hen kidneys fail, waste
products such as urea and
creatinine build up in the
One way to remove these wastes
is a process called peritoneal dialysis
The walls of the abdominal cavity
are lined with a membrane called the
During PD, a mixture of
dextrose (sugar), salt, and other miner-
als dissolved in water, called dialysis
solution, is placed in a person’s abdomi-
nal cavity through a catheter.
body’s peritoneal membrane enclosing
the digestive organs allows waste prod-
ucts and extra body fluid to pass from
the blood into the dialysis solution.
These wastes then leave the body when
the used solution is drained from the
Each cycle of draining and
refilling is called an exchange.
the solution remains in the abdomen
between exchanges is called the dwell
During this dwell time, some of
the dextrose in the solution crosses the
membrane and is absorbed by the body.
Many factors affect how much waste
and extra fluid are removed from the
Some factors—such as the
patient’s size and the permeability, or
speed of diffusion, of the peritoneum—
cannot be controlled.
comes in 1.5-, 2-, 2.5-, or 3-liter bags.
The dialysis dose can be increased by
using a larger bag, but only within the
limits of the person’s abdominal capaci-
Everyone’s peritoneum filters wastes
at a different rate.
In some people, the
peritoneum does not allow wastes to
enter the dialysis solution efficiently
enough to make PD feasible.
Other factors that determine how effi-
ciently a person’s blood is filtered can
include the number of daily exchanges
and the dwell times.
When fresh solu-
tion is first placed in the abdomen, it
draws in wastes rapidly.
As the solution
becomes more nearly saturated with
wastes, it cleans the blood less efficient-
For example, a patient may perform
one exchange with a 6-hour dwell time,
during which the solution becomes
nearly saturated with urea.
But in the
second half of that dwell time, urea is
being removed from the blood very
If the patient performed two
exchanges with 3-hour dwell times
instead, the amount of urea removed
would be substantially greater than that
removed in one 6-hour dwell time.
Another way to increase the amount
of fluid and waste drawn into the peri-
toneal cavity is to use dialysis solution
with a higher concentration of dextrose.
A higher dextrose concentration moves
fluid and more wastes into the abdomi-
nal cavity, increasing both early and
long-dwell exchange efficiency.
ally, however, the body absorbs dextrose
from the solution.
As the concentration
of dextrose in the body comes closer to
that in the solution, dialysis becomes
less effective, and fluid is slowly
absorbed from the abdominal cavity.
National Institute of Diabetes and Digestive and Kidney Diseases