When the kidneys fail, waste products and excess water can be removed from the blood by hemodialysis or peritoneal dialysis. In hemodialysis, blood is removed from the body into a dialyzer (called an artificial kidney), which filters the blood. An artificial connection between an artery and a vein (arteriovenous fistula) is made to facilitate the removal of blood. In peritoneal dialysis, the peritoneum is used as a filter. The peritoneum is a membrane that lines the abdomen and covers the abdominal organs, creating a space within the abdomen called the peritoneal space or abdominal cavity. Waste products from the body drain across the peritoneum into the fluid (dialysate) in the abdominal cavity.