Kidney Stones More Common With Type 2 Diabetes


People with type 2 (non — insulin-dependent) diabetes have highly acidic urine, a metabolic feature that explains their greater risk for developing uric acid kidney stones, according to a study at the University of Texas Southwestern Medical Center in Dallas.

Individuals with type 2 diabetes are at increased risk for kidney stones in general, especially the uric acid type.

"Our next step is to find out what causes type 2 diabetics to have an abnormally acidic urine, and what other urinary factors protect some diabetics who do not form uric acid stones," said Dr. Mary Ann Cameron, a postdoctoral trainee in internal medicine.

Obesity and a diet rich in animal protein are associated with abnormally acidic urine. In earlier studies, uric acid stones were associated with insulin resistance and type 2 diabetes (See Nutrition Health Review, Issue #88).

In this latest study, however, when researchers accounted for these components, type 2 diabetic patients continued to have more acidic urine levels than nondiabetic patients. These findings suggest that other factors associated with type 2 diabetes or insulin resistance account for the overly acidic urine in this population.

"Diet intake and obesity, those two factors alone, don't explain the whole picture," said Dr. Nairn Maalouf, Assistant Professor of internal medicine. "So, other unrecognized factors may play a role."

Dr. Khashayar Sakhaee, senior author of the study and Chief of mineral metabolism, said that the team was the first to determine that the more overweight a person is, the more likely he or she is to form uric acid kidney stones.

More than 18 million people in the United States live with diabetes, a chronic disease that affects the body's ability to produce or respond to insulin and that can lead to life-threatening illness, including heart disease and stroke.

Kidney stones are solid deposits that form in the kidneys from substances excreted in urine. When waste materials in urine do not dissolve completely, microscopic particles begin to form and, over time, grow into stones (calculi). These solid deposits can remain in the kidney, or they can break loose and travel down the urinary tract.

Small stones can pass out of the body naturally, but larger stones can get stuck in a ureter, the bladder, or the urethra. The stones can block the flow of urine, often causing intense pain.

Uric acid stones are more difficult to diagnose than other types of stones because they do not show up on regular abdominal x-ray films. This may delay the diagnosis and lead to the continued growth of the stone.

(Source: Journal of the American Society of Nephrology, May 2006.)

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