What is it?
Haemolytic uraemic syndrome (HUS) is a rare kidney condition. Common features of HUS include:
- Anaemia – a shortage of red blood cells. In HUS this is caused by the destruction of red blood cells.
- A low platelet count. Platelet cells are involved with blood clotting and a shortage of these cells can cause bruising on your skin and excessive bleeding.
- Kidney failure. This is caused by damage to tiny blood vessels within your kidney’s filtering system which become blocked by blood clots.
- Severe HUS can also affect the brain, also the gut, heart, liver and pancreas, although when it does this it begins to look more like a related condition known as TTP (Thrombotic Thrombocytopenic Purpura).
- These conditions can be difficult to tell apart. Diseases like this are sometimes called Thrombotic Microangiopathies (TMA)
What are the causes
HUS has two main causes, known medically as STEC-HUS and atypical HUS.
STEC-HUS, also known as Typical HUS and D+ HUS.
STEC-HUS is the most common type of HUS and usually occurs with gastroenteritis caused by bacteria that produce a toxin called Shiga-toxin (also known as verotoxin). In most cases, Shiga-toxin is produced by E.coli O157 bacteria, hence the name Shiga-toxin producing E.coli, or STEC. This is the most common cause of acute (sudden) kidney failure in children in Western Europe and North America.
- E.coli O157 can be found in the intestines of healthy cattle, goats and sheep, but can cause a severe gastroenteritis with bleeding in humans. Outbreaks can occur when contaminated meat is not cooked properly or when fresh products (cold meat, vegetables or salads) are contaminated with the bacteria.
- Those most likely to be affected are the very young (under 5), and very old
- HUS typically develops a few days after a bout of bloody diarrhoea
- Only about 1 in 20 people with E.coli O157 gastroenteritis get HUS as a complication
Atypical Haemolytic Uraemic Syndrome (aHUS) is a very rare and serious kidney condition caused by a fault in the complement system – a natural immune system which is designed to help destroy bacteria and viruses. If left untreated, it can become life threatening and will almost certainly result in kidney failure.
Other causes of HUS
Sometimes HUS may be associated with other medical problems and can develop:
- As a complication of organ transplantation, including bone marrow transplants
- As a reaction to certain drugs
- As a complication of cancer
- As a result of very high blood pressure
- As a result of pre-eclampsia, a serious complication of pregnancy
In STEC-HUS the first likely symptoms are the same as those caused by severe gastroenteritis:
- Bloody diarrhoea
- Vomiting (sometimes)
- Severe abdominal pain
In atypical HUS, patients sometimes report a ‘trigger’ such as minor illness or diarrhoea.
Regardless of the type of HUS, the symptoms of HUS are similar and can include:
- Reduced urine production
- Poor appetite
HUS is usually diagnosed through:
- Blood tests which may confirm you have anaemia and a reduction in platelets
- Blood and urine tests which may show a reduction in your kidney function
- A kidney biopsy (a medical procedure to take small samples of the kidney to look at under the microscope) [A1] may also be required to make an accurate HUS diagnosis
- Other specialist tests may help to confirm the cause of HUS and can include Blood and stool sample tests which may confirm the presence of E.coli O157 and Shiga-toxin.
Treatments will depend on how severe HUS is and the cause. They may include:
- Dialysis – usually this is only temporary, for a few days or weeks (especially if you have STEC-HUS)
- Blood transfusions
- Medication to reduce high blood pressure
- Plasma exchange – until the doctor is sure that you don’t have TTP. Plasma exchange is a procedure that removes plasma (a clear, straw-coloured liquid, which holds platelets, red and white blood cells in suspension) from the blood and replaces it with new plasma fluid.
If your HUS has been caused by an E.coli O157 infection, your local Environmental Health Department/Communicable Disease Unit will be informed and some extra precautions may be taken to prevent any spread of infection.
If another cause of HUS is suspected, then other specific treatments might help.
The outlook for patients with STEC-HUS is generally good and for most patients, there is recovery with little evidence of kidney damage. However, HUS is a serious disease and some people can have severely damaged kidneys or die as a result of HUS.
After recovery, you may be left with mild permanent kidney damage, but sometimes it can be more severe. In the most severe cases, other organs may be damaged too.
The outlook for patients with atypical HUS used to be poor, with many patients needing long-term dialysis with a high risk of the disease returning if transplanted. New treatments have become available that have improved outcomes in recent years.
The outlook for patients with other causes of HUS is unclear.
Help for you
If you have been diagnosed with HUS and have any questions or concerns about your illness don’t hesitate to speak to your kidney specialist or your nurse specialist at the kidney unit. The National aHUS Service – a team of aHUS experts based at the Newcastle upon Tyne Hospitals NHS Foundation Trust and Newcastle University – can also provide further information about HUS.
Reviewed April 2019
Need for more research
Research continues to have an important role in HUS and is ongoing to help us better understand the different causes of HUS. This may ultimately lead to better ways to manage these conditions.
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