Struvite urolithiasis in a litter of miniature Schnauzer dogs.

Magnesium ammonium phosphate calculi developed in the urinary bladders and urethras of four of five offspring of Miniature Schnauzer parents with recurrent struvite urolithiasis. Calculi were detected by radiograhy when the dogs were 12 to 15 months old. Males and females were affected. A significant number of urease-producing staphylococci were identified in the urine of three of four dogs before urolith formation, and in one dog after urolith formation. The dogs were evaluated until they were 26 months old. Serum concentrations of calcium, phosphorus, and magnesium were inside usual limits throughout the study. Abnormalities that might predispose to urinary tract infection were not identified by radiography or necropsy studies. In one dog, bladder calculi recurred after surgical removal of multiple cystoliths. In another, urethral obstruction and acute generalized pyelonephritis induced a lethal uremic crisis. Gross and microscopic lesions, detected after necropsy of all dogs with uroliths, were typical of bacterial infection.