Analyzing the Impact of Bariatric Surgery in Kidney Function: a 2-Year Observational Study
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Obesity is an independent risk factor for chronic kidney disease (CKD). Our aims were: (1) to evaluate the impact of bariatric surgery (BS) on kidney function, (2) clarify the factors determining postoperative evolution of glomerular filtration rate (ΔGFR) and urinary albumin-to-creatinine ratio (ΔUACR), and (3) access the occurrence of oxalate-mediated renal complications.
We investigated a cohort of 1448 obese patients who underwent BS. Those with baseline-estimated GFR (eGFR0) < 30 mL/min or without information about the 2-year post-surgical eGFR (eGFR2) were excluded.
A total of 725 patients were included. At baseline, 38(5.2%) had hyperfiltration with eGFR0 ≥ 125 mL/min/1.73m2 (G0), 492 (67.9%) had eGFR0 90–124 mL/min/1.73m2 (G1), 178 (24.6%) had eGFR0 60–89 mL/min/1.73m2 (G2), and 17 (2.3%) had eGFR0 < 60 mL/min/1.73m2 (G3). ΔGFR significantly increased in 96.6% (ΔGFR = 23.8 (IQR 15.9–29.8)) and 82.4% (ΔGFR = 18.6 (IQR 3.6–44.0)) of the subjects with G2 and G3 CKD, respectively (p < 0.001). The variables independently associated with ΔGFR were baseline body mass index (BMI) (positively), high blood pressure (HBP) (negatively), and fasting plasma glucose (FPG) (negatively), as well as FPG variation (positively). An overall prevalence of high UACR (≥ 30 mg/g−1) of 17.9% was found, with 81.5% of these subjects presenting A2(30–300 mg/g−1) and 18.5% A3(> 300 mg/g−1) UACR. UACR significantly decreased after BS (p < 0.001). Significant predictors of ΔUACR were BMI, systolic blood pressure, and HbA1c. Urinary excretion of calcium oxalate crystals was found in 77(11.1%) patients, with only 1 presenting oxalate-mediated renal complications.
ΔGFR seems to be influenced by the initial kidney function, as it decreases in subjects with hyperfiltration but tends to increase in those with kidney dysfunction. These results suggest that BS is associated with improvement of kidney outcomes, without a significant increase in renal complications.
KeywordsAlbuminuria Bariatric surgery Glomerular filtration rate Renal function
High blood pressure
Chronic kidney disease
Urinary albumin excretion
Estimated glomerular filtration rate
Roux-en-Y gastric bypass
Baseline-estimated glomerular filtration rate
2-Year post-surgery estimated glomerular filtration rate
Body mass index
Systolic blood pressure
Diastolic blood pressure
White blood cells count
Fasting plasma glucose
Urinary albumin-to-creatinine ratio
Isotope dilution mass spectrometry
Chronic kidney disease epidemiology collaboration formula
Kidney disease improving global outcomes
Glomerular filtration rate variation
Urinary albumin-to-creatinine ratio
Variance inflation factor
Adjustable gastric band
Excess weight loss
High-density lipoprotein cholesterol
Low-density lipoprotein cholesterol
All authors participated in the collection of data. DM interpreted the data and wrote the manuscript. All authors read and approved the final manuscript.
This research did not receive any specific grant from any funding agency in the public, commercial, or not-for-profit sector.
Compliance with Ethical Standards
Conflict of Interest
The authors declare that they have no conflict of interest.
All procedures performed in this study 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.
Informed consent was obtained from all individual participants included in the study.
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