HUS (Haemolytic Uraemic Syndrome) Frequently Asked Questions

What is Haemolytic Uraemic Syndrome?
Haemolytic Uraemic Syndrome (HUS) refers to a group of clinical features (syndrome) that includes:

• Haemolytic Anaemia: Low levels of the oxygen carrying molecule of our body, called haemoglobin, due to damage to the red blood cells
• Acute renal (kidney) failure: Failure of the kidneys to adequately filter out waste products from our blood
• Thrombocytopaenia: Low levels of the blood cell fragments, called platelets, that are important in forming blood clots

In HUS, the damaged red blood cells and the haemologlobin that is released from them, block the kidneys which leads to kidney failure.

The commonest cause of HUS is verocytotoxigenic E. coli (VTEC) gastroenteric infection; HUS is the commonest cause of kidney failure in children.

HUS is notifiable in Ireland and each year about 30 cases of VTEC-related HUS are reported, mostly in children.

What causes HUS?
HUS can have infectious and non-infectious causes. Most HUS is due to infectious causes.

• Infectious causes (known as diarrhoea-associated HUS or D + HUS): Most cases are caused by VTEC. However, Shigella dysenteriae, Campylobacter, Streptococcus pneumoniae, Clostridium butyricum, and HIV infections can cause HUS too.
• Non-infectious causes (known as atypical HUS or D – HUS): This type of HUS can be caused by certain drugs (like contraceptive pills or cyclosporine antibiotics), malignancy, can happen after pregnancy, or have an unknown cause. Unlike the infectious kind, this form of HUS isn’t associated with diarrhoea and kidney function is more likely to recover.

Who is most at risk of HUS?
Young children, elderly people and people with weakened immune systems are at highest risk of developing VTEC associated HUS.

What are the clinical features of HUS?
HUS following VTEC infection usually appears about seven days after the onset of the diarrhoea (range 2-14 days). Anaemia and kidney failure usually present with weakness, floppiness and sleepiness. Irritability in children may be an early symptom. There may be bruising on the skin.

• General: fatigue, irritability, low/no urinary output, swelling or arms, legs and face, and confusion.
• Kidneys: there may be blood in urine. Often the red blood cells can only be seen through a microscope (called microscopic haematuria), or the urine may look red and bloody (called gross haematuria). Kidney failure can range from mild to severe (which requires dialysis)
• Heart: HUS patients have a normal blood pressure. High blood pressure can occur in the non-infectious form with damage to the retina. Heart failure can occur particularly in women who have recently had a baby.
• Nervous System: damage to small blood vessels can lead to developmental delay in babies and small children and difficulty moving arms and legs. Convulsions are not uncommon.
• Gastrointestinal System: very occasionally perforation (puncture) of the bowel due to lack of blood supply can occur. In children, intussusception (intestinal obstruction) can occur.
• Skin: Paleness and bruising (purpura).

What are the things I should look out for in my child?
The principal features of HUS in children are:

• Failure to pass urine (i.e. dry nappies)
• Generalised weakness (or floppiness in babies)
• Difficulty in waking; sleepiness
• Pale face/skin
• Bruising
• Nosebleeds
• Swelling of face, wrists/hands, ankles/feet
• Especially if such signs are associated with bloody diarrhoea, or if the child has a diagnosis of VTEC infection

HUS is a medical emergency. If you see such features in your child, (especially if they have been diagnosed with VTEC infection, or have had bloody diarrhoea in the previous week), you should call your GP urgently. If you cannot contact your GP, you should take your child to your local hospital’s Emergency Department.

How is HUS treated?
Children who develop any of these symptoms are admitted to hospital for specialist care. There is no specific treatment of HUS; antibiotics are not used in the treatment of VTEC infection. 

The main dangers to a child with HUS are kidney damage and dehydration, so in hospital, a child will be given intravenous fluids (through a drip). Sometimes, a child whose haemoglobin level is low may require blood transfusion.

Occasionally, the child may require dialysis while their kidneys are recovering. Rarely, the child may require plasmapheresis, in which case, antibodies and other harmful substances in the blood that may attack the body are also removed. 

What other investigations are likely?
As HUS is almost always due to VTEC infection, it will be important to determine where this infection may have come from.

If your child develops HUS, as well as being looked after by clinical physicians in the hospital, you will be contacted by Public Health physicians who investigate VTEC cases to work out how your child may have acquired their infection and how far it may have spread. Stool samples may be requested from you and your family and you may be asked about where you ate and what water you had consumed recently.

What is the outlook for HUS?
The outlook is excellent, especially in small children. Children under the age of five tend to recover rapidly. Occasionally children whose kidneys were damaged may require prolonged therapy such as dialysis. In elderly people the prognosis is not as good as in children. Rapid intervention with fluids is crucial, so it is important to identify HUS as early as possible in all ages.

Can HUS be prevented?
Infections that cause HUS can be prevented by following some precautions, especially for those groups at greatest risk:

• By drinking pasteurised milk
• By ensuring proper hand hygiene
• By storing meat at safe temperatures and cooking it thoroughly (to a temperature of at least 75°C).
• By preventing cross contamination in the fridge and on preparation surfaces, separating raw meat from ready to eat food items, and handling them with different tools (or tools that have been washed before using again).
• Cleaning utensils properly
• Ensuring clean kitchen surfaces.

Last updated: 4 February 2025