What is Portal Hypertension?
Portal hypertension is a pathological increase in portal venous pressure, defined as a hepatic venous pressure gradient (HVPG) above 5 mmHg, with clinically significant portal hypertension (CSPH) occurring at HVPG ≥10 mmHg. 1
Pathophysiology
Portal hypertension develops through two key mechanisms that follow the hydraulic equivalent of Ohm's law where "Pressure = Resistance × Flow": 2, 1
Increased intrahepatic resistance is the primary driver, consisting of:
Increased portal blood flow occurs secondary to splanchnic vasodilation and hyperdynamic circulation, which aggravates the elevated pressure 2
The increased portal pressure forces blood to find alternative routes, leading to the development of portosystemic collaterals at sites where portal and systemic circulation communicate. 2
Clinical Significance and Pressure Thresholds
The severity of portal hypertension directly correlates with clinical outcomes: 2, 1
- Normal HVPG: 1-5 mmHg
- Portal hypertension: HVPG >5 mmHg
- Clinically significant portal hypertension (CSPH): HVPG ≥10 mmHg (associated with higher risk of clinical decompensation)
- High mortality risk: HVPG ≥16 mmHg (strongly associated with death)
Patients with compensated cirrhosis and HVPG ≥10 mmHg have significantly higher risk of developing portal hypertension-related complications, while HVPG ≥16 mmHg predicts mortality. 2
Major Complications
Portal hypertension is the most common complication of chronic liver disease and the main determinant in developing life-threatening sequelae: 2
Gastroesophageal varices: Dilated submucosal veins that develop when portal pressure exceeds a threshold, with 1-year bleeding incidence of approximately 12% (5% for small varices, 15% for large varices) 2, 3
Variceal bleeding: A leading cause of mortality in cirrhotic patients, with mortality rates of 12-22% despite modern treatment, and rebleeding rates up to 60% within 1 year without prophylaxis 2
Ascites: The most common complication, with survival decreasing from 80% at 5 years in compensated cirrhosis to 50% when ascites develops 1
Hepatic encephalopathy: Results from portosystemic shunting and hepatocellular dysfunction 2
Splenomegaly and hypersplenism: Leading to thrombocytopenia and leukopenia 3
Hepatorenal syndrome, hepatopulmonary syndrome, and portopulmonary hypertension: Serious systemic complications 2
Diagnostic Approach
HVPG measurement via hepatic vein catheterization is the gold standard for diagnosing and quantifying portal hypertension. 2, 1 However, its invasiveness limits routine clinical use.
Non-invasive alternatives include: 2, 1
- Transient elastography (liver stiffness measurement): Sensitivity 90-96%, specificity 48-50% at 15 kPa cutoff; CSPH is highly unlikely at LSM ≤15 kPa and likely at LSM ≥25 kPa
- Blood-based tests (APRI score): 56% sensitivity, 68% specificity
- Doppler ultrasound: First-line investigation for extrahepatic portal vein obstruction 1
Underlying Causes
Cirrhosis from any chronic liver disease is the predominant cause of portal hypertension, accounting for the majority of cases. 4 The condition develops in the vast majority of patients with cirrhosis. 2
Important considerations: 2, 4
- Varices are present in 52.2% of cirrhotic patients undergoing screening endoscopy
- Incidence is significantly higher in Child-Pugh class B/C (48-72%) versus class A (35-43%)
- Primary biliary cirrhosis can develop portal hypertension early, even before established cirrhosis
Prognostic Importance
HVPG is considered the single best predictor of outcome available to clinicians. 2 An HVPG reduction of ≥10% after therapy is associated with decreased risk of first variceal hemorrhage in compensated cirrhosis. 2, 1
Risk factors for variceal bleeding include: 2, 3
- Larger variceal size
- Presence of red wale marks (red color signs on varices)
- Decompensated liver disease (Child-Pugh class B/C)