Term: Dialysis

Dialysis is used in the event of kidney failure. One of the kidney's many natural functions is to filter waste product from the blood. Dialysis can take on the role of the patients kidneys. There are two types of dialysis, hemodialysis and peritoneal dialysis. Both types of dialysis will filter a patients blood to get rid of harmful wastes, salt and water. Currently, there are over 200,000 people utilizing dialysis machines as they await transplants.

Types of Dialysis

Treatment for hemodialysis takes place in a hemodialysis unit. This is a special building that is equipped with machines that perform the dialysis treatment. Special equipment adds the proper materials to purified water for the dialysis machines. The dialysis unit is also the place where patients can receive dietary counseling and help with social needs.
Patients generally go to the dialysis unit three times a week for treatment. For example, the schedule is either Monday, Wednesday, and Friday or Tuesday, Thursday, and Saturday. Before treatment, patients weigh themselves so that excess fluid accumulated since the last dialysis session can be measured. Patients then go to assigned chairs that are like lounge chairs. The area of the graft or fistula (the connection between the artery and vein), is cleaned thoroughly. Two needles are then inserted into the graft or fistula. One takes the blood to the machine where it is cleaned. The other needle allows blood that is returning to the patient to go back into the patient's body.
Treatments last from 2 ½ to 4 ½ hours. During this time, the dialysis staff checks the patient's blood pressure frequently and adjusts the dialysis machine to ensure that the proper amount of fluid is being removed from the patients body. Patients can read, watch television, , or do other work during treatment.

Peritoneal Dialysis
Peritoneal dialysis requires the patient to play a more active role in their dialysis treatment. Of primary importance is the patient's responsibility for maintaining a clean surface on the abdomen, where treatment is administered, in order to prevent infection.
In this process, the patient weighs herself/himself to determine the fluid to be used. The patient then puts on a mask and cleans the peritoneal catheter site. Fluid that has been allowed to stay in the peritoneal cavity is drained back into the plastic bag that originally contained the fluid. The patient then disconnects this bag and connects a new bag of solution that is allowed to drain into the peritoneal cavity. Once the fluid is in the body, the new bag is rolled up and placed in the patient's underwear until the next treatment. This procedure usually takes 30 minutes to accomplish and must be done four to five times a day. As an alternative to this treatment, some patients on peritoneal dialysis use a machine called a "cycler." This cycler is used every night. Five to six bags of dialysis fluid is used on the cycler and the machine automatically changes the fluid while the patient sleeps.

Hemofiltration is a replacement therapy that is similar to hemodialysis that is used mostly in a intensive care setting. Basically it is the removal of waste products from the blood by passing it through extra corporeal filters. During Hemofiltration there is convective transport of the solute through ultrafiltration across the membrane. It is reported to be more effective than diffusion in removing higher-molecular weight solutes from the blood, particularly in the treatment of uremia. When a patient is going to go through this it requires the weight lost of that patient to be loss. This way the solute is able to be transfer across semipermeable membrane by pressure that is induced by water flow. The rate of solute removal is proportional to the applied pressure that can be adjusted to meet the needs of the clinical situation. Solutes, both small and large, get dragged through the membrane at a similar rate by the flow of water that has been engendered by the hydrostatic pressure.

Intestinal Dialysis
In intestinal dialysis, the diet is supplemented with soluble fibers such as acacia gum, which is digested by colonic flora, thereby increasing the amount of nitrogen that is eliminated as fecal waste inside the colon. In a diseased kidney, there are only two ways left for just a small amount of toxic nitrogen to be eliminated, the gut and the sweat glands, but this is not enough to sustain life and usually the patient receives routine dialysis sessions. Other types of intestinal dialysis may include the use of other non-absorable concoctions such as polyethylene glycol or mannitol.

How to Prepare for the Test

When possible, patients should prepare for dialysis before dialysis is absolutely necessary.
It is important to stick to the diet and medicines prescribed by the dialysis staff and your kidney specialist (nephrologist).
The health care provider will make the following assessments before beginning the hemodialysis procedure:
  • Blood pressure
  • Breathing rate
  • Chest assessment
  • Examination of vein access
  • Heart rate
  • Temperature
  • Weight

  • The first type of dialysis is hemodialysis. Hemodialysis is done with a machine. During this form of dialysis, the patients blood flows from their body into the dialysis machine witch contains a "dialysis membrane" that removes waste and other elements from the blood. The clean blood then flows back into the patients body.
  • The second type of dialysis is peritoneal dialysis. This type of dialysis uses the patients own abdominal tissue around the intestines to act as a filter for the blood. A catheter is used to pump a special solution into the abdominal cavity, where the solution will break down wastes if comes into contact with through the intestines. After a certain amount of time, the solution will be drained out via the catheter. This process generally takes place up to 4 or 5 times a day.


The immediate risks include:
  • A small bubble of air in the blood that travels to a blood vessel in another part of the body (air embolism)
  • Bleeding from the access site
  • Cramps
  • Dialyzer reaction
  • Electrolyte imbalance
  • Infection
  • Irregular heartbeat or ischemia
  • Low blood pressure (hypo-tension)
  • Nausea and vomiting
  • Hernias
  • Anemia
  • Depression
Long-term risks include:
  • Blood loss leading to iron deficiency
  • Cardiovascular disease
  • Dialysis-associated amyloidosis
  • Dialysis dementia
  • Autonomic neuropathy

Web Resources:
National Library of Medicine: Dialysis
Vascular Web

Related Terminology:
Peritoneal dialysis
Intestinal Dialysis




Wikipedia: Dialysis
Dialysis Access