Nutritionally Managed Diseases

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Nutritionally Managed Diseases

• Urolithiasis and Renal Failure

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Urolithiasis
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Urolithiasis in Cats and Dogs

• Lower urinary tract disease affects 7 of all
  cats and 3 of all dogs
• Urolithiasis is specific lower UTD characterized
  by presence of urinary crystals (uroliths or
  calculi)
• In cats, urolithiasis is considered one
  manifestation of a collection of UTD referred to
  as feline lower urinary tract disease (FLUTD)

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Incidence of Urolithiasis

• Disease of primarily adult animals
• Cats 2 to 6 yrs of age
• Dogs 6 to 7 yrs of age
• Gender predispositions
• Female cats higher prevalence of struvite
  urolithiasis than male cats
• Breed predispositions
• Himalayans and Persians have higher risk of FLUTD
• More common in Miniature Schnauzers, Lhasa Apsos,
  and certain Terrier breeds

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Clinical Signs of Urolithiasis

• Frequent urination
• Urination in inappropriate places
• Prolonged squatting or straining following
  urination
• Dribbling of urine
• Anorexia
• Vomiting
• Diarrhea
• Dehydration

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Urolith Mineral Type

• Most common
• Struvite (magnesium ammonium phosphate)
• Calcium oxalate
• Most common difference between dogs and cats
• Most struvite uroliths in cats are not associated
  with a urinary tract infection (sterile struvite)

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Struvite Urolithiasis in Cats

• 95 of uroliths were struvite
• Until recently
• Incidence of calcium oxalate have increased over
  past 10 years
• 3 types
• Sterile struvite
• Infection-induced struvite
• Urethral plugs containing high concentration of
  struvite

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Struvite Formation

• Sufficient concentration of Mg, NH3, and PO4 must
  be present
• These minerals must remain in urinary tract long
  enough for mineralization to occur
• Thus production of low volumes of concentrated
  urine is key!
• pH for crystalline formation must exist
• Crystallization occurs at pH above 7.0
• However, urine may not be consistently alkaline

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Dietary Risk Factors

• Foods urinary acidifying properties
• Level of Mg
• Digestibility
• Caloric density
• Water content

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Dietary Risk Factors

• Factor presence of composite minerals
• Feline urine high in ammonium due to high protein
  requirement and intake
• Urine phosphate in healthy cats is also high
  enough for struvite formation regardless of P
  intake
• Urinary Mg is low and affected by diet

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Dietary Risk Factors

• Factor presence of composite minerals
• Specifically Mg
• Most commercial cat foods only contain 0.1 Mg
  and in studies it took from 0.4 to 1.0 Mg to
  induce struvite formation
• Recent evidence suggests that dietary Mg is less
  significant than urine pH, urine volume, and
  water balance

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Dietary Risk Factors

• Factor urine pH
• Healthy cats have a urine pH of 6.0 to 6.5
• Except after meals there is a rise in pH referred
  to as postprandial alkaline tide (compensation
  for loss of gastric acids secreted during
  digestion)
• Magnitude is dependent on meal size and the
  alkaline/acidic component of that meal
• Can increase pH to 8.0 in some cats

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Dietary Risk Factors

• Factor urine pH
• Type of food may alter urine pH
• Urine pH highest in cats fed dry food (7.55) and
  lowest in those fed canned food (5.82)
• Those fed canned foods had NO incidence of
  struvite formation
• In the lab when added NaOH to urine-struvites
  formed!
• At similar levels of energy, DM, and Mg intake,
  the most important factor is URINE pH

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Dietary Risk Factors

• Factor urine pH
• Type of food may alter urine pH
• Cats are carnivores
• Carnivorous diet has the effect of increasing
  acid excretion and lowering urinary pH
• Result of high concentrations of sulfur AA in
  meats
• Oxidation of sulfur AA increases sulfate
  excretion in urine and thus decreasing pH
• Thus, inclusion of high levels of cereal grains
  and low level of meat products may contribute to
  struvite formation (exceptioncorn gluten meal
  has high sulfur AA concentration)

