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Medical and Dietary Therapy Strongly Recommended to Prevent Kidney Stones in Obese Patients: Presented at AUA

By Jill Stein

CHICAGO, IL -- April 29, 2003 -- Physicians should make a strong effort to evaluate their obese patients for the risk of kidney stones and, when needed, institute appropriate medical and dietary therapy, researchers said here on April 29^th at the 98^th Annual Meeting of the American Urological Association.

Wesley Erekuo, a medical student at Duke University Medical Center, presented findings from a study that identified and evaluated obese individuals within the institution's nephrolithiasis patient population. Risk factors for stone formation and the impact of selective medical therapy on stone recurrence in these patients were evaluated.

Coauthors of the study included Drs. Barbara Mathias, Fernando Delvecchio, and Glenn Preminger.

"The obesity epidemic continues to escalate, with 61% of the U.S. population defined as overweight or obese," Erekuo said. "Prior studies suggested that obesity may be associated with an increased incidence of nephrolithiasis. Additional studies suggest that recurrence rates for stone disease are significantly higher among obese patients."

Erekuo and colleagues conducted a chart review that identified obese (defined as a body mass index greater than 30) stone formers.

Comprehensive metabolic evaluations identifying risk factors for stone formation and response to medical therapy were reviewed for these patients. The control group comprised non-obese age- and sex -matched stone patients.
The stone patient population included 1021 patients. Of these, 14% were obese. Eighty-three obese patients with stones had complete medical evaluation and received medical therapy.

Sixty-three percent of obese patients had stones versus 11% of control patients.

In obese patients, median uric acid concentration decreased from 754 mg/dL before medical therapy to 625 mg/dL after therapy. In control patients, the median uric acid concentration decreased from 535 mg/dL to 474 mg/dL. A normal uric acid concentration is less than 600 mg/dL.

Mean calcium concentration in the obese group was 301 mg/dL before therapy and 240 mg/dL afterwards, while in the control group it was 190 mg/dL and 198 mg/dL respectively. A normal calcium concentration is less than 200 mg/dL.

Overall, the average number of stones per patient per year was 1.8 in obese patients before therapy and 0.2 afterwards, while in controls it averaged 1.7 stones per year before therapy and 0.1 afterwards.

Gouty diathesis, hyperuricosuria and hypercalciuria are the most common metabolic findings in obese patients, Erekuo said. These abnormalities, taken with the high incidence of uric acid stones, suggest that dietary factors, such as purine gluttony, may play a significant role in stone formation in this patient population. Selective medical therapy and dietary recommendations including decreased purine intake, corrects these metabolic abnormalities and significantly reduces stone formation, he added.


[Study title: Impact of Medical Therapy on the Management of Nephrolothiasis in Obese Patients. Abstract 1269]

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