Oakley stones 1 Flashcards
etiology of bladder stones
- Several theories
- Supersaturation of urine with minerals
- Formation of crystals
- Decrease inhibitors of crystalisation
- Aggregation of crystals
simple vs mixed vs compounds stones
Simple stone
* No nidus or shell,
* ≥ 70% of one type of mineral
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Mixed
* < 70% of one mineral
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Compound
* Nidus or stone with ≥ 1 surrounding layers of different mineral composition
how common are different types of stones? what is most common, generally?
- 85-91% : struvite & calcium oxalate
- Calcium Oxalate 42-45%
> 98% (Fe) and 50% (Dog) of upper calculi - Struvite 43-44%
- Purine 5%
- Calcium Phosphate 1%
- Cystine 1 % (recently doubled)
- Silicate <1%
Epidemiology of Canine Urolithiasis
most common types in female vs male dogs?
Female dogs : struvite uroliths
Male dogs : oxalate, cystine
Epidemiology of Canine Urolithiasis
more common stones in younger cats and dogs?
Younger dogs : Struvite > oxalate
Young cats: urate
what are the most common stone types in canada?
- calcium oxalate 49.5%
- struvite 35.5%
- urate 3.4%
- calcium phosphate 2%
- silicate
- cysteine
which type of stones tend to be found in kidneys, ureter, bladder?
Kidneys:
- calcium oxalate
- silicate?
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Ureter
- silicate?
- dried solidified blood
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bladder, lower system
- cysteine
- suture
- struvite
- urate
- xanthine
Major Complaints due to bladder stones
- Pollakiuria
- Stranguria
- Hematuria
stones - what might we find on physical exam?
- Stone may be felt at the bladder palpation
- /- tense abdomen
- Rectal examination: some stones palpable in urethra
bladder stone differentials
- Urinary tract infection (UTI)
- Urolithiasis
- Cystitis
- Tumor
abdominal radiographs for stones, pros and cons
- radiolucent stones
- other techniques that can help here?
Pros
* Can measure and count stones
* Can look at urethra
* Rule out kidney and ureteral stones
Cons
* Radiolucent Stones: urate and cystine
* (“I Can’t see yoU”)
* Less true with digital radiographs
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* Contrast radiographs can help us
- ultrasound is better as we can see all stone types
abdominal ultrasound for uroliths pros and cons
pros
- all stones visible
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cons
- Can not count or measure them
- Urethra not seen
What can help guesstimating the type of urolith?
- Crystals
- Urine pH
- Shape
- Breed
- Underlying disease
- UTI
urinalysis - what do we see with uroliths?
- Hematuria and proteinuria common with stones
- Bacteriuria and pyuria common with struvite and urate stones
- Crystals?
- pH?
- Urine Specific Gravity (USG)?
Does the presence of crystals indicate the presence of stones?
NO
the presence of crystals in urine depends on what?
- how should we treat our sample to best see them?
- significance?
Depend on many factors
* In vivo: diet, infection
* In vitro: duration of urine storage, temperature, pH, contaminants
* Iatrogenic causes: Radiocontrast media, allopurinol
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* Use fresh urine sample
* Avoid refrigeration
* Rarelly clinically significant
Types of Uroliths and Urine pH that they form in (acid vs alkaline)
- important consideration for this when trying to deduce type in clinic?
Acid pH (<7)
- cystine
- silicate
- acid uric
- calcium oxalate
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Alkaline pH (>7)
- Struvite
- Calcium phosphate
- Ammonium urate
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pH at stone formation vs pH at visit
Cystine uroliths- Particularity in who?
- Males(98%)
- Except Newfoundland
> Young/both genders
> Nephroliths+++
cystine stone geography
- 1-2% in NA
- 8-26% in Europe
Silicate stones - predisposing causes in environment?
- Soil
- Soybean Hull
- Rice hull
- Corn gluten feed
- Homeopathy
- +++ Kenya
Urate Stones and Genetics
- what breeds and why
- dalmations (2/3), english bulldogs, black russian terriers
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Dalmatians - Autosomal Recessive Gene
- Missense mutation SLC2A9
- Urate transporter
- All dalmatians homozygous
- 25% of males have stones
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Non-Dalmatians - Same mutation BUT no hepatic dysfunction
Cystine Stones and Genetics
- what breeds and why?
- is there anything we can do to avoid issues?
Newfoundland, Landseer
- Autosomal Recessive Gene
- Missense mutation SLC3A1
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Labrador Retriever
- Different mutation of SLC3A1
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Australian Cattle dog, Border Collie, Mini Schnauzer
- Different mutation of SLC7A9
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BREED SPECIFIC MUTATION TEST Detects cystinuric AND asymptomatic carrier
Cystine Stones and Genetics in Cats
- Recent reports:
- SLC3A1 mutation in 1 cat
- SLC7A9 gene variants in 4 cats
exam?
Androgen- dependent type III Cystinuria
- what is this condition?
- who gets it? when? signs?
- genes?
