2. Aggregations of sedimented urinary
solutes (minerals, proteins)
Central nidus (usually protein),
surrounded by laminar ”stone” and
surface crystals
Uroliths
3. 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
4. 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
5. 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
6. 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
7. 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
8. 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
