How does haemodialysis (kidney dialysis) work?

Written by: Dr Ravi Rajakariar
Published: | Updated: 11/12/2018
Edited by: Jay Staniland


Haemodialysis is a lifesaving dialysis treatment for patients with chronic kidney disease (CKD), which has progressed to end stage renal disease (kidney failure). Dialysis replaces the functions that normal healthy kidneys would perform, such as cleaning the blood and removing excess urine. There are two types of dialysis; haemodialysis and peritoneal, but the following is about haemodialysis.



How does a haemodialysis machine work?


During haemodialysis a dialysis machine with a filter and an artificial kidney (haemodialyser) is used to clean the blood. To achieve access to the blood and to get blood into the dialyser, a minor surgery is performed using either a fistula, graft or a catheter.

Blood is removed from the body and circulated through a fluid circuit (outside of the body), where it is cleaned using dialysate and then returned to the patient. Dialysate is a washing fluid that helps remove the unwanted waste products from the blood and helps electrolytes and minerals to reach the correct level in the body. The machine also monitors the flow of blood and sometimes releases the sound of an alarm if something needs to be checked.


What waste products are removed by haemodialysis?


All waste products from the kidney will be removed such as those found in the blood. These include urea, creatinine, potassium and extra urine that pass through the membrane, which are washed away.


What are the risks of haemodialysis?


Haemodialysis is efficient in replacing some of the kidney’s lost functions but other conditions can be caused through the treatment, such as:

  • Low blood pressure
  • High blood pressure
  • Anaemia
  • Bone diseases
  • Heart palpitations
  • Fluid overload

How long does a haemodialysis procedure take?


It can take between three to four hours and is done three times a week. It can be done in a hospital or at home. If a patient decides to have the treatment at home, then the dialysis may happen four to seven times a week with shorter hours. The patient and doctor will determine the best place, depending on the medical condition of the patient.

By Dr Ravi Rajakariar

Dr Ravi Rajakariar is one of London's leading nephrologists. He privately practices at The Harley Street Clinic, London Bridge Hospital, in London, and The Holly Private Hospital in Essex, specialising in clinical nephrology, hemodialysis, diabetic nephrology, nephrectonomy and proteinuria. His NHS base is Barts Health NHS Trust.

Dr Rajakariar has an impressive educational history. He graduated from the University of Leicester with a BSc and first class MB ChB, both with Honours, and underwent his postgraduate training at the renowned Renal Unit at Barts Health in London. Dr Rajakariar also has a PhD from the William Harvey Research Institute, for his research into resolution of inflammation. 

Dr Rajakariar, whose clinical interests include transplantationlupus and vasculitis, and how they are connected to kidney disease, alongside diabetic renal disease, chronic kidney disease and microscopic haematuria (non-visible haematuria), is heavily involved in research in his field. He is currently involved in investigative research into lupus and renal disease. He also led the development of new services such as a day-case renal biopsy service, developing the renal service at Newham General Hospital, and the development of a renal-lupus service at Barts Lupus Centre. 

Dr Rajakariar has been published in a range of prestigious peer-reviewed journals and regularly gives talks during GP seminars. Furthermore he's a member of professional organisations including the American Society of Nephrologists and the Royal College of Physicians, and is involved in teaching, serving as an academic year tutor and a trainer of junior doctors at Queen Mary University, London.

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