Background

We previously demonstrated how kidney-injury in patients with severe-obesity can be reversed following bariatric surgery (BaS). Based on our experience, we hypothesize that this reversible kidney-injury might be secondary to post-operative changes improving RBF.

Methods

We conducted a retrospective analysis of patients who underwent BaS at our institution from 2002-2019. We assessed the BUN/Creatinine (Cr) ratio pre and post-operatively to determine a pre-renal (decreased RBF) vs. intrinsic-component as a causative agent in patients with baseline-CKD. Decreased RBF was defined as BUN/Cr >20. To determine kidney-function the estimated glomerular filtration rate (eGFR) from the CKD Epidemiology Collaboration Study (CKD-EPI) classification system was utilized.

Results

Our analysis included N=2,924 patients of which 11% (N=325) presented decreased RBF. From our original sample only N=228 patients had the complete data necessary to assess both eGFR and RBF (BUN/Cr). The pre-operatively Systolic-blood pressure was134 ± 16 mmHg and HbA1c 5.7±0.8%. Patients with baseline CKD stage-2 demonstrated a pre-operative BUN/Cr 20.85±10.23 decreasing to 14.99±9.10 at 12-months follow-up (p<0.001). Patients with baseline CKD stage-3 presented with a pre-operative BUN/Cr 23.88±8.75, after 12 months follow-up BUN/Cr ratio decreased to 16.38±9.27 (p<0.001). Patients with CKD stage-4 and ESRD (eGFR<30) did not demonstrate statistically significant difference for pre and post-operative BUN/Cr 21.71±9.28 and 19.21±14.58 respectively

Conclusions

According to our findings, the improvement in kidney-function in CKD stages 2-3 could be secondary to changes in RBF following BaS, introducing an unstudied reversible mechanism of Kidney-injury in the bariatric population. These findings require confirmation with larger retrospective and prospective trials.