Dietary Therapy of Renal Failure
Many aspects of kidney failure require attention. Diet can be used to help in many ways and we are lucky to have commercially available diets made specifically for renal patients. There are even diets made for different stages of kidney failure. The goal of therapy, dietary or otherwise, is to prevent or at least postpone advanced uremia (poisoning by toxins that the kidneys could not adequately remove) and extend life expectancy.
In one famous study where 38 dogs in kidney failure were tracked for 2 years, dietary therapy reduced the risk of dying by 69% over dogs allowed to continue eating regular dog food.
Another study in dogs showed that beginning the renal diet when the creatinine was between 2.0 and 3.1 delayed the onset of uremic crisis by 5 months.
A study of 50 cats with stable, naturally occurring renal failure were divided into two groups, one receiving a renal diet and the other receiving regular food. The cats on the renal diet survived over twice as long as the others.
Clearly there is tremendous benefit to the patient in switching to a therapeutic renal diet. Unfortunately, these diets tend to be more bland than what the pet may be used to and they are not always acceptable to the pet.
- Do not attempt to starve the pet into eating the new food. Change more gradually.
- Consider using another brand that might have a different flavor. Remember, therapeutic foods are guaranteed so that even opened bags can be returned to your clinic for a full refund.
Let’s review some basic features of a desired diet. There are many misconceptions about an appropriate diet for renal disease. In fact, what dietary modifications should be made depend on the stage of renal disease. Some basic desired qualities in a renal diet are:
- Protein restriction
- Phosphate restriction
- Sodium restriction
- Supplementation with omega-3 fatty acids
Since a number of renal toxins come from the metabolism of protein, one way to give the kidneys less work to do is to eat less protein. How much less protein depends on how serious the kidney disease is. Older animals tend to require a higher dietary protein level in general when compared to their younger counterparts. Protein also adds palatability to the food so that if we try to restrict protein too much we may end up with a pet who will not eat at all.
Further, there is a metabolic requirement for protein below which a diet cannot dip. This has led to diets with differing protein restrictions to fit with different stages of disease, less restriction for earlier stages.
- There is no protective value to restricting protein prior to the onset of kidney failure.
- High protein diets do not cause kidney failure (though they certainly make the patient worse after kidney failure is present).
This is an important part of a renal diet since phosphorus balance is crucial. Phosphorus comes into the body via the diet and leaves the body via the kidney, only in renal failure phosphorus is not well removed as it is supposed to. Obviously using less phosphorus in the diet may be adequate to keep the blood phosphorus levels normal, thus balancing the intake with the output, but sometimes addition of medication (i.e. a phosphate binder) is needed to further reduce intake. Restricting dietary phosphate has been shown to slow the progression of renal disease.
If the goal phosphorus level has not been achieved in 2 to 4 weeks after starting the renal diet, a phosphorus binder should be used.
Omega 3 Fatty Acids
Studies suggest that kidney failure patients taking omega 3 fatty acids are likely to live longer than patients who do not take them. This has led to the supplementation of most renal diets with fish oils. The full import of fatty acid supplementation is still being worked out.
Other dietary features include B vitamin supplementation (since the damaged kidneys tend to lose excess B complex), which have non-acidifying features to help control acidosis.
At What Point Should a Special Diet be Started?
This question has been controversial for a long time. For many animals, changing diet to a less palatable food represents a definite reduction in life quality. There was some thinking that we are changing the diet too soon. On the other hand, if a pet is in a more advanced state of disease before the switch is made, the pet will be much less willing to change to a food of less palatability. The companies that make these foods have put a great deal of research into improving palatability over the years, which has helped tremendously.
Now the International Renal Interest Society finally has guidelines. They recommend changing the diet to a renal food when a dog’s creatinine level is in the 2.1-5 mg/dl range (Stage III renal failure). For cats, the diet should change when the creatinine reaches approximately 2.0 mg/dl (middle Stage II renal failure).
These guidelines allow the patient to benefit the most from the preventive advantages of the diet. If the pet finds the diet palatable, then there should be no life quality issues with changing foods.
Home Cooking a Renal Diet
Home cooking an appropriate renal diet is a complicated task but it can be done. Because different pets experience different problems with their renal disease (potassium depletion or not, pH issues or not, different degrees of phosphorus restriction needed, etc.), the diet should ideally be tailored to the individual.
Your veterinarian can get you an appropriate recipe through Balance IT. (Because these are therapeutic diet formulas, you cannot access them on your own.)
Several recipes have been published by Dr. Donald Strombeck, one of the internal medicine specialists at the University of California at Davis. These recipes can be viewed in his book, Home-Prepared Dog & Cat Food Diets.
Your veterinarian may be able to provide appropriate recipes, but not all veterinarians are comfortable giving nutritional advice. Discuss with your veterinarian whether referral to a veterinary nutritionist would be best for you and your pet. There are several university nutrition departments that offer this service but I prefer the service from a private company called Pet Diets.
Expect a consultation with a veterinary nutritionist to cost anywhere from $150 to $200.
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