Which feature best distinguishes a portal vein thrombosis from a hepatic vein thrombosis (Budd–Chiari syndrome) in terms of clinical presentation and collateral circulation?

Explanation

## Portal Vein Thrombosis vs. Hepatic Vein Thrombosis (Budd–Chiari Syndrome) ### Pathophysiological Distinction **Key Point:** These two conditions affect different segments of the hepatic vascular tree and produce distinct patterns of blood flow obstruction and collateral development. | Feature | Portal Vein Thrombosis | Hepatic Vein Thrombosis (BCS) | |---------|------------------------|-------------------------------| | **Site of obstruction** | Extrahepatic or intrahepatic portal vein | Hepatic veins (suprahepatic IVC) | | **Primary haemodynamic effect** | Increased pressure PROXIMAL to liver (portal hypertension) | Increased pressure WITHIN liver (hepatic congestion) | | **Liver perfusion** | Maintained via hepatic artery (50% of blood flow) | Severely compromised; hepatic artery cannot compensate | | **Splenomegaly** | Marked (due to portal hypertension) | Mild or absent | | **Oesophageal varices** | Present (portal hypertension) | Absent or late (no portal hypertension) | | **Ascites** | Develops gradually; often with preserved synthetic function | Acute, severe; with hepatic dysfunction | | **Hepatomegaly** | Absent or mild | Marked (hepatic congestion) | | **Liver synthetic function** | Often preserved initially | Impaired early (hepatic necrosis) | | **Collateral circulation** | Develops via coronary vein, splenic vein, mesenteric veins | Develops via intrahepatic portosystemic shunts, retroperitoneal veins | ### Clinical Presentation Patterns **High-Yield:** Portal vein thrombosis → **portal hypertension without hepatic dysfunction** (splenomegaly, varices, ascites with preserved liver function). Hepatic vein thrombosis → **hepatic congestion and liver failure** (hepatomegaly, jaundice, coagulopathy, ascites with impaired synthetic function). **Clinical Pearl:** In portal vein thrombosis, the liver is perfused by the hepatic artery, so hepatic synthetic function is often preserved despite portal hypertension. In Budd–Chiari syndrome, outflow obstruction causes hepatic congestion, ischaemia, and necrosis, leading to acute liver failure. ### Collateral Development **Mnemonic:** **PVTO** = Portal Vein Thrombosis → Oesophageal varices (via coronary vein); **BCS** = Budd–Chiari → Caput medusae and intrahepatic shunts (via congestion). ```mermaid flowchart TD A[Venous Obstruction]:::outcome --> B{Site?}:::decision B -->|Portal vein<br/>Extrahepatic/Intrahepatic| C[Portal Hypertension]:::action B -->|Hepatic veins<br/>Suprahepatic IVC| D[Hepatic Congestion]:::action C --> E[Liver perfused by HA<br/>Synthetic function preserved]:::action D --> F[Hepatic ischaemia<br/>Synthetic dysfunction]:::action E --> G[Splenomegaly<br/>Oesophageal varices<br/>Ascites gradual]:::outcome F --> H[Hepatomegaly<br/>Jaundice<br/>Ascites acute<br/>Coagulopathy]:::urgent ```