Urolithiasis Flashcards
Describe the history and presenting clinical signs in a dog with bladder stones
- Variable - asymptomatic to complete urinary tract obstruction
- Pollakiuria
- Dysuria / urinary tenesmus
- Discomfort / vocalisation on urination
- Haematuria
Describe the physical exam findings in a dog with bladder stones
May feel stones in bladder
May be abdominal pain (usually not)
How are canine bladder stones diagnosed?
Imaging
Describe the use of imaging for bladder stones
Imaging tells you the presence of uroliths and location, number, size, shape, and density
The preferred contrast technique for uroliths is double contrast
Urates are found normally in which breed?
Dalmations
Crystal type may suggest the urolith type, but when is this not true?
- If diet has changed, may be different
- UTI (development or cure) can lead to different crystal types
How is USG related to bladder stones?
A high urine specific gravity suggests an increase in concentration of urolithic precursors.
How is pH related to bladder stones?
Ph can suggest which urolith is present - oxalate, purines, and cystine uroliths form typically in urine with a pH less than 7.0, whereas struvite calculi form typically in urine with a pH greater than 7.0
How is culture related to bladder stones?
Culture indicated because urinary tract infections may occur secondarily in patients with urolithiasis or may induce urolith formation
Which crystal has a coffin shaped appearance?
Struvite
Which crystal has a pyramidal shape?
Calcium oxalate dihydrate
Are blood tests useful in cases of bladder stones?
Yes
- Underlying diseases e.g. hypercalcaemia
- Effects of obstruction
- Liver function if urate stones found
Why is analysis of the urolith performed?
Essential to prevent recurrence!
If uroliths recur, resubmit!
Describe the composition of uroliths
- A urolith is composed primarily of 1 or more minerals in combination with small quantities of organic matrix.
- Layers of stone are: the nidus, stone, shell, and surface crystals
Why is the nidus of the stone important?
The nidus is the area of obvious initiation of stone growth. – not necessarily right in the middle.
Nidus needs to be the focus of prevention
Describe the advantages and disadvantages of medical dissolution of stones
Advantage - Less invasive
Disadvantages
- Owner compliance with diet
- Repeated radiographs, urinalysis and culture
- Some stones do not dissolve
- May block urethra
Which stones dissolve, and which dont?
Do = Struvite, urate, cystine
Don’t = Oxalate, silicate, phosphate
List the indications for calculi removal
Obstruction
Increase in size or number of calculi
Persistent clinical signs
Lack of response to therapy
Voiding urohydropropulsion can be used to remove uroliths of what size?
1 to 3 mm in male dogs
up to 10 mm in female dogs
Does struvite form in acidic or alkaline urine?
Alkaline
What can predispose the formation of struvite crystals?
A urinary tract infection needs to occur for struvite to form
Do struvite crystals form in the lower or upper urinary tract?
LUT (95%) > UUT (5%)
What other elements must be present in the urine fot struvite to form?
urine must be oversaturated with magnesium, ammonium, and phosphate ions
How are struvite crystals treated/managed?
- Treat the UTI
- Feed a diet with reduced protein, phosphorus and magnesium that promotes formation of acidic urine (i.e. pH <6.5)
- High moisture food is preferred
- Give appropriate antimicrobial agent during the entire time of medical dissolution