- Detected later in life
- Less severe clinically
- ONLY MALES
- Castration lower cystine excretion
- No gene mutation identified
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Preliminary test to identify dogs at risk of stone formation being evaluated….
Predisposing Conditions for Stones dogs
- hyperadrenocorticism
> calcium oxalate
<><> - hyperparathyroid
> calcium oxalate, calcium phosphate
<><> - portal anomaly
> urate
<><> - hematuria
> dried solidified blood
<><> - UTI
> struvite
what factors can lead to xanthene uroliths
Diet high in purine (meat based)
+
allopurinol
what 5 of recurrent stones are suture induced
~ 9.5 % of recurrent stones are suture induced
can weight affect urolith formation?
obesity is. apredisposing factor
Struvite and Urinary Tract Infection
- what is the connection?
- In dogs: struvite secondary to alkaline urine caused by Urease- producing bacteria
Sterile Struvite - urine pH? infection?
- Alkaline urine
- No infection
Likely Struvite if we see these 4 things:
- female dog
- UTI
- struvite crystals
- alkaline urine
likely ammonium urate if we see these things
- PSS
- Dalmation or English Bulldog
Likely Calcium Oxalate if we see these 3 things
- acidic urine
- schnauzer
- male
when should we treat uroliths? - depends on what?
Depends on
* Clinical signs > Only treat if clinical signs!
* Location of the stones
* Type of stones
* Presence of discomfort or obstruction requiring immediate removal
treatment for kidney stones?
- Do NOTHING
> High morbidity and mortality rate with kidney surgery - Unless obstruction, or recurrent infection or pain
- If obstruction
> Dogs: ureteral stents
> Cats: subcutaneous ureteral bypass
options for treatment of uroliths
Medical
> dissolution
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Removal
> surgery
> minimally invasive
medical urolith dissolution
- goals
- efficacy
Goal
* ↓ concentration of calculogenic salts
* ↑ urine volume
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Efficacy
* High for struvite in dogs and cats
* moderate for urate and cystine in dogs
medical urolith dissolution disadvantages, contraindications
Disadvantages
* Owner compliance
* Cost of medical dissolution ≈ surgical treatment
* Low efficacy for nephro/ureteroliths
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Contra-indications
* Obstruction
* Large solitary urolith filling the bladder
* Comorbidities
Treatment based on type of stone and location - reccomendations for:
* Bladder stones and likely struvite
* Bladder stones and likely NOT struvite
* Obstructive urethral stones
- Bladder stones and likely struvite
> Dissolution= 1st choice unless lots of
pain - Bladder stones and likely NOT struvite
> Removal of stones - Obstructive urethral stones
> Urgent removal
Does the size of the stone affect the success of medical dissolution?
B.No
Treatment Plan for Struvite
- Hill’s s/d (acidifying diet) or Royal Canin Urinary S/O
- Small meals throughout the day (avoids alkaline tide)
- Antibiotic treatment (amoxicillin or based on sensitivity)
- Recheck after 2 w and then every 4 w
> Radiographs : size of the stone
> Urinalysis : pH, USG, crystals??
> Urine culture
Struvite Uroliths - hills urinary diet > how fast does it work? how does it work?
- how long should we continue with it?
- when is it not great?
- Dissolved by Hill’s s/d in 8-10 weeks
> Markedly restricted in P, Ca,
Magnesium diet
> High salt content → more acidic urine - Continue ≥ 1 month after calculi no longer visible on radiographs
- Recheck urine culture 4 weeks after
- Limitations of the diet
> Not effective if UTI persists or if ureteroliths or nephroliths
Contra- indications Medical Dissolution
- Restricted protein content
> Pregnant or lactating female, growing animals or after a surgery - High salt content
> Congestive heart failure, hypertension or nephrotic syndrome - High fat content
> Risk of pancreatitis in miniature schnauzers
When can we stop antibiotics for a urolith?
The antibiotics should be continued throughout the course of the medical dissolution treatment
- this may change in the future
When can we stop s/d diet in dogs?
C. 1 month after we can not see any stone on radiographs
Is it necessary to maintain an acidifying diet life long to prevent struvite in dogs ?
No
Is it necessary to maintain an acidifying diet life long to prevent struvite in cats?
YES (vs no for dogs)
> alkaline pH problem in cats, we don’t know why
Prevention of Struvite Recurrence
- Eradication /prevention of UTI
> Based on the results of urine culture and sensitivity findings - Maintaining acidic urine in cats
> Hill’s c/d = good maintenance diet
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↑ water consumption - Canned diet (>70% moisture)
- Water fontain, flavoring water
- Several bowls of water
- Several meals per day
- Late meal late
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Maintain - USG < 1.020 in dogs
- USG < 1.045 in cats
<><> - Monitor urine pH and sediment- MAKE OWNER BUY A REFRACTOMETER
Reevaluation of the Patient after urolith - when to recheck? what to do if no improvements after 2 months?
- Recheck every 2 weeks: UA +/- Urine culture, rads or US
- If no dissolution after 2 months
> Owner compliance, persistent UTI, and urolith type?
> Surgical removal should be considered
