Peritoneal Dialysis is a very simple and effective treatment that does not require technically advanced equipment. It differs from Hemodialysis in, that the blood is treated without being removed from the body. Instead the dialysis fluid is introduced to the patient’s abdominal cavity through a catheter placed in the lower part of the abdomen.
This method of cleaning the blood takes advantage of the peritoneum, the membrane that lines the abdominal cavity. The peritoneum acts as a filter. Normally, this cavity only contains between 50 – 100 ml of fluid, which acts as a lubricant, but can accommodate from 1 – 3 liters depending on the size of the patient. The peritoneum has a rich blood supply and good venous and lymphatic drainage. It is a semi-permeable membrane, allowing the passage of both water and solutes.
In PD, the dialysis fluid is instilled into the peritoneal cavity via a surgically implanted catheter. Uremic toxins and solutes move across the membrane, by diffusion, from the blood stream to the dialysis fluid, or vice versa, depending on the concentration gradient. Fluid removal takes place by osmosis, by the addition of an osmotic agent, usually glucose, to the dialysis fluid. After a certain time the fluid is drained and replaced by new fresh fluid.
The continuous nature of PD mimics the action of the kidney more closely than Hemodialysis, which tends to be intermittent. This means that the patient is more stable, with no great fluctuations in levels of toxins in the blood. Peritoneal Dialysis is mainly a self-care treatment and is usually performed by the patient at home.
Peritoneal dialysis can be performed manually or by a machine. Peritoneal dialysis is similar to the dialysis performed by kidneys, and operates 24 hours per day, 7 days per week.
The process is made up of three main phases:
- Fill phase – Fluid is introduced into the abdominal cavity.
- Dwell phase – The fluid is left in the cavity for a certain period of time.
- Drain phase – The fluid is drained out as waste.