We describe a case of brachiocephalic fistula vein wall dissection (VWD) occurring in a 36-year-old female hemodialysis patient. Unlike subcutaneous or subfascial infiltrations for which the mechanism is blood extravasation, VWD seems to be due to disruption of the fistula vein layers caused by misplacement of the outflow (venous) needle bevel. In this setting, the pressure of the dialysis blood pump acts as the driving force of the dissecting column, extending it proximally. Gray-scale and color Doppler sonography proved to be very useful in the differential diagnosis of VWD, particularly with thrombosis of the fistula. Sonography also helped us decide when to resume cannulations.