A 58-year-old man with cirrhosis undergoes imaging for hepatic resection planning. The radiologist identifies collateral vessels in the porta hepatis and ascites. Which feature best distinguishes portal hypertension due to intrahepatic obstruction from extrahepatic portal vein thrombosis?

Explanation

## Portal Hypertension: Intrahepatic vs. Extrahepatic Obstruction ### Pathophysiological Distinction Portal hypertension can result from obstruction at three levels: prehepatic (extrahepatic), intrahepatic, and posthepatic. The key discriminator between intrahepatic and extrahepatic obstruction lies in the **patency of the portal vein itself** and the **site of pressure elevation**. **Key Point:** In intrahepatic portal hypertension (cirrhosis, fibrosis), the portal vein is patent but blood flow through the liver parenchyma is obstructed, causing pressure to rise within the portal system. In extrahepatic obstruction (portal vein thrombosis, external compression), the portal vein itself is narrowed or thrombosed. ### Comparison Table | Feature | Intrahepatic (Cirrhosis) | Extrahepatic (PV Thrombosis) | |---------|--------------------------|------------------------------| | **Portal Vein Patency** | Patent | Thrombosed/Narrowed | | **Portal Pressure Gradient** | Elevated (>12 mmHg) | Elevated | | **Liver Function** | Impaired (jaundice, coagulopathy) | Preserved initially | | **Ascites** | Common (due to liver dysfunction) | Rare (unless variceal bleed) | | **Splenomegaly** | Present | Present | | **Varices** | Esophageal > gastric | Gastric > esophageal | | **Imaging Finding** | Patent portal vein with cirrhotic liver | Absent/thrombosed portal vein | **High-Yield:** The **portal vein patency on imaging** is the single best discriminator. Doppler ultrasound or CT/MRI will show a patent portal vein in cirrhosis but a thrombosed or absent portal vein in extrahepatic obstruction. ### Clinical Correlations **Intrahepatic Portal Hypertension (Cirrhosis):** - Portal vein remains patent - Pressure gradient measured across liver (hepatic venous pressure gradient, HVPG) is elevated - Liver synthetic function is impaired → jaundice, coagulopathy, hypoalbuminemia - Ascites develops due to combination of portal hypertension + liver dysfunction **Extrahepatic Portal Vein Thrombosis:** - Portal vein is thrombosed or severely narrowed - Liver function is initially preserved (normal bilirubin, normal PT) - Ascites is uncommon unless there is variceal bleeding - Collateral vessels (cavernous transformation) develop around the thrombosed vein **Clinical Pearl:** A patient with portal hypertension and normal liver function tests (normal bilirubin, normal PT) suggests extrahepatic obstruction. Conversely, portal hypertension with jaundice and coagulopathy suggests intrahepatic disease (cirrhosis). **Mnemonic:** **PIPE** = Patent In Parenchymal (intrahepatic); **PLUG** = Plugged/thrombosed in prehepatic (extrahepatic)