Obesity increases risk of kidney stones

Overweight individuals are more likely to have more acidic urine, as measured by a lower urinary pH, along with an increased risk of uric acid kidney stones. Patients with type 2 diabetes also are more likely to develop uric acid kidney stones compared with the general population of patients with kidney stones. Insulin resistance in the kidneys leads to more acidic urine and uric acid stone formation. In addition to its effect on glucose metabolism, excess insulin in the kidneys may influence urinary acid excretion. This leads to abnormally acidic urine, which precipitates and results in uric acid stones. Researchers from the University of Texas Southwestern Medical Center in Dallas, USA, tested the hypothesis that urinary pH and body weight are inversely related. They evaluated 4883 patients with kidney stones. The researchers found that subjects with more acidic urine had higher body weights, after excluding the effects of age and patient factors that could affect urinary pH. These findings suggested that insulin resistance might be one of the important causes of gout and uric acid kidney stones.

As an approach to treating uric acid kidney stones in obese patients, the researchers are testing the effect of an oral insulin sensitiser versus placebo, which will be followed by a weight reduction regimen.

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