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Peer Reviewed ACVN NUTRITION NOTES
NUTRITIONAL MANAGEMENT
OF CHRONIC KIDNEY
DISEASE IN CATS & DOGS
RACE-APPROVED Martha G. Cline, DVM, Diplomate ACVN
CE CREDIT Red Bank Veterinary Hospital, Tinton Falls, New Jersey
ARTICLE
The American College of Veterinary Nutrition (acvn.org) and Today’s Veterinary Practice are
delighted to bring you the Nutrition Notes column, which provides the highest quality, cutting
edge information on companion animal nutrition, provided by the ACVN’s foremost nutrition
specialists.
The primary objectives of the ACVN are to:
• Advance the specialty area of veterinary nutrition
• Increase the competence of those practicing in this field
• Establish requirements for certification in veterinary nutrition
• Encourage continuing education for both specialists and general practitioners
• Promote evidence-based research
• Enhance dissemination of the latest veterinary nutrition knowledge.
The ACVN achieves these objectives in many ways, including designating specialists in animal
nutrition, providing continuing education through several media, supporting veterinary nutrition
residency programs, and offering a wide array of resources related to veterinary nutrition, such
as this column.
Nutritional intervention is a cornerstone in TABLE 1.
the treatment of patients with chronic kidney Nutritional Assessment Checklist for
Turn to page 66 to disease (CKD). However, a complete nutritional Patients with Chronic Kidney Disease
read this article’s assessment and staging of the patient’s kidney Diet history
learning objectives disease are indicated before any dietary Appetite
and accompanying recommendations are made (Table 1). Guidelines Current diet
continuing for complete nutritional assessment are available Evaluation of current protein
education quiz. through the World Small Animal Veterinary intake
CE credit and 1 Treats/table foods
Association. Foods for medication
RACE-approval The International Renal Interest Society (IRIS) administration
provided by recommends nutritional intervention in both cats Supplements
vetmedteam.com. and dogs at IRIS stage 2, but in my opinion, a Laboratory Creatinine
diet change at IRIS stage 1 may be required once values Blood urea nitrogen
a complete assessment of the patient has been Phosphorus
performed. IRIS guidelines are available at: Potassium
• Staging of CKD: iris-kidney.com/guidelines/ Albumin
staging.aspx Bicarbonate (HCO )
3
• Treatment recommendations for CKD: iris- Urine specifi c gravity
kidney.com/guidelines/recommendations.aspx. Urine protein-to-creatinine ratio
Patient Body weight
EFFICACY OF THERAPEUTIC DIETS assessment Body condition score
Therapeutic kidney diets are used to improve a Muscle condition score
patient’s quality of life by controlling signs of Systolic blood pressure
58 TODAY’S VETERINARY PRACTICE | March/April 2016 | tvpjournal.com
ACVN NUTRITION NOTES Peer Reviewed
uremia and increasing life span by altering disease spontaneous IRIS stage 2 or greater CKD were
progression. fed a therapeutic kidney diet (n = 21) or adult
Double-blinded, randomized, controlled clinical maintenance diet (n = 17) and evaluated for 24
4
trials have compared the effectiveness of diets months. Dogs in the therapeutic kidney diet
formulated for CKD with adult maintenance diets in group had a median time to uremic crisis of 615
dogs and cats. The studies evaluated characteristics of days (1.7 years) and a median time of 594 days
therapeutic kidney diets, such as reduced phosphorus, (1.6 years) before deaths occurred, while those in
protein, and sodium and the addition of omega-3 the maintenance diet group had median times to
fatty acids (eicosapentaenoic acid [EPA] and uremic crisis of 252 days (0.7 years) and 188 days
docosahexaenoic acid [DHA]) (Table 2). (0.5 years) before deaths occurred, respectively.
At the end of the study, only 33% of dogs in the
In the Literature: Cats therapeutic kidney diet group died of a renal-
In a study by Ross and colleagues, cats with related cause compared with 65% of dogs in the
spontaneous IRIS stage 2 and 3 CKD were fed maintenance group.
a therapeutic kidney diet (n = 22) or an adult
maintenance diet (n = 23) and evaluated for 24 KEY NUTRIENTS FOR CKD
2
months. In the therapeutic diet group, no cats Key nutrients that need to be considered when
experienced a uremic crisis and no renal-related feeding patients with CKD include:
deaths occurred, whereas, in the maintenance diet • Protein
group, 26% of cats had uremic crisis and 21.7% of • Phosphorus
cats died of renal-related causes. • Omega-3 fatty acids
In a study by Elliott and colleagues, client- • Sodium
owned cats with spontaneous stable CKD were • Potassium.
fed a therapeutic kidney diet (n = 29) or an Additional nutrient considerations include fat,
adult maintenance diet (n = 21).3 Those fed a acid–base balance, antioxidants, and fi ber.
maintenance diet received one because they refused In the November/December 2015 issue of
a therapeutic kidney diet or their owners did not Today’s Veterinary Practice, the article—The
want to change their diet. Feeding a therapeutic Protein Paradigm: Assessing Dietary Protein
kidney diet helped reduce plasma phosphate, in Health & Disease—provided an in-depth
blood urea nitrogen, and parathyroid hormone discussion of the implications of dietary protein
concentrations. The median survival time for cats in both healthy dogs and cats and those affected
receiving a therapeutic kidney diet was 633 days by obesity, urinary tract and kidney disease, food
(1.7 years) compared with 264 days (0.7 years) for allergies, and liver disease.
cats receiving a maintenance diet.
