Renal diets have some characteristics:
- controlled protein level, with proteins of high quality
- low phosphorus & sodium
- alkalizing agents to control metabolic acidosis often associated to CKD
- high content of Vit.B complex
- high content in fibers
- polyunsatured Omega-3 fatty acids (PUFA) and antioxidants
It is wrong to consider a renal diet a “low protein diet” as there are still many diets with a lower content in proteins, addressed to other diseases, that are not good to be administered to patients affected by CKD.
Some renal diets underwent clinical trials in order to establish their efficacy in slowing the progression of renal damage or reducing the risk of mortality because of uremic crisis in patients affected from renal failure.
There is no consensus about the ideal protein content of renal diets for dogs and cats, although it is accepted clinical signs of uremia improve after a renal diet is administered to patients in IRIS stage 3 & 4. For IRIS stage 1 patients there is no consensus about the utility of a renal diet, but it can be introduced to treat other conditions such as proteinuria. The theoretical utility of a low protein diet in slowing the progression of renal damage in IRIS 2 dogs has not been demonstrated yet and is, therefore, anecdotally applied based on studies carried out in other species.
Clinical trials of efficacy
The efficacy of a renal diet in reducing both uremic crisis and mortality of dogs in IRIS stage 3 has been demonstrated in a randomized controlled clinical trial (RCCT). Dogs feeding a renal diet reduced their risk to develop uremic crisis of 75% as well as of 66% for the risk of renal related mortality, compared to dogs fed with a maintenance diet. In the same study, dogs feeding a renal diet showed better quality of life too.
In another trial, cats with serum creatinine between 2.0 and 4.5 mg/dL were randomized into two groups, one feeding a renal diet and the other feeding a maintenance one; the renal diet reduced the risk of developing uremic crisis and death for renal causes.
Furthermore, a clinical trial studied the difference in survival times of cats feeding a renal diet compared to ones eating a maintenance one. Also in this case, there was a significant difference in survival time between the groups: a median of 633 days for cats fed with a renal diet and 264 for those eating a maintenance one.
It takes its time to make a patient accept a new diet. Passing to a new diet too fast as well as a force-feeding are all reasons potentially leading a patient to food aversion. Changing a diet too fast can also cause diarrhea, subsequent dehydration and worsening of renal function. The new diet has to be introduced in growing percentage compared to the old one, subdividing the period in 4 phases. Cats, and dogs with selective appetite, will be changing their diet in 4 weeks, while easier patients will be doing it in 2 weeks.
|1st period||25% renal diet + 75% current diet|
|2nd period||50% renal diet + 50% current diet|
|3rd period||75% renal diet + 25% current diet|
|4th period||100% renal diet|
Therapeutic suggestions and evidence based medicine
Clinical trials demonstrated the efficacy of renal diet in both improving quality of life and survival time, other than reducing the risk of uremic crisis in dogs in IRIS stages 3&4 and cats in stages 2, 3&4. The real utility of a renal diet for dogs in IRIS stage 2 has not been demonstrated yet, although hyperphosphatemic patients may take advantage of a low phosphorus diet. Regardless the IRIS stage, the renal diet should be used in both proteinuric dogs and cats; its efficacy in reducing serum creatinine and urea is evaluated in 4 weeks.
Omega 3 fatty acids are widely used in both dogs and cats affected from chronic kidney disease (CKD). In dogs with proteinuric renal disease, clinical trials demonstrated the efficacy of Omega3 in reducing the protein loss and slowing the progression of renal disease and glomerular damage particularly if administered in association with antioxidants. In cats, no clinical trials evaluating the efficacy of Omega3 in slowing the progression of renal disease is available, although a retrospective study evaluating survival times of cats feeding different diets have showed a longer life-span in those cats eating the greater content of Omega3 fatty acids.
No data is available about the efficacy of Omega3 administered not in association to a renal diet. Both EPA and DHA are useful in course of CKD, even though diet should be supplemented with fish oils mainly represented from EPA and a fewer amount of DHA, at high concentration in EPA and low DHA.
On a side note, it has to be stressed Omega3 deriving from vegetal oils contain ALA, and are converted to a minimal part in EPA and DHA in canines, while cats are not able to convert ALA at all thus resulting in a lack of efficacy in case of CKD.
Content of EPA to be administered to renal patients is 80 mg/kg daily if associated to a renal diet. Pharmacross kcMEGA3, due to its high content of omega 3 fatty acids and the optimal EPA:DHA ratio meets the EPA content requirements for the health of the kidneys.