Diagnostic Role of the Hepatic Venous Pressure Gradient and Elastography in Porto-sinusoidal Vascular Disorder With Portal Hypertension

Porto-sinusoidal vascular disorder (PSVD) is considered a rare cause of portal hypertension (PH), resulting from specific histological alterations that essentially affect the small portal branches and sinusoids, in the absence of cirrhosis. In recent years, the recognition and importance of PSVD has increased, notably due to the widespread use of transient elastography (TE). However, the definitive diagnosis of PSVD can only be established through liver biopsy. Recent data show that PSVD should be suspected in patients with PH and TE ≤ 20 kPa and liver biopsy should be considered in this context. The investigators hypothesize that hepatic venous pressure gradient (HVPG) and magnetic resonance liver elastography (MRE) may help in the selection of liver biopsy candidates for the diagnosis of PSVD. Primary objectives are: * To describe the measurement of the hepatic venous pressure gradient (in mmHg) in patients with portal hypertension and transient hepatic elastography ≤ 20 kPa. * To describe hepatic (in kPa) and splenic (in kPa) stiffness measured by magnetic resonance elastography in patients with portal hypertension and transient hepatic elastography ≤ 20 kPa. * To describe the frequency of major histological findings for the diagnosis of portal sinusoidal vascular disorder (obliterative portal venopathy, regenerative nodular hyperplasia and incomplete septal cirrhosis) in patients with portal hypertension and transient hepatic elastography ≤ 20 kPa. Secondary objectives are: * To describe the frequency of hepatic vein-to-vein communications in patients with portal hypertension and transient hepatic elastography ≤ 20 kPa. * To describe the frequency of minor histological findings for the diagnosis of portal sinusoidal vascular disease (portal tract abnormalities, architectural disturbances, nonzonal sinusoidal dilatation, mild perisinusoidal fibrosis) in patients with portal hypertension and transient hepatic elastography ≤ 20 kPa. * To compare the serum values of von Willebrand antigen factor (IU/mL) between patients diagnosed with porto-sinusoidal vascular disorder and those diagnosed with cirrhosis, after analysis of liver biopsy. * To compare the serum titers of procollagen III amino-terminal peptide (mcg/l) between patients diagnosed with portosinusoidal vascular disorder and those diagnosed with cirrhosis, after analysis of liver biopsy. * To compare the serum titers of anti-endothelial cell antibodies between patients diagnosed with portosinusoidal vascular disorder and those diagnosed with cirrhosis, after analysis of liver biopsy. 50 patients will be included, prospectively and retrospectively, in a comparative study between diagnostic methods, with a cross-sectional design.