What is Dialysis | How Does Dialysis Work | Types of Dialysis
(Updated 16 April 2021)
Table of Contents
What does dialysis mean?
Dialysis is a medical procedure to remove excess waste, salt and fluids from the blood when the kidneys are not working properly (end stage kidney failure) by diverting blood to a dialysis machine to be cleansed.
When our kidneys are functioning properly, excess fluids and waste products are filtered and removed by our kidneys via urine to be passed out of our body. Our healthy kidneys also help our body to regulate blood pressure, maintain strong bones and produce erythropoietin, the hormone responsible for the production of red blood cells.
Why do I need dialysis?
When our kidneys are not working as they should due to long-term kidney failure (or advanced chronic kidney disease), then our kidneys are not able to clean our blood properly.
This causes excess fluids and excess waste to build up in our body and if left untreated, it will result in various unpleasant symptoms and even be fatal in the long run.
That is why we need kidney dialysis for patients to be able to filter the excess waste and fluids as soon as possible.
When diagnosed with renal disease, whether it’s chronic kidney disease (CKD) (gradual decline in kidney function) or acute kidney injury (AKI) (where there’s a rapid loss of kidney function), you should go on dialysis as soon as possible to slow down the progression of kidney disease and damages so you can improve your quality of life.
But take note that dialysis is not a cure for kidney disease. A better treatment for kidney disease is actually a successful kidney transplantation.
Types of dialysis: Haemodialysis & peritoneal dialysis
There are 2 main types of dialysis: Haemodialysis and peritoneal dialysis. Both long-term dialysis treatments help remove toxins and extra fluid from the blood. Depending on your lifestyle circumstances, mobility, health condition, and affordability of the kidney health care costs in your area, you can choose the type of treatment plan that suits you best.
Organizations such as the National Kidney Foundation (NKF) and Kidney Dialysis Foundation provide highly subsidized dialysis treatments and health care to needy patients in Singapore, so the thousands of kidney patients do not have to stress themselves or their family over the dialysis costs.
What is the difference between haemodialysis and peritoneal dialysis?
The main difference lies on how the filtering process is done.
Haemodialysis uses a kidney machine to clean the blood for the dialysis patients, while peritoneal dialysis uses the abdomen’s lining (the peritoneum) for the filtering process.
Choosing between the two types of dialysis treatments is based on the patient’s medical condition, lifestyle, and personal preference.
Failing kidneys and different treatment option (video via DocMikeEvans)
How does haemodialysis work?
Haemodialysis treatment uses an artificial kidney machine to imitate the filtering function of a healthy kidney.
To prepare for haemodialysis, the patient will need a blood vessel called an arteriovenous fistula (AV fistula) created in the arm via a minor surgery. This blood vessel is created via the surgical connection between an artery to a vein, and makes it easier to transfer the blood into the dialysis machine and back into the body.
Image source: https://en.wikipedia.org
The AV fistula surgery is usually carried out around 4 to 8 weeks before haemodialysis to allow the tissue and skin surrounding the fistula to heal.
A tube is attached to a needle in your arm to create the vascular access for the blood to go in and out during haemodialysis.
What Happens During Haemodialysis
Image source: https://www.niddk.nih.gov
During haemodialysis, the blood is extracted and channelled into the artificial kidney machine via the soft tube, where the toxins and excess fluids are removed.
The dialysis machine contains a series of membranes that act as filters and a special cleansing fluid called dialysate, which filter toxins and excess fluids from your blood, which are passed into the dialysate fluid.
Hemodialysis Dialyzer Illustration
Image source: https://www.niddk.nih.gov
This special fluid is then pumped out of the dialyser, and the filtered blood is channelled back into your body via the second vascular access.
When you’ve been on haemodialysis for a long period of time, your doctor may suggest you to perform peritoneal dialysis at home if you’re ready.
How does peritoneal dialysis work?
Peritoneal dialysis uses the inner lining of the abdomen (the peritoneum or the peritoneal membrane) as a natural filter of the blood.
Similar to the kidneys, our peritoneum contains thousands of tiny blood vessels that can help with the filtering function.
