Intestinal calcium absorption may ID individuals at risk of developing kidney stones

Measuring intestinal calcium absorption may help to identify individuals who are prone to develop kidney stones, according to a study appearing in an upcoming issue of the Clinical Journal of the American Society of Nephrology (CJASN).

Individuals with hypercalciuria have kidneys that put out higher levels of calcium in urine than normal, which increases their risk of developing kidney stones. Only a portion of hypercalciuric individuals will develop stones, however, and there are no criteria to distinguish them from those who remain free of stones.

To look for such distinguishing factors, Giuseppe Vezzoli, MD (San Raffaele Scientific Institute, in Milan, Italy) and his colleagues evaluated absorption of calcium in the first part of the small intestine as well as urinary excretion of calcium in 172 hypercalciuric stone formers and 36 hypercalciuric patients without a history of kidney stones.

The researchers found that both absorption and excretion of calcium were faster in hypercalciuric stone formers than in hypercalciuric patients without a history of stones.

"To our knowledge this is the first study comparing calcium metabolism in hypercalciuric patients with or without calcium stones," said Dr. Vezzoli. "Its findings identify a characteristic of calcium metabolism that may predispose hypercalciuric patients to calcium stone formation, and highlight the role of intestinal absorption in stone formation."