Uroliths

Question 1

Struvite

Answer 1

Smooth stone, Radio-opaque

• esp. female dogs usually concurrent UTI (urease producing bacteria -> cleave urea -> ammonium + bicarbonate
• Sterile in cat
• Treat with diet change (acidifying diet) + potassium citrate to prevent calcium oxalate stones
• Alkaline urine in cattle + high dietary phosphate and magnesium levels favors formation of struvite stones.

Question 2

Calcium oxalate

Answer 2

Spikey, radiolucent
- esp. in cats, may be due to inappropriate use of acidifying diet (for struvite stone)
- favors acidic urine
- breed predispositions
- terrors, poodles, schnauzers
- burnese, himalayan, persian
- males>females, older animals, upper urinary tract
- medical dissolution possible
often present in ruminant urine and may be incorporated in small amounts into other types of stones

Question 3

Ammonium urate

Answer 3

Radiolucent
- Dalmation - reduced conversion of uric acid to allantoin
- hepatic dysfunction: PSS
- Bulldogs & other breeds
correct underlying cause, dissolution possible, reduce purines
- Allopurinol therapy may reduce uric acid production but ti requires monitoring as it may predispose dogs to different types of stones (xanthine)
- Soy is high in purines and is not recommended for dogs prone to forming urate stones

Question 4

Cystine

Answer 4

Radio-opaque

• breed predisposition
• renal tubular defect resulting in excess urine cysteine which is poorly soluble
• middle aged dog
• cysteine secretion decreased by castration, dissolution possible but expensive

Question 5

Calcium phosphate

Answer 5

• Primary hyperparathyroidism

Question 6

Calcium carbonate

Answer 6

• Most common type in horse & rabbit -> increased calcium in urine
• Sheep grazing clover, pasture high in calcium and oxalates

Question 7

Silicate

Answer 7

• GSDs predisposed but rare

- seen in sheep and cattle grazing western U.S. rangelands

Question 8

Apatite stones

Answer 8

composed of calcium and phosphate - feedlot cattle

Question 9

Xanthine stones

Answer 9

Allopurinol is used in the treatment of urate stone forming in Dalmations. It acts by inhibiting the enzymes, xanthine oxidase, which metabolizes xanthine. The idea is that by stopping the purine metabolism pathway at this point, uric acid will not be formed in high quantities. However, if given at too high of a dose, xanthine will accumulate to levels where xanthine stones will form.