Are Hepatic Venous Pressure Gradient and Portosystemic Pressure Gradient the Same?
No, hepatic venous pressure gradient (HVPG) and portosystemic pressure gradient (PSG) are not identical measurements, though they are closely related and highly correlated in most clinical scenarios. 1
Key Definitions
HVPG is calculated as wedged hepatic venous pressure (WHVP) minus free hepatic venous pressure (FHVP). This measures sinusoidal pressure and reflects the pressure gradient across the liver parenchyma. 1
PSG (also called portal pressure gradient or PPG) is calculated as WHVP minus right atrial pressure (or inferior vena cava pressure). This represents the true pressure difference between the portal venous system and systemic venous circulation. 2
Clinical Correlation
The two measurements show strong correlation but are not interchangeable:
In a 2021 study of 178 patients, both HVPG and PSG demonstrated similar diagnostic performance for cirrhosis (area under ROC curve 0.79 vs 0.78), with no statistical difference between measurements at the 9 mmHg cutoff. 2
A 2025 study found high correlation between HVPG variants (r=0.946), but importantly showed that HVPG consistently underestimates the actual portal pressure gradient. 3
The correlation between HVPG and true portal venous pressure varies significantly by HVPG level, with best agreement in the 20-24 mmHg range (ICC=0.68) and poorest agreement at lower gradients. 4
Why the Difference Matters
The distinction becomes clinically significant when:
Right atrial pressure is elevated (heart failure, volume overload): PSG will be lower than HVPG because the denominator (systemic venous pressure) is higher. 1
FHVP differs from right atrial pressure by >2 mmHg: In these patients, PSG correlates more closely with actual portal pressure than HVPG does. 3
Presinusoidal or prehepatic portal hypertension exists: HVPG will be normal despite elevated portal pressures because the wedged pressure doesn't reflect portal vein pressure in these conditions. 1
Practical Clinical Application
Use HVPG as the standard measurement because:
- It is the established reference standard in all major guidelines 5, 1
- Normal HVPG is 3-5 mmHg 1
- HVPG ≥10 mmHg defines clinically significant portal hypertension 1
- HVPG thresholds (10,12,16,20 mmHg) have validated prognostic significance for varices, bleeding, decompensation, and mortality 1
Consider PSG when:
- Right heart pressures are abnormal
- You need to assess true portosystemic shunting
- HVPG seems discordant with clinical picture
Critical Caveat
Both measurements have limitations: Recent evidence shows HVPG significantly underestimates actual portal pressure gradient, particularly at lower HVPG levels where up to 95.7% of patients show >10% discrepancy. 4 This means HVPG should not be used to exclude patients from interventions like TIPS. 3 The measurements are most reliable in sinusoidal portal hypertension (cirrhosis from alcohol, HCV, NASH) and least reliable in pre-sinusoidal causes. 1