In Depth: The Types of Renal Dialysis

There are two basic types of dialysis, hemodialysis and peritoneal dialysis.

Hemodialysis

Hemodialysis is the process of pumping blood through a machine which takes blood from the patient via a catheter, filtering the blood through a semi-permeable membrane and returning the filtered blood through another catheter back into the patient. Most often the treatment is performed three times a week for 3 to 5 hours each time. Twice a week sessions are limited to patients who have some residual kidney function.

There are three primary methods for access to blood from the dialysis patient. These include intravenous catheters, arteriovenous fistulas and synthetic grafts. The type of access used is influenced by things such as the expected time that the patient might experience renal failure and the condition and structure of the arteries and veins of the patient.

Intravenous Catheters, also called Central Venous Catheters are usually inserted into a large vein of the patient such as the vena cava by way of either the large vein in the patient's neck (internal jugular vein) or through the large vein in the groin area (femoral vein). The catheter is usually composed of two plastic tubes known as lumen, one to remove the blood from the patient and the other to return the processed blood back to the patient.

There are two basic varieties of intravenous catheters, "non-tunneled" and "tunneled". Non-tunneled catheters are used for short durations of time and treatments, normally up to 10 days, however often only for one dialysis treatment. This type of catheter emerges from the skin of the patient at the site of entry into the vein. Tunneled catheters are longer catheters, placed in the jugular vein of the neck and "tunneled" under the skin from the point of entrance of the vein to an exit point on the chest wall. The placement of the catheter is performed in this manner to try and form a natural barrier to infection. These catheters are used for short to medium term access that normally is no longer than a couple of months.

An (AV) Arteriovenous fistula is considered the preferred method of access to the patient's blood for dialysis. This approach requires that a vascular surgeon join an artery and vein together called an anastomosis. The anastomosis is usually performed on the non-dominant arm of the patient and offers the advantage of a reduced potential for infection as well as providing an optimal point of entrance for longer term treatment. This approach to accessing blood has fewer complications, such as clotting or infection and lasts longer than the intravenous catheter options. In fact, the Centers for Medicare & Medicaid (CMS) has set up a "Fistula First Initiative" with the objective to increase utilization of this approach for dialysis patients.

Another approach to providing access to the patient's blood for hemodialysis is an AV graft. AV (arteriovenous) grafts are very similar to fistulas with the primary difference being the use of an artificial vessel which is employed to join the artery and vein together in much the same way as an AV fistula. This approach is normally used when the patient's own veins and arteries will not permit a fistula. Some problems with AV grafts are clotting, infection and narrowing of the vein just downstream from where the graft has been sewn to the vein.

Peritoneal Dialysis

Peritoneal dialysis is the process of using the patients' own peritoneum which is the semi-permeable membrane that lines the patients' abdominal cavity to filter out the waste in the blood.

This procedure is performed by taking a sterile and warmed fluid know as the dialysate which is introduced via a surgically installed, permanent catheter into the peritoneum where the fluid is allowed to remain for a defined period of time (4 to 6 hours). The dialysate contains a sugar called dextrose that helps pull fluid from the blood through the peritoneum into the abdominal cavity. The waste and extra fluid leaves your body when the dialysate is drained from your body back into the delivery system. Once this process is complete fresh dialysate is reintroduced into the abdomen, and the process repeats.

There are different types of peritoneal dialysis. These include continuous ambulatory dialysis (CAPD), continuous cycler-assited peritoneal dialysis (CCPD) and manual intermittent peritoneal dialysis (IPD)

Continuous ambulatory dialysis (CAPD) allows individuals a degree of freedom and control over their care as this method does not require the use of machines or assistance from the dialysis centers.

Continuous Cycler-Assisted Peritoneal Dialysis (CCPD) uses an automatic cycler that provides three to five exchanges of dialysate per night while the patient is sleeping, sort of like CAPD but with exchanges at night, not during the day.

Manual Intermittent peritoneal dialysis (IPD) is much like CCPD, however it is usually performed in a hospital. The treatment time may last as long as 24 hours and are done several times a week. IPD is rarely performed anymore.

Your doctor will explain more to you about these options and will advise you as to the method most appropriate for your care and treatment. Infection is the most common problem for patients on peritoneal dialysis. It is important that you work with your healthcare team so that you know how to keep your catheter bacteria-free to avoid an infection of your peritoneum, a condition called peritonitis.

Some of the steps you can take to minimize the chances of infection are:

• Wash your hands every time you handle your catheter.
• Check each bag of solution you use for any signs of contamination.
• Do your exchanges in areas that are clean, dry and well-lit.
• Clean the exit site with antiseptic every day.
• Store your supplies in a cool, dry and clean place.

See also:

Chronic Kidney Disease and Failure
Treating Kidney Disease