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Dialysis, Types

Dialysis is a way to remove waste products and extra water from the blood of patients with kidney failure. The two main types of dialysis are hemodialysis and peritoneal dialysis.

Hemodialysis (HD)

The Procedure

In hemodialysis, your blood is removed from your body, a few ounces at a time through some form of IV access. A machine pumps the blood through tubing to a filter, or dialyzer. The dialyzer is a canister that contains thousands of fibers that filter out the wastes and extra fluid. The clean blood is then pumped through tubing and returned to the body. Removing the harmful wastes and extra salt and fluids helps control blood pressure and keep the proper balance of chemicals like potassium and sodium in the body.

Adjusting to Hemodialysis

One of the biggest adjustments when starting hemodialysis treatments is following a rigid schedule. Hemodialysis is usually performed in a clinic under the supervision of a nurse and kidney specialist, and generally requires anywhere from three times a week (most common schedule) to five treatments a week. Indications for increased treatment frequency can be driven by the need for additional fluid removal or for medical conditions that require extensive clearance. Each treatment can last for about three to four hours. For example, a Monday-Wednesday-Friday schedule or a Tuesday-Thursday-Saturday schedule is possible. In addition, a morning, afternoon, or evening shift will be dependent upon availability and capacity at the dialysis unit. Options for scheduling treatments (including both the frequency and length of treatments) will be discussed prior to initiation of dialysis.

In order to perform hemodialysis, vascular access must be placed so the blood can be readily removed for the procedure; vascular access is typically placed by a surgeon. Options for vascular access include creating a fistula (a surgery that directly connects an artery and vein, often in the arm), placing a graft (tubing under the skin that connects an artery to a vein; also often in the arm but can be placed in other parts of the body), or placement of a dialysis catheter (a large IV catheter with two separate openings placed into a large vein).

Fistulas and grafts involve placing IV needles though the skin to connect to the dialysis machine tubing and filter. Fistulas and grafts often need to heal for some amount of time prior to their use; in addition, fistulas need to mature so that the blood vessel becomes large enough to stick with the needles. However, the benefit of fistulas and grafts is that they have a lower risk of infection, they also allow for showering, swimming, and other activities. Patients with catheters have a higher risk of infections at baseline; they are not allowed showering or swimming due to these infection risks.

Peritoneal Dialysis (PD)

The Procedure

In peritoneal dialysis, a soft tube called a catheter is used to fill the abdominal cavity with a cleansing liquid called dialysate solution. The walls of the abdominal cavity are lined with a membrane called the peritoneum, which allows waste products and extra fluid to pass from your blood into the dialysate solution. The solution contains a sugar called dextrose that will pull extra fluid into the abdominal cavity.

These wastes and fluid then leave the body when the dialysate solution is drained and that used solution is then discarded. The process of draining and filling is called an "exchange" and may be done a few or several times each day, depending on the individual patient’s needs. Peritoneal dialysis can be performed in the home, usually while the child sleeps, without a health professional present. Training is available under this circumstance.

Similar to vascular access for hemodialysis, the PD catheter is also surgically placed. Ideally, the PD catheter insertion site is fully healed prior to initiation of peritoneal dialysis. Once the catheter is fully healed, patients can shower regularly, take baths (as long as exit site and catheter are not submerged), and swim in a private chlorinated or saline pool or the ocean. Because of the risk of infection, swimming in public pools, ponds, lakes, and rivers is not allowed.

Alternative Forms of Peritoneal Dialysis

Different types of PD will have different schedules of daily exchanges. One form of PD, continuous ambulatory peritoneal dialysis (CAPD), doesn't require a machine but exchanges may be done manually a few times during the day. As the word “ambulatory” suggests, the patient can walk around with the dialysate solution in the abdomen. Another form of PD, continuous cycler-assisted peritoneal dialysis (CCPD), requires a machine called a cycler to fill and drain the abdomen, usually at night while the patient is asleep. CCPD is also sometimes called automated peritoneal dialysis (APD).