Urinary Calculi Flashcards
Uroliths
Polycrystalline concentrations located within the urinary tract
- >90% weight is composed of inorganic/organic crystalloid, with remainder consisting of organic matrix
Canine bladder uroliths are commonly _______
Struvite!
Most common stone is seen in the _____
Bladder
Most common bladder stones are seen in _____
Female dogs
Most female bladder stones are ______
Struvite
_____ stones are common in dogs that eat sand
Silica
Most common stone in cats is ______
Oxalate
Urolith matrix
- matrix substance A
- tamm-horsfall mucoprotein
- uromucoid
- albumin
- globulins
Initiation phase
Formation of a crystal nidus (nucleation) in the presence of urine supersaturation with calculogenic crystalloids
Growth phase
Continued circumferential crystal deposition around the crystal nidus
Do stones form in the ureters/urethra?
NO
Urolith formation is influenced by
- urine supersaturation
- organic matrix
- urine pH
- crystal transit time
- crystallisation inhibitors or promoters
Which stones form in acidic urine?
Oxalate
Which stones form in alkaline urine?
Struvite
Citrate in urine is a stone _____
Inhibitor
Urine analysis
Urine sediment, collect by cystocentesis!
- crystalluria
- bacteriuria
- pyruia
Crystalluria
Presence of crystals in urine
- limited diagnostic meaning, some crystals are found in normal urine
- nature of crystalluria does not always reflect type of calculus!
Struvite crystals
House roofs
Calcium oxalate dihydrate crystals
Square envelopes
Calcium oxalate monohydrate crystals
Double ended picket fences
- do not form stones!
- end point of ethelene glycol toxicity
Urate crystals
Brown, spiky
- not normally seen in urine, except Dalmations
- usually sign of severe liver dysfunction
- not benign
Cystine stones
6 sided
- hereditary, common in bulldogs
- not normal in other breeds
- prone to cystine stones
Imaging techniques
- plain radiography
- contrast radiography
- ultrasonography
_____ and _____ are the same density on radiographs
Bladder and urine
Radiopacity of uroliths
From radiodense to radiolucent:
- phosphate –> oxalate –> cystine –> uric acid/urate
Every stone shows up on _______
Ultrasound!
- may miss stones in the urethra
A renal calculus is also known as a _____
Nephrolith
Severe hydronephrosis
End stage kidney dz secondary to ureter obstruction due to a stone that did not pass
Stone analysis
- chemical or physical
- surgery is often the only means of obtaining a stone for analysis
With a mixed stone, you would treat based on the type of stone in the ______
Middle
- the nidus
Which stones are dissolvable?
Struvite and urate
Which stones are resistant to dissolution?
- oxalate
- silica
- cystine
- calcium phosphate
Non-surgical alternatives
- voiding urohydropropulsion
- ureteral stents
- lithotripsy: intracorporeal and exttracorporeal
Struvite
Magnesium ammonium phosphate hexahydrate
- most common in dog, relatively common in cat
Infection induced struvite
Most commonly associated with urinary tract infection with urease-producing organisms
- staph, proteus, ureaplasmas
Sterile struvites
Struvite calculi may (less commonly) occur in the absence of infection
Medical management of struvite
- antibiotics
- calculolytic diet
- urinary acidifiers
(bottom 2 are for sterile stones)
Calcium oxalate
Most common in cats, most common nephrolith
Calcium oxalate contributing factors
- hypercalciuria
- hypocitraturia
- hyperoxaluria
- decreased inhibitors
Can you medically get rid of calcium oxalate stones?
No
- surgical removal
- voiding urohydropropulsion
- lithotripsy
Medical management of calcium oxalate to prevent recurrence
- find/correct hypercalcemia
- dietary modification
- urinary alkalinization
- thiazide diuretics
Dalmation urate urolith formation
Excrete excessive uric acid in urine due to defective uric acid metabolism, and are prone to urate stones
Can you see urate stones on x ray?
NO
Urate urolith in dalmations - medical management
- calculolytic diet
- urinary alkalinisers
- xanthine oxidase inhibitors (allopurinol)
