Urolithiasis

1. Urolithiasis

2. Uroliths • Aggregations of sedimented urinary solutes (minerals, proteins) • Central nidus (usually protein), surrounded by laminar ”stone” and surface crystals

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

9. Thanks