Uroliths:
Aggregations of sedimented urinary solutes (minerals, proteins)
Central nidus (usually protein), surrounded by laminar ”stone” and surface crystals
Uroliths
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Causes obstructions usually in males’ ureter
At the site of obstruction, there is local pressure necrosis, ulceration of the mucosa and acute hemorrhagic urethritis
Often in cats, dogs and ruminants
Seldom in horses and pigs
Causes:
Causes Urinary pH
Reduced water intake causes crystallization
Feeding; for exaple low vitamin A, high phosphorus in ruminants, magnesium in cats causes mucosal damage which produces nidi for the stones
Inflammation; leukocytes, fibrin, epithelial cells also serve as a nidus
Inborn error of metabolism
Struvite stones:
Struvite stones Magnesium ammonium phosphate (MAP)
Most common type in dogs
Also in cats and ruminants
Females are most commonly affected
Bacterial ureases -> pH h -> struvite solubility i
Oxalate stones:
Oxalate stones consist of calcium oxalate
development is not well understood
caused by hypercalciuria and hyperoxaluria
dietary magnesium and citrate inhibit formation
common in male dogs and rare in ruminants (plants -> acute death), related to diet in cats
Urate stones:
Urate stones contain either ammonium urate with some uric acid and phosphate or sodium urate
often in male Dalmatians (inherited)
incomplete conversion of uric acid to allantoin in liver -> uric acid in urine
also dogs with liver disorders
portosystemic shunts, cirrhosis
Cystine stones:
Cystine stones Consist of pure cystine
may also contain calcium oxalate, struvite and complex urates
Occur in dogs, rarely in cats
Almost exclusively in males
Inborn error of metabolism -> defective proximal tubular reabsorption from glomerular filtrate -> high levels of urinary cystine
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