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Peritoneal dialysis is another method of removing waste products and excess
fluid from the body. Here, the process of removal of waste products and excess
fluid takes place within the patients own body, in the peritoneal or abdominal
cavity, rather than outside the body in an artificial kidney as it happens with
hemodialysis.
The peritoneum is a thin membrane which covers the
intestines and other contents of the abdominal cavity. The peritoneum basically
functions the same way as the semipermeable membrane used in the artificial
kidney. Since it contains a whole network of tiny blood vessels called
capillaries, the peritoneum is constantly able to provide a new supply of blood
to be filtered. The access to the peritoneal cavity is gained via a flexible
hollow tube (catheter), which is implanted through the wall of abdomen into the
abdominal cavity
The process of dialysis works like this :
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The dialysate (diaysis fluid similar to that used for hemodialysis except that
it has a higher glucose concentration which helps removal of excess fluid by way
of osmosis) is introduced into the peritoneal cavity and allowed to stay there
for some time.
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As blood flows through the capillaries in the peritoneum, waste product are
filtered through diffusion and excess fluid removed through osmosis.
The dialysate with the waste products and excess fluid is then removed. Such
cycles of introducing the dialysate in the peritoneal cavity, allowing it to
remain for some time and then draining out the fluid are repeated every 4 to 6
hours during the day with each exchange taking approximately 40 minutes (20
minutes to introduce and 20 minutes to drain dialysate). Each day, the last
exchange is performed right before the patient goes to bed at night. The process
described will make one realise that this dialysis process goes on continuously.
Moreover the patient does not have to be hooked to the machine and can remain
ambulatory. Therefore this type of dialysis is called continuous ambulatory
peritoneal dialysis (CAPD). Since the patient is continually dialyzing, there
are usually few dietary restrictions. Further, there is no blood loss with CAPD
and so patients on CAPD maintain higher hemoglobin then patients on
haemodialysis and thus require less of expensive drug, erythropoietin (Eprex,
Zyrop & Recormon)
Continuous Cycling Peritoneal Dialysis (CCPD) is very similar to CAPD. In this
case, the exchanges are performed at night while the patient sleeps. To
facilitate this process the patient is hooked up to an automatic cycling pump.
This pump makes several evenly spaced exchanges during the night and a final one
just before the patient gets up in the morning. During the day no exchanges are
made.
A potential problem with peritoneal dialysis is peritonitis which is an
infection of the peritoneal membrane. Therefore, the process of introducing
dialysis fluid into peritoneal cavity and removing it from the cavity must be
done under strict aseptic conditions. With CCPD, since only one connection is
done in a day compared to four connections in a day required with CAPD, the risk
of peritonitis is lower.
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