Urolithiasis in small animals

Formation of urinary calculi (uroliths) has been hypothesized to occur through multiple mechanisms or processes. Three of the more common of these theories are the precipitation‐crystallization theory, the matrix‐nucleation theory, and the crystallization‐inhibition theory. Urine is commonly supersaturated with crystalloids, and this is a prerequisite for urolith formation. Factors that predispose to urine stasis also play an important role in urolithiasis formation. Risk factors for calcium oxalate uroliths in dogs include sex, and they occur more commonly in male than female dogs. Hepatic dysfunction is associated with a reduced ability to convert ammonia to urea and uric acid to allantoin. Therefore, dogs suffering from hepatic dysfunction may develop hyperammonuria and hyperuricuria, which may result in urate urolith formation. Urolithiasis typically induces inflammatory urine sediment, such as pyuria (presence of white blood cells), hematuria (red blood cells), and proteinuria.