Further Observations on the Experimental Production of Urinary Calculi*
In previous communications,1,2,3 it has been demonstrated that if white rats were maintained for a period of time on a diet deficient in vitamin A, urinary calculi would develop in a large percentage.
In our researches, it was found that when animals were fed a diet deficient in vitamin A for a period of 250 days, postmortem study revealed the presence of vesical calculi in 88 per cent and of renal calculi in 42 per cent of the animals. It likewise was shown that if vitamin A alone were added to the deficiency diet, the formation of calculi was prevented. After the presence of calculi, which were too large to pass spontaneously from the kidney or bladder of the rats, had been demonstrated roentgenographically, an excess of vitamin A was added to the deficiency diet, and in every instance, provided the experimental animal survived, the calculus then underwent spontaneous solution and disappeared. This solution occurred in a comparatively shorter length of time when a co-existing urinary infection was not present. The calculi produced in this experimental work varied in diameter from 0.5 to 12 mm. They were light brown in color, spherical in shape, and they were composed chiefly of calcium phosphates with traces of carbonates. No oxalates or uric acid were present. A small amount of mucoid substance was noted also.
After these researches, the question arose as to whether the chemical constituents of the calculi could be changed by altering the diet. As reported previously, a decrease in. . .