Urolithiasis in the Rat

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Abstract
In the course of studies on the influence of dietary minerals on the severity of caries in the NMRI-D, caries-susceptible, strain of rat, it was observed that numerous animals died when fed what appeared to be an adequate diet. Autopsies revealed extensive stone formation in the urinary tract. The casein-mineral ratio of the diet appears to be the determining factor in the formation or prevention of the uroliths. Thus, a high casein level or a low concentration of Hubbell, Mendel and Wakeman salt mixture in the diet, or both resulted in normal animals without the appearance of calculi. Rats of the NMRI-D strain formed numerous calculi on a diet containing 15% of casein and 2% of Hubbell, Mendel and Wakeman salt mixture, whereas only a few of the Sprague-Dawley rats showed small concretions and none of the Long-Evans rats showed any sign of calculi on autopsy. This suggests that the NMRI-D strain is the most sensitive of the three strains to dietary alterations. The stones formed in the present experiment consisted almost entirely of calcium citrate. This type of concretion has been reported previously in rats only under conditions of extremely low phosphorus intake.