DIETARY PROTEIN
In the Literature: Dogs Protein restricted diets are commonly recommended
In a study by Jacob and colleagues, dogs with for the management of CKD in both cats and dogs.
TABLE 2.
Ranges of Dietary Components in Typical Therapeutic Renal Diets
COMPONENT THERAPEUTIC AAFCO THERAPEUTIC AAFCO
RENAL DIETS MINIMUM* RENAL DIETS MINIMUM*
DOGS CATS
Protein (g/1000 kcal) 25–55 45 58–82 65
Phosphorus (g/1000 kcal) 0.4–1.2 1 0.8–1.35 1.25
Sodium (g/1000 kcal) 0.4–1.2 0.2 0.5–1 0.5
Potassium (g/1000 kcal) 0.8–2.1 1.5 1.4–2.6 1.5
EPA + DHA (g/1000 kcal) 32–1200 n/a 31–1910 n/a
* 2016 AAFCO adult dog maintenance minimum
tvpjournal.com | March/April 2016 | TODAY’S VETERINARY PRACTICE 59
Peer Reviewed ACVN NUTRITION NOTES
TABLE 3.
Protein Requirements & Levels in Adult Cats & Dogs
NRC MINIMUM NRC AAFCO LOW MODERATE HIGH
REQUIREMENT RECOMMENDED MINIMUM PROTEIN PROTEIN PROTEIN
ALLOWANCE
Cats 40 50 65 < 80 80–120 > 120
Dogs 20 25 45 < 60 60–90 > 90
Notes
• Values in table are expressed as g/1000 kcal.
• Low, moderate, and high descriptors are a general comparison among commercial pet foods.
The primary reasons a protein restricted diet is quirement of adult cats based on the maintenance
recommended include reduction in nitrogenous 9
of lean body mass.
wastes and glomerular proteinuria. • Nitrogen balance was achieved with a diet
Nitrogenous wastes can contribute to: containing 56 g protein/1000 kcal. Nitrogen
• Clinical signs associated with azotemia and balance can be achieved on a low protein diet;
uremia however, this may be at the expense of lean body
• Polyuria and polydipsia; reduction in mass through the utilization of endogenous
nitrogenous wastes can improve polyuria and proteins. A diet containing 95 g protein/1000
polydipsia by reducing the solute load to the kcal was needed to maintain lean body mass.
kidney • On the basis of regression analysis, the
• Anemia through gastrointestinal ulceration and researchers suggested that, although 1.5 g
blood loss. Nitrogenous wastes may also shorten protein/kg body weight is required for nitrogen
5
the life span of red blood cells and cause platelet balance in adult cats, 5.2 g/kg is recommended
6
dysfunction as demonstrated in the human to maintain lean body mass.
literature. This study was performed in healthy adult male
However, the necessity of protein restriction cats, and additional studies are needed to evaluate
for both dogs and cats has remained a point of the protein requirement to maintain lean body
controversy and discussion for many years. This mass in dogs and cats with CKD.
includes the timing at which protein restriction
should occur and the provision of suffi cient dietary Protein Restriction
protein to avoid protein malnutrition and loss of The amount of protein needed to achieve restriction
lean body mass. The role of protein restriction in the is not clearly defi ned. Categories for low, moderate,
10
progression of CKD in both cats and dogs is unclear. and high protein diets are provided (Table 3)
but, for some animals, protein restriction may be
Protein Requirements relative to their current intake based on an accurate
Protein requirements for adult dogs and cats have diet history (see Examples of Protein Restriction
been established through use of nitrogen balance Relative to Current Intake). In addition,
studies, wherein nitrogen intake is equivalent to protein restriction does not equate to feeding
nitrogen loss. The National Research Council below the established NRC minimum nutritional
(NRC) Ad Hoc Committee on Dog and Cat requirements.
