Application of 4D flow MRI for exploring the anatomical and haemodynamic characteristics of pelvic veins and their correlations

ObjectiveThere is currently a lack of studies evaluating the anatomy and haemodynamics of the pelvic veins in clinical practice. Four-dimensional flow magnetic resonance imaging (4D flow MRI) can simultaneously obtain information on vascular anatomy and haemodynamics. The goal of this study was to use 4D flow MRI to explore the anatomical and haemodynamic characteristics of pelvic veins and their correlations in an asymptomatic population. MethodsFour-dimensional flow MRI was used to measure anatomical parameters, including the pelvic vein area, common iliac vein-inferior vena cava angle, iliac vein tortuosity, and common iliac vein stenosis rate, and haemodynamic parameters, including the pelvic venous blood flow, average blood flow velocity, and external iliac vein-inferior vena cava pressure difference, in 30 asymptomatic volunteers. The correlation between iliac vein anatomy and haemodynamics was analysed. ResultsThere were correlations between the anatomical parameters of the iliac vein and the haemodynamic parameters. A larger iliac vein area was correlated with a higher blood flow. A greater iliac vein stenosis rate was correlated with a lower blood flow, lower mean velocity of the external iliac vein, and higher external iliac vein-inferior vena cava pressure difference. A greater common iliac vein-inferior vena cava angle was associated with a lower iliac vein flow velocity and a higher external iliac vein-inferior vena cava pressure difference. Finally, a greater the iliac vein tortuosity was correlated with a lower iliac vein velocity and higher external iliac vein-inferior vena cava pressure difference. There were differences in the anatomical and haemodynamic parameters of the bilateral common iliac vein and external iliac vein. The left pelvic vein common iliac-inferior vena cava angle, iliac vein tortuosity and iliac vein stenosis rate were higher than those of the right side. The flow and average velocity of the left common iliac vein and the left external iliac vein were lower than those of the right, and the pressure of the left external iliac vein was higher than that of the right. ConclusionThe anatomical structure of the pelvic vein, including the iliac vein area, common iliac vein-inferior vena cava angle, iliac vein tortuosity, and iliac vein stenosis rate, are important factors that affect haemodynamic changes in the pelvic vein. There are correlations between parameters related to the anatomical structures and haemodynamic changes of the pelvic veins. Differences in the anatomy and haemodynamics of the bilateral pelvic veins may be one reason why the left extremity is more prone to chronic venous disease (CVD)-related symptoms.