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Dietary Risk Factors

• Factor urine volume
• Dry foods contribute to decrease fluid intake and
  urine volume
• Cats will increase voluntary water consumption,
  but not enough to compensate for lower water
  content of food
• Fat content and caloric density influences water
  turnover in cats
• High fat diet causes increased water in urine
• Water content in urine similar to cats consuming
  low-fat, canned ration as those eating dry cat
  food
• water excreted in urine is directly related to
  fat and energy content of the diet regardless if
  is dry or canned

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Dietary Risk Factors

• Factor feeding method
• Feeding cats ad libitum increases frequency of
  urination and volume of total urine produced
• As size of meal increases due to meal-feeding,
  the change in urine pH is more dramatic and the
  presence of struvites increased

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Dietary Management

• Goal urine Ph of 6.6 or less
• Diet should produce a slightly acidified urine,
  be moderate in caloric density, and high in
  digestibility, and contain relatively low levels
  of Mg
• pH should be 6.0 to 6.5
• Increase urinary acid excretion by using animal
  proteins
• Consumed in smaller amounts, lower DM and Mg
  intake
• Lower DM intake decreased fecal matter and
  fecal water, thus increasing urine volume

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Struvite Urolithiasis in Dogs

• Sterile versus Infection-induced Struvite
• Incidence of sterile struvite low in dogs
  compared to cats
• Of 11,000 cases, 54 of females and 3- of males
  had Staphylococcus in urine
• Dogs produce urine with high concentrations of
  urea are more susceptible
• Bacteria converts urea to ammonia

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Struvite Urolithiasis in Dogs

• Sterile versus Infection-induced Struvite
• Infection-induced higher in female dogs may be
  due to anatomical difference
• Shorter urethra of female dogs allows bacteria to
  move up urethra to bladder to cause infection
• Suggested that dogs confined indoor for longer
  periods of time may also be more susceptible

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Dietary Management in Dogs

• Acidifying diets as in cats not as successful
• Feeding a food that results in acidified urine
  and reduces concentration of struvite components
• Preventing recurrence of UTI

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Calcium Oxalate Urolithiasis

• Incidence increasing due to increased use of
  urine-acidifying diets containing low levels of
  Mg
• Cats and dogs with this type of urolithiasis have
  slightly acidified urine and mild acidemia
  resulting in Ca and P mobilization from bone to
  buffer excess acid
• Resulting in more Ca in urine for urolith
  formation

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Risk Factors

• Urine-acidifying diets
• Low Mg intake
• Excess sodium consumption (increases renal
  excretion of Ca)
• Excess Vitamin C (ascorbic acid is precursor for
  oxalate)
• Low water intake

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Dietary Management

• Reduce urinary concentration of Ca
• Maintain dilute urine between pH 6.3 and 6.9
• Highly digestible diet containing more moisture
  (canned food or add water to dry food)
• Highly digestible diet contain adequate Ca and Mg

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Chronic Renal Failure
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Renal Failure

• Characterized by irreversible and progressive
  loss of kidney function and the development of
  clinical signs reflecting the kidneys inability
  to perform normal functions

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Renal Failure

• Causes
• Trauma
• Infection
• Immunological disease
• Decreased blood flow to the kidney (ischemia)
• Genetic anomalies
• Exposure to toxins

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Kidney Function

• Nephrons are the functional unit
• Consist of glomerulus and system of tubules where
  reabsorption and excretion occur
• Glomerulus is a tuft of capillaries where water,
  waste products, and electrolytes are filtered
  from the blood
• Tubules originate at base of glomerulus and
  reabsorb products in the glomerulus filtrate
• At end of tubule filtrate only contains what is
  to be excreted

