Non-invasive measurement of azygos venous blood flow using magnetic resonance

Monitoring treatment efficacy in patients with portal venous hypertension has been limited by the difficulty of direct or indirect assessment of portal vein pressure. The majority of currently available haemodynamic tests, such as hepatic vein wedge pressure or azygos vein flow measurement by thermodilution catheter, are invasive which has restricted their application. We describe a non-invasive cine phase contrast magnetic resonance technique for quantitative measurements of bulk volume flow and for demonstrating flow changes during the cardiac cycle in the azygos vein. The technique was used to analyse the azygos vein flow in seven adult volunteers and five patients with biopsy-confirmed chronic liver disease, portal hypertension and endoscopically proven oesophageal varices. In the volunteers the mean volume flow rates varied between 81 and 241 ml/min with a mean for the group of 171 ml/min. The patients had a significantly higher mean volume flow rate of 628 ml/min (p<0.01), with a range of 339 to 945 ml/min. These preliminary results suggest that cine phase contrast magnetic resonance angiography is a practical non-invasive method for measuring absolute azygos vein flow, and may provide a non-invasive method of monitoring portal hypertension.