Subclinical kidney injury before and one year after bariatric surgery among adolescents with severe obesity

OBJECTIVE: To assess subclinical kidney injury in severely obese adolescents by measuring biomarkers of early kidney disease and to assess changes in the levels of these biomarkers following bariatric procedure. METHODS: 22 severely obese adolescents undergoing bariatric surgery with no microalbuminuria and normal kidney function were selected. Urinary NGAL, IL-18, and KIM-1 were measured at baseline, 6, and 12 months post-operatively. Biomarker levels were compared to 44 age-gender-matched lean controls. RESULTS: Obese subjects had a mean baseline BMI of 48 kg/m(2) that decreased by 34% at 1 year follow-up. Urine NGAL, IL-18 and KIM-1 were significantly elevated in obese compared to lean controls at baseline. The obese cohort had a further significant increase in NGAL and KIM-1 at 6 months, followed by decline at 1 year. The overall change in levels of all three biomarkers through 1 year after surgery, however, was not significant compared to baseline. CONCLUSIONS: Adolescent severe obesity is associated with increased urinary excretion of novel biomarkers of kidney injury, despite no microalbuminuria or decreased kidney function. This subclinical kidney injury persists 1 year after significant weight loss induced by bariatric surgery, suggesting that close long-term follow up of kidney status is warranted in these adolescents.