Preoperative radiological assessment for vascular access.

There is increasing evidence that routine preoperative duplex scanning ultrasound cannot only increase the utilisation of native AVF for dialysis access but also allow proper selection of a target vessel with adequate luminal diameter to improve outcome. A minimum arterial diameter of 2mm is associated with successful fistula formation. A threshold for minimal venous diameter is difficult to establish. Most clinical studies use a value of 2.5mm for AVF and 4mm for prosthetic grafts. Traditional contrast venography is mandatory where there is suspicion of central vein stenosis. In predialysis patients where there is a risk of contrast nephropathy MR venography is emerging as a possible alternative.