Urinary Flashcards
DER and RER calculation
- RER = 70 x (BW in kg)0.75
DER = RER X some factor
best way to measure food dose
weight, rather than volume
components of a good feeding plan (2)
Nutritional assessment performed
Diet history obtained
- Identify key nutritional factors
- Compare products and select best choice
- Determine energy requirement
- Calculate food dose
- Recommend feeding managements strategies
- Follow-up plan
what are uroliths, and basic pathogenesis
- Condition where calculi form in the urinary tract (kidneys, ureters, bladder, urethra)
Urolith formation
* Result of multiple pathophysiologic processes resulting in high concentrations of poorly soluble crystalloids in the urine
common types of uroliths for dogs and cats
- calcium oxalate
- struvite
- urate
others
systemic disorders that can lead to uroliths, and what type of urolith
- Hypercalcemia (calcium oxalate)
- Cushing’s disease (calcium oxalate, struvite)
- Defects in purine metabolism e.g. portal vascular abnormalities (ammonium urate)
urinary tract disorders that can lead to uroliths, and what type of uroliths
- Urease-producing bacterial infection (struvite)
- Foreign material e.g. suture or catheters (struvite mainly, sometimes calcium oxalate)
- Renal tubular acidosis (calcium oxalate)
what is crystalluria and how do we evaluate
- Excretion of crystals in urine
- Need to evaluate in fresh urine
> Artifacts in stored/refrigerated urine
> Restore to room temperature before examining - Trace crystals may be normal in highly concentrated urine (high USG)
- Presence of crystals does not mean uroliths
what is RSS? what is its purpose?
RELATIVE SUPER SATURATION (RSS)
RSS is used to assess the DIET-SPECIFIC RISK of crystal/urolith formation in urine of dogs and cats
* i.e. How likely is the animal to form crystals/uroliths?
examples of what RSS looks at to assess urolith risk
- Calculogenic ions
- Urine pH
- Urine volume
how is RSS measured?
- the formula of interest is fed to a minimum of 6 cats or dogs during a 7 day adaptation period
- the total urine produced is then collected for the next 3 days while the cats or dogs are still fed the formula
- the urine volume, pH and ionic composition are measured
- the solute activity is calculated - this is the concentration of the constituents that are free and available to form uroliths
- the activity product is then calculated - this represents the number of potential interactions or complexes between these constituents, and is obtained by multiplying all the solute activities relevant to a given urolith
- this activity product is then divided by a known constant thermodynamic solubility product fo a given urolith to determine the RSS
ZONES/LEVELS OF URINARY SATURATION from RSS
Undersaturated
* No crystal nidus formation or growth
* Dissolution possible
Metastable
* Nucleation possible but minimal growth
* Dissolution no longer possible
Oversaturated
* Spontaneous nucleation with maximal growth
* Dissolution not possible
RSS reccomendation to dissolve pure struvite urolith
RSS for struvite <1
pH effect on uroliths
different materials are soluble at different pH, and so the type of uroliths that can form are influenced pH
what is the composition of a struvite crystal?
MAGNESIUM AMMONIUM PHOSPHATE
pathogenesis of struvite crystal
- UTIs with urease-producing bacteria→alkaline urine
- Cats usually sterile, occasionally UTIs (e.g. diabetes)
- Diet: magnesium, phosphorus, protein (ammonium)
struvite crystals most prevelant in what breeds…
- Breed: Miniature schnauzers, Beagles, Bichon Frises, Shih Tzus, Pugs,
Dachshunds - Age: younger cats
biologic behaviour of struvite crystals
- Fast growth; smooth; dissolvable; alkaline environment; high recurrence rate (UTIs); radio-dense
STRUVITE – TREATMENT AND PREVENTION
- Dissolution is possible
> Removal only if necessary, with stone analysis and culture & sensitivity - Treat the underlying UTI with antibiotics
> Requires long-term antibiotic therapy as stones dissolve because they hang on to the bacteria (e.g. months of treatment)
> Ideally based on culture/sensitivity
What nutrient is the most important to consider for ALL uroliths?
WATER
>goal is increasesed consumption
what helps cats drink water, reduces RSS for struvite?
increased sodium intake through diet
KNFS FOR STRUVITE, summary
- Protein – Restrict (dogs; less in cats)
> protein = high ammonia
>lower BUN helps promote polyuria
>Restrict significantly for dissolution and moderately for prevention - Magnesium – Restrict
- Phosphorus – Restrict
diet acidifiers to help dissolve struvite
-DL-methionine
-Ammonium chloride
CALCIUM OXALATE uroliths characteristics: radiology, pH, dissolution?
- Radio-opaque
- Not pH dependent like some other stones
- Not amenable to dissolution
CALCIUM OXALATE RISK FACTORS
-Males > females
-Middle aged to older
Dogs: Small breeds (Lhasa Apso,
Bichon Frise, Pomeranian, Miniature Poodle, Miniature Schnauzer, ShihTzu,Yorkie)
Cats: Burmese, Persian, Himalayan, Siamese
CALCIUM OXALATE RISK FACTORS
- High USG/low urine volume
- Excess solute excretion
- Excess supplementation of vitamin C, vitamin D
- Diseases (hypercalcemia, Cushing’s, obesity)
- Drugs: steroids (promote urinary calcium excretion)
CALCIUM OXALATE TREATMENT AND PREVENTION
- Dissolution is not the solution!
