3 fatty acids and antioxidants combined are better at slowing the progression of chronic kidney disease than either one alone.
5) Fermentable Fiber – adding this type of fiber to the diet promotes the excretion of nitrogen in the feces and allows dogs to consume adequate amounts of protein. Renal diets that are supplemented with fiber from beet pulp, fructooligosaccharide, and gum arabic help increase the number of intestinal bacteria, which draws urea (a nitrogen-containing waste product) into the feces.
Multiple studies show that in dogs with Stage 3 kidney disease, renal diets are superior to regular maintenance diets in slowing the progression of chronic kidney disease and prolong survival time. In one study, 70 percent of dogs on a renal diet survived three times longer than did dogs who ate a maintenance diet.
Dogs should only be switched to a renal diet once any dehydration, nausea and vomiting has been corrected. If a dog feels sick when offered a new food, he may associate the new food with the illness and develop an aversion to it. A veterinarian familiar with the details of a dog’s case is in the best position to recommend a particular food and how best to make the transition to it.
Dr. Jennifer Coates
- Sanderson, S.L. Nutritional Management of Renal Disease: An Evidence-Based Approach. Today’s Veterinary Practice. 2014, Jan/Feb.
- Vaden, S.L. Can We Halt Progression of Renal Disease? Presented at the British Small Animal Veterinary Congress, Raleigh, N.C. 2007.