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Urolithiasis: Small Animals - Coggle Diagram
Urolithiasis: Small Animals
Differentiate from crystals
Do not causes clinical signs
May be representative of urolith type
Form when urine is supersaturated
Diagnosis
Physical Examination
+/- hydronephrosis/irregular kidneys
Often unremarkable
Radiography
Plain film
May reveal radiodense uroliths if sufficiently large
Contrast
Excretory urogram for nephroliths, ureteroliths
Double contrasts for bladder
Retrograde for urethra
Ultrasound
For non-radiopaque uroliths
Location
Nephroliths and Ureteroliths
Asymptomatic
Pyelonephritis
Renal failure (if bilateral obstruction or infection)
Renal colic
Cystoliths
Dsyuria, pollakiruia and haematuria
Innappropriate urinartion
Generally not palpable
Urethroliths
Abdominal discomfort
Poor or no urine stream
Licking of genital area
Obstruction and post-renal azotaemia
Enlarged painful badder, may be palpable per rectum or at base of os penis
Treatment
Nephroliths/Ureteroliths
Surgical removal
Urinary bypass
Dietary dissolution
Must be non-obstructed
Calcium oxalate NOT amenable
Extra-coporal shock wave lithotripsy
Only considered in dogs
80-85% success rate
Cystoliths
Dietary dissolution
Urohydropropulsion
Peri-procedural antibiotics
Surgery
Cystotomy/minimally invasive cystotomy
Urethroliths
Retrograde flushing
Surgery
ONLY if necesary
Medical management
If no obstruction
No contra-indications to dietary therapy
Urolith composition amenable
Struvite, cystine and urate
Increase water intake to decrease urine concentration
Increase solubility of salts by changing urine pH with diet
Treat any predisposing cause
Types
Struvite
Signalment
Most dog breeds
Concurrent UTI
Females predisposed
Urease producing bacteria
Saph, Proteus
Alkaline urine pH
Sterile in cats
Markedly radiopaque
Treatment
Treat underlying UTI (3-4 weeks) after radiographic resolution
Dissolution diet
Reducing urinary magnesium, ammonium, phosphate
Maintain acidic pH until resolution
Low protein - DON'T use in pregnant, lactating or young animals
Increase voluntary water intake
Monitor progress with successive radiographs (size, density and number)
Monitor pH 6-6.5, USG <1.015, negative sediment and culture
Calcium Oxalate
Aetiology
Upper urinary tract
Increased incidence especially in cats; inappropriate use of acidifying diets
Signalment
Cats: Burmese, Himalayan, Persian
Males > Females
Older animals
Dogs: terriers, schnauzers, poodles
Treatment
Surgery
Urohydropropulsion
Medical dissolution NOT possible
Benign neglect (i.e., ignore)
Laser lithotripsy
Prognosis
60% recurrence within 3 years
Prevention
Increase water intake
Sodium supplementation
Induces diuresis
Somewhat controversial
Neutral/marginally alkaline urine pH
Solubility of calcium oxalate is NOT pH dependent
Acidifying diets promote calcium excretion
Hydrochlorothiazide for repeat stone formers
Decreases calcium excretion
Ammonium Urate
Signalment
Dalmatians
Defective transport uric acid into hepatocytes and out of the urine
Reduced conversion of uric acid to allantoin
Hepatic dysfunction
Portosystemic shunt
Increased excretion of ammonia and urea
Bulldogs
Treatment
Treat underlying liver diseases, correct PSS
Dissolution is possible
Treat underlying UTI
Reduce purines, neutral to alkaline pH
Hills U/D, Royal Canin UC
Allopurinol
Competitively inhibits xanthine oxidase, reducing uric acid this can result in xanthine stones if protein not restricted
Cystine
Renal tubular defect resulting in excess urine cystine
Radiolucent
Medical dissolution possible but expensive
Cystine excretion decreased by castration
Calcium Phosphate
Primary hyperparathyroidism; may also occur as part of a mixed urolith, mineralisation of a blood clot
Calcium carbonate
Most common in rabbits and horses - high Ca in urine
Silica
GSDs predisposed; but rare - associated with poor diets