Nonalcoholic Fatty Liver Disease: Portal Hypertension Due to Outflow Block in Patients without Cirrhosis

Abstract

To prospectively evaluate whether the characteristics of hepatic blood flow change during the early stages of fibrosis in patients with nonalcoholic fatty liver disease (NAFLD). All participants provided written informed consent, and the study protocols were approved by the institutional ethics committee. A total of 121 patients with NAFLD that was diagnosed at histologic examination were enrolled. Hepatic blood flow was measured by means of Doppler ultrasonography (US), and the ratio of arterial to portal blood flow (arterioportal ratio) was calculated. Elasticity of the spleen was measured by means of real-time tissue elastography. The elastic ratio was measured as the value in the small splenic vessel divided by the value of the splenic parenchyma. The arterioportal ratio and splenic elasticity were compared in patients with all stages of fibrosis (F0-F4) and with all levels of platelet counts. Correlations among the resistive index of the hepatic artery and that of the splenic artery, the fibrosis 4 index, hepatic elasticity, arterioportal ratio, splenic elasticity, and platelet counts were analyzed. Univariate and multivariate logistic regression analyses were performed. Correlations in patients with platelet counts greater than 200 000/μL also were analyzed. The mean ± standard deviation arterioportal ratio was significantly higher at fibrosis stage 2 (2.4 ± 0.6) than at fibrosis stage 0 (1.8 ± 0.4) in patients with NAFLD (P < .01). Increased splenic stiffness at earlier stages of fibrosis also was observed in patients with NAFLD (fibrosis stage 2, 4.4 ± 2.3; fibrosis stage 0, 3.2 ± 1.9; P < .05). In patients with NAFLD with platelet counts higher than 200 000/μL, pericellular fibrosis was the only significant predictor of hepatic hemodynamic change at multivariate analysis (odds ratio, 7.17; 95% confidence interval: 1.33, 57.13; P = .021). Change in hepatic blood flow occurred during the earliest stage of hepatic fibrosis in patients with NAFLD because of outflow block in the sinusoidal area.