- Surgical removal
- Stone analysis
- Prevention
> Therapeutic urinary diet with RSS testing
KNFs FOR CALCIUM OXALATE
- WATER
- Calcium - Restrict?
- Recall, Ca2+ efficiently and tightly regulated (homeostasis)
> Low serum [Ca2+]→↑ absorption of Ca2+ and bone resorption
> High serum [Ca2+]→hypercalciuria (i.e. more Ca2+ in urine)
> Answer: moderate restriction - Oxalates – Restrict?
- Absorption affected by serum [Ca2+]:
> If ↓serum [Ca2+]→oxalate hyper-absorption from GIT to accompany Ca2+ hyper-absorption→hyperoxaluria - Answer: avoid high oxalates and balance with moderate calcium restriction
- Vitamin C - Restrict
> Precursor for oxalate
> Limit to prevent oxalate formation (especially supplements) - Protein
- Excessive protein (i.e. >40% DM for dogs) contributes to hypercalciuria
- Excessive protein contributes to hypocitraturia
> Citrate (negatively charged) in urine binds Ca2+ →↓ Ca2+ available to complex with oxalate - Also promotes oversaturated urine
- Phosphorous
> If severely restrict can get ↑ Ca2+ absorption from GIT and more
resorption from bone→hypercalciuria - Magnesium
- Can inhibit calcium oxalate formation by binding both Ca2+ and oxalates→prevent complexing
- However, too much can promote hypercalciuria
URINE ALKALINIZING AGENTS
- Potassium citrate
how do we manage recurrence of calcium oxalate uroliths? is it common?
- Common!
- Radiographs every 3-6 months first year
- UA at 2 &4 weeks post op, then every 3 months for first year
- USG within target (at-home monitoring)
AMMONIUM URATE risk factors
- Genetic mutation: Dalmatian, English Bulldog
- Portosystemic vascular shunts: Yorkie (other toy breeds), Mini Schnauzer, Cats (less frequent)
- Sex: Male>female
- Age: <1 year
difference between purine processing normally and in dogs with problems
uricase enzyme non-functional in some dogs, eg. dalmations
>cannot convert uric acid –> allantoin
-results in increased uric acid in urine (2-4x)
-small % of dogs actually form stones
how do ammonium urate stones form in non-dalmations
- Liver dysfunction:
> Portal vascular anomalies
> End-stage failure/cirrhosis - Inadequate conversion of uric acid→allantoin
- Inability to convert ammonium→urea
- End result: ↑ uric acid and ammonia in blood and urine
KNFs FOR AMMONIUM URATE
- Water - Increase
- Purines (protein) - Restrict
> Shellfish, fish, goose, heart, kidney, liver, gravies
> Restrict at least within first 3 ingredients
> No high purine treats - Sodium
- Salt can help increase thirst and urine volume
- May cause hypercalciuria
- pH of 7.1-7.5 (canine) and 6.8-7.2 (feline)
> Can use potassium citrate or sodium bicarbonate
> pH >7.5 should be avoided as it could predispose to calcium phosphate crystals
AMMONIUM URATE - TREATMENT
- Presumes crystal character on UA = urolith type (e.g. ammonium urate crystals)
- +/- Dissolution (dissolve, grow, or static)
- Removal: surgery, lithotripsy, urohydropropulsion
- Stone analysis
- Medical management
> Diuretics
> Xanthine oxidase inhibitor (e.g. allopurinol) - DOGS
> Urine alkalinizing agents (e.g. potassium citrate) - Need allopurinol (xanthine oxidase inhibitor) in addition to dietary change
ALLOPURINOL - what is it, what is its use
- Xanthine oxidase inhibitor
> Decreases production of uric acid
> Only prescribe if feeding low purine diet to minimize amount of xanthine formed
> Otherwise can see ↑ xanthine uroliths
for ammonium urate treatment
FELINE IDIOPATHIC CYSTITIS - what is it, what are symptoms and types
- Most common cause of LUTD in cats (55-66%)
- Similar clinical signs (stranguria, hematuria, pollakiuria)
- Non-infectious
- Inflammatory
- Chronic, intermittent with acute flare ups
- Diagnosis of exclusion
main cause of feline idiopathic cystitis
- STRESS
- Leads to an exaggerated SNS response, blunted endocrine response
- Affects bladder, as well as other body systems
FIC - RESOLUTION
- For most cats, resolves within 1 week – for some 2 to 3 days
- Recurrence common (chronic condition)
- Analgesics often required during flare up
FIC-TREATMENT
- Manage environment
- Identify potential stressors
- Litterbox placement
- Routine – minimize changes
- Other animals
- Pheromone therapy, medications
- Environmental enrichment
- Nutrition?
KNFs FOR FIC
- WATER
> May reduce irritation to bladder wall - “Calming nutrients”
> Alpha-casozepine
> L-tryptophan
struvite summary: treatment
- Dissolution → feed diet one month beyond resolution
- Treat UTI (dogs) → culture & antibiotics
- Surgical removal only if necessary (based on case)
calcium oxalate summary: treatment
- Surgical removal
- Prevention of recurrence → high moisture, appropriate diet and/or urine alkalinizer
ammonium urate summary: treatment
- Dissolution → diet low in purines
- Surgical removal (based on case)
- Xanthine oxidase inhibitor (allopurinol) if indicated
FIC treatment summary
- Manage environmental stress
- Dilute urine
- Add calming agents
