Venous duplex sonography is used for the assessment of the veins’ function and for imaging the veins’ patterns and flow conditions. This examination is necessary prior to interventions in the vein system and has replaced x-rays using a contrast medium (phlebography) as the method of choice. In addition, with imaging ultrasound it is possible to identify also vein inflammations, deep vein thrombosis or congenital vascular malformations. This examination should be carried out prior to every treatment of venous conditions.