portal hypertension

Portal hypertension is defined as hepatic venous pressure gradient (HVPG) greater than 5 mmHg. HVPG is a surrogate for the portosystemic pressure gradient. Clinically significant portal hypertension is defined as a gradient greater than 10 mmHg and variceal bleeding may occur at a gradient greater than 12 mmHg.

Pathology

Causes can be split by their relation to the hepatic sinusoids:

Prehepatic causes

• portal vein thrombosis
• extrinsic compression of portal vein
• congenital portal vein stenosis
• arteriovenous fistula
• SVC obstruction (downhill varices)

Hepatic / sinusoidal causes

• cirrhosis
• viral hepatitis
• Schistosomiasis (S. mansoni or S. japonicum)
• congenital hepatic fibrosis
• infiltrative liver diseases
• polycystic liver disease
• nodular regenerative hyperplasia
• idiopathic portal hypertension

Posthepatic causes

• Budd-Chiari syndrome
• sinusoidal obstruction syndrome
• congestive cardiac failure
• constrictive pericarditis

Subtypes

• sinistral portal hypertension 

Radiographic features

Ultrasound

• dilated portal vein (>13 mm): non-specific
• biphasic or reverse flow in portal vein (late stage): pathognomonic
• recanalization of paraumbilical vein: pathognomonic
• portal-systemic collateral pathways (collateral vessels/varices)
• splenomegaly
• ascites
• cause of portal hypertension often identified, most commonly cirrhosis

CT and MRI

• dilated portal vein +/- mesenteric veins
• contrast enhancement of paraumbilical vein: pathognomonic
• collateral vessels/varices: these are many and can include
  • ​coronary venous collaterals: considered one of the commonest
  • esophageal collaterals
  • paraumbilical collaterals
  • abdominal wall collaterals
  • perisplenic collaterals
  • retrogastric collaterals
  • paraesophageal collaterals
  • omental collaterals
  • retroperitoneal collaterals
  • mesenteric collaterals
  • splenorenal collaterals
  • gastrorenal collaterals
• splenomegaly
• ascites
• cause of portal hypertension often identified, most commonly liver cirrhosis

Treatment and prognosis

• dietary restriction
• medication: propranolol, diuretics
• interventional procedures
  • transjugular intrahepatic portosystemic shunt (TIPS)
  • surgical portosystemic shunt
  • surgical splenorenal shunt 
  • balloon dilatation of hepatic vein (in case of thrombosis/web in hepatic vein)
  • transhepatic clot thrombolysis (in portal vein thrombosis)
  • splenic artery embolization
  • liver transplantation
• treatment of complications

Complications

• ascites
• esophageal varices and gastric varices
  • variceal bleeding (30-50% mortality with each bleed)
• portal hypertensive gastropathy/enteropathy/colopathy
• hepatic encephalopathy
• hepatorenal syndrome
• hepatopulmonary syndrome
• congestive splenomegaly and hypersplenism

Differential diagnosis

Dilatation of splenic veins at the splenic hilum without splenomegaly may occur in situations such as state of increased perfusion of splenic tissue associated with an immune response .