What is the definition of portal hypertension?

Definition of Portal Hypertension

Portal hypertension is defined as a portal pressure gradient (the difference between the portal vein and the hepatic veins) greater than 5 mm Hg, as measured by the hepatic venous pressure gradient (HVPG). 1

Measurement and Classification

Portal hypertension is most accurately assessed through catheterization of the hepatic vein with determination of the HVPG, which is calculated as:

• HVPG = Wedged (occluded) hepatic venous pressure - Free hepatic venous pressure 1
• Normal HVPG is 3-5 mm Hg 1

Portal hypertension is further classified based on severity:

• Mild portal hypertension: HVPG > 5 but < 10 mm Hg 1
• Clinically significant portal hypertension (CSPH): HVPG ≥ 10 mm Hg 1

Anatomical Classification

Portal hypertension can be classified based on the anatomical location of increased resistance to blood flow:

1. Prehepatic: Involving splenic, mesenteric, or extrahepatic portal vein (e.g., portal vein thrombosis)

   • HVPG measurement is normal 1

2. Intrahepatic:

   • Presinusoidal: Cirrhosis from cholestatic liver disease, schistosomiasis, idiopathic portal hypertension
   • Sinusoidal: Most common in Western countries, typically from cirrhosis due to alcohol, hepatitis C, or NASH
   • HVPG is elevated in sinusoidal type 1

3. Posthepatic/Postsinusoidal:

   • Sinusoidal obstruction syndrome
   • Right heart failure
   • HVPG may be normal or elevated depending on specific condition 1

Clinical Significance of HVPG Values

Different HVPG thresholds correlate with specific clinical outcomes:

• HVPG > 10 mm Hg: Complications of portal hypertension become more likely (varices, clinical decompensation) 1
• HVPG > 12 mm Hg: Identifies bleeding risk; reducing HVPG below this threshold is associated with protection from variceal hemorrhage 1
• HVPG > 16 mm Hg: Indicates higher risk of death 1
• HVPG > 20 mm Hg: Predicts failure to control bleeding, early rebleeding, and death during acute variceal hemorrhage 1

Diagnostic Methods

While HVPG measurement is the gold standard for diagnosing portal hypertension, it has limitations:

• Invasive procedure
• Requires specific expertise
• Relatively expensive
• Not available in all centers 1

Therefore, noninvasive methods are increasingly used:

1. Physical examination:

   • Spider nevi
   • Visible abdominal portosystemic collaterals
   • Note: Absence of physical signs cannot rule out CSPH 1

2. Laboratory data:

   • Low platelet count (most common laboratory sign)
   • APRI and FIB-4 scores (though with limited accuracy) 1

3. Imaging techniques:

   • Ultrasound: Presence of portocollateral circulation, recanalized paraumbilical vein, spontaneous splenorenal circulation
   • Transient elastography (TE): At 15 kPa, sensitivity 90-96% and specificity 48-50%; at 25 kPa, sensitivity 57-85% and specificity 82-93% 1
   • CSPH is highly unlikely at LSM ≤15 kPa and likely at LSM ≥25 kPa 1

Clinical Implications

Understanding portal hypertension is critical because:

• It predicts risk of developing complications in cirrhosis 1
• It guides treatment decisions for preventing variceal bleeding 2
• It helps monitor response to therapy (reduction in HVPG >20% from baseline or to <12 mmHg is considered protective) 2

Portal hypertension management focuses on reducing portal pressure through non-selective beta-blockers and preventing complications such as variceal bleeding, ascites, and hepatic encephalopathy 2.