Peritoneal dialysis uses the lining of your abdomen as a natural filter to clean your blood. A sugar-based solution is pumped into your abdominal cavity through a small catheter, where it draws waste products and excess fluid out of your bloodstream through the thin membrane that lines your organs. After a set period, the used solution drains out, carrying those wastes with it. The process repeats multiple times each day.
How the Peritoneal Membrane Filters Blood
The peritoneum, the membrane lining your abdominal cavity, is laced with tiny blood vessels. When dialysis solution fills the space around your organs, two key processes happen simultaneously across that membrane: diffusion and osmosis.
Diffusion is the simpler one. Waste products like urea and creatinine are at high concentrations in your blood but absent from the fresh dialysis solution. They naturally move from the high-concentration side (blood) to the low-concentration side (dialysis fluid), passing through small pores in the membrane’s capillary walls. The rate depends on the size of the molecule and how much membrane surface area is available for transport. Small molecules cross easily; larger ones take longer.
Osmosis handles fluid removal. The dialysis solution contains glucose (or sometimes a starch-based molecule called icodextrin), which creates osmotic pressure that pulls water out of your blood and into the abdominal cavity. Your peritoneal membrane even has specialized water channels called aquaporin 1 that allow pure water to cross without carrying any dissolved substances along with it. Glucose in the solution actually stimulates these channels to open more. The net effect is that excess fluid leaves your body each time you drain the solution.
Not all the fluid that crosses into the cavity stays there. A significant fraction gets reabsorbed back into tiny blood vessels and through lymphatic channels under your diaphragm. What you actually drain out is the net difference between what crossed over and what got reabsorbed. This is why the glucose concentration in the solution matters so much: stronger solutions create more osmotic pull and remove more fluid.
What Goes Into the Dialysis Solution
Standard dialysis solutions come in different glucose concentrations, typically ranging from about 1.5% to 4.25% dextrose. Higher concentrations pull more fluid from the blood. In clinical testing with a 2.5% dextrose solution over four hours, the amount of fluid removed varied dramatically depending on how fast a person’s membrane transported substances. People with slower transport rates removed around 462 ml, while those with faster membranes removed only about 172 ml, because the glucose got absorbed more quickly and lost its osmotic pull sooner.
For longer overnight dwells, some people use a solution containing icodextrin instead of glucose. Because icodextrin is a large molecule that can’t cross capillary walls, it maintains its fluid-pulling effect for much longer periods, making it well suited for extended dwell times.
Two Ways to Do It: Manual vs. Machine
Peritoneal dialysis comes in two forms, and both accomplish the same thing with different schedules.
With continuous ambulatory peritoneal dialysis (CAPD), you do three to five exchanges per day by hand. You connect a bag of fresh solution to your catheter, drain out the used fluid (which takes about 60 to 90 minutes to complete), then fill with new solution and go about your day while it dwells inside. No machine is involved, but you need to repeat the process several times during waking hours.
Automated peritoneal dialysis (APD) uses a machine called a cycler that does the work while you sleep. The cycler performs about six fill-and-drain cycles over an eight-hour session, running three to five exchanges per night. You connect before bed and disconnect in the morning. Some people on APD also keep solution in their abdomen during the day for an additional long dwell.
Your Membrane Type Shapes Your Prescription
Not everyone’s peritoneal membrane works at the same speed. A test called the peritoneal equilibration test (PET) measures how fast solutes cross your membrane, categorizing you as a slow, slow-average, fast-average, or fast transporter.
This matters practically. Fast transporters absorb glucose from the solution quickly, which means the osmotic gradient disappears sooner and fluid removal drops off. To compensate, they benefit from shorter, more frequent exchanges, higher glucose concentrations, or icodextrin for longer dwells. That’s why fast transporters are often placed on automated PD, which cycles through exchanges rapidly overnight.
Slow transporters have the opposite profile. They keep their osmotic gradient longer and remove fluid well, but they need more time for waste products to cross the membrane. Longer dwell times with each exchange give those solutes enough time to diffuse across. These patients often do well with manual CAPD and its longer daytime dwells.
Getting the Catheter Placed
Before you can start peritoneal dialysis, a soft, flexible catheter is surgically placed through your abdominal wall into the peritoneal cavity. One end sits inside your abdomen; the other exits through a small opening in your skin, usually near or below your navel.
After placement, a sterile bandage covers the exit site, and the area is left undisturbed for the first 7 to 10 days. A PD nurse handles the first bandage change under sterile conditions. The skin around the catheter needs to stay dry for 10 to 14 days while initial healing occurs, and the exit site is considered fully healed at 4 to 6 weeks. Training on how to perform exchanges typically begins during this healing window.
Infection Risk and Prevention
The biggest risk with peritoneal dialysis is peritonitis, an infection of the peritoneal membrane. It can cause abdominal pain, cloudy drainage fluid, and in serious cases, hospitalization or loss of the catheter. Every time you connect or disconnect from your catheter, bacteria have a potential entry point.
Prevention centers on meticulous sterile technique during every exchange: clean hands, a clean workspace, careful handling of connections. Programs also emphasize proper exit-site care, including preventive treatment against staph bacteria, thorough initial training, and periodic retraining sessions. Good PD programs track every infection episode, look for the root cause, and adjust protocols accordingly. The learning curve is real, but infection rates drop significantly once technique becomes routine.
How It Compares to Hemodialysis
Peritoneal dialysis and hemodialysis achieve the same goal through very different approaches. Hemodialysis filters blood through an external machine, typically three times per week at a clinic for several hours per session. Peritoneal dialysis happens continuously or nightly at home, which gives you more schedule flexibility and avoids the blood pressure swings that come with removing large volumes of fluid in a short hemodialysis session.
Survival outcomes between the two are broadly comparable. A 2025 study in Kidney360 looking at patients with severe kidney failure found 90-day mortality of 20.8% for those starting on peritoneal dialysis versus 29.1% for hemodialysis, though after statistical adjustment for patient differences, the gap was not significant. Both modalities work. The choice often comes down to lifestyle preference, home environment, and individual medical factors rather than one being clearly superior to the other.