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Portal haemodynamics: modern diagnostics for portal hypertension and liver cirrhosis

Portal haemodynamics describes the complex blood flow conditions in the portal vein system and forms the basis for diagnostics and therapy management in portal hypertension. This specialised discipline of vascular diagnostics enables gastroenterologists and hepatologists to precisely assess haemodynamic changes in liver cirrhosis, portal vein thrombosis and other hepatic diseases. The recording and evaluation of portal pressure values and flow measurements are an essential part of modern liver diagnostics.

Basics of portal circulation

The portal vein (vena portae) is formed by the confluence of the superior mesenteric vein and the splenic vein and carries blood from the gastrointestinal tract, the spleen and the pancreas to the liver. Within the sinusoids, the blood from the portal circulation mixes with the arterial blood from the hepatic artery. Normal portal pressure is 5 to 10 mmHg and exceeds the pressure in the inferior vena cava by 4 to 5 mmHg (portal venous gradient).

Portal haemodynamics is determined by various parameters. The portal vein pressure is equal to the product of the transhepatic blood flow and the flow resistance in its flow path. Both an increase in resistance and an increased portal blood flow therefore have an influence on portal pressure.

Pathophysiology of portal hypertension

Portal hypertension is defined as elevated pressure in the portal vein above the normal range (3-6 mmHg). Gastroesophageal varices are only to be expected at pressures > 12 mmHg. The most important trigger of portal hypertension is cirrhosis of the liver, in which connective tissue changes and regeneration lead to increased resistance in the sinusoids and in the terminal portal vessels.

Additional factors can contribute to portal hypertension:

  • Sinusoidal cell contractility: Increased contractility of stellate cells
  • Vasoactive substances: Production of endothelin and nitric oxide (NO)
  • Systemic mediators: Arteriolar resistance changes
  • Hepatocyte swelling: Cell swelling in acute damage

Modern diagnostic procedures

Duplex sonographic measurement

Duplex sonography has established itself as a “non-invasive splenoportography” and is highly regarded in diagnostics. The procedure enables the haemodynamics of the entire portal venous and hepatic venous system to be assessed with high sensitivity for portal vein and splenic vein thrombosis, Budd-Chiari syndrome and portosystemic collaterals.

Duplex sonography is used to determine the maximum flow velocity, vessel diameter and flow volume in the portal vein and superior mesenteric artery. In patients with liver cirrhosis, the maximum flow velocity in the portal vein is significantly lower than in healthy subjects, typically below 20 cm/s.

Functional haemodynamic tests

The influence of a standardised test meal on portal haemodynamics shows characteristic differences between healthy subjects and patients with liver cirrhosis. After a test meal, the flow velocity increases by only 22% and the flow volume by 29% in patients with liver cirrhosis, while an increase of 76% and 131%, respectively, is observed in controls.

These functional tests enable:

  • Improved diagnostics: More accurate diagnosis of portal hypertension
  • Early detection: Detection of haemodynamic changes before clinical symptoms occur
  • Therapy monitoring: Monitoring of the effects of drug treatment

Clinical manifestations

Development of collateral circulation

Over time, portal hypertension leads to portosystemic venous collateral formation. These bypass circuits can slightly reduce portal vein pressure, but can also cause serious complications. Portosystemic blood flow develops in vessels that connect to the superior or inferior vena cava, bypassing the liver.

Characteristic collateral formations include:

  • Oesophageal varices: dilated submucosal vessels with a risk of bleeding
  • Caput medusae: abdominal wall varices around the navel caused by reopening of the umbilical vein
  • Splenogastric collaterals: connections between the spleen and the stomach wall
  • Splenorenal shunts: Venous connections between the spleen and kidney

Systemic haemodynamic changes

In advanced portal hypertension, a hyperdynamic circulation develops. Increased synthesis or release of vasodilating substances such as nitric oxide, substance P or calcitonin gene-related peptide in the arterioles of the intestines lead to increased blood flow and exacerbate portal hypertension.

Specialised measurement methods

Invasive haemodynamic evaluation

With more than 350 liver vein catheter measurements per year, the Vienna Hepatic Hemodynamic Lab has established itself as a leading centre. Indirect liver vein pressure measurement is considered the clinical gold standard in the prognosis of patients with liver cirrhosis and enables precise determination of the hepatovenous pressure gradient (HVPG).

Telemetric monitoring

Modern telemetry probes enable continuous measurement of:

  • Portal vein pressure: Continuous pressure recording
  • Arterial blood pressure: Systemic haemodynamic parameters
  • Heart rate: Cardiovascular monitoring
  • Body temperature: Metabolic status monitoring

This real-time monitoring is performed over extended periods of time in a non-anaesthetised state and provides precise data on portal haemodynamics.

Therapeutic implications

Drug interventions

Quantitative duplex sonography is becoming increasingly important in clinical practice for assessing portal hypertension and the risk of bleeding from oesophageal varices. It provides valuable information for monitoring drug therapy to prevent bleeding, particularly when beta-blockers are used.

Interventional procedures

The transjugular intrahepatic portosystemic shunt (TIPS) procedure is an important therapeutic option. Duplex sonography is suitable for monitoring progress after portocaval shunt surgery and intrahepatic stent placement, as well as for diagnosing vascular complications after liver transplantation.

Non-invasive prognostic parameters

Elastography procedures

Transient elastography (FibroScan) enables quantitative measurement of liver stiffness and is a recognised alternative to liver biopsy. Depending on the technique used, shear wave-induced elastography or strain-based methods are employed, which provide important information about portal haemodynamics.

Biomarker development

Research into biomarkers of NO/sGC/cGMP signal transduction in patients with liver cirrhosis is contributing to the development of new therapeutic strategies. Soluble guanylyl cyclase (sGC) is the only receptor for nitric oxide that can be pharmacologically influenced.

Technological innovations

Smart monitoring systems

Modern portal haemodynamic measurement systems integrate smart keyboard functionality with haptic feedback and digital control. Zero calibration and real-time processing enable precise measurements even under complex haemodynamic conditions.

Integration of artificial intelligence

The integration of machine learning algorithms improves the accuracy of parameter determination and enables predictive analyses for the prognosis of portal hypertension complications.

Precise portal haemodynamics for optimal liver diagnostics

Portal haemodynamics has established itself as a fundamental discipline in hepatology and enables the precise assessment of complex vascular changes in liver disease. The combination of non-invasive duplex sonography, invasive pressure measurements and modern imaging techniques offers gastroenterologists comprehensive diagnostic options.

 

Note: This article is for informational purposes only and does not replace specialist advice from qualified gastroenterologists and hepatologists. The use of portal haemodynamic measurement techniques requires specialised training and appropriate certification.