Impact of bariatric surgery on renal functions in patients with type 2 diabetes: systematic review of randomized trials and observational studies.

BACKGROUND: The impact of bariatric surgery on renal functions in patients with type 2 diabetes (T2D) remains uncertain.

OBJECTIVES: To assess the impact of bariatric surgery on renal functions in patients with T2D.

SETTING: Systemic review and meta-analysis of randomized trials and observational studies.

METHODS: We searched PubMed, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) from inception to April 3, 2016. We included studies assessing bariatric surgery for renal functions in patients with T2D. We analyzed changes in renal functions before and after surgery and compared outcomes between surgeries versus nonsurgical treatments.

RESULTS: Twenty-nine studies (4 randomized controlled trials, 5 cohort studies, 20 before-and-after studies; all at moderate to high risk of bias) were eligible, involving 18,172 patients. Analyses of changes before and after surgeries suggested a significantly lower proportion of albuminuria (difference -21.2%, 95% confidence interval [CI] -28.8% to -13.5%), 24-hour urine albumin excretion rate (weighted mean difference -48.78 mg/24 hr, 95% CI -75.32 to -22.24) and urine albumin-to-creatinine ratio (uACR) (weighted mean difference -16.10 mg/g, 95% CI -22.26 to -9.94) after surgery. Compared with nonsurgical treatment, bariatric surgery was associated with a statistically lower level of uACR and lower risk of new-onset albuminuria (odds ratio .18, 95% CI .03-.99 from randomized controlled trials). The effects on glomerular filtration rate, serum creatinine, creatinine clearance, and risk of end-stage renal disease were not statistically significant.

CONCLUSIONS: Low-quality evidence suggests that bariatric surgery possibly improves albuminuria and uACR in patients with T2D; its effects on other outcomes were uncertain. Well-conducted, adequately powered, randomized controlled trials are warranted to examine the effect of bariatric surgery on renal functions in the T2D population.