CAPD, or continuous ambulatory peritoneal dialysis, is a form of kidney dialysis you perform yourself at home, without a machine. Instead of filtering your blood through an external device like hemodialysis does, CAPD uses the lining of your own abdomen as a natural filter. You fill your abdominal cavity with a special fluid, let it sit for several hours while it draws waste and extra water out of your blood, then drain it and replace it with fresh fluid. Most people do this four times a day.
The “continuous” part means dialysis is always happening. The “ambulatory” part means you’re free to move around, go to work, or carry on with your day while the fluid dwells inside you. It’s one of two main types of peritoneal dialysis, the other being automated peritoneal dialysis (APD), which uses a machine to cycle fluid while you sleep.
How Your Body Filters the Blood
The peritoneum is a thin membrane that lines your abdominal cavity and covers your organs. In adults, it has a surface area of roughly 1 to 1.3 square meters, about the size of a large bath towel. This membrane is naturally semi-permeable, meaning it allows some substances to pass through while blocking others.
When dialysis fluid (called dialysate) is placed in your abdomen, waste products like urea and creatinine move from your blood, through the tiny blood vessels in the peritoneal membrane, and into the fluid. This happens through passive diffusion: substances naturally drift from where they’re more concentrated (your blood) to where they’re less concentrated (the clean fluid). The most important barrier in this process is the wall of the capillaries in the membrane, not the membrane’s outer cell layer, which lets most substances pass through relatively easily.
Removing excess water works differently. The dialysate contains glucose, which makes it more concentrated than your blood plasma. This concentration difference creates an osmotic pull that draws water out of your bloodstream and into the abdominal cavity. Higher glucose concentrations pull more water. Over the course of a day, the fluid absorbs somewhere around 120 grams of carbohydrate from the glucose in the dialysate, which is something to be aware of since it adds calories to your daily intake.
What an Exchange Looks Like
Each cycle of draining old fluid and filling with new fluid is called an “exchange,” and it takes about 30 to 40 minutes. The process has three steps:
- Drain. You connect your catheter tubing to a drain bag and let the used dialysate flow out of your abdomen by gravity. Near the end, you may feel a mild tugging sensation as the last of the fluid drains.
- Flush. Before filling with fresh fluid, you let a small amount of new solution flow into the drain bag. This clears air from the tubing.
- Fill. You clamp the drain line, open the line to a hanging bag of fresh dialysate, and let it flow into your abdomen.
Once the fresh fluid is in, you disconnect, secure the catheter, and go about your day. The fluid stays in your belly for a “dwell time” of 4 to 6 hours during the day. Most people do four exchanges: three during waking hours and one before bed, sleeping with the solution in overnight for a longer dwell of around 8 to 9 hours.
The Catheter and Getting Started
Before you can begin CAPD, a surgeon places a thin, flexible tube called a catheter through your abdominal wall. One end sits inside your peritoneal cavity, and the other comes out through a small opening in your skin, called the exit site. This is the port you’ll connect your bags to for every exchange.
After placement, the exit site needs time to heal. For the first 7 to 10 days, the site is typically left alone under a sterile gauze bandage. The surrounding skin should stay dry for about 10 to 14 days, which means sponge baths instead of showers during that window. Full healing of the exit site takes 4 to 6 weeks. Your care team will train you during this break-in period so you’re comfortable doing exchanges on your own by the time the site is ready.
Caring for Your Catheter
Infection is the biggest ongoing risk with peritoneal dialysis, and most infections start at the catheter exit site. Keeping this area clean is essential. Your dialysis team will teach you a daily cleaning routine, and you’ll learn to watch for signs of trouble: redness, swelling, pain, or discharge around the exit site. Exchanges themselves also require careful hand hygiene and a clean environment to prevent bacteria from entering the abdominal cavity, which can cause a serious infection called peritonitis.
Diet on CAPD
One advantage of doing dialysis every day rather than a few times a week (as with in-center hemodialysis) is that waste and fluid don’t build up as much between sessions. This generally means your dietary restrictions are less strict than they would be on hemodialysis.
Potassium is one area where CAPD actually reverses the usual rule. Hemodialysis patients are often told to limit potassium, but peritoneal dialysis can remove too much of it. You may need to eat more potassium-rich foods like bananas, oranges, potatoes, and tomatoes to keep your levels in a healthy range. The extra glucose absorbed from the dialysate also means additional daily calories, so your dietitian may adjust your meal plan to account for that. Phosphorus and sodium limits still apply, but your overall diet tends to feel less restrictive.
CAPD vs. Automated Peritoneal Dialysis
The main alternative to CAPD within peritoneal dialysis is automated peritoneal dialysis, or APD. With APD, a bedside machine called a cycler does the exchanges automatically while you sleep, typically over 8 to 10 hours. You connect before bed and disconnect in the morning.
Some people prefer CAPD because it requires no machine and allows complete flexibility during the day. Others prefer APD because it frees up daytime hours and involves less manual handling. A propensity-matched study published in PLOS One found that APD was associated with somewhat better survival rates compared to CAPD, though both remain effective long-term options. Your kidney team will help determine which approach fits your lifestyle, medical profile, and remaining kidney function.
What Daily Life Looks Like
Because exchanges take only 30 to 40 minutes and can be done almost anywhere with a clean surface, many people on CAPD continue working, traveling, and staying active. You’ll need to carry supplies when you’re away from home, and you’ll need a clean, private space for each exchange. Most people build exchanges into their routine around meals: morning, midday, late afternoon, and bedtime.
Swimming in lakes or public pools is generally discouraged because of infection risk at the exit site, though some people swim in well-chlorinated pools once their catheter is fully healed, with their care team’s guidance. Showering is fine once the site has healed, and many people use a protective cover or waterproof dressing as an extra precaution. Exercise is encouraged, though heavy lifting or straining the abdominal muscles may need to be modified to avoid displacing the catheter.
The biggest adjustment most people describe is the feeling of fluid in their abdomen. With roughly 2 liters of dialysate inside you during a dwell, you may feel full or bloated, especially at first. This sensation typically becomes less noticeable over the first few weeks as your body adjusts.