Abstract
Although renal calculi spontaneously occur only rarely in rats (Sprague-Dawley), it was found that animals used actively and repeatedly for breeding purposes had a significantly higher incidence. Twenty-nine % of male and 3% of female breeders had renal calculi. The calculi were larger in the former group than in the latter. The formation of calculi was independent of diet, serum calcium, urinary pH, urinary tract infection, and urinary citric acid levels.