Urolithiasis

Question 1

What are the most common uroliths in dogs and cats?

Answer 1

struvite and calcium oxalate

Question 2

What stones are not typically able to be dissolved?

Answer 2

calcium oxalate

Question 3

What uroliths are radiolucent?

Answer 3

cystine and urate

Question 4

What are 3 important parts of general management of all types of uroliths?

Answer 4

1. increase urine volume and dilution with high moisture content food
2. reduce crystal-forming substrates
3. increase urine solubility of crystal-forming substrates (acidify/alkalinize urine)

Question 5

What crystal is this?

Answer 5

struvite

• coffin lids

Question 6

What causes the formation of struvite stones? How are they treated?

Answer 6

urinary tract infection with urease positive microbes

• low magnesium and phosphate diet
• high quality, reduced protein diet to reduce urine urea that is converted into ammonia (not as important in cats with sterile struvite crystals)
• treat UTI with appropriate antimicrobials based C&S

Question 7

What crystal is this?

Answer 7

calcium oxalate

• envelope

Question 8

What treatment is most likely required for calcium oxalate stones?

Answer 8

surgery, voiding hydropulsion, or lithotripsy –> unlikely to dissolve

Question 9

What are 3 options for preventing calcium oxalate stones?

Answer 9

1. avoid excessive proteins, calcium, oxalate, vitamin D, and sodium in the diet
2. provide adequate phosphorus (to prevent vitamin D activation), magnesium, and vitamin B6
3. alkalinized diet - unlikely to dissolve stones, but will prevent new stones from forming

Question 10

What dietary management is used to prevent cystine stone formation? What 2 specific treatments are available?

Answer 10

reduced protein, sodium restricted, urine alkalizing diet

1. potassium citrate, sodium bicarbonate - urine alkalizers
2. 2 mercaptopropionyl-glycine (Thiola) - binds to cystine to form a more soluble compound

Question 11

What crystal is this?

Answer 11

cystine

• octagon-like

Question 12

What breed is predisposed to forming urate stones?

Answer 12

Dalmatians

Question 13

What dietary management is recommended to treat urate stones? What 2 treatments are available?

Answer 13

reduced protein, urine alkalizing diet

1. potassium citrate, sodium bicarbonate - urine alkalinizer
2. allopurinol - decreases uric acid by inhibiting conversion of hypoxanthine –> xanthine –> uric acid

Question 14

Why is it important to carefully treat urate stones?

Answer 14

giving allopurinol without a reduced protein diet may lead to the formation xanthine stones or create a xanthine shell around a preexisting urate stone

Question 15

What crystal is this?

Answer 15

urate

• yellow/brown amorphous