Dialysis is a clinical procedure that performs the essential functions of the kidneys when they are no longer able to work effectively on their own. It acts as an artificial filtration system, removing waste products, toxins, and excess fluid from the blood while balancing vital minerals like potassium and sodium. In the UK, dialysis is typically required when a person reaches Stage 5 Chronic Kidney Disease (CKD), meaning their kidney function (eGFR) has dropped below 15 ml/min/1.73m^2 and they are experiencing symptoms of kidney failure.
The kidneys are the body’s primary waste-management plant. When they fail, metabolic ‘rubbish’ begins to pile up in the blood, leading to a condition called uremia, which can be fatal if left untreated. Dialysis serves as a life-sustaining ‘bridge’ for those waiting for a kidney transplant or as a long-term management strategy for those for whom a transplant is not an option. There are two main methods of dialysis: haemodialysis, which uses a machine to clean the blood outside the body, and peritoneal dialysis, which uses the lining of your abdomen as a natural filter. This article explains the clinical necessity of dialysis, the different types available within the NHS, and what the transition to this treatment looks like for patients with advanced CKD.
What We Will Cover in This Article
- The physiological purpose of dialysis in replacing kidney function.
- When clinicians decide it is time to start dialysis (the ‘threshold’).
- How haemodialysis works and the role of the dialysis machine.
- Peritoneal dialysis: using the body’s internal lining for filtration.
- Common symptoms that signal the need for urgent dialysis.
- Preparing for treatment: AV fistulas and peritoneal catheters.
- Managing life and diet while on renal replacement therapy.
When Is Dialysis Needed?
The decision to start dialysis is based on a combination of blood test results and physical symptoms. Clinically, it is considered when a patient’s kidney function (eGFR) falls below 15, but it is rarely started based on a number alone. Many patients can be managed with medication and diet until their eGFR is significantly lower, often around 7 to 10.
Doctors look for ‘uraemic symptoms’ signs that the buildup of toxins is starting to affect the rest of the body. If a patient is suffering from severe fatigue, persistent nausea, or dangerous fluid buildup in the lungs that cannot be managed with tablets, dialysis becomes a necessity.
- eGFR Threshold: Usually considered once function is below 15 ml/min/1.73m^2.
- Fluid Overload: When the body can no longer clear enough water, causing breathing difficulties.
- Electrolyte Imbalance: Specifically when potassium levels become dangerously high and threaten heart rhythm.
- Uraemic Symptoms: Loss of appetite, metallic taste, itching, and cognitive ‘brain fog’.
Haemodialysis: Filtering Outside the Body
Haemodialysis is the most common form of dialysis in the UK. During this procedure, blood is diverted from the body into a machine called a dialyser. Inside the dialyser, the blood flows past a special semi-permeable membrane. On the other side of this membrane is a cleaning fluid (dialysate). Waste products and excess water move from the blood into the cleaning fluid through osmosis and diffusion.
To perform haemodialysis, doctors need ‘access’ to your bloodstream. This is usually done via an AV Fistula (a surgical connection between an artery and a vein in the arm) or a Central Venous Catheter (a tube in the neck or chest). Most patients attend a hospital or satellite dialysis centre three times a week for sessions lasting about four hours each.
Peritoneal Dialysis: Using the Body’s Lining
Peritoneal dialysis (PD) is an alternative that can be performed at home, often overnight while you sleep. Instead of an external machine, PD uses the peritoneum the thin membrane that lines your abdominal cavity as the filter. A soft tube (catheter) is surgically placed into the abdomen, and a special dialysis fluid is drained into the space.
The fluid stays in the abdomen for several hours, drawing waste and excess water out of the blood vessels in the peritoneum. The ‘used’ fluid is then drained out and replaced with fresh fluid. This process is continuous and can offer more flexibility for patients who wish to maintain a working life or travel.
| Feature | Haemodialysis (HD) | Peritoneal Dialysis (PD) |
| Location | Usually hospital or clinic | At home |
| Frequency | 3 times per week | Daily (often overnight) |
| Access Type | AV Fistula or Neck Line | Abdominal Catheter |
| Dietary Limits | Stricter (potassium/fluid) | Slightly more flexible |
| Procedure | Blood is cleaned by a machine | Fluid is exchanged in the abdomen |
Preparing for Dialysis: The Transition
Starting dialysis is a significant life event that requires months of physical and psychological preparation. In the UK, the ‘Pre-Dialysis’ or ‘Low Clearance’ clinic helps patients navigate this transition. One of the most important steps is ‘creating access’. An AV fistula, for example, needs several weeks or months to ‘mature’ and become strong enough to be used for dialysis needles.
If kidney function drops suddenly due to an infection or injury, ’emergency dialysis’ may be started using a temporary line in the neck. However, the clinical goal is always a planned start, ensuring the patient is educated on their options and their access is ready for use.
To Summarise
Dialysis is a life-saving treatment used when the kidneys reach Stage 5 failure and can no longer maintain the body’s internal balance. Whether through haemodialysis (using an external machine) or peritoneal dialysis (using the abdomen’s lining), the goal is to remove toxins and excess fluid to improve quality of life. The decision to start is tailored to the individual, balancing their eGFR scores with physical symptoms like fatigue and fluid overload. While it represents a major change in lifestyle, dialysis effectively manages the complications of kidney failure and allows patients to live active lives while awaiting a transplant or managing long-term disease.
If you experience severe, sudden, or worsening symptoms, call 999 immediately.
Does dialysis hurt?
The treatment itself is painless, though the needles used in haemodialysis can cause a brief sting, and some people feel tired or ‘washed out’ after a session.
Can I still work while on dialysis?
Yes, many people continue to work, especially those using peritoneal dialysis at night or those who choose home haemodialysis.
How long can someone live on dialysis?
Many people live for 10, 20, or even 30 years on dialysis, though the long-term outlook depends on other health factors like heart health.
Can I go on holiday while on dialysis?
Yes, ‘holiday dialysis’ can be arranged at centres across the UK and abroad, and peritoneal dialysis supplies can often be shipped to your destination.
Is dialysis a permanent treatment?
For some, it is a permanent way of life; for others, it is a ‘bridge’ until a suitable donor kidney becomes available for a transplant.
What happens if I miss a dialysis session?
Missing a session is dangerous as toxins and fluid will build up rapidly, which can cause heart rhythm issues or breathing difficulties.
Authority Snapshot
This article outlines the clinical indications and procedures for dialysis based on NICE (NG107) and NHS renal guidelines. Dr. Rebecca Fernandez, a UK-trained physician with experience in internal medicine, cardiology, and emergency care, has reviewed this content. Her background in managing acute renal failure and stabilising patients for renal replacement therapy ensures that this information is accurate and highlights the clinical importance of timely dialysis for patient safety.
