Weight Loss Surgery Reduces Microalbuminuria

NASHVILLE— The prevalence of kidney disease is high in morbidly obese patients, and research findings presented at the National Kidney Foundation’s Spring Clinical Meeting suggest that gastric bypass surgery substantially decreases the level of urinary albumin excretion (UAE) in these patients, and can reduce by up to half the prevalence of microalbuminuria.

“The effect of Roux-en-Y bariatric surgery on microalbuminuria—a known marker of endothelial dysfunction and kidney disease, with prognostic implications in cardiovascular disease—has been reported previously. However, unlike earlier cohorts, our cohort is predominantly Hispanic American and predominantly nondiabetic and nonhypertensive,” Dr. Jennifer Tan said.

Dr. Tan and associates at HarlemHospitalCenter and ColumbiaUniversity in New York reviewed the records of 55 patients who had pre- and post-operative urinary albumin excretion measured within a year of surgery. Twenty-two had significant UAE, defined as > 20 mg/g, prior to surgery.

After surgery, the average level of UAE decreased significantly, from 98.6 to 33.4 mg/g, while the prevalence of microalbuminuria fell from 40 percent to 20 percent, “closer to that of the general population,” the researchers said.

The decline in UAE was significantly correlated with baseline UAE but not with weight loss, and it was not influenced by the presence of diabetes or hypertension.

“In patients with diabetes and hypertension, the temporal relationship of improved glycemic control, lowered blood pressure and weight loss with the apparent improvement of endothelial dysfunction and microalbuminuria remains to be elucidated,” Tan noted. “Even in nonhypertensive nondiabetic patients, subtle changes in blood pressure and insulin resistance may play a role in observed changes in albumin excretion. These could be possible areas of future research.”

Moreover, she added, “Additional studies are required in order to determine the impact of bariatric surgery on endothelial dysfunction and urinary albumin excretion and ultimately on clinical outcomes.”