Patients who have undergone obesity surgery may be more likely to suffer from kidney stones, researchers have warned.
Specialists at the Mayo Clinic College of Medicine found that patients who had undergone gastric bypass surgery 12 months previously showed a number of chemical changes in their urine, including an increase in oxalate, which has previously been shown to increase the risk of kidney stones.
In addition, the patients' urine contained lower-than-average levels of citrate – a compound which helps to dissolve the crystals which can lead to kidney stones.
However, patients who had undergone surgery only six months previously were yet to show any significant changes in oxalate or citrate levels in their urine.
"Gastric bypass surgery appears to lead to changes in the chemical composition of urine that could favour the formation of kidney stones," said Dr. Rajiv Kumar, one of the study's authors at the Mayo Clinic College of Medicine.
"Based upon this information, we suggest that patients take appropriate measures to reduce the potential for kidney stone formation," he advised.
The researchers presented a paper on their findings at the American Society of Nephrology's 39th annual meeting and scientific exposition in San Diego last week.
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