Portal hypertension

Section: Hepatobiliary Sub-section: Liver Curriculum: Curriculum, page 86

Definition

 - Pathological increase in vascular resistance to blood flow within the portal system that leads to a sustained increase in the pressure gradient between the portal and systemic venous circulation.

• Hepatic venous pressure gradient (HVPG) >5 mmHg

When discussing or thinking about PH it is important to keep in mind that there are usually two issues 1. PH 2. underlying liver disease - AB

Aetiology

• Prehepatic (extrahepatic portal vein)
  • Thrombosis of the portal, mesenteric and splenic veins
  • Extrinsic compression of the portal vein (e.g. by tumour or lymph nodes).
• Posthepatic (at the level of the hepatic venous outflow)
  • (Budd–Chiari syndrome)
  • Cardiac causes
    • Right heart failure
    • Constrictive pericarditis
• Intrahepatic (within the liver)
  • Pre-sinusoidal
    • Schistosomiasis
    • Sarcoidosis
    • Primary Biliary Cirrhosis
  • Sinusoidal
    • Cirrhosis Causes
    • Congenital Hepatic Fibrosis
    • Idiopathic Portal HTN
    • Polycystic Liver Disease
  • Post-sinusoidal
    • Veno-occlusive disease
    • Vitamin A toxicity → Excessive fibrosis

Pathology

Main factors which drive portal hypertension 

• Increased vascular resistance to portal flow - in cirrhosis is driven by increased resistance of the hepatic microcirculation due to fibrosis and scarring
• Increase in the portal flow – due to the hyperdynamic circulation triggered from splanchnic vasodilatation - cause by release of NO due to increased sheer stress

Anatomical Site	Portal Vein Involved	Systemic Vein Involved	Clinical Significance
Esophagus	Left gastric vein (coronary vein)	Azygos and hemiazygos veins	Esophageal varices → Risk of life-threatening bleeding
Rectum	Superior rectal vein	Middle and inferior rectal veins	Hemorrhoids (specifically, internal hemorrhoids)
Umbilicus	Paraumbilical veins (veins of Sappey)	Superior and inferior Epigastric veins	Caput medusae (dilated periumbilical veins)
Retroperitoneal	Colic and retroperitoneal veins	Lumbar veins	Silent collaterals; often asymptomatic
Bare area of the liver	Small veins from the liver capsule	Inferior phrenic veins	Typically subclinical
Sites of previous surgery

Diagnosis

• Non-invasive modalities 
  • CT and USS 
    • Splenomegaly 
    • Re-canalized umbilical vein 
    • Ascites 
    • Dilated portal vein >13mm or SMV > 11mm 
    • Heterogenous and nodular liver.  
    • Collateral veins in retroperitoneum and abdominal wall.  
    • Caudate hypertrophy.  
  • USS specific 
    • Reduced portal vein flow velocity.  
    • Reversal of portal vein flow - hepato-fugal flow.  
• Invasive modalities 
  • Hepatic venous pressure gradient measurement.  
    • Catheter is inserted into middle hepatic vein via internal jug.  
    • Middle hepatic venous pressure is measured - free hepatic venous pressure 
    • Vein is occluded then wedge pressure is measured - this will allow an estimate between the portal vein and IVC.  
    • Difference diagnosis portal hypertension 

      • 12mmHg is considered significant.

Risk of variceal bleeding:

• HVPG > 12 mmHg
• Large varices > 5 mm diameter on endoscopy
• Severity of liver disease: MELD Score or Child-Pugh Score
• Decompensated

Clinical

Presentation:

• Acute life-threatening variceal bleeding
• At diagnosis of portal hypertension (non-specific symptoms of malaise, anorexia, weight loss, encephalopathy)
• At endoscopy
• Screening given cirrhosis

Complications

• Oesophageal varices
• Gastric varices
• Portal hypertensive gastropathy
• Hepatic encephalopathy
• Ascites
• Spontaneous bacterial peritonitis
• Hepatorenal syndrome
• Hepatic hydrothorax
• Hepatopulmonary syndrome
• Portopulmonary hypertension
• Cirrhotic cardiomyopathy
• Portal cholangiopathy

Investigations

• Normal portal blood pressure is 5-10 mmHg.
• Hepatic venous pressure gradient (HVPG)
  • Seldom used in clinical practice due to the need for invasive central venous catheters
    • Normal HVPG 3-5 mmHG.

    • 5 mmHg is portal hypertension.

    • HVPG > 12 mmHg is threshold for variceal bleeding and ascites.
• Hepatic ultrasound elastography (surrogate)
  • Accuracy for diagnosis of hepatic fibrosis
  • Severity of fibrosis detected correlates well with portal pressure

Imaging findings

• Dilated portal vein (>13 mm): non-specific
• Biphasic or reverse flow in the portal vein (late stage): pathognomonic
• Enlarged paraumbilical veins: pathognomonic
• Portal-systemic collateral pathways (collateral vessels/varices)
• Splenomegaly
• Ascites