Colour Coded Duplex Ultrasound of Native Arterio-venous Fistula for Haemodialysis With Venous Pressure Measurement Using Controlled Compression Ultrasound as a Predictor for Shunt Maturation in the Early Postoperative Phase

Inclusion criteria: * Patients after creation of a native arterio-venous fistula at the cephalic vein for hemodialysis access; * Informed consent. Exclusion criteria: * Former creation of a native arterio-venous fistula at the same arm; * Known upper extremity occlusive arterial disease; * Situation when ultrasound examination is not suitable: extreme swelling of the arm, post-operative pain, hematoma, local infections.