Automated peritoneal dialysis (APD) is a form of kidney dialysis you do at home, typically while you sleep. A small bedside machine called a cycler automatically fills your abdomen with a cleansing fluid, lets it sit long enough to draw out waste and extra water from your blood, then drains it and repeats the process. Most sessions run 8 to 12 hours overnight, with three to six exchanges happening while you’re in bed.
APD is one of two main types of peritoneal dialysis. The other, continuous ambulatory peritoneal dialysis (CAPD), requires you to do each exchange by hand, three to five times throughout the day. APD shifts most of that work to a machine and to nighttime hours, freeing up your daytime almost entirely.
How the Cycler Machine Works
The cycler is roughly the size of a carry-on suitcase. Before bed, you connect bags of dialysis solution to a disposable cassette that snaps into the machine, then attach a tube from the cassette to the permanent catheter in your abdomen. From there, the cycler handles everything.
Each exchange has three phases: fill, dwell, and drain. During fill, the machine uses air pressure to push solution through the cassette and into your peritoneal cavity, the space surrounding your intestines. During the dwell, that fluid sits in your abdomen while the lining of the cavity (the peritoneal membrane) acts as a natural filter, pulling waste products and excess fluid from tiny blood vessels into the solution. During drain, the machine reverses pressure to pull the used fluid back out and into a separate drain line that empties into a toilet, bathtub, or household drain.
You program the cycler with your prescribed fill volume (typically over 1,000 mL per exchange for adults, though smaller volumes are available for children or people under about 100 pounds), the number of cycles, and the total session length. The machine calculates fill and drain times automatically and sounds an alarm if flow rates drop below expected levels, for instance if the catheter kinks or shifts position while you move in your sleep.
What Goes Into the Dialysis Solution
The fluid that does the actual filtering relies on osmotic agents, substances that pull water across your peritoneal membrane. The most common agent is glucose (dextrose) at varying concentrations. Higher glucose concentrations remove more fluid but also expose the membrane to more sugar over time, which can gradually damage it.
For longer dwells, especially daytime dwells that may last 12 hours or more, a starch-based solution derived from cornstarch is sometimes used instead. This alternative maintains steady fluid removal over extended periods without the high sugar load, and studies show it helps maintain a healthier fluid balance compared to glucose-only regimens.
Dry Days vs. Wet Days
After your overnight session ends, your doctor may prescribe one of two daytime approaches. A “dry day” means your abdomen stays mostly empty until the next night’s session. A small amount of fluid (100 to 500 mL) is often left in to prevent discomfort from the catheter sitting in a nearly empty space. During a dry day, the tissue around your peritoneal cavity gradually returns to its normal hydration level as residual fluid slowly seeps out of the tissue.
A “wet day” means a full dose of solution stays in your abdomen for a single long daytime dwell, continuing to filter waste while you go about your routine. This keeps your peritoneal tissue more hydrated throughout the full 24 hours. Wet days are typically prescribed when someone needs more dialysis than overnight sessions alone can provide, often because their remaining kidney function has declined further.
How APD Compares to Manual Exchanges
The core chemistry is identical between APD and CAPD. Both use the same peritoneal membrane, the same types of solution, and the same catheter. The difference is logistics. CAPD requires you to stop what you’re doing three to five times a day, wash your hands, connect and disconnect bags, and sit for 20 to 30 minutes per exchange. APD consolidates all of that into one nighttime session with a single connection and disconnection.
In patient satisfaction surveys, people on APD reported significantly more time for work, family, and social activities. APD also tends to reduce daytime back pain and body image concerns, since your abdomen isn’t carrying a liter or more of fluid during waking hours (unless you’re on a wet day schedule). These quality-of-life advantages make APD particularly popular among people who work, attend school, or care for young children.
Clinical outcomes between the two are broadly similar. The overall peritonitis (abdominal infection) rate is 0.52 episodes per patient-year with APD compared to 0.58 with CAPD, but after adjusting for other factors, the risk is statistically the same. APD does show a slight edge against certain bacterial infections, with lower rates of gram-positive peritonitis, though it carries a modestly higher rate of gram-negative peritonitis. Neither modality is clearly safer than the other.
Who Can and Can’t Use APD
APD is an option for most people whose kidneys have failed and who choose peritoneal dialysis over in-center hemodialysis. It tends to work especially well for younger patients, working adults, and families where a caregiver handles exchanges for someone who can’t do them independently.
Peritoneal dialysis of any kind isn’t possible if the peritoneal membrane has lost its filtering ability, a condition confirmed through testing. Other situations that rule it out include active abdominal infections or abscesses, severe inflammatory bowel disease, active diverticulitis, and ischemic bowel disease. Multiple prior abdominal surgeries that left extensive internal scarring can also make catheter placement or fluid flow unreliable. Conditions like an existing ostomy, severe malnutrition, or heavy protein loss in the urine are relative contraindications, meaning they don’t automatically disqualify you but require careful evaluation.
Setting Up Your Home
APD doesn’t require a dedicated medical room, but it does need some practical accommodations. The cycler sits on a nightstand or small table near your bed. You’ll need a standard electrical outlet (your equipment team will confirm it’s the right type), access to a drain for used fluid, and storage space for supplies. Most people dedicate a closet-sized area to holding boxes of dialysis solution, cassettes, and tubing. Deliveries typically arrive monthly and can fill a significant amount of shelf space, since each night’s session uses several liters of fluid.
Traveling With a Cycler
APD doesn’t lock you at home. For trips lasting a week or longer, supply companies can ship dialysis bags and cassettes directly to your destination, whether that’s a hotel, a family member’s house, or a rental. Smaller, more portable cycler models are available that are easier to bring on airplanes and fit in tighter spaces like campers or cruise ship cabins. For shorter trips, you can pack enough supplies to cover your stay plus a backup buffer. Planning ahead is essential, but regular travel is realistic and common among APD patients.