Hemodialysis cleanses the blood of toxins after the kidneys can no longer carry out this role well enough to keep the body from getting sick. Blood is usually drawn through a needle inserted into the arm. The blood is sent through a dialysis machine that removes impurities and excess fluid. The cleansed blood is returned to the body through another tube and needle.

Hemodialysis is the primary treatment for end-stage renal disease, the leading cause of which is diabetes (diabetic nephropathy). Usually the procedure is done at a dialysis center three times a week for two to four hours. Some patients undergo training to do it at home, which allows greater flexibility. However, these patients still must adhere to a schedule of treatments.

Hemodialysis is generally not painful. A common side effect, however, is fatigue due to anemia (insufficient red blood cells) and uremia (toxins in the blood that hemodialysis does not completely remove or that build up between treatments).

Ideally, weeks before the procedure begins, a surgeon prepares a site on the body (usually the arm) that will make it easier to draw blood. If hemodialysis must begin immediately, a tube called a catheter can be temporarily placed in a vein.

Treatment usually continues for life, and people requiring dialysis can die within weeks if they discontinue the treatments. Some studies have indicated that some people on dialysis have the potential to live without the treatments because of regained kidney function, but other research has reported a dangerous underuse of hemodialysis. Patients are advised to have their condition regularly and thoroughly monitored and are cautioned not to stop dialysis without a physician’s approval.

Peritoneal dialysis uses the peritoneum (a membrane inside the abdominal cavity) to filter out wastes, fluids and salt from the blood when the kidneys can no longer perform this function. It is one of two types of dialysis used to treat end-stage renal disease (ESRD), which is caused by conditions including diabetic kidney disease (diabetic nephropathy), high blood pressure, lupus and some kidney disorders such as polycystic kidney disease.

ESRD occurs when the kidneys have lost 85 to 90 percent of function. At this point, filtration is seriously impaired, and the kidneys are unable to regulate the body’s balance of salt and water. Production of urine slows or stops. Waste products and water accumulate in the body, leading to a potentially life-threatening overload of these substances.

Though dialysis cannot cure chronic kidney failure, it can extend life until a kidney transplant may become available.

A permanent tube, called a catheter, is surgically implanted in the abdomen. A small section of the tube remains outside the abdomen to be connected to a bag containing dialysis solution (dialysate). The other end of the tube empties into the peritoneal cavity, the space between the abdominal muscles and organs.

The peritoneum is a thin membrane that has two layers. The inner layer covers the abdominal organs and holds them in place. The outer layer lines the abdominal wall. It is able to carry out the kidney’s waste-filtering function because it is permeable, allowing molecules to enter and exit.

The dialysis solution contains glucose, mineral salts and other chemicals that attract the body’s waste materials. It is supplied through the tube and enters the abdominal cavity.

The membrane allows the dialysate to pull the toxins from the bloodstream into the solution in the abdominal cavity which is then removed from the body. There are differences in dialysis solutions, and patients receive a prescription for the dialysate appropriate for their treatment.

Each peritoneal dialysis session has three parts:

• Draining. The used solution from the previous session is removed from the patient’s abdomen and discarded.
  
  
• Filling. The fresh solution is added. Draining and filling together is called an exchange. An exchange takes about 30 to 40 minutes.
  
  
• Dwell time. This is the period between the exchanges, when the solution remains inside the body. Dwell time lasts for four or more hours. The patient is allowed to resume normal activities during the dwell time until the next exchange.

Peritoneal dialysis is generally a continuous process with several consecutive daily sessions.  It can be done with a machine that helps fill and drain the dialysate, but more commonly uses gravity to exchange the solution.

Peritoneal dialysis has some advantages over hemodialysis, such as lower cost and, according to some research, improved quality of life. But it also has risks including hyperglycemia (high blood sugar) and cannot be used in some cases. Researchers believe that improved patient education about the benefits and risks of peritoneal dialysis would increase its use. According to research at Johns Hopkins University, only 10 percent of the 100,000-plus Americans starting dialysis each year use peritoneal dialysis.