ESRD is End Stage Renal Disease and the presently your father is in renal failure and needs to drain away the bodily wastes artificially for which frequent dialysis is done. As a part of carrying out the dialysis the AV created. An arteriovenous (AV) fistula is an abnormal passageway between an artery and a vein. Although it most often occurs in the legs or arms, an AV fistula can occur anywhere in the body, including the brain. An AV fistula may also be created surgically to provide access for hemodialysis in people with end-stage kidney failure as in your father?s case. Normally, blood flows from arteries through capillaries and back to the heart in veins. When an AV fistula is present, blood flows directly from an artery into a vein, bypassing the capillaries. If the volume of diverted blood flow is large, tissues downstream receive less blood supply. In addition, heart failure may occur due to the increased volume of blood returned to the heart.