A common misconception is that renal diets are simply low-protein diets. Renal diets encompass a variety of modifications,
including limited quantities of phosphorus and salt, enhanced levels of omega-3 polyunsaturated fatty acids, fiber and vitamin
D, and a neutral pH effect. Indeed, the principal beneficial effects of these diets may not accrue from their low-protein
content. Thus, simply replacing a renal diet with a standard manufactured diet that is lower in protein content is insufficient.
Since inappropriate diets can exacerbate clinical signs of uremia and promote progression of chronic kidney disease, cats
and dogs with chronic kidney disease should be fed a renal diet.
TABLE 4: Therapeutic Measures for Dogs and Cats with Chronic Kidney Disease
Re-evaluate dogs and cats receiving diet therapy every three to four months.
#2 Ensure adequate nutrition. Owners often consider food consumption to be a premier indicator of their pets' quality of life, and they are often happy
when their pets show any interest in food. However, it is inappropriate to accept a pet's consumption of some food as a goal
of therapy. Mal nutrition is a major cause of morbidity and mortality in dogs and cats with chronic kidney disease stages
3 and 4.5 Ideally, patients should consume sufficient calories from an appropriate diet to maintain a body condition score of 4 or
5/9.4 Increased efforts are indicated to ensure sufficient calorie intake for patients with body condition scores of 3/9 or lower
or when patients fail to consume adequate calories to maintain a stable, appropriate body weight.
The evidence-based medicine hierarchy
In addition to inattention to adequate nutrition, some factors that may contribute to malnutrition in dogs and cats with chronic
kidney disease include consumption of inappropriate diets and metabolic factors related to uremia (especially uremic gastrointestinal
signs and metabolic acidosis). Failure to adequately address uremic gastritis, uremic stomatitis, and dental health can promote
anorexia. Metabolic acidosis can promote protein catabolism and malnutrition.1 Force-feeding new diets, exposing patients to new diets while hospitalized, or administering medications or other unpleasant
events during and around feeding times should all be avoided. A renal diet should be introduced to patients gradually.
Consider placing a feeding tube when patients fail to spontaneously consume adequate food. Feeding through a gastrostomy or
esophagostomy tube is a simple and effective way to provide an adequate intake of calories and water. In addition, feeding
tubes simplify drug administration. Although there is only weak evidence (grade 4) to support the effectiveness of feeding
tubes in achieving nutritional goals in dogs and cats with chronic kidney disease, there is no proven effective alternative.
CORRECT DEFICITS AND EXCESSES IN FLUIDS, ACID-BASE BALANCE, AND ELECTROLYTES
#3 Maintain serum phosphorus concentrations below target levels. Excessive phosphorus intake and inappropriately high serum phosphorus concentrations appear to promote progressive kidney
injury.4,6 Intervention is indicated in dogs and cats with chronic kidney disease stages 2 through 4 when the phosphorus concentrations
rise above stage-specific therapeutic target concentrations. The targets proposed for serum phosphorus concentrations reflect
a consensus of expert opinion (evidence grade 4).
Ideally, the serum phosphorus concentration should be below 4.5 mg/dl in stage 2 chronic kidney disease, below 5 mg/dl in
stage 3, and below 6 mg/dl in stage 4. When the serum phosphorus concentration exceeds these target concentrations, initiate
dietary phosphorus restriction by feeding a renal diet. In most dogs and cats with chronic kidney disease stages 2 and 3,
dietary phosphorus restriction alone will maintain the concentration below the target concentration. However, in some patients
with stage 3 chronic kidney disease and in most patients with stage 4 disease, adding an intestinal phosphate-binding agent
will be necessary. If calcium-based phosphate binding agents are used, it is particularly important to monitor serum calcium
concentrations. In patients with elevated serum calcium concentration or reduced serum albumin concentrations, it is desirable
to measure ionized calcium concentrations.