heart and blood vessel disorders
Arteriovenous Fistula
Introduction
An arteriovenous fistula is an abnormal channel between an artery and a vein. Rarely, a large fistula may divert enough blood to cause symptoms of reduced blood flow in the affected arm or leg (steal syndrome). Although doctors may be able to hear the distinctive sound of blood flow though a fistula by using a stethoscope, imaging tests are often needed. Fistulas can be cut out or eliminated with laser therapy, or sometimes substances are injected into the fistula to block the blood flow. (See also Overview of the Venous System .) Arteries carry blood with oxygen and nutrients away from the heart to the rest of the body. Veins return blood to the heart from the rest of the body. Capillaries are tiny, extremely thin-walled vessels that act as a bridge between arteries and veins. The thin walls of the capillaries allow oxygen and nutrients to pass from the blood into tissues and allow waste products to pass from tissues into the blood. Normally, blood flows from arteries into capillaries and then into veins. An arteriovenous fistula is an abnormal connection directly between an artery and a vein. With an arteriovenous fistula, some blood flows directly from an artery into a vein, bypassing the capillaries. Arteriovenous fistulas may be Congenital, meaning the person was born with one Acquired, meaning that it developed (or was created) after birth Congenital arteriovenous fistulas are uncommon. Acquired arteriovenous fistulas can be caused by any injury that damages an artery and a vein that lie side by side. Typically, the injury is a piercing wound, as from a knife or bullet. The fistula may appear immediately or may develop after a few hours. The area can swell quickly if blood escapes into the surrounding tissues. 