A fistula is a connection between two body parts, such as an organ and a blood vessel, or another structure that normally do not connect. When a fistula is created for dialysis, an artery and a vein are connected. The vein enlarges and thickens over time, allowing two needles to be placed and the dialysis process to occur.

Patients undergoing dialysis treatment must have vascular access that is working properly to maintain the blood flow to and from the hemodialysis machine. A fistulagram is an endovascular procedure where contrast dye can be inserted into the fistula to determine the problem of the malfunctioning fistula. An angioplasty can be performed with a balloon catheter being placed into the fistula to expand a blocked area, restoring the flow. If the vessel walls are too weak, a stent – or a mesh wire tube – is inserted to support the vessel walls and maintain blood flow. When the blood flow becomes inadequate due to the narrowing of the blood vessels, a surgical graft may be needed to restore flow.