Peritoneal dialysis (PD) is based on the same filtering process as hemodialysis. But instead of using an artificial kidney as the filter, the peritoneal membrane is used. The peritoneal membrane — also called the peritoneum — is a thin membrane that lines the abdominal cavity. To gain access to the peritoneum, a catheter, or flexible hollow tube, is surgically placed in the lower abdomen. It’s about a foot long, but only four or five inches of it lies outside the body. Catheter insertion is done in an operating room, often with local anesthesia. During dialysis, the abdominal cavity is filled with a dialysate solution. Because the peritoneum is rich in tiny blood vessels, it continually provides a supply of blood to be filtered by osmosis and diffusion. The excess fluid and toxins in the blood move toward the dialysate, which is drained and replaced periodically.