BACKGROUND The association between nonalcoholic fatty liver disease (NAFLD) and renal function changes remains inconclusive. We explored whether the histological severity of NAFLD is associated with early deterioration of renal function.

METHODS Patients with biopsy-proven NAFLD were prospectively followed for renal function monitoring. A renal outcome was defined as a ≥ 50% increase in serum creatinine, a < 30% decrease in the estimated glomerular filtration rate (eGFR) or an eGFR < 45 mL/min/1.73 m².

RESULTS Among 455 NAFLD patients, 221 (48.6%) had nonalcoholic steatohepatitis (NASH), and no difference in baseline eGFR was found between NASH and NAFL patients. During a median follow-up of 32 months, a renal outcome occurred in 15 patients; the incidence rate was 12.3 per 1,000 person-years. Compared with NAFL, NASH did not increase the risk of renal outcomes. Among the histological components of NAFLD, lobular inflammation (≥ 2), fibrosis (≥ F3), and portal inflammation (≥ 3) significantly increased the risk of renal outcomes in the crude analysis (HR 3.35, 95% CI 1.10-9.11; HR 3.25, 95% CI 1.12-8.84; and HR 7.73, 95% CI 2.86-22.22). After adjustment for risk factors for renal dysfunction, including sex, age, diabetes, hypertension, and chronic kidney disease, only portal inflammation significantly increased the risk of renal outcomes (HR 5.88, 95% CI 1.87-18.42, p = 0.002).

CONCLUSIONS Portal inflammation predicts early deterioration of renal function in patients with biopsy-proven NAFLD. Individualized monitoring of renal function based on the histological severity of NAFLD may be helpful for early identification of long-term renal outcomes.