Urolithiasis - Green Flashcards
Does the observation of individual crystal types in urine mean
the patient is at risk for developing Urolithiasis?
Not necessarily
What are the different types of urolithiasis?
-
Mixed
- < 70 1 type of crystal
- no identifiable nidus or shell
-
Compound
- Nidus of 1 crystal w/ surrounding layers of another crystal (common)
-
Matrix urolith
- matrix w/o appreciable crystalloid
What are the 2 most common types of stones in Dog & Cats?
- Struvite
- Oxalate
In struvite urolithiasis, where is the most common site for stones?
Does it recur?
- Bladder (dogs & cats)
- High recurrence (>20%)
What types of animals will you most commonly see struvite stones in?
Younger animals
What type of urine will you see struvite stones in?
Alkaline urine
due to decreased solubility
In dogs, what is the pathogenesis of struvite urolithiasis?
UTI w/ urease positive bacteria ⇒makes urine more alkaline
You would not normally remove stones from the kidney b/c of complications. What are the two exceptions to this rule?
- Stone in kidney associated w/ infection
- Stone in renal pelvis associate w/ recurrent pyelonephrits or obstruction
In CATS, does UTI play a primary role in struvite urolithiasis?
NO!
What must you do for every patient you dx w/ stones?
Urine Culture
Oxalate crystals are found where in dog?
Where in Cats?
- Dogs→ Bladder
- Cats→ Kidneys, ureters, bladder
Is UTI a predisposing factor or complication of Oxalate Urolithiasis?
A Complication
(oxalate stones have jagged edges)
What are risk factors for oxalate urolithiasis in dogs?
- Breed: Mini schnauzer, Lhaso apso, Yorkie, Bichon frise, Shihtzu, Mini poodle
- Age: > 4yrs (8-12 highest risk)
- Neutered males
- Overweight
- Pet vs working
What are risk factors for oxalate urolithiasis in cats?
- Exclusive acidifying diet
- Middle-age to older: (over 20, any cat can get no other predispositions matter)
- Males > females
- Breed: Persian, Himalayan
- Exclusive indoor cat
What is the pathogenesis of Oxalate Urolithiasis?
-
Hypercalciuria ( any cause of hypercalcemia)
- Absorptive (GI) hypercalciuria
- Renal leak Hypercalciuria
- Resorptive (bone) hypercalciuria
- Primary hyperparathyroidism
- Chronic acidosis & acidifying diets
What other conditions are associated with Oxalate Urolithiasis?
-
Hyperadrenocorticism (dogs)
- Increased risk of calcium containing stones
- Idiopathic hypercalcemia of Cats (IHC)
- 33% of cats w/ oaxalate stones have (IHC)
- Hx of acidifying diets
- Other causes of hypercalcemia
Urate Urolithiasis is most common in what two dog breeds?
- Dalmations
- English Bulldogs
If you have a dog with recurring urate urolithiasis (not a dalmation or Eng. Bulldog) and high post prandial bile acids what should be your top rule out?
- Portosystemic shunt
- these animals may also have struvite stones
Is UTI a complication or predisposing factor to Urate urolitiasis?
Complication
Where does Urate urolithiasis occur most commonly?
- Bladder
- Urethra
- Males > Females
What is the recurrance rate for patients with Urate Urolithiasis?
30-50%
What is the predisposing factor of Dalmations to geting Urate urolithiasis?
Defective uric acid metabolism
Describe how defective uric acid metabolism predisposes Dalmations & Eng Bulldogs to Urate urolithiasis.
- Urate derived from metabolism of purines
- Converted to allantoin by uricase in normal dogs
- Dalmations: Impaired transport of urate into hepatocytes (where the uricase lives so it cant get converted properly)
- Urate reabsorption decreased and secretion increased in the dalmation kidney = more urate in the urine
Is cyctine urolithiasis common in dogs and cats?
- Dogs ⇒ Uncommon
- Cats ⇒ Rare
What are the high points of Cystine Urolithiasis?
(4)
- Usually in Bladder & Urethra
- UTI is complication not predispoing factor
- High recurrence (47-75%)
- Cystinuria decreases in severity w/ age (>5yrs) in some dogs
Which stones look like “jacks”?
What is their prevelance?
- SIlicate stones
- Dogs ⇒ Uncommon
- Cats ⇒ extremely rare
What is the “textbook” history of a dog with Struvite Urolithiasis?
- Mini Schnauzer, Bichon frise, Lhasa apso, Shih tzu, Mini Poodle
- Female > Male
- Younger
What is the “textbook” history of a dog with Oxalate urolithiasis?
- Mini Schnauzer, Bichon frise, Lhasa apso, Shih tzu, Yorkie, Mini Poodle
- Male > Female
- Older
What is the “textbook” history of a dog with Urate urolithiasis?
- Dalmation, English bulldog
- Male > Female
- Middle aged (unless PSS, then can be young)
What is the HX of a dog with urolithiasis in the Kidney?
- No signs - very common seen on x-rays taken for another reason
- Flank Pain
- Painless Hematuria
- Signs of infection
- Signs of renal failure
What is the History of a dog/cat with urolithiasis in the Ureter?
- None (cats especially)
- Flank pain (acute uretal obstruction)
- Signs of post renal azotemia (if bilateral obstruction or rupture)
What is the History of a dog with urolithiasis in the Bladder?
