An arteriovenous fistula is an abnormal connection or passageway between an artery and a vein. It may be congenital, surgically created for hemodialysis treatments, or acquired due to pathologic process, such as trauma or erosion of an arterial aneurysm.
If you are starting hemodialysis treatments in the next several months, you need to work with your health care team to learn how the treatments work and how to get the most from them. One important step before starting regular hemodialysis sessions is preparing a vascular access, which is the site on your body where blood is removed and returned during dialysis. To maximize the amount of blood cleansed during hemodialysis treatments, the vascular access should allow continuous high volumes of blood flow.
A vascular access should be prepared weeks or months before you start dialysis. The early preparation of the vascular access will allow easier and more efficient removal and replacement of your blood with fewer complications.
The three basic kinds of vascular access for hemodialysis are an arteriovenous (AV) fistula, an AV graft, and a venous catheter. A fistula is an opening or connection between any two parts of the body that are usually separate—for example, a hole in the tissue that normally separates the bladder from the bowel. While most kinds of fistula are a problem, an AV fistula is useful because it causes the vein to grow larger and stronger for easy access to the blood system. The AV fistula is considered the best long-term vascular access for hemodialysis because it provides adequate blood flow, lasts a long time, and has a lower complication rate than other types of access. If an AV fistula cannot be created, an AV graft or venous catheter may be needed.
What is an AV (arteriovenous) fistula?
An AV fistula requires advance planning because a fistula takes a while after surgery to develop—in rare cases, as long as 24 months. But a properly formed fistula is less likely than other kinds of vascular access to form clots or become infected. Also, properly formed fistulas tend to last many years—longer than any other kind of vascular access.
A surgeon creates an AV fistula by connecting an artery directly to a vein, frequently in the forearm. Connecting the artery to the vein causes more blood to flow into the vein. As a result, the vein grows larger and stronger, making repeated needle insertions for hemodialysis treatments easier. For the surgery, you’ll be given a local anesthetic. In most cases, the procedure can be performed on an outpatient basis.
Hemodialysis fistulas are surgically created communications between the native artery and vein in an extremity. Direct communications are called native arteriovenous fistulas (AVFs). Polytetrafluoroethylene (PTFE) and other materials (Dacron, polyurethane, bovine vessels, saphenous veins) are used or have been used as a communication medium between the artery and the vein and are termed prosthetic hemodialysis access arteriovenous grafts (AVGs). The access that is created is routinely used for hemodialysis 2-5 times per week.
Many patients who are not candidates for renal transplantation or those for whom a compatible donor cannot be secured are dependent on hemodialysis for their lifetime. This situation results in the long-term need for and use of dialysis access. The preservation of patent, well-functioning dialysis fistulas is one of the most difficult clinical problems in the long-term treatment of patients undergoing dialysis. As many as 25% of hospital admissions in the dialysis population have been attributed to vascular access problems, including fistula malfunction and thrombosis.
Historically, native fistula or graft malfunction and thrombosis were treated by using surgical thrombectomy and revision, resulting in the eventual exhaustion of the veins and the need to create a new access. Initially applied in the 1980s, percutaneous techniques such as balloon angioplasty (percutaneous transluminal angioplasty [PTA]), thrombolysis, and mechanical thrombectomy allowed the treatment of stenosis and fistula thrombosis without surgery.
Vascular surgeons have increasingly been involved in angiographic evaluation and treatment of malfunctioning and occluded hemodialysis access. The multidisciplinary management of dialysis access coordinated among vascular surgeons and nephrologists has proven extremely effective in prolonging the patency of the vascular access and decreasing the morbidity and mortality of patients with chronic renal failure.