An arteriovenous fistula is an abnormal connection between an artery and a vein. This condition allows blood to flow directly from the artery into the vein, bypassing the capillaries. It can occur naturally or be created surgically for medical purposes, such as for dialysis in patients with kidney failure. These fistulas can lead to various complications, including changes in blood flow and pressure. While some people may not experience symptoms, others might notice swelling or pain in the affected area. Monitoring and management are essential to prevent potential issues related to this condition.