Gastric bypass surgery can change patients' urine composition that may raise their risk of developing kidney stones, research from UT Southwestern Medical Center investigators suggests.
Published in the March issue of The Journal of Urology, the study found that some of these urinary changes place weight-loss surgery patients at higher risk for developing kidney stones than obese patients who do not undergo the procedure.
To reach the conclusion, researchers collected urine samples from 38 study participants. There were 16 women and three men in each of two groups. One group had undergone Roux-en-Y gastric bypass (RYGB) surgery; the second group contained normal obese individuals. RYGB, which is one of the most commonly performed weight-loss procedures, involves the creation of a small gastric pouch and allows food to bypass part of the small intestine.
The researchers found that the excretion of a material called oxalate in urine was significantly greater in the participants who had the surgical procedure than those who did not (47 percent, compared with 10.5 percent, respectively). In addition, the amount of a chemical called citrate in the urine was low in many gastric bypass patients in comparison to the obese nonsurgical group (32 percent to 5 percent).