Patients whose kidneys have failed need to receive dialysis treatment, most commonly with a dialysis machine. In order to be connected to the machine an operation is often performed to join an artery to a vein in the arm. This forms what is known as an arteriovenous fistula. The fistula causes an increase in the flow of blood through the vein and the vein reacts to this by becoming bigger and thicker, making it easier to connect the patient to the machine.

The success rate for the operation is relatively low and only approximately 65 from every 100 operations is still working after a year. It is thought that one factor that may cause problems with the fistula is the ability of the vein to stretch in response to increased blood flow. Previous research has shown that veins in kidney failure patients look different to those of people whose kidneys are working when viewed under a microscope.

The investigators aim to study the structure of the vein that is used in making fistulas with a microscope and also to test it in an engineering laboratory to see how much it will stretch. The investigators hope that gaining information about the structure of the vein and its ability to stretch will help determine what it is about the vein that affects how well it works as part of a fistula. This information may help surgeons select the best possible vein in a given patient to give the best chance of a working fistula in the future.

Inclusion Criteria:

1. Patients referred to vascular consultants for AV fistula formation for haemodialysis access.
2. Ability to give informed written consent
3. Aged over 18 at time of referral

Exclusion Criteria:

1. Veins identified on preoperative ultrasound scanning to be of a calibre too small to allow sufficient material to be obtained for biomechanical testing (<3mm diameter).
2. Inability to give informed written consent
3. Aged under 18 at time of referral
4. Inability to attend follow-up appointments

All patient referred for access formation