CAPD stands for continuous ambulatory peritoneal dialysis, a form of kidney dialysis you perform yourself at home without a machine. Instead of filtering your blood through an external device like traditional hemodialysis, CAPD uses the natural lining of your abdomen as a filter. You fill your belly with a sterile solution through a small permanent catheter, let it sit for several hours while it draws out waste and extra fluid, then drain it and start again. Most people repeat this process four to six times a day.
How CAPD Filters Your Blood
The inside of your abdomen is lined with a thin membrane called the peritoneum, which is rich in tiny blood vessels. When you fill your abdominal cavity with dialysis solution, two things happen simultaneously. First, waste products like urea and creatinine move from your blood through the membrane and into the solution, drawn by a natural concentration difference. Second, excess water moves out of your blood and into the solution because the solution contains a sugar (usually glucose) that pulls water through microscopic channels in the blood vessel walls.
After a few hours, the solution has absorbed enough waste and fluid to be drained out and replaced with a fresh bag. The continuous part of CAPD means that solution is almost always sitting in your belly, cleaning your blood around the clock rather than in a few concentrated sessions per week.
What a Typical Day Looks Like
Each “exchange” has three phases: drain, fill, and dwell. You connect a fresh bag of solution to the catheter in your abdomen, drain the old fluid into an empty bag (which takes about 15 to 20 minutes), then let fresh solution flow in. Once the new solution is in place, you disconnect the bag, cap the catheter, and go about your day. The solution sits in your belly for several hours while it works. This resting phase is the dwell time.
Most people do four to six exchanges spread across their waking hours, with one longer overnight dwell while they sleep. Each exchange itself takes about 30 to 40 minutes for the drain and fill steps. Between exchanges, you’re free to work, exercise, travel, and handle daily activities. The used solution gets discarded in a toilet or bathtub. No electricity, no machine, no clinic visit required.
CAPD vs. Automated Peritoneal Dialysis
The main alternative within peritoneal dialysis is APD (automated peritoneal dialysis), which uses a machine called a cycler to perform exchanges automatically while you sleep. CAPD requires you to do exchanges by hand throughout the day, while APD does most of the work overnight.
A large meta-analysis found that APD carries a modestly lower mortality risk compared to CAPD, with about a 13% reduction in overall death risk. However, both methods perform similarly in terms of how long patients can stay on peritoneal dialysis before needing to switch to hemodialysis. The choice often comes down to lifestyle: CAPD offers more flexibility during nighttime hours but requires daytime interruptions, while APD ties you to a machine at night but leaves your days completely free.
Getting Started: Catheter and Training
Before you can begin CAPD, a surgeon places a soft, flexible catheter through your abdominal wall. One end sits inside your abdominal cavity, and the other end exits through your skin, usually near your belly button or to one side. The site needs a few weeks to heal before you start dialysis.
Training typically takes about five days, averaging three hours per day, though some programs spread it over up to ten days with shorter sessions. By the end, you need to demonstrate that you can perform the entire exchange using sterile technique, recognize when contamination has occurred and know what to do about it, detect signs of complications, and understand how fluid balance affects your blood pressure. A nurse walks you through every step until you’re confident performing exchanges independently at home.
Who Can and Cannot Use CAPD
Most people with kidney failure can choose CAPD, but certain conditions make it a poor fit. The main physical disqualifier is an unrepaired hernia, because the pressure of fluid in your abdomen would worsen it. Inflammatory bowel conditions like Crohn’s disease or ulcerative colitis, active abdominal infections, and advanced liver disease with fluid buildup are also contraindications.
People with a BMI above 35 face a specific challenge: abdominal fat tissue can fall over the catheter tip and block flow. That doesn’t necessarily rule out CAPD, but it means the catheter needs to be placed surgically (often laparoscopically) rather than at the bedside, so the surgeon can position it carefully. A history of extensive abdominal surgery can also complicate things due to scar tissue, though laparoscopic placement can sometimes work around adhesions.
Peritonitis: The Main Risk
The most significant complication of CAPD is peritonitis, an infection of the peritoneal membrane. It typically happens when bacteria enter the abdominal cavity during an exchange, usually through a break in sterile technique. Warning signs include cloudy drainage fluid, abdominal pain, fever, nausea, and vomiting.
Infection rates vary widely depending on the setting and the care taken during exchanges. International guidelines from the ISPD set a target of fewer than 0.5 episodes per patient per year, though real-world rates often run higher. A multicenter study in Vietnam found rates between 0.71 and 1.13 episodes per patient-year, illustrating how much variation exists. Most episodes respond well to treatment when caught early, but repeated infections can damage the peritoneal membrane over time and eventually force a switch to hemodialysis.
How Long CAPD Typically Works
The peritoneal membrane doesn’t last forever as a dialysis filter. Over years of use, it gradually changes in structure and becomes less effective. A 25-year retrospective study found that 88% of patients remained on peritoneal dialysis at one year, 69% at three years, and 48% at five years. By seven years, only 30% were still using it. The rest had transitioned to hemodialysis, received a kidney transplant, or stopped dialysis for other reasons.
This doesn’t mean CAPD is a short-term option. For many people, it serves as a bridge to transplant or as a years-long treatment that preserves independence and avoids the schedule demands of in-center hemodialysis. The gradual decline in membrane function is expected, and your care team monitors it over time so the transition, if needed, can be planned rather than sudden.
Diet on CAPD
One meaningful advantage of CAPD over hemodialysis is dietary flexibility. Because dialysis is happening continuously rather than three times a week, waste products and fluid don’t build up as dramatically between sessions. This generally means fewer restrictions on potassium, phosphorus, and fluid intake compared to hemodialysis, though some limits still apply depending on your lab results.
Protein needs actually increase on CAPD. The dialysis solution pulls some protein out of your blood along with waste, so you need to eat more protein than you did before starting dialysis to compensate. This is a reversal from the low-protein diet often recommended for people with advanced kidney disease who aren’t yet on dialysis. A renal dietitian will help you figure out the right balance for your specific situation.