Supplementary Material for: Ultrasound Characteristics of Budd-Chiari Syndrome - A Multi-Centre Analysis

Introduction: Budd–Chiari syndrome (BCS) is a rare obstruction of hepatic venous outflow that can culminate in liver failure. It is classified as primary, caused by thrombotic endoluminal lesions, or secondary, produced by external compression or invasion of the hepatic veins or inferior vena cava (IVC). Despite numerous single‑patient ultrasound reports, the absence of cross‑regional datasets has impeded uniform diagnostic criteria. Methods: We retrospectively reviewed ultrasound examinations performed between 2010 and 2020 in 118 consecutive BCS patients from China (n = 59), Germany (n = 26), India (n = 18) and Italy (n = 15). Standardised protocols combined B‑mode, Doppler and contrast‑enhanced ultrasound to document venous patency, caudate lobe size and collateral pathways. Results: The cohort (65 men, 53 women; mean age 46 years) presented mainly with chronic disease (74 %). Primary, thrombotic BCS predominated (n = 96; 81 %), whereas secondary, mass‑related obstruction was uncommon (n = 7; 6 %). Ultrasound showed hepatic vein thrombosis in 70 %, collateral venous circulation in 83 %, caudate lobe hypertrophy in 30 % and portal vein thrombosis in 14 %. Regional variation was evident: IVC thrombosis occurred in 33 % of Chinese patients, while occlusion at the hepatic‑vein confluence predominated in the European cohorts. Conclusions: This first multinational ultrasound series in BCS delineates reproducible hallmarks—hepatic vein thrombosis, extensive collaterals and caudate enlargement—and highlights geographic phenotypes. Harmonised ultrasound protocols therefore constitute a pivotal step toward earlier diagnosis, consistent classification and improved outcomes in this uncommon yet life‑threatening disorder.