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Kidney Function

• Waste products
• Products of protein catabolism (urea, ammonia)
• Electrolytes, trace minerals
• Loss of at least 70-85 of functional capacity
  occurs before a pet will show signs of renal
  failure

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Signs of Renal Failure

• Increase water consumption
• Increased urination
• Reduced capacity to concentrate urine
• Increase volume of urine produced
• Regress in housebreaking training
• Involuntarily empty bladder while sleeping

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Signs of Renal Failure

• Many of clinical signs are associated with
  presence of azotemia or uremia
• Azotemia accumulation of nitrogenous waste
  products in the blood (urea or creatinine)
• Uremia elevated concentration of urea in blood
  and commonly refers to collection of clinical
  signs of renal failure

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Signs of Renal Failure

• Anorexia
• Vomiting
• Depression
• Electrolyte imbalance
• Weight loss
• Chronic diarrhea
• Neurological signs

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Signs of Renal Failure

• Elevated BUN
• Elevated plasma creatinine levels
• Indicators of renal function
• Not most sensitive, but easy and inexpensive tests

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Role of Diet in Disease Progression

• In contrast to rats, feeding elevated levels of
  protein has not been shown to cause a progression
  of renal disease in dogs
• Additionally, studies do not show that
  restricting dietary protein will inhibit onset or
  progression of disease
• May be more detrimental (protein deficiency)

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Role of Diet in Disease Progression

• Dietary restriction of P has been reported to
  slow progression and clinical signs of renal
  failure
• Will not stop progression of the disease all
  together!
• Level suggested 0.4 P

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Role of Diet in Disease Progression

• Amount and type of fat may alter disease
  progression
• Dogs and cats with renal dysfunction often
  exhibit elevated serum cholesterol and
  triglycerides
• Feeding PUFA decreases serum lipids in dogs (fish
  oil, safflower oil) compared to dogs fed diets
  containing saturated fats

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Role of Diet in Disease Progression

• Omega 3 content may be more important

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Goals of Dietary Management

• Minimize accumulation of protein catabolites in
  blood but still provide adequate protein for
  maintenance
• Provide adequate calories from nonprotein sources
  so pet is not breaking down body stores

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Protein

• Generation and excretion of urea is proportional
  to daily turnover of dietary and body protein
• Protein in excess of reqt.
• When protein used for energy
• Dogs in renal failure need 1.25 to 1.50 g
  protein/kg BW
• Diet containing 12-25 CP on DMB
• Cat diets must account for higher CP reqt.
• Feed max level of CP that will control uremia
• Determine CP intake as of calories and slowly
  decrease until signs have diminished

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Fat

• Enough calories to spare protein from being used
  as energy source
• Type of fat important
• Omega 3 fats (marine fish oils, flax oil)
• Omega 3Omega 6 ratio of 51

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Phosphorus

• Normalize serum P and prevent bone
  demineralization and Ca deposition in soft
  tissues
• Dietary CP is principle source of P
• Lower CP intake lowers P intake
• As disease progresses dietary restriction of P
  may not be enough
• Use of phosphate-binding agents

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Dietary Fiber

• Reduced ability of kidneys to excrete nitrogenous
  end products of protein catabolism is cause of
  clinical signs of disease
• Second way to mange N excretion is by altering
  the route of excretion
• Shift from urine to feces using fermentable fiber
  sources (FOS, gum arabic, beet pulp)

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Dietary Fiber action in Renal Failure
Nitrogen
Carbohydrate
Bacterial Cell
Bacterial fermentation of N and CHO results in
SCFA production
Division and growth into 2 bacterial cells
Increased intestinal blood flow
Urea pulled from the blood into the colon
Twice as much N in form of bacterial CP
N excreted safely from the body in the form of
spent bacterial cells in the feces
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Dietary Fiber action in Renal Failure
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Dietary Fiber action in Renal Failure
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Dietary Fiber

• Success limited to dogs
• Reduces protein and energy digestibility
• Cats have higher CP and fat requirement
• Limited ability for fermentation