Kidneys filter out waste products and water from the blood. When kidneys fail to function properly, dialysis can clean waste products artificially. There are two forms of dialysis: a kidney machine that filters the blood (hemodialysis) and an exchange process that uses the lining of the inside of the abdomen as a filter (peritoneal dialysis). In peritoneal dialysis, a cleansing liquid drains from a bag into the abdomen through a tube. Over several hours, waste products and water pass through the lining of the abdomen into the liquid. The waste-filled liquid is then drained from the abdomen. The exchange process is repeated several times each week.