Portal hypertension - pathogenesis, vascular and organ-specific manifestations, complications
Portal hypertension is increased resistance in the portal system, most commonly caused by cirrhosis due to the fibrosis that occurs (see above for full pathogenesis of cirrhosis). Less common causes include schistosomiasis, fatty changes and diffuse granulomatous diseases.
Remember: causes by level of the block –
- prehepatic: portal vein thrombosis
- intrahepatic: cirrhosis (by far the commonest), schistosomiasis
- posthepatic: Budd–Chiari syndrome, severe right heart failure, constrictive pericarditis
In cirrhosis we see increased pressure at the level of the sinusoids due to perivenular fibrosis and expanded parenchymal nodules. This goes on to cause ascites (collection of fluid in the peritoneal cavity, splenomegaly (due to congestion of venous blood in the spleen), esophageal varices, caput medusae and hemorrhoids, as well as the symptoms from normal liver cirrhosis.
As the portal pressure rises, portosystemic shunts develop, the principal sites are the rectum (hemorrhoids) and the cardioesophageal junction (esophageal varices), as well as the retroperitoneum and falciform ligament of the liver. These varices bleed easier and appear in a high percentage of patients with cirrhosis.
Caput medusae in portal hypertension – large, tortuous veins on the abdominal wall, filled through the reopened paraumbilical veins of the falciform ligament (a portosystemic shunt).
Image: “ఉదరకుడ్యంలో ఉబ్బుసిరలు ( Caput Medusae )” by డా. గన్నవరపు నరసింహమూర్తి, CC0, via Wikimedia Commons.
Long standing portal hypertension also causes splenomegaly, as the splenic vein feeds into the portal system, decreased flow through the portal system causes venous blood to build up in the spleen. This can cause a variety of hematologic abnormalities.