 An arteriovenous fistula is an abnormal connection between an artery and a vein. Normally, blood flows from your arteries to your capillaries and then onto your veins. But with an arteriovenous fistula, blood flows directly from an artery into a vein by bypassing some capillaries. AV fistulas can develop anywhere in the body and they are also often surgically created For use in dialysis in people with severe kidney disease, small arteriovenous fistulas often won't have any symptoms and usually don't need treatment. But symptoms of large AV fistulas include purplish bulging veins seen through your skin, swelling in the arms or legs and decreased blood pressure. If a diagnosed AV fistula in your body needs treatment, your doctor may prescribe ultrasound guided compression or catheter embolization. Large arteriovenous fistulas may require surgery. The type of surgery you'll need depends on the size and location of your fistula, which includes microsurgery or stereotactic radiosurgery.