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Portal Hypertension

by | 4 Dec, 2020

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Introduction

Hypertension of the portal vein frequently complicates cirrhosis but also has other causes.

The portal vein is formed by the splining and superior mesenteric veins. Normally, the pressure is 5-8 mmHg with only a small gradient between the liver and hepatic vein. Clinically significant portal hypertension occurs when pressure is >10 mmHg with the risk of variceal bleeding increasing when it is >12 mmHg.

Causes

Causes can be classified into:

  1. Pre-hepatic: blockage of portal vein before the liver
  2. Intrahepatic: distortion of liver architecture
  3. Post-hepatic (rare): venous blockage outside the liver

The commonest cause is cirrhosis.

Pre-hepatic causes

  • Portal vein thrombosis e.g. sepsis, procoagulopathy
  • Abdominal trauma

Intrahepatic causes

  • Cirrhosis
  • Schistosomiasis: common cause in developing countries
  • Primary biliary cirrhosis
  • Drug-induced e.g. methotrexate
  • Metastatic malignant disease
  • Sarcoidosis

Post-hepatic causes

  • Budd-Chiari syndrome
  • Right heart failure
  • Constrictive pericarditis

Pathophysiology

As portal pressure rises above 10 mmHg, the compliant venous system dilates and collaterals develop within the systemic venous system. He main sites of collaterals are:

  • Gastro-oesophageal junction
  • Rectum
  • Left renal vain
  • Anterior abdominal wall (umbilical vein)

Therefore, there is a gradual reduction in the flow of portal blood to the liver and increased shunting to collaterals. As collateral formation progresses, more than 50% of portal blood flow may be shunted.

Clinical features

Portal hypertension is often asymptomatic and the only clinical evidence is splenomegaly. Clinical features are principally due to portal venous congestion and collateral vessel formation.

Clinical features include:

  • Splenomegaly
  • Haematemesis and/or malaena from bleeding oesophageal varices. Characterised by painless, massive bleeding
  • Rectal varices, which are often mistaken for haemorrhoids
  • Ascites
  • Fetor hepaticus (faecal breath) due to portosystemic shunting, allowing thiols to enter the lungs
  • Renal failure

The most important feature is variceal formation, which is usually within 3-5 cm of the gastro-oesophageal junction. These are friable vessels that can bleed. Drugs that cause mucosal erosion (e.g. NSAIDs) can precipitate bleeding.

Investigations

Diagnosis is often made clinically. Portal venous measurements are rarely needed, although can be done using a transjugular balloon catheter.

Blood tests: FBC shows thrombocytopaenia due to hypersplenism

Endoscopy: Very important in determining if oesophageal varices are present

Ultrasound scan: can show features of portal hypertension e.g. splenomegaly, collateral vessel formation

CT/MRI angiography: determine portal vein patency and identify clots

Management

Treating the underlying cause is the main method of treating portal hypertension. Therefore, its management is largely focused on prevention and control of variceal haemorrhage.

Acute variceal bleed

Acute bleeding should be treated as a medical emergency as bleeding may be massive and patients can rapidly progress to circulatory shock.

  1. IV fluids
  2. Antibiotics
  3. Terlipressin is vasoconstrictive and effective at slowing haemorrhage. It should be used before transferring patients to endoscopy
  4. Endoscopy can provide definitive treatment of varices through band ligation or sclerotherapy

Primary prevention of variceal haemorrhage

Beta-blocker therapy is effective e.g. carvedilol, propranolol.

Secondary prevention of variceal haemorrhage

Beta-blockers and a regular banding programme are indicated to prevent bleeding in the long-term.

Refractory cases may be treated with transjugular intrahepatic portosystemic shunting (TIPSS). This involves creating a channel between the portal vein and the hepatic vein, allowing the blood to bypass the liver. Refractory ascites is another indication for TIPSS.

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