Peritoneal dialysis, illustration. Dialysis, or haemodialysis, is required when the kidneys are no longer able to filter waste products from the blood properly. Peritoneal dialysis uses the patient's peritoneum (lining of the abdominal cavity) as a filter. The catheter inserted in the abdomen can become infected, so training needs to be given to the patient to minimise the risks involved. The catheter consists of three segments: an external segment, an intramural segment (between the skin the peritoneum), and the intraperitoneal segment.