Nutrition has established minimum requirements At this time, typical therapeutic diets labeled
and recommended allowances in adult cats and for various stages of CKD range from 25 to 55
7
dogs based on these types of studies (Table 3). g/1000 kcal for dogs and 58 to 82 g/1000 kcal for
The Association of American Feed Control cats, with allowance for some tailoring of protein
Offi cials (AAFCO) also recommends a minimum content to a patient’s needs.
crude protein content for adult dogs and cats,
taking into account not only recommendations Proteinuria in Dogs
from the NRC for healthy adults but also changes In dogs with proteinuria secondary to glomerular
in protein digestibility that occur during the disease, the American College of Veterinary
8 Internal Medicine Consensus Statement
processing of pet food (Table 3).
A more recent study evaluated the protein re- 11
recommends reduced protein intake.
60 TODAY’S VETERINARY PRACTICE | March/April 2016 | tvpjournal.com
ACVN NUTRITION NOTES Peer Reviewed
In dogs with hereditary nephritis, feeding a
protein restricted therapeutic renal diet reduced Examples of Protein Restriction Relative to Current Intake
structural damage to glomeruli by decreasing Two 10-kg spayed female mixed breed dogs with glomerular proteinuria
glomerular basement membrane splitting and and IRIS stage 1 CKD are consuming approximately 550 kcal/day
12 0.75
delaying the progression of renal failure. In both (calculation, 1.4 × (70 × kg body weight )). Diet recommendations are
humans and rats, protein causes direct injury to the listed in Table 4.
tubulointerstitium through release of vasoactive Dog A
and infl ammatory substances that trigger renal Diet history:
13
scarring and loss of function. • Adult maintenance dry food (100 g protein/1000 kcal); consuming
Additional studies have shown that dogs with approximately 500 kcal/day for a total of 50 g protein/day
spontaneous CKD and urine protein-to-creatinine • ¼ cup boiled, chopped, boneless, skinless chicken breast; consuming
ratios (UPCs) of 1 or greater are at increased approximately 53 kcal and 10 g protein/day
risk for uremic crisis and death compared with • No other treats or table foods provided
14 • Total protein intake approximately 60 g protein/day or 109 g
dogs that have UPCs less than 1. In dogs with protein/1000 kcal
inherited glomerulonephropathy, proteinuria was
reduced signifi cantly when they were switched Dog B
from a diet containing 72 g protein/1000 kcal to Diet history:
one containing 33 g protein/1000 kcal, but this • Adult maintenance dry food (60 g protein/1000 kcal); consuming
fi nding was not evaluated in relation to patient approximately 525 kcal/day for a total of 31.5 g protein/day
15 • One commercial dog treat (20 g protein/1000 kcal); consuming
morbidity and mortality.
A reduction in dietary protein intake by 25% to approximately 25 kcal/treat and 0.5 g protein/day
50%, based on severity of proteinuria, azotemia, • No other treats or table food provided
16 • Total protein intake approximately 32 g protein/day or 58 g
and clinical signs, has been recommended. protein/1000 kcal
Proteinuria in Cats TABLE 4.
Proteinuria is inversely associated with survival in Dietary Recommendations for Protein Restriction
azotemic cats and signifi cantly associated with the PROTEIN
17,18 DOG DIETARY NEEDS RECOMMENDED DIET
development of azotemia in nonazotemic cats. REDUCTION
Studies investigating the role of reduced protein Dog A 25%–50% Diet containing • Commercial adult
diets in cats are limited to those with confounding reduction approximately maintenance dry
dietary variables, such as phosphorus restriction. 54–82 g food (containing 60 g
As a result, the independent infl uence of protein protein/1000 kcal protein/1000 kcal)
on disease progression in these patients is not well • Discontinuation of
known. chicken breast
Later Stage CKD Dog B 25%–50% Diet containing • Therapeutic renal
reduction approximately diet (containing 39 g
In both dogs and cats with IRIS stages 3 and 4 29–44 g protein/1000 kcal)
CKD, reduced protein intake may help reduce protein/1000 kcal • One current
accumulation of nitrogenous wastes from protein commercial dog
metabolism that contribute to azotemia and treat/day
uremia. High protein intake may exacerbate
uremia, contributing to the morbidity associated Cachexia
with CKD. Cachexia—loss of lean body mass—is common
Studies in both dogs and cats with CKD have in patients with CKD and may alter strength,
demonstrated that modifying protein intake immune function, wound healing, and overall
2,3 While urea is not a
reduces blood urea nitrogen. 19
major uremic toxin in cats and dogs, it is a marker survival. Although the overall prevalence of renal
for nitrogenous wastes that contribute to uremia. cachexia is unknown in dogs and cats, a recent
Additionally, hyporexia, which occurs commonly study found that underweight dogs—those with a
with late stage CKD and/or suboptimal protein body condition score (BCS) of 1 to 3 out of 9—
intake, can increase the production of uremic had reduced survival compared with dogs with a
toxins through endogenous protein catabolism. BCS of 4 or greater.20
tvpjournal.com | March/April 2016 | TODAY’S VETERINARY PRACTICE 61
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