Calcium oxalate (CaOx) uroliths are one of the more common stone types to develop in the urinary tract of dogs. As occurs with other stone types, a sequence of events leads to a supersaturation of the urine (with the mineral / metabolite type) resulting in crystal formation (crystalluria) and subsequent formation of the urolith.
Last year, the Minnesota Urolith Center (MUC) reported on epidemiologic data collected from 1981-2013. Their data showed that over a 30+ year period, there has been a substantial increase in the incidence of calcium oxalate uroliths in both dogs and cats (and a decrease in the incidence of struvite stones). By way of comparison, in 1981, calcium oxalate stones accounted for 5% of canine uroliths and in 2013, CaOx represented 42% of canine uroliths submitted to the MUC.
The exact mechanism for calcium oxalate urolith formation is poorly understood. Factors postulated to increase the risk for CaOx uroliths include:
Although there are reports on the incidence of hypercalciuria in dogs with CaOx uroliths, until recently little has been known about individual dog breed risk factors for CaOx stone formation. Knowledge of breed-associated risk factors would, theoretically, be helpful for making specific recommendations in affected dogs.
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