Page 759 - Small Animal Clinical Nutrition 5th Edition

Chronic Kidney Disease 787

VetBooks.ir Box 37-4. Dietary Protein Needs in Dogs and Cats with Chronic Kidney Disease and
Maintenance of Lean Body Mass.

Minimum protein requirements for patients with chronic kidney dis- of cats with induced CKD, those that consumed adequate calories
ease (CKD) are assumed to be similar to those for healthy dogs and of a low-protein food (28% dry matter protein; 20% protein as calo-
cats; however, this has not been well evaluated. Ten cats with CKD ries) maintained stable or increasing body weights, hematocrit val-
and nine healthy cats were fed foods (free choice) with different ues and serum albumin concentrations and had no clinical signs of
amounts of protein (16, 20 or 24% of calories as metabolizable protein-calorie malnutrition. In the absence of metabolic acidosis,
energy [ME]) for four months. Body weight, lean body mass, nitro- dietary protein requirements did not appear to be different between
gen balance and laboratory parameters (hematocrit and serum cats with CKD and control cats with normal renal function. In anoth-
concentrations of urea nitrogen, albumin and total protein) were er study of cats with naturally occurring CKD, mean body weight of
measured to assess adequacy of dietary protein intake. Based on the control group that received the higher protein food continued to
study findings, the authors concluded that the protein requirement decline, with most of the cats experiencing weight loss, compared
for cats with CKD and healthy controls appeared to be approxi- with a mean weight gain in the group receiving a commercial vet-
mately 20% ME, which is similar to results from previous studies erinary therapeutic renal food with less protein. Although clinical
that evaluated protein requirement in healthy cats. condition (halitosis, gingivitis, appetite and body condition) deterio-
The amount of protein contained in most commercially available rated in both groups of cats, it was less apparent in the lower pro-
veterinary therapeutic renal foods is more than adequate to meet tein group based on observations by pet owners and veterinary
minimum protein requirements of dogs and cats with CKD; howev- clinical evaluations. The methods for assessing these observations
er, there is a common perception that these foods are protein defi- were not indicated. In addition, packed cell volume, serum albumin
cient. The terminology used to describe therapeutic foods formulat- and total protein increased in the lower protein group and
ed for management of kidney disease may encourage this percep- decreased in the higher protein group. In another clinical study of
tion. It may be more appropriate to refer to these foods as “formu- cats with CKD that received either a veterinary therapeutic renal
lated to avoid excessive protein” or “modified protein foods” instead food or a typical maintenance food, no significant differences in
of being “protein restricted”, which may incorrectly be interpreted body weights or hematocrit values were noted between groups at
as protein-deficient by pet owners and health care team members. the midpoint of the study. In a randomized, double-blinded clinical
Loss of lean body mass occurs in patients with kidney disease study of cats with CKD managed by feeding either a veterinary ther-
and may contribute to the perception that veterinary therapeutic apeutic renal food or a control food (with higher protein), there were
renal foods do not contain adequate amounts of protein. Potential no significant differences in body weights or body condition scores
mechanisms for decreased lean body mass in dogs and cats with at the midpoint and end of the two-year study.
CKD include inadequate dietary protein or caloric intake, altered In a double-blinded clinical study of dogs with naturally occurring
response to decreased protein intake, increased protein loss (e.g., CKD that received either a veterinary therapeutic renal food or a
proteinuria), metabolic acidosis and activation of cytokines by control food (with higher protein), health-related quality of life was
chronic inflammation. Failure to consume an adequate amount of determined using a content-validated questionnaire to obtain
calories may result in catabolism of muscle protein as a source of owner assessments. Nutritional status was assessed by periodic
energy; this is one reason why veterinary therapeutic renal foods physical examinations and measurement of laboratory parameters.
have relatively higher amounts of dietary fat. It is important to The renal food was superior to the control food for maintaining
ensure adequate dietary protein intake; however, protein that is health-related quality of life and nutritional status; the renal food
consumed in excess of the patient’s needs is metabolized and used group remained stable based on body weights, body condition
for energy, which could worsen clinical signs of uremia. Metabolic scores, hematocrit values and serum albumin concentrations.
acidosis, a common complication of uremia, stimulates the degra- It is highly likely that beneficial effects of feeding a veterinary
dation of branched-chain amino acids and proteins and blocks the therapeutic renal food are due to a combination of key nutritional
ability of the patient to respond appropriately to lower protein factors (in addition to limited dietary protein). However, results of
intake. The specific mechanisms involve increased activity of studies described above demonstrate that nutritional status can be
branched-chain ketoacid dehydrogenase and the ubiquitin-protea- maintained and quality of life improved in dogs and cats with CKD
some proteolytic pathway. Besides acidosis, cytokines activate the when fed a commercial veterinary therapeutic renal food contain-
ubiquitin-proteasome proteolytic pathway and cytokine release ing less protein than typical adult maintenance pet foods. Re-
occurs with chronic inflammation. These potential mechanisms for gardless, all patients with CKD should be monitored for signs of
loss of muscle mass emphasize the importance of controlling meta- protein-calorie malnutrition so that treatment can be adjusted to
bolic acidosis, infection and other stressors in patients with CKD. maintain body condition and improved quality of life.
Although some patients with CKD lose lean body mass, evidence
supports that these patients can maintain body condition and The Bibliography for Box 37-4 can be found at
weight while eating a veterinary therapeutic renal food. In a study www.markmorris.org.

and mononuclear cell infiltration whereas lower phosphorus of dietary phosphorus restriction were studied in dogs that were
intake (0.42% DM phosphorus) was not (Ross et al, 1982) fed either a low-phosphorus (0.44% DM) food or a high-phos-
(Figure 37-10). Progressive changes in GFR were not detected; phorus (1.44% DM) food for 24 months (Brown et al, 1991).
however, in either the high- or low-phosphorus group. Effects Both foods provided reduced amounts of protein (17% DM).