Nonalcoholic fatty liver disease increases risk of incident chronic kidney disease: A systematic review and meta-analysis.

BACKGROUND: Recent studies examined the prognostic impact of nonalcoholic fatty liver disease (NAFLD) on the risk of incident chronic kidney disease (CKD). However, the extent to which NAFLD may confer risk of incident CKD is uncertain. We performed a meta-analysis of relevant studies to quantify the magnitude of the association between NAFLD and risk of incident CKD.

METHODS: We searched PubMed, Scopus and Web of Science from January 1, 2000 to August 31, 2017 using pre-defined keywords to identify large observational cohort studies with a follow-up duration of at least 1year, in which NAFLD was diagnosed by biochemistry, fatty liver index or ultrasonography. No studies with biopsy-proven NAFLD were available for the analysis. Data from selected studies were extracted, and meta-analysis was performed using random-effects modeling.

RESULTS: A total of 9 observational studies with 96,595 adult individuals (34.1% with NAFLD) of predominantly Asian descent, and 4653 cases of incident CKD stage ≥3 (i.e., defined as occurrence of estimated glomerular filtration rate<60ml/min/1.73m2 , with or without accompanying overt proteinuria) over a median period of 5.2years were included in the final analysis. Patients with NAFLD had a significantly higher risk of incident CKD than those without NAFLD (random-effects hazard ratio [HR] 1.37, 95% CI 1.20-1.53; I2 =33.5%). Patients with more 'severe' NAFLD (according to ultrasonography and non-invasive fibrosis markers) were also more likely to develop incident CKD (n=2 studies; random-effects HR 1.50, 95% CI 1.25-1.74; I2 =0%); this risk appeared to be even greater among those with ultrasound-diagnosed NAFLD and a high-intermediate NAFLD fibrosis score (n=1 study; random-effects HR 1.59, 95% CI 1.31-1.93). Sensitivity analyses did not alter these findings. Funnel plot and Egger's test did not reveal significant publication bias.

CONCLUSIONS: This largest and most updated meta-analysis to date shows that NAFLD (detected by biochemistry, fatty liver index or ultrasonography) is associated with a nearly 40% increase in the long-term risk of incident CKD. However, the observational nature of the eligible studies does not allow for proving causality. Our findings pave the way for future large, prospective, histologically-based studies.