CS: Urolithiasis Flashcards
CS - upper urinary tract uroliths
- variable
- haematuria
- CS compatible with acute kidney injury secondary to ureteral obstruction
Normal canine USG
1.015 - 1.045
Varies with fluid intake, hydration
Normal feline USG
1.035-1.060
Varies with fluid intake, hydration
What are the 2 most radioopaque crystals
calcium oxalate and struvit
What urine pH favours struvite and calcium oxalate formation?
- STRUVITE: alkaline
- CALCIUM OXALATE: acidic to neutral
T/F: uroliths >1cm likely to be struvite
True
T/F: sterile struvite uroliths rarely form in dogs
True - common in cats
Why do you need a stone sample?
detect what mineral type and whether different mineral layers are present.
What should you do if urine culture is negative in a dog with struvite uroliths?
the stone and/or bladder mucosa can also be cultured to be certain that a bacterial pathogen is not present
What is medical management of struvite sotnes?
dissolution and prevention of stone reformation (aim to reduce concentrations of ammonium, magnesium and phosphate in urine
Advantages - sx tx of struvite bladder stones
Most direct
Healing may commence say day
Disadvantages - sx tx of struvite bladder stones
Those inherent to sx (anaesthetic risk, post-op pain)
Risk of contaminating abdomen with infected urine
Incomplete removal nidus for recurrence
Bladder stitches not holding
Indications - sx removal of struvite bladder stones
- immediate/ emergency removal (e.g. blocked animal)
What is VUH?
= voiding urohydropulsion
- anaesthesia
- for small stones
- fill bladder via urinary catheter (sterile saline), agitating bladder so stones float freely in urine. Hold animal upright, remove catheter, then generating a high pressure urine stream to force stones out
What is cystoscopy?
- if stones small enough and avoiding sx is key
- cystoscope passed into bladder and stones retrieved with special basket (or fragmented via laser lithotripsy)
Advantages/ disadvantages of cystoscopy
o DISADVANTAGES: Special equipment, referral, generally more expensive than sx
o ADVANTAGES: recovery much faster
Outline medical management of struvite bladder stones
- dietary
o Uroliths should decrease in size within 3-4 weeks (if good owner compliance)
o Only feed until stone dissolved
o ABs needed as long as stones present in bladder (bacteria encrusted in stone and as stone dissolves they are released).
Reasons for tx failure when medically managing struvite bladder stones
- poor compliance with diet / ABs
- stone has layers of calcium phosphate in form of appatite or may not contain struvite
Disadvantages - medical management of struvite bladder stones
o DISADVANTAGES: long tx time, possibility of UT obstruction as stone gets smaller, v high in fat and salt and low in protein (not for patients with hx of pancreatitis, heart disease, kidney insufficiency or high BP)
CI - medical management of struvite bladders stones
urethroliths causing obstruction or if patient’s CS are severe.
Prevention - struvite stones
- high moisture diets
that produces a urine pH
What is a typical crystal appearance for ammonium urate?
‘thorn-apple’ appearance
Why is it often not possible to count the # of urate stones?
there are so many and range in size from grain of sand to ball bearing
How do you image a dalmation’s bladder after urate stone removal?
- ULTRASOUND as urate stones are radiolucent to faintly radioopaque so unlikely to be detected with radiography
What is the medical management for urate bladder stones?
- Allopurinol for dissolution for 4 weeks (this reduces uric acid)
- DIET: low protein, high moisture, urine-alkalising, high value protein
- CI: GCs, immunosuppressive drugs, renal failure, PSS
Why may xanthine stones form treating urate stones with allopurinol?
Because xanthine is a metabolite in the pathway to uric acid. Allopurinol stops this pathway to reduce the amount of uric acid (and hence reduce urate stone formation) but increases the amount of xanthine metabolite hence potentially causing xanthine stones. TO prevent keep on the low protein, high moisture diet.
What is detected in genetic tests for dalmations with tendency of forming urate stones?
- SLC2A9 gene is mutated in dalmations (this causes altered transport of uric acid in hepatic/ renal transport)
- homozygous recessive mutation
- buccal swab to collect DNA
What is recurrence rate of urate crystals?
variable, 33-50%
How to monitor efficacy of urate stone medical management?
- UA every 3 months
- imaging every 6 months
T/F: all damations are homozygous recessive for hyperuricosuria
True
What are low uric acid dalmations?
when a purebred dalmation has been crossed with another breed
How to reduce prevalence of urolithiasis in dalmations
- Increase water intake
- Low protein low purine diet
- Let outside regularly to toilet
- Exercise to prevent stagnant urine
- Allopurinol (competitive inhibitor of xanthine oxidase)
