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Info & Treatments for Kidney Stones & Kidney Disease

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Dialysis is a method for artificially cleansing the blood of waste materials and contaminants. This cleansing is something that is normally done by the kidneys, but when the kidney function is severely impaired as in acute or late-stage chronic renal disease, waste products can accumulate in the blood and present a serious health hazard. Dialysis makes use of the principle of diffusion to remove contaminants dissolved in the blood. Diffusion is the principle that dissolved substances in a liquid, such as blood plasma, will tend to move from an area of higher concentration to one of lower concentration. All forms of dialysis bring the blood into contact with a fluid called a dialysate which is free of the dissolved waste materials to be removed from the blood, with a semi-permeable membrane between the blood and the dialysate. The contaminants cross the membrane and are transferred from the blood to the dialysate. The used dialysate is then discarded and fresh dialysate used to cleanse the next quantity of blood.

Peritoneal vs. Hemodialysis

When we think of dialysis, most people think of the process in which the blood is removed from the body and processed in a machine called a dialysis machine, then returned to the body after cleansing. This is the most common kind of dialysis and is called hemodialysis. It employs an artificial permeable membrane and pumps to drive the blood and dialysate through the machine. Peritoneal dialysis employs the same principles, but the membrane used is a naturally-occurring one in the human body: the peritoneum, which surrounds the abdominal cavity.

The blood is not removed from the body but circulates naturally in the blood vessels, with contaminants filtering into the dialysate which is inserted into the abdominal cavity using a catheter. The waste products in the blood pass through the blood vessels and the peritoneum into the dialysate, which is then removed from the body and replaced with fresh dialysate. Continued below....

Thus the whole process takes place within the patient's body rather than in a machine. Peritoneal dialysis lends itself better to home use than hemodialysis, which normally requires a clinic setting.


The first step in peritoneal dialysis is a surgical procedure that inserts a catheter into the abdominal cavity. This step, unlike the dialysis itself, needs to be done in a clinic or hospital setting. It can be done on an outpatient basis, however. The catheter remains in the body as long as the procedure is needed. In the case of acute renal failure, dialysis needs to be performed until the body repairs the damage to the kidneys and natural kidney function is restored. In the case of late stage (or stage 5) chronic renal failure, however, the damage is usually irreversible, and so dialysis will need to continue indefinitely or until a kidney transplant is performed. The catheter is used to introduce fresh dialysate into the abdominal cavity and to remove spent dialysate for disposal.

The treatment method involves pumping dialysate fluid into the abdominal cavity through the catheter, leaving it there for a period of time, and then removing it and replacing it. The amount of dialysate varies, but usually is up to 2.5 liters. The exact composition of the dialysate depends on the specific condition and the contaminants to be cleansed from the blood. The dialysate remains in the abdominal cavity for a length of time known as a "dwell," usually four to six hours. The circulation of blood by the body brings it into contact with the peritoneum and allows the waste materials and contaminants to pass through the peritoneum and into the dialysate. The body's own blood circulation is used for this process instead of artificial pumps.

In most cases, three or more dwells are performed each day, so that the entire process can take twelve hours or more. Peritoneal dialysis is less efficient in terms of time than hemodialysis, which can be done in a single four-hour clinic procedure. However, it can be done at home, which hemodialysis can't, and it can also be done during the patient's sleep or while he is engaged in other activities.

Types Of Peritoneal Dialysis

Peritoneal dialysis is sometimes divided into two categories, called continuous ambulatory peritoneal dialysis or CAPD and automated peritoneal dialysis or APD. CAPD is manually-controlled and done during the patient's waking hours. APD uses a machine to control the insertion and removal of dialysate and is typically done while the patient sleeps.

Risk Factors

Compared to hemodialysis, the only risk of peritoneal dialysis involves the ongoing presence of the abdominal catheter, which creates a danger of bacterial infection and peritonitis. Any infections that result are best treated with a direct infusion of antibiotics into the abdominal cavity through the catheter itself.


In the United States, total medical costs for patients undergoing peritoneal dialysis averaged $130,000 per year including treatment of complications in a 2009 study.

Peritoneal Dialysis

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