Internal Medicine: Urogenital: Urolithiasis Flashcards
What different uroliths can form?
- Struvite
- Calcium oxalate
- Urate
- Cystine
- Silicates
- Calcium phosphate
What is used for diagnosis of uroliths?
- History and clinical signs
- Physical examination
- Imaging- US/double contrast Radio
What crystals are normal and do not need investigating?
- Cystine
- Urates
Unless dalmation
What uroliths form in acidic and alkaline urine?
Acid
* Calcium oxalate
* Purines
* Cystine
Alkaline
* Struvite
What can be used for urinalysis for urolith diagnosis?
- USG
- pH
- Culture
What can be medically dissolved?
What are the indications for removal?
What are the pros and cons of dissolution?
- Struvite, urate and cystine
Indications
* Obstruction
* Increase in size or number
* Persistent clinical signs
* Lack of response to therapy
Dissolution
Adv
* Less invasive
Dis
* Owner compliance with diet
* Repeated radiographs, urinalysis and culture
* Some stone do not dissolve
* May block urethra
- What is struvite?
- What pH or urine do they form in?
- What predisposes?
- Magnesium ammonium phosphate hexahydrate
- Form in alkaline- radiopaque
- Urinary tract infections
What size stones can be removed from voiding urohydropropulsion?
- 1-3mm in male dogs
- Up to 10mm in female dogs
Why does UTI predispose to struvite formation?
- Bacteria produce urease
- Urease converts urea to ammmonia and bicarb
- Ammonia irritiant and ingridient
- Bicarb increases pH
How are struvite uroliths dissolved and treated?
- Treat UTI - clinicals signs
- Feed a diet with reduced protein, phospohrus and magnesium that promotes formation of acidic urine
- High moisture food is preferred
How should dissolving of struvite be monitored?
Urinalysis and imaging 4-6 weeks
* Expect USG < 1.02 and 20% reduction
* Repeat every 4-6 weeks
Continue for 2-4 weeks after radiographic cure
Core of oxalate
How can struvite be prevented?
- Prevent UTI from recurring
- Treat bacterial infections as they arise
- Dietary mod does not prevent infection-induced struvite uroliths
- Many breeds predisposed
- What urine produced calcium oxolate?
- How do they appear on radiographs?
- What predisposes?
- Neutral to acid urine
- Radiodense
- Hypercalaemia, breeds, older dogs
How are calcium oxalate uroliths treated?
Must be removed physically
How is calcium oxolate prevented?
Rule out
* hypercalcaemia
* metabolic acidosis
* vitamin D excess
Increase urine volume
* Increase voiding frequency
* high-moisture foods
* aim for USG < 1.020
- What is the most common urate?
- What urine pH?
- How do they appear radiographically?
- Ammonium acid urate
- Acid
- Radiolucent, smooth, round or oval
What are two situations that cause urate sontes?
What tests should be run?
- Inherited alteration of urate transporter
- Portosystemic shunt
Serum bile acid concs,
Genetic hyperuricosuria testin
How are urate uroliths disolved in dogs without liver disease?
Diet
* Low in protein
* Low in purines
* Produce alkaline urine
Alkalinise urine if necessary with potassium citrate or sodium bicarbonate
How is urate uroliths recurrence prevented?
Continue feeding the low purine diet
Check
* Urine pH >7
* SG < 1.020
* BUN low
* Sediment- no crystals
Drugs
* Consider allopurinol- stops formation
* Potassium citrate is urine pH less than 6.6
- What causes cystine uroliths?
- How do they appear radiographically?
- What does their sediment look like?
- Inherited disorder of renal tubular transport
- Radiolucent, smooth, small
- Crystals flat, colourless, hexagonal
- What breed is predisposed to cystine uroliths?
- How are they treated?
- Male daschunds
- Encourage water intake
Suitable dissolution diet
What can be done in male dogs which may prevent cystine uroliths?
Neutering
Androgen-dependent cystinuria suggested to occur in multiple:
* Mastiff
* Staffordshire bull terrier
* Scottish deerhound
* Irish terrier
Why can uroliths not always be straight forward?
Mixed composition stones
