Peritoneal dialysis is ideal for patients who may find hemodialysis too exhausting, such as elderly people, babies and children. Peritoneal dialysis may be done at home by the patient who has been trained to operate the dialysis machine.
Although peritoneal dialysis is not as efficient as hemodialysis, it is carried out for longer periods. The net effect in terms of total waste product and salt and water removal is about the same as hemodialysis.
Before having peritoneal dialysis, the patient needs to have a small surgical procedure to insert a catheter into the abdomen. This is kept closed off, except when fluid is being introduced or taken out of the abdomen.
A sterile (dialysate) solution rich in minerals and glucose is run through a tube into the peritoneal cavity, the abdominal body cavity around the intestine, where the peritoneal membrane acts as a semi-permeable membrane.
The abdomen is the area between the chest and hips – it contains the stomach, small intestine, large intestine, liver, gallbladder, pancreas and spleen. Peritoneal dialysis uses the natural filtering ability of the peritoneum – the internal lining of the abdomen. In other words, peritoneal dialysis uses the lining of the abdomen as a filter of waste products from the blood.
The dialysate is left there for some time so that it can absorb waste products. Then it is drained out through a tube and discarded. This exchange, or cycle, is generally repeated several times during the day – with an automated system it is often done overnight. The elimination of unwanted water (ultrafiltration) occurs through osmosis – as the dialysis solution has a high concentration of glucose, it results in osmotic pressure which causes the fluid to move from the blood into the dialysate. Consequently, a larger quantity of fluid is drained than introduced.
There are two principal types of peritoneal dialysis:
- Continuous ambulatory peritoneal dialysis (CAPD) – this requires no machinery and can be done by the patient or a caregiver. The dialysate is left in the abdomen for up to eight hours. It is then replaced with a fresh solution straight away. This happens every day, about four to five times per day.
- Continuous cyclic peritoneal dialysis (CCPD) – a machine does the dialysis fluid exchanges. It is generally done during the night while the patient sleeps. This needs to be done every night. Each session lasts from ten to twelve hours. After spending the night attached to the machine, the majority of people keep fluid inside their abdomen during the day. Some patients may require another exchange during the day.
Peritoneal dialysis may not be suitable for all patients. Also it requires complete training for operating the dialysis machine at home. Instances of power failure may affect dialysis process. Patients should undergo peritoneal dialysis only with advice of their doctor and after undergoing training.