Renal Function 1 Year After Bariatric Surgery: Influence of Roux-en-Y Gastric Bypass and Identification of Pre-Operative Predictors of Improvement
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While evidence of improved renal function following gastric bypass exists, pre-operative predictors of this improvement are not completely known.
To assess the glomerular filtration rate (GFR) 1 year after Roux-en-Y gastric bypass (RYGB) and to identify pre-operative predictors associated with the improvement of renal function.
A historical cohort study, which included 109 obese patients before and 12 months after RYGB, was classified into subgroups according to GFR (normofiltration, hypofiltration (GFR < 5th percentile), and hyperfiltration (GFR > 95th percentile)). The 5th and 95th percentiles were 90 and 120 mL/min/1.73 m2, respectively. The primary outcome was the variation of GFR (%GFR) estimated by the Chronic Kidney Disease - Epidemiology Collaboration (CKD-EPI) formula, calculated using serum creatinine, ethnicity, and gender.
The mean age was 38.3 ± 10.3 years and 77% were female; 52.3% presented hypertension and 27.5% type 2 diabetes. One year after surgery, the mean BMI decreased from 36.7 ± 3.6 to 28.8 ± 3.3 kg/m2 (p < 0.001). Pre-surgically, 37.6% presented hypofiltration, 47.7% normofiltration, and 14.7% hyperfiltration. The overall GFR increased from 95.5 ± 19 to 104 ± 16.4 mL/min (10.9%) (p < 0.001). The overall post-surgical %GFR was negatively correlated with the pre-surgical GFR (R = − 0.687; p < 0.001). In the hypofiltration and normofiltration subgroups, the post-surgical %GFR was negatively correlated with age (R = − 0.328, p = 0.036; and R = − 0.355, p = 0.004, respectively) and pre-surgical GFR (R = − 0.436, p = 0.04; and R = − 0.528, p < 0.001, respectively).
RYGB led to a significant improvement in renal function, mainly among patients with a worse pre-operative renal function. In the hypofiltration and normofiltration subgroups, a younger age was associated with better outcomes.
KeywordsKidney diseases Obesity Gastric bypass Bariatric surgery Glomerular filtration rate
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Conflict of Interest
The authors declare that they have no conflict of interest.
Statement of Informed Consent
Informed consent was obtained from all individual participants included in the study.
Statement of Human and Animal Rights
The study was approved by the local committee of ethics in research under the reference number 2.237.978/Unicamp and all participants signed an informed consent form. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.