In the last issue of Grapevine, we discussed the option of haemodialysis after kidney failure. In this issue, we will concentrate on another modality of kidney replacement therapy known as peritoneal dialysis. A short and concise comparison between haemodialysis and peritoneal dialysis will be presented at the end of this article. In the next issue of Grapevine, the last option of kidney replacement therapy - kidney transplantation - will be discussed.

Peritoneal Dialysis
Like haemodialysis, peritoneal dialysis (PD) is also a treatment process that cleanses the blood of a patient with end-stage kidney failure. However, peritoneal dialysis takes place entirely within the body. There is no external dialyser or artificial kidney involved. Instead, the process uses the natural membrane lining of the abdominal cavity as a dialyser. This membrane covers the organs that are in the abdomen, such as the stomach and liver. Peritoneal dialysis uses this membrane to cleanse the blood during dialysis.

Peritoneal dialysis is performed by infusing the cleansing solution (dialysate) into the abdominal cavity by way of a soft catheter. This catheter is surgically implanted into the abdominal cavity just below the waistline. The catheter usually requires 2-3 weeks after implantation before it can be used. The dialysate contains salts and high content of glucose (sugar). Waste products and excess water pass from the bloodstream, through the abdominal membrane, into the dialysate which is then drained out of the body and discarded.

Typically during a peritoneal dialysis session, two to three liters of dialysate are infused into the abdominal cavity. The dialysate is then allowed to remain inside the abdomen for a period of 4-6 hours. During this period, waste products and excess water will be removed from the bloodstream into the dialysate. The used dialysate (now filled with waste products and excess water removed from the bloodstream) is drained from the abdomen and replaced with another 2-3 liters of fresh dialysate and the process of cleansing starts over again. The draining and replacing of the dialysate is called an “exchange” or “cycle”. Usually 3-4 exchanges are required daily to cleanse the blood and each exchange usually takes 4-6 hours to complete.

Peritoneal dialysis is usually carried out by the patient and his or her relatives at home, or even at work. It is an ideal treatment for end-stage kidney failure patient who works and or travels most of the time. It is also suitable for patient who cannot withstand the haemodialysis treatment because of heart problem. It is usually the treatment of choice for patient who has exhausted all the vascular access option, i.e. there is no more vascular access available for haemodialysis treatment. There are two types of peritoneal dialysis: continuous ambulatory PD (CAPD) and automated PD (APD).

In CAPD, the dialysis is self-administered by the patient 7 days per week with 4 to 5 exchanges per day. It requires no machine. The dialysate of the last exchange in the evening remains inside the abdomen overnight, i.e. the patient sleeps with about 2-3 liters of dialysate inside the abdomen. In APD, the exchanges of the dialysate are done by a machine while the patient sleeps at night. The patient is connected to an APD machine at bedtime, 7 days per week, for about 10 hours each night. The APD machine will control the filling and draining of the dialysate solution in and out of the abdomen while the patient sleeps. In the morning, the APD machine does the final exchange and fills the abdomen with dialysate which will not be drained until bedtime again.

In order to perform peritoneal dialysis, the patient and his or her family member are usually required to undergo a training course which usually takes about 7-10 days. There are complications of peritoneal dialysis. They include infection, catheter blockage, abdominal hernia and failure of the abdominal membrane to act as a dialyser from repeated infections. The most common complication of PD is infection of the abdominal cavity (so called peritonitis) and sometimes infection around the catheter (exit site infection). When the abdominal membrane fails to act as a dialyser, the patient may need to be switched to haemodialysis or kidney transplant.

Comparison between Haemodialysis And Peritoneal Dialysis

Dr. William Chau,
(Consultant Nephrologist)