What is Dialysis?
Dialysis is the process of artificially removing waste products and fluid from the blood.
This function is usually performed by our kidneys; but when our kidneys aren’t working properly, dialysis is required. Dialysis is usually only started when someone’s kidney function is severely reduced.
Dialysis performed outside of an acute hospital setting is usually for chronic kidney failure. People with chronic kidney failure often need regular dialysis for the rest of their lives unless they receive a kidney transplant. Sometimes, people who are acutely ill may need to have dialysis for short periods when they’re in an intensive care setting.
What is Peritoneal Dialysis?
In haemodialysis, blood is run through a machine which filters out waste products then returns the blood to the body. In peritoneal dialysis, a small permanent port is created on the abdomen and a specially prepared fluid called dialysate is introduced into the abdominal cavity – the space around the organs inside the abdomen. This fluid draws out waste products and excess fluid from the bloodstream before being drained out of the body.
How Does Peritoneal Dialysis Work?
Peritoneal dialysis works on the principles of osmosis and diffusion.
Osmosis describes the process where a solvent, such as water, crosses a semi-permeable membrane from an area of low solute (i.e. dissolved salts and sugar) concentration to an area of high solute concentration.
Diffusion is the process where particles move from an area of high concentration to an area of low concentration.
The combination of osmosis and diffusion effectively equalise the concentration of fluids and dissolved particles in a vessel, even where separated by a membrane.
The peritoneum is the membrane that lines the whole of the abdominal cavity. If we fill the abdominal cavity – the space inside the peritoneum but outside and around the organs – with a fluid that has a high concentration of sugar and certain salts, then fluids and other substances will be drawn from the body’s blood and tissues.
Dialysis fluid is hyperosmolar; this means that it has a high concentration of certain types of molecules such as salts and sugar. Different strengths and formulations of dialysate are available and your doctor will prescribe you the right one based on your individual needs. Regular blood tests may be needed to help doctors plan effective dialysis. The length of time the dialysis fluid is left in the abdominal cavity also influences how much fluid and waste it draws out of the blood.
Before peritoneal dialysis, you have to have a small surgical procedure where an incision is made into the abdomen to place a port for administering and draining the dialysate.
Why is Peritoneal Dialysis carried out?
Peritoneal dialysis is used when someone has kidney disease and the kidneys no longer work well enough to allow you to stay healthy. Peritoneal dialysis does the job of the kidneys; it removes waste products and balances fluid and electrolytes. Peritoneal dialysis has some benefits over haemodialysis, but haemodialysis may be recommended for people who need closer monitoring or who cannot manage dialysis at home.
Benefits of Peritoneal Dialysis
Once you and your carers have practiced and become comfortable using the dialysis equipment, peritoneal dialysis can be carried out at home, which many people find much less disruptive than haemodialysis. This is usually the main benefit that people who need dialysis report; with haemodialysis, people usually have to spend around three days each week in a hospital clinic.
Peritoneal dialysis tends to have a gentler, slower impact on the electrolyte balance of the blood, electrolytes so there is a reduced risk of imbalances, although haemodialysis may be more appropriate if close hospital monitoring is required.
Peritoneal dialysis has the benefit of not needing vascular access – although you will need regular blood tests, you won’t need to have ports or cannulas repeatedly fitted in the veins.
Types of Peritoneal Dialysis
There are two types of peritoneal dialysis: Automated Peritoneal Dialysis (APD) and Continuous Ambulatory Peritoneal Dialysis (CAPD).
Automated Peritoneal Dialysis (APD)
With automated peritoneal dialysis, you are attached to a dialysis machine overnight, which automatically pumps the right amount of fluid in then allows it to drain after a set length of time. The machine will run several cycles in one night and the individual will usually have to be attached to the machine for 8-10 hours. This reduces the amount of disruption to your life, and tends to be more popular among people needing dialysis.
Continuous Ambulatory Peritoneal Dialysis (CAPD)
With continuous ambulatory peritoneal dialysis, individuals have to do several short cycles of dialysis throughout the day. It is a machine-free process PD bag system that uses gravity to fill and empty the abdomen.
With fill time, dwell time (the length of time the fluid needs to stay inside your abdomen), and drain time, each cycle typically takes at least an hour, although your dialysis team will prescribe a specific set pattern for you. It needs to be repeated several times a day, which can be disruptive, though many people are able to fit it into their lifestyles pretty well, with some even performing dialysis cycles while at work or studying.
Diet and Nutrition for Peritoneal Dialysis
The diet you follow when you have kidney failure can make a big difference in how you feel. People on haemodialysis have to be quite strict about the food and drinks they take in, but people who have peritoneal dialysis can usually be a little more relaxed. However, there are a few things you need to watch out for when you’re having dialysis:
You may be advised to limit your fluid intake while you’re having dialysis. Your renal team will give you personalised advice for your particular regime.
Some protein is lost during dialysis so dietitians recommend a reasonable intake of high-quality lean proteins which will keep your protein levels up while reducing unnecessary waste products.
Dialysis can cause deranged electrolytes – these are the essential salts in your blood. Your dialysis team should give you advice on whether you should eat or avoid foods high in potassium or other essential electrolytes. People on PD often have to limit their sodium intake and increase their intake of potassium.