First, an incision (cut) is usually made just below your belly button to place a catheter (a thin tube) into the peritoneal cavity (the space inside the abdomen). This opening will normally be left to heal for a few weeks before treatment starts.
During the peritoneal dialysis, a bag of dialysis solution (dialysate) is pumped into the abdomen via the catheter and left there for a few hours.
Image source: https://nkfs.org
As blood passes through the blood vessels lining the peritoneal cavity, excess fluids and toxins are drawn out from the blood into the dialysis fluid.
The kidney patient is then free to move around and carry on with his/her activities for a few hours.
This dialysis fluid will absorb excess fluids and toxins from the blood, and is drained out via the catheter after a few hours into the waste bag.
Fresh fluid from a fresh bag is then passed into your peritoneal cavity and left there until the next session.
Between treatment sessions, the end of the catheter is sealed and the bags are disconnected.
How long does dialysis take?
How long does haemodialysis take?
At dialysis centres, haemodialysis is usually performed 3 times a week, and each session usually lasts around 4 hours.
Haemodialysis can also be performed at home, ranging from 3 to 6 times a week, depending on the patient’s medical condition.
How long does peritoneal dialysis take?
A fresh input of dialysis fluid absorbs the blood toxins quickly and this ability decreases over time. Therefore, the exchange of fluids is necessary every few hours.
The change usually takes 30 to 40 minutes, and is typically carried out 4 to 6 times a day, depending on the patient’s medical condition.
This change of dialysis solution can also be done by a machine overnight while you sleep.
Can dialysis be done at home?
Both haemodialysis and peritoneal dialysis can be done at home safely and effectively for end stage renal disease (ESRD) patients who want to receive the kidney care they need while still enjoying a certain extent of freedom to carry out their daily activities.
For home haemodialysis (HHD), the patient will need to have the artificial kidney machine installed at home to carry out haemodialysis 3 times a week. The patient would need to be trained on how to operate the dialysis machine or hire a professional caregiver.
Image source: https://www.kidneybuzz.com
There are 2 types of home hemodialysis, i.e. short daily home hemodialysis and traditional home hemodialysis. One of the main advantages of home dialysis is that the treatment schedule can be tailored to a patient’s lifestyle and health condition.
Short daily home hemodialysis
Short daily home hemodialysis is usually 5 to 6 times a week for 3 hours per session.
Traditional home hemodialysis
Traditional home hemodialysis is generally done 3 times a week for 4 hours per session, similar to the treatment at a dialysis centre. The patient has the option to perform dialysis more more often for better clinical results.
Home Peritoneal Dialysis
For peritoneal dialysis, though it has to be done daily as compared to haemodialysis (3 times a week), the patient does not need the artificial kidney machine, so it is a more convenient option that can be carried out at home easily.
Home Peritoneal Dialysis
Image source: https://www.yourdialysisjourney.co.uk
However, an automated peritoneal dialysis machine (APD) can also be used to facilitate the change of the dialysis solution while you sleep. You just need to attach a fresh bag of dialysate fluid to the APD machine before going to bed. As you sleep, the machine automatically performs a number of fluid exchanges. The fluid exchange can be temporarily interrupted if you need to go to the bathroom.
Automated Peritoneal Dialysis Machine (APD)
Image source: https://www.yourdialysisjourney.co.uk
Which type of dialysis is best?
Both haemodialysis and peritoneal dialysis are effective for most patients, so the choice lies in your medical condition, lifestyle circumstances, and personal preference.
Pros & Cons of Haemodialysis
Advantages of Haemodialysis
You only need to do the treatment 3 times a week, which means you can plan your activities more easily during the 4 dialysis-free days.
Haemodialysis is also a helpful and easier option for fellow patients who are in poor health, visually impaired, or suffering from dementia, which makes it difficult for them to perform peritoneal dialysis on their own every day.
For those who opt for home haemodialysis, they may also choose to carry out the dialysis overnight, which will help them to have a normal daytime routine.
Disadvantages of Haemodialysis
The haemodialysis treatment sessions last longer and you need to visit the dialysis centre every time, so you need to plan your life around the dialysis sessions (unless you opt for home haemodialysis, where you need to be trained on how to use the dialysis equipment so you can dialyse at your preferred times or hire a professional caregiver).
