Supplementary Material for: Longitudinal Impacts of Bariatric Surgery on eGFR in CKD Patients

Background
Obesity is associated with chronic kidney disease (CKD) incidence and progression. We examined whether bariatric surgery is associated with change in eGFR trajectory among patients with and without CKD.
Methods:
Patients who underwent bariatric surgery at two health systems were identified using ICD-9/ICD-10 and CPT codes. Linear mixed models were fit on estimated glomerular filtration rate (eGFR) trajectory pre- and post-surgery among patients with or without CKD. Models were adjusted for age, sex, race, ethnicity, body mass index, hypertension, diabetes, follow-up duration, and type of bariatric surgery. Post-surgery eGFR trajectory among patients with CKD was also compared following 1:2 propensity score matching to (1) patients without CKD who underwent surgery and (2) patients with CKD who did not undergo surgery.
Results:
Patients with CKD (n=139) at Michigan Medicine had a slower annual rate of eGFR decline post-surgery compared to patients without CKD (n=278) (1.54 [-2.26, -0.81] vs. 3.15 [-3.41, -2.87] mL/min/1.73m2; p<0.001), despite adjusting for degree of weight loss. Among patients with CKD, surgery was associated with a slower annual rate of eGFR decline (-0.20 [-0.83, 0.43] post-surgery vs. -1.11 [-1.37, -0.85] mL/min/1.73m2 for non-surgery patients; p<0.001). In an external validation study of patients with CKD in the Providence health system, bariatric surgery predicted an average increase in annualized eGFR slope by 1.19 [0.12, 2.25] mL/min/1.73m2 (p=0.03).
Conclusion:
Bariatric surgery is associated with less eGFR decline and may have weight-independent effects on preserving kidney function among persons living with obesity and CKD.