Vitamins & Minerals
Some vitamins and minerals are lost during dialysis and your renal team may advise you to take prescribed vitamin supplements. It’s important to take the supplements they recommend and not over-the-counter supplements, which could be harmful for people on dialysis.
Everyone is different and your renal team should give you advice for following a healthy diet based on your own medical history and blood test results.
Potential Complications of Peritoneal Dialysis
Like almost any medical procedure, there are some possible complications, and if you’re doing dialysis in your own home, you and anyone who helps you should be aware of what signs might show that something isn’t right. Some of the complications of PD can include:
Leakage of Fluid around the Catheter Site
This can make dialysis less effective and increase your risk of infections. The dialysis fluid can also irritate the skin so if your PD catheter is leaking, it’s important to see your renal team.
Usually if a PD catheter isn’t draining, it’s something that’s easy to fix. It may simply be that the tubing is kinked or compressed, or it could indicate that the open end inside the body is situated against some structure such as an organ wall. You should have equipment for flushing the catheter which can usually fix the problem. Sometimes simply changing your position, such as lying on your side, can be enough to move the catheter a little and allow it to drain.
Infection around the Catheter Site
Watch for signs of infection in the skin around the port. Redness, heat, swelling and pain are signs of cellulitis.
Infection within the Peritoneum
Peritonitis, an infection of the peritoneum inside the abdominal cavity can be very serious. Signs of infection include a change in the appearance of the PD fluid when it drains from the abdomen – if it appears cloudy, bloody, or discoloured, it’s important to seek medical advice straight away.
Having a PD port can make some people more likely to develop a hernia. This is a swelling where one part of a body tissue – usually bowel – pokes through an opening. Hernias can cause problems so if you notice any lumps or develop localised pain, see your doctor.
Deranged Blood Sugars
Sometimes, PD fluid can raise people’s blood sugar so tests for blood sugar levels might be added into your routine renal blood tests. People who already take insulin may need to increase their dose.
Some people feel uncomfortable when they have the full amount of PD fluid in them. You may experience mild shortness of breath or feel like you have indigestion. Most people are able to tolerate PD without any problems and can even sleep through it if they’re having APD.
How do I prepare for Peritoneal Dialysis?
A peritoneal dialysis catheter needs to be fitted into the abdomen – this is a port for administering and draining the dialysis fluid. These catheters are fitted under surgical conditions, but not normally under a full general anaesthetic. The tube is tunnelled through the layers of skin into the abdominal cavity. If they’re intended to be left in for a long time, they have a cuff on the inside to secure them and prevent leakage. You’ll be advised about how to prepare for the procedure. It usually takes around two weeks before the catheter site is healed enough to begin using it for dialysis.
Besides preparing your body for dialysis, your home needs to be ready too. Bags of PD fluid can be quite large and you’ll need to have a sufficient supply of them, with enough space to receive regular deliveries too.
Where can Peritoneal Dialysis be carried out in Singapore?
One of the main benefits of PD is that you can do it yourself at home. Your dialysis team will ensure you’re set up and comfortable with the procedure and you should be given a number to call any time if you have concerns. You do need to be able to lift the heavy PD fluid bags and handle the equipment, so some people may prefer engaging a nurse to help them with their dialysis at home. The National Kidney Foundation also has a programme to support individuals having PD at home, including training for caregivers and support for everybody involved.
- National Kidney Foundation (2020) What Is Peritoneal Dialysis? NKFS.org https://nkfs.org/treatment-options/what-is-peritoneal-dialysis/
- Rabindranath, K. S., Adams, J., Ali, T. Z., MacLeod, A. M., Vale, L., Cody, J. D., … & Daly, C. (2007). Continuous ambulatory peritoneal dialysis versus automated peritoneal dialysis for end‐stage renal disease. Cochrane Database of Systematic Reviews https://dx.doi.org/10.1002%2F14651858.CD006515
- Roumeliotis, A., Roumeliotis, S., Leivaditis, K. et al. (2020) APD or CAPD: one glove does not fit all. Int Urol Nephrol. https://doi.org/10.1007/s11255-020-02678-6
- Mizuno, M., Suzuki, Y., Sakata, F. et al. (2016) Which clinical conditions are most suitable for induction of automated peritoneal dialysis?. Ren Replace Ther. https://doi.org/10.1186/s41100-016-0057-8
- National Institute of Diabetes and Digestive and Kidney Diseases (2018) Eating and Nutrition for Peritoneal Dialysis. NIDDK.nih.gov https://www.niddk.nih.gov/health-information/kidney-disease/kidney-failure/peritoneal-dialysis/eating-nutrition
- National Institute of Diabetes and Digestive and Kidney Diseases (2018) Peritoneal Dialysis. NIDDK.nih.gov https://www.niddk.nih.gov/health-information/kidney-disease/kidney-failure/peritoneal-dialysis
- Balda, S., Power, A., Papalois, V., & Brown, E. (2013). Impact of hernias on peritoneal dialysis technique survival and residual renal function. Peritoneal Dialysis International, 33(6), 629-634. https://dx.doi.org/10.3747%2Fpdi.2012.00255