urinary system notes pt 2

Question 1

what species are silica uroliths important in?

Answer 1

• important in ruminants > pastured animals
• less common in dogs

Question 2

how to reduce formation of silica uroliths in ruminants

Answer 2

• Silica urolith formation can be reduced by adding salt to rations as this leads to increased water consumption

Question 3

silica urolith shape in ruminants, generally

Answer 3

• Silica uroliths in cattle are hard, dark-brown to white, often laminated, up to 1 cm in size and are round to oval
• can be more angular if formed in the kidneys

Question 4

silica stones in dogs
- where found?
- breeds?
- shape /. composition in dogs
- risk factor

Answer 4

• mostly in males
• usually found in the urethra and bladder
• German shepherd dogs and old English sheepdogs
• Unlike in cattle, silica bladder stones are very irregular in shape with multiple projections, often in a ‘jackstone’ configuration, and often contain struvite and/or calcium oxalate
• Dry feed containing high levels of plant-derived ingredients are thought to predispose

Question 5

struvite stone
- compositions
- colour / shape
- species
- dog breed

Answer 5

• composed of magnesium ammonium phosphate hexahydrate
• stones tend to be white to grey, chalky, usually smooth and they are easily broken
• common in dogs, also cats and cattle
  > Pugs

Question 6

struvite stone relationship with infection

Answer 6

• commonly associated with infection, and ureases produced by some bacteria (e.g. Staphylococcus, Proteus) contribute to struvite supersaturation by increasing the urine pH and ammonium ion levels

Question 7

biggest problem that struvites cause in cats?
- most common in who?

Answer 7

• struvite containing sabulous (matrix/crystalline) urethral plugs that occur, mostly in male cats
  > combination of struvite crystals, protein, and cellular debris
  > most common in 2-7-year-old cats
  > castrated males have a higher risk and spayed females are least affected.

Question 8

struvite in cattle
- how it generally causes issues?
- risk factor / prevention?

Answer 8

• similar to cats > struvite crystals usually combine with a proteinaceous matrix rather than forming a hard calculus
• cattle and sheep on high grain rations
• can lead to obstruction in up to 10 % of steers
• Dietary alterations can help prevent these stones from forming.

Question 9

Oxalate uroliths general character
- predispositions?
- prevention?
- common in who?
- diets?

Answer 9

• usually large, solitary stones found in the bladder that are hard, heavy, and white to yellow, often with jagged spines on the surface
• hypercalcuria and hyperoxaluria predispose
• dietary magnesium and citrate can help prevent urolith formation
• (older, male) dogs, also cats (male and neutered animals)
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  Diets designed to lower urine pH to help control struvite urolithiasis increase the occurrence of oxalate urolithiasis

Question 10

oxalate calculi associated with what neoplasia

Answer 10

parathyroid neoplasia

Question 11

urate uroliths
- common in who? why?
- character / shape
- predispositions

Answer 11

Urate (purine) calculi
- most common in dogs, esp Dalmations
> secrete high levels of uric acid in the urine due to an autosomal recessively inherited defect in hepatocellular uptake of uric acid
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- hard green to brown, laminated, spherical stones usually less than 5 mm and are usually multiple
- usually ammonium urate
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- males
- PSS

Question 12

Xanthine calculi
- what is xanthene?
- when do we see stones?
- breeds?

Answer 12

• Xanthine is a purine metabolite not normally found in urine due to degradation by xanthine oxidase to uric acid
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  In dogs:
• primary autosomal recessively inherited form > animals have a defective xanthine oxidase enzyme
• secondary iatrogenic form in animals treated with allopurinol > binds and inhibits xanthine oxidase activity
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• Dachshunds, dalmations

Question 13

cystine uroliths
- species
- character
- pH
- who is affected

Answer 13

• dogs, some ferrets and cats
• usually small, irregular light-yellow to red-brown, soft, friable, waxy stones
• often contain other components
• acidic urine causes precipitation
• obstruction generally in males
  > nephroliths are common in Newfoundlands, as well as Irish and Scottish Terriers > defective reabsorption through proximal tubules
  > genetic predisposition