Key Points

In individuals undergoing bariatric surgery, the magnitude of decline in GFR postbariatric surgery is directly associated with presurgery GFR.Reductions in GFR postsurgery were only weakly correlated with weight loss.In obese individuals, GFR-estimating equations performed best when deindexed and when applied in people with reduced kidney function.

Background

Important questions remain about how bariatric (i.e., weight loss) surgery affects measured GFR (mGFR) and eGFR as well as what factors influence change in mGFR postsurgery.

Methods

Data were pooled from all seven available studies (dates: 2004–2018) measuring GFR prebariatric and postbariatric surgery using gold standard methods. Change in postsurgery mGFR, factors that could influence change in mGFR, and effects on five GFR-estimating equations were analyzed using standard statistical methods.

Results

The cohort included 105 individuals from the United States and Europe. Sixty-eight percent were female, 97% were White, the mean age was 50 years (range, 24–70), and the mean body mass index was 46±8 kg/m2. The mean presurgery mGFR of 107 ml/min (range, 31–215) fell to 92 ml/min (−14%; 95% confidence interval, −21 to −10) postsurgery, with a strong linear relationship existing between presurgery mGFR and % change in GFR (r=−0.51; −0.64 to −0.35). Individuals with presurgery mGFR ≥90, 60 to

Conclusions

In individuals with obesity undergoing bariatric surgery, the magnitude of postsurgical decline in mGFR was directly associated with presurgery GFR and weakly correlated with weight loss. In addition, GFR-estimating equations' performance improved when deindexed and used in people with reduced kidney function, with the combined creatinine/cystatin C equations having the best overall performance.