Effects of hydrochlorothiazide and diet in dogs with calcium oxalate urolithiasis

Objective-To determine whether hydrochlorothiazide (HCTZ) reduces urinary c alcium excretion in dogs with calcium oxalate urolithiasis. Design-Original study. Animals-8 dogs with calcium oxalate urolithiasis. Procedure-4 treatment protocols were evaluated in each dog ia low calcium, low protein diet designed to prevent calcium oxalate urolith formation with and without administration of HCTZ [2 mg/kg (0.9 mg/lb) of body weight, PO , q 12 h] and a maintenance diet with higher quantities of protein and calc ium with and without administration of HCTZ). At the end of each 2-week tre atment period, 24-hour urine samples were collected. Blood samples were col lected during the midpoint of each urine collection period. Analysis of var iance was performed to evaluate the effects of HCTZ and diet on urine and s erum analytes. Results-Hydrochlorothiazide significantly decreased urine calcium and potas sium concentration and excretion. Hydrochlorothiazide also significantly de creased serum potassium concentration. Compared with the maintenance diet, the urolith prevention diet significantly decreased urine calcium and oxali c acid concentration and excretion. Dogs consuming the urolith prevention d iet had significantly lower serum concentrations of albumin and urea nitrog en. Conclusions and Clinical Relevance-Administration of HCTZ decreased urine c alcium excretion in dogs with a history of calcium oxalate urolith formatio n. The greatest reduction in urine calcium concentration and excretion was achieved when dogs received HCTZ and the urolith prevention diet. Results o f this study suggest that the hypocalciuric effect of HCTZ will minimize re currence of calcium oxalate urolith formation in dogs; however, long-term c ontrolled clinical trials are needed to confirm the safety and effectivenes s of HCTZ.