- None
- Dysuria
- Pollakiuria
- Hematuria
What is the History of a dog with urolithiasis in the Urethra?
- Signs of obstruction
- Signs of post-renal azotemia
- Dysuria
- Pollakiuria
- Hematuria
- None (uncommon)
What are the physical findings of urolithiasis in the Kidney or ureter?
- Renomegaly, if hydronephrosis or pyonephrosis present
- Abdominal pain
- None, if kidneys are not enlarged or palpable
What are the physical findings of urolithiasis in the bladder?
- Palpable stones
- Thickened bladder wall (palpable only if severe)
What are the physical findings of urolithiasis in the Urethra?
- Large distended bladder suggestive of obstruction
- Stone palpable on rectal or perineal exam
What are the laboratory findings of urolithiasis with urinalysis?
- Urine pH variable
-
Struvite: Alkaline if urease(+) UTI
- Staph, proteus, klebsiella, pseudomonas
- Cystine: acidic
- Finding cystin crystals is ABNORMAL & DIAGNOSTIC ALWAYS, other crystals not diagnostic
- Oxalate, Urate, Silicate variable
-
Struvite: Alkaline if urease(+) UTI
What are the laboratory findings of urolithiasis in urine culture?
- Staph or Proteus in dogs w/ struvite urolithiasis & urease (+) UTI
- Usually NEGATIVE in cats - Still culture!
- UTI may complicate metabolic stone types
- Oxalate, Urate, Cystine, Silicate
What are the laboratory findings of urolithiasis in Stone analysis?
-
Qualitative analysis not recommended b/c
- Xanthine & silicate not detected
- Oxalate frequently not detected
- False + results for urate & cystine
- Cannot tell which crystals are primary or secondary
-
Quantitative Analysis (optical crystallography)
- University of Minnesote & UC Davis
- Commercial medical Labs
List the stones/crystal types from most radiopague to most radiolucent.
(6)
- Calcium Phosphate
- Calcium Oxalate
- Silicate
- Struvite
- Cystine
- Urate
What are the general principles of managing a pt w/ Urolithiasis?
- Relieve obstruction
- Correct fluid, electorlyte, &/or acid-base issues
- Non-surgical retrieval OR
- Surgical removal (if ness) OR
- Medical dissolution of uroliths
- Preventative therapy - increase water intake (wet food)
What are the requirements for nonsurgical removal of uroliths (voiding urohydropropulsion)?
- Stones must be small
- < 7mm female dog
- <5mm male dog or female cat
- General Anesthesia
- Distend bladder with saline via cystoscope
- then manually express bladder externally
- Radiograph afterward
What are the nonsurgical methods of urolith removal?
- Voiding Urohydropropulsion
- Catheter-assisted retrieval
- Lithrotripsy
What are the two types of lithotripsy?
- Electrohydraulic shock wave lithotripsy
- Shock wave generated in close proximity to urolith in bladder under cytoscopic visualization
- Extracorporeal schock wave lithotripsy
- Shock wave generated outside of the body and transmitted to patient through water (nephroliths & ureteroliths
What types of crystals can be medically dissolved?
- Struvite
- Urate
- Cystine
What are the general principles of managing polyuria during urolithiasis via NaCl?
- Decrease USG <1.025
- Allow animal to void frequently
- 0.5-10g salt perday
- No controlled studies for this recommendation
What are the general principles of eradicating UTI during urolithiasis?
- UTI may predispose or complicate urolithiasis
- Culture urine to ID UTI
- Treat w/ appropriate antibiotics
- Follow up to document eradication of infection
How do you medically manage struvite urolithiasis?
- Eliminate UTI (#1)
- If urine pH still alkaline search for another reason
- Diet
- Metabolic (distal renal tubular acidosis
- Calculolytic diet
What will a calculolytic diet do for Struvite urolithiasis?
- Disolve stove - takes 2-3mths
- SE:
- PU/PD (from excess Na)
- Decreased BUN, serum phosphorus & albumin
- Increased SAP
- Possible passage of nephrolith into ureter
Can you dissolve oxalate urolithiasis with diet?
NO! Must surgically remove
(can modify diet to prevent recurrence)
How do you medically manage Oxalate urolithiasis after surgical removal?
- Potasium Citrate PO
- Hydrochlorothiazide (not common in vet med)
- Vit. B6
- Diet
- Low Ca & Oxalate
- Less animal protien
- Citrate
- Avoid Vit. C
- Do not restrict, phosphorus, magnesium or Na
How does giving dogs allopurinol help medically manage Urate Urolithiasis?
- Competitive inhibitor of xanthine oxidase
- Feed low prurine diet to reduce risk of xanthine stone formation!
How does alkalinization help medically manage urate urolithiasis?
- Uric acid moresoluble in alkaline urine
- Alkalinizatio ndecreases urniary NH4 & H concentrations
- Potassium citrate may be better than NaHCO3 b/c natriuresis may enchance calciuresis
What are some of the complications fo urolithiasis?
- Dogs: recurrence rate is highest for metabolic stones & lowest for struvite
- Post renal azotemia and associated electrolyte, acid base imbalances
- Drug & special diet SE
- UTI