While on haemodialysis, your diet and the amount of fluid you drink is severely restricted. You need to avoid foods such as those with phosphate additives (a preservative in processed food) and high potassium, bananas, nuts, salty meats, and chocolates. Read this guide from NKF on “Eating Right for Dialysis Patients” for more info.
The amount of fluid you’re allowed to drink will depend on your size and weight. Most people are only allowed to drink 1,000 to 1,500ml (2 to 3 pints) of fluid a day.
Your fluid intake, depending on your size and weight is restricted to around 1 litre to 1.5 litre (2 to 3 pints) per day.
This is because if you take too much fluid, the dialysis machine cannot remove too much excess fluid in just 4 hours, and this can lead to excess fluid build up in your blood, tissues, and even the lungs.
To manage your thirst, some dietitians may give you alternatives such as frozen grapes or ice chips.
Another disadvantage of haemodialysis is that when traveling overseas, haemodialysis patients have to arrange access to dialysis facilities beforehand.
The staff at your dialysis centre may be able to refer you to a dialysis unit at your destination, or you may check the Global Dialysis’ database of dialysis centres around the world.
Pros & Cons of Peritoneal Dialysis
Advantages of Peritoneal Dialysis
Unlike haemodialysis, peritoneal dialysis does not require regular visits to a dialysis centre, as it can be carried out quite easily at home.
There are also fewer diet and fluid intake restrictions for those on peritoneal dialysis, compared with those going through haemodialysis.
Peritoneal dialysis is suitable for both young children and adults who do not have serious health issues such as cancer or heart disease.
Disadvantages of Peritoneal Dialysis
One primary disadvantage of peritoneal dialysis is that it needs to be carried out every day, which will disrupt your lifestyle to a certain extent.
Some patients also find it uneasy to have the catheter (a thin tube) placed permanently in their abdomen.
Also, those who are on peritoneal dialysis are at risk of developing peritonitis, an infection of the thin membrane that lines the abdomen.
The patient or caregiver needs to be adequately trained for peritoneal dialysis to reduce the risk of infection. The dialysis patient should also avoid soaking in a hot tub or swimming in a lake, river, or non-chlorinated pool.
Another possible (though rare) problem is having the peritoneum (abdomen lining) thickened and scarred, and this is when the patient has to switch to haemodialysis for a while.
The dialysis fluid used in peritoneal dialysis can cause a reduction in protein levels, which can lead to a lack of energy, which will affect your drive and performance in your daily activities.
Can Dialysis Be Temporary (Stopped Once Started)?
In some cases, chronic kidney disease may be a temporary health issue and renal dialysis can be stopped if the kidneys can recover.
But generally, a patient with kidney failure will need a kidney transplant, though it is usually not possible to undergo a renal transplantation immediately, because a suitable donor is required.
That is why dialysis is required to filter and remove the excess waste products and fluids from the body while waiting for a suitable kidney donor.
In some cases, for kidney patients who are not well or strong enough for a major transplant surgery, dialysis may be required for the rest of their lives.
Dialysis Side Effects
While dialysis is a life-saving treatment that can help prolong your life, both haemodialysis and peritoneal dialysis will make you feel exhausted, and they come with certain risks and side effects.
Haemodialysis Side Effects
Some of the side effects of haemodialysis include muscle cramps, itching, sepsis (blood poisoning), sleeping difficulty, high blood potassium levels, anemia, irregular heartbeat and sudden cardiac arrest.
Peritoneal Dialysis Side Effects
Peritoneal dialysis can put you at risk of developing peritonitis, an infection of the thin membrane that surrounds your abdomen. Other side effects may include fever, stomach pain, weight gain, high blood sugar due to dextrose in the dialysis fluid (dialysate), or hernia.
Get Personalised Medical Advice on Dialysis & Chronic Kidney Disease
Need personalised advice and treatment recommendations from a kidney doctor on dialysis and chronic kidney disease?
Important information on chronic kidney disease
What is chronic kidney disease (CKD)?
Signs and symptoms of chronic kidney disease
Stages of chronic kidney disease
Diagnosing chronic kidney disease
Treatments for chronic kidney disease
How can I prevent chronic kidney disease?
Renal diet for chronic kidney disease patients