You have a kidney function of (GFR 14 ml/min) which means a kidney function of 14 % (stage V of chronic kidney disease). In stage V, you require renal replacement therapy in the form of dialysis or kidney transplantation. You are already close to requiring dialysis so there should be no question of closing the AV fistula. If there is an aneurysm in the fistula that may have to be repaired. You should not close the fistula as you will require dialysis soon.