Advances in portal pressure measurement: Endoscopic techniques, challenges, and implications for liver transplantation

Table 1 Classification of portal hypertension and differences in pressure measurement

Classification type	Definition	Etiology	Location of obstruction/resistance	Key characteristics	Pressure measurement differences
Prehepatic PH	Increased pressure in the portal venous system before it enters the liver	PV thrombosis, splenic vein thrombosis	PV, splenic vein	PV obstruction before liver: Minimal liver damage	FHVP: Normal, WHVP: Normal, HVPG: Normal
Intrahepatic presinusoidal PH	Increased resistance before liver sinusoids due to portal venous inflammation	Portal fibrosis, early cirrhosis, granulomatous diseases	PV, periportal space, and small vessels	Early stage of cirrhosis or hepatic fibrosis: Less severe than sinusoidal or post-sinusoidal	FHVP: Normal, WHVP: Normal/high, HVPG: Normal/high
Intrahepatic sinusoidal PH	Increased resistance in the liver sinusoids due to sinusoidal injury	Alcoholic liver disease, viral hepatitis, cirrhosis, metabolic dysfunction-associated steatohepatitis	Liver sinusoids and hepatic microcirculation	Significant increase in intrahepatic resistance: Due to severe sinusoidal damage	FHVP: Normal, WHVP: High, HVPG: High
Intrahepatic post-sinusoidal PH	Increased resistance beyond the sinusoids due to changes in venous outflow	Veno-occlusive disease, granulomatous phlebitis	Hepatic venules, post-sinusoidal vessels	Obstruction of hepatic venules and post-sinusoidal spaces: Less common than sinusoidal	FHVP: Normal, WHVP: High, HVPG: High
Post-hepatic PH	Increased pressure after the liver due to obstruction in the venous outflow	Budd-Chiari syndrome, right-sided heart failure, constrictive pericarditis	Hepatic veins, inferior vena cava	Obstruction after liver affects venous outflow: Liver often preserved in function	FHVP: High, WHVP: High, HVPG: Normal/high

FHVP: Free hepatic venous pressure; HVPG: Hepatic venous pressure gradient; PH: Portal hypertension; PV: Portal vein; WHVP: Wedged hepatic venous pressure.

Table 2 Non-invasive imaging modalities for assessment of clinically significant portal hypertension

Imaging modality	Description	Sensitivity (%)	Specificity	Limitations
Ultrasound elastography (liver stiffness measurement)	Uses shear wave elastography or transient elastography to assess liver stiffness, which correlates with portal pressure	0.81 (0.73–0.87)	0.83 (0.77–0.88)	May be less accurate in obese patients or those with ascites. Affected by liver inflammation and cholestasis
Spleen stiffness measurement	Measures spleen stiffness to estimate portal pressure and PH severity. Reflects not only increased intrahepatic vascular resistance but also splenic haemodynamic and fibrosis	0.85 (0.69–0.93)	0.86 (0.74–0.93)	A dedicated device is required. Difficult to measure without splenomegaly
Magnetic resonance elastography	Uses MRI technology to assess liver stiffness, capable of covering the whole liver	80-90	90-95	High cost, limited availability
Doppler ultrasound	Measures the velocity of blood flow in the PV and hepatic veins, used to infer PH	70-90	70-90	Operator-dependent, limited by technical factors (e.g., patient positioning)
Computed tomography or MRI-based imaging (with contrast)	Involves imaging of the PV, spleen, and liver, providing visual signs of PH, such as varices or splenomegaly	70-90	75-90	Limited sensitivity in detecting mild PH, expensive

MRI: Magnetic resonance imaging; PH: Portal hypertension; PV: Portal vein.