Dialysis: What It Is, How It Works, and What to Expect
Dialysis is a medical procedure that removes excess waste, salt, and fluids from the blood when the kidneys are no longer able to do so adequately. It is a life-sustaining treatment — not a cure — for patients with advanced kidney failure.
When our kidneys are functioning normally, excess fluids and waste products are filtered and removed via urine. Healthy kidneys also regulate blood pressure, maintain bone health, and produce erythropoietin — the hormone responsible for red blood cell production. When kidney function fails, dialysis steps in to perform these filtering functions partially.
Why Is Dialysis Needed?
When the kidneys can no longer clean the blood properly — due to long-term kidney failure or advanced chronic kidney disease — excess fluids and waste build up in the body. Left untreated, this causes serious symptoms and can be fatal.
Dialysis is required for patients diagnosed with end-stage kidney failure, whether from chronic kidney disease (CKD) or acute kidney injury (AKI). Starting dialysis as soon as it is indicated helps slow disease progression and improve quality of life.
Dialysis is not a cure for kidney disease. A kidney transplant, where medically feasible, offers better long-term outcomes for most patients. Dialysis sustains life while a transplant is being arranged, or in cases where transplantation is not suitable.
The Two Main Types of Dialysis
There are two main types of dialysis: haemodialysis and peritoneal dialysis. Both remove toxins and excess fluid from the blood. The right choice depends on your medical condition, lifestyle, mobility, and personal preference.
In Singapore, organisations such as the National Kidney Foundation (NKF) and the Kidney Dialysis Foundation provide heavily subsidised dialysis treatment for needy patients.
The key difference lies in how the filtering is done. Haemodialysis uses an artificial kidney machine to clean the blood; peritoneal dialysis uses the lining of the abdomen as a natural filter.
Failing kidneys and treatment options (via DocMikeEvans)Haemodialysis
Haemodialysis uses an artificial kidney machine to imitate the filtering function of a healthy kidney. Blood is drawn from the body, passed through the machine where toxins and excess fluids are removed, and returned clean.
Preparation: The AV Fistula
Before starting haemodialysis, a blood vessel called an arteriovenous (AV) fistula is created in the arm via a minor surgical procedure. This connects an artery to a vein, creating reliable vascular access for the dialysis machine. The surgery is usually performed 4 to 8 weeks before the first session to allow healing.
AV Fistula — Image source: wikipedia.org
How the Session Works
During each session, blood is channelled through a soft tube into the dialysis machine, which contains membranes that act as filters alongside a special cleansing fluid called dialysate. Toxins and excess fluids pass into the dialysate, which is then pumped out. The cleaned blood is returned to the body.
What Happens During Haemodialysis — Image source: niddk.nih.gov
Haemodialysis Dialyzer — Image source: niddk.nih.gov
Duration and Frequency
At a dialysis centre, haemodialysis is typically performed 3 times a week, with each session lasting around 4 hours. Home haemodialysis can be done 3 to 6 times per week depending on the patient's condition.
Peritoneal Dialysis
Peritoneal dialysis uses the inner lining of the abdomen — the peritoneal membrane — as a natural blood filter. Like the kidneys, the peritoneum contains thousands of tiny blood vessels capable of filtering function.
How It Works
A small incision below the belly button allows a catheter (thin tube) to be placed into the peritoneal cavity. This is left to heal for a few weeks before treatment begins. During each session, a bag of dialysis solution is pumped into the abdomen and left for several hours. As blood passes through the peritoneal blood vessels, toxins and excess fluid pass into the solution, which is then drained out via the catheter. Fresh solution is introduced for the next cycle.
Peritoneal Dialysis — Image source: nkfs.org
Duration and Frequency
The fluid exchange takes 30 to 40 minutes and is typically carried out 4 to 6 times a day. Alternatively, an automated peritoneal dialysis (APD) machine can handle fluid exchanges overnight while you sleep — you simply attach a fresh bag of dialysate before bed, and the machine performs the exchanges automatically.
Automated Peritoneal Dialysis (APD) Machine — Image source: yourdialysisjourney.co.uk
Can Dialysis Be Done at Home?
Yes. Both haemodialysis and peritoneal dialysis can be performed safely and effectively at home for end-stage renal disease patients who want to maintain greater freedom in their daily lives.
Home Haemodialysis
Requires an artificial kidney machine installed at home. The patient must be trained to operate it, or a professional caregiver engaged. Two formats are available:
- Short daily: 5–6 times per week, 3 hours per session
- Traditional: 3 times per week, 4 hours per session — with the option to dialyse more frequently for better results
Home Haemodialysis
Home Peritoneal Dialysis
Does not require a kidney machine, making it more convenient to carry out at home independently. Performed daily, either manually during the day or automatically overnight via an APD machine.
Home Peritoneal Dialysis
Comparing the Two Types
Both treatments are effective for most patients. The right choice depends on your medical condition, lifestyle, and personal circumstances. Your nephrologist will guide you through the decision.
Haemodialysis
Advantages
- Only 3 sessions per week — 4 dialysis-free days to plan activities
- Easier for patients in poor health, visually impaired, or with dementia
- Home option available with overnight sessions for a normal daytime routine
Disadvantages
- Sessions last 4 hours; requires visits to a dialysis centre unless home dialysis is set up
- Strict dietary restrictions — avoid high-phosphate, high-potassium foods and processed meats
- Fluid intake limited to approximately 1–1.5 litres per day
- Overseas travel requires pre-arranging access to dialysis facilities
Peritoneal Dialysis
Advantages
- No need for regular clinic visits — can be done entirely at home
- Fewer dietary and fluid restrictions compared with haemodialysis
- Suitable for children and adults without serious co-existing conditions
- APD machine handles overnight exchanges automatically
Disadvantages
- Requires daily treatment — disrupts lifestyle to some extent
- Permanent catheter in the abdomen can be uncomfortable for some patients
- Risk of peritonitis (abdominal membrane infection) if hygiene is not maintained
- Dialysis fluid may reduce protein levels, causing fatigue
- In rare cases, the peritoneum may thicken and scar, requiring a switch to haemodialysis
Side Effects of Dialysis
While dialysis is life-sustaining, both forms come with side effects and risks that should be discussed with your nephrologist.
Haemodialysis
- Muscle cramps
- Persistent itching
- Sepsis (blood poisoning)
- Sleeping difficulties
- High blood potassium levels
- Anaemia
- Irregular heartbeat or sudden cardiac arrest
Peritoneal Dialysis
- Peritonitis (abdominal membrane infection)
- Fever and stomach pain
- Weight gain
- High blood sugar (from dextrose in dialysate)
- Hernia
- Protein loss leading to fatigue
Can Dialysis Be Stopped Once Started?
In some cases — particularly acute kidney injury — the kidneys may recover and dialysis can be stopped. However, for patients with permanent kidney failure, dialysis is lifelong unless a successful kidney transplant is performed.
For patients awaiting a transplant but not yet eligible or able to undergo surgery, dialysis bridges the gap. For those who are not strong enough for transplantation, dialysis may be required indefinitely.
Dialysis does not cause kidney dependency — it simply replaces a function the kidneys can no longer perform. The decision to continue or stop dialysis is always made in consultation with your nephrologist based on your individual situation.
Get Personalised Advice on Dialysis & Kidney Disease
Dr. Francisco Salcido-Ochoa provides specialist nephrology consultations — in-clinic in Singapore or via international teleconsultation.
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