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How Does Peritoneal Dialysis (PD) Work?


Functioning kidneys are essential for health and life. When kidneys are no longer able to do their jobs, treatment is necessary to replace their lost yet indispensable processes. The treatment options include dialysis. There are 2 types of dialysis: peritoneal dialysis (PD) and hemodialysis (HD). Although the life-preserving goals of these kidney-replacement therapies are the same, they accomplish these in very different ways.

How does PD procedure differ from HD

While HD uses artificial membranes to filter unnecessary wastes and other substances from the blood, PD uses the natural membrane lining the abdominal cavity (peritoneum) as the blood filter. This is made possible because of the many small blood vessels flowing within the peritoneal membrane. When a dialysis solution (dialysate) flows into the peritoneum, small molecules such as minerals and waste products can readily pass from the blood vessels, through the peritoneal membrane, and into the dialysate. After a period of time, this solution is drained and replaced with fresh dialysate.

To conduct PD, it is necessary to insert a long-lasting catheter that goes through the skin and into the peritoneum. This is an extremely common procedure. It is through this catheter that the dialysate flows in and out.

Benefits of PD

Although the efficiency of PD is significantly less than that of HD, the long periods that blood is exposed to the dialysate can make up for that difference. Among the benefits of PD are:

  • more easily controlled fluid and mineral balance,
  • frequently, a less restricted diet,
  • fewer medications may be required,
  • easier to travel,
  • fewer trips to your physician or dialysis center.

PD can be carried out at home, at the office, or while on the road. However, not all people with kidney failure have the option of peritoneal dialysis:

  • You or a partner (often a family member) must demonstrate the ability to perform PD after receiving training at your dialysis center.
  • Some impairments or diseases might make PD unsuitable.
  • Prior abdominal surgery, infections, or other sources of injury to the peritoneal membrane can prevent successful PD.
  • Living conditions must allow for good sterile technique.
  • There must be space at home to store large amounts of dialysate.
  • Diabetes is the most common cause of ESKD. The very high concentrations of sugar (glucose) in the dialysate may require some adjustments to diabetes treatment.
  • PD tends to be less effective in obese people.
  • Infections are the number one risk, often occurring at the peritoneal tube insertion site. Infections within the peritoneal cavity are more serious, usually transmitted by poor sterile technique when exchanging dialysate, and may cause permanent peritoneal membrane damage.

Types of PD

Two basic PD methods provide flexible options for the patient: Continuous Ambulatory PD and Automated PD. Both use the peritoneal catheter for the “exchanges” of dialysate; the catheter is inconspicuous under clothing.

Continuous Ambulatory Peritoneal Dialysis (CAPD)

  • CAPD is done continuously throughout the day and night.
  • A bag of sterile dialysate is attached to the peritoneal tube and allowed to flow into the peritoneum. The bag is then detached, and the tube capped.
  • After some time period of time, usually around 6 to 8 hours, the dialysate, now containing waste products and other desired substances from the blood, is drained and exchanged for a fresh dialysis solution. The whole exchange process takes around 30 minutes.
  • After a period of adjustment, the sensation of having fluid in your peritoneal cavity diminishes or disappears.
  • CAPD is done by the patient or a qualified caregiver, and treatments can be given at home, school, work, or nearly everywhere else.

Automated (nightly) Peritoneal Dialysis (APD)

  • APD works much like CAPD. The difference is that a machine fills and drains the dialysate automatically rather than doing manual dialysate exchanges throughout the day. The machine is usually located at home.
  • APD is usually done at night while you are asleep. Recently, remote APD monitoring capability has been studied for its feasibility and effectiveness. The degree to which remote monitoring improves the overall effectiveness of APD remains to be seen.

Key takeaways

PD results are comparable to HD and can offer the patient more independence, self-reliance, and often an easing of life-style demands and medication needs.

Peritoneal dialysis is typically a daily process, more comparable to the functioning of the kidney.

The type of PD selected can offer greater personal flexibility to best accommodate work, personal needs, and lifestyle.

To minimize the risk of serious infections, PD requires careful and consistent adherence to sterile technique. Peritonitis is not only a dangerous infection, but consequences can include hospitalization, loss of PD effectiveness due to scarring of the peritoneal membrane and removal of the dialysis tube that sometimes cannot be replaced.

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