Estimated GFR Before and After Bariatric Surgery in CKD

BACKGROUND: Several reviews have recently detailed the beneficial effects of weight loss surgery for kidney function. However, these studies have a number of limitations, including small sample size, few done in chronic kidney disease (CKD) stages 3 and 4, and many not including the main bariatric surgery procedures used in the United States today. STUDY DESIGN: This was an observational retrospective cohort study comparing propensity score-matched bariatric surgery patients and nonsurgery control patients who were referred for, but did not have, surgery. Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy were also compared using propensity matching. SETTING & PARTICIPANTS: Patients (714 surgery patients; 714 controls) were from a large integrated health care system, a mean of 58±8 (SD) years old, and mostly women (77%) and non-Hispanic whites (56%) and had diabetes mellitus (66%) and/or hypertension (91%). PREDICTOR: Predictors at the time of surgery or referral to surgery were age, sex, race/ethnicity, weight, and presence of diabetes and/or hypertension. OUTCOMES: The primary outcome for this study was change in estimated glomerular filtration rate (eGFR) from serum creatinine level over a median 3-year follow-up period. MEASUREMENTS: Serum creatinine was used to calculate eGFR using the CKD-EPI (CKD Epidemiology Collaboration) creatinine equation. RESULTS: Surgery patients had 9.84 (95% CI, 8.05-11.62) mL/min/1.73m² greater eGFRs than controls at a median 3 years' follow-up and RYGB patients had 6.60 (95% CI, 3.42-9.78) mL/min/1.73m² greater eGFRs than sleeve gastrectomy patients during the same period. LIMITATIONS: This study is limited by its nonrandomized observational study design, estimation of GFR, and large changes in muscle mass, which may affect serum creatinine level independent of changes in kidney function. CONCLUSIONS: Bariatric surgery, especially the RYGB procedure, results in significant improvements for up to 3 years in eGFRs for patients with CKD stages 3 and 4.