Haemolytic Uraemic Syndrome

Overview

Haemolytic uraemic syndrome (HUS) is a rare condition that mainly affects the blood and the kidneys. It happens when small blood vessels become damaged and inflamed. This damage causes three things to happen at the same time: red blood cells get broken up too early (haemolytic means blood cell breakdown), the number of platelets in the blood drops (platelets are tiny cells that help blood clot), and the kidneys stop working as well as they should. Most people who get HUS are children, and most recover well with good hospital care. HUS is serious, so it needs to be treated in hospital quickly, but many people make a full recovery.

No, HUS is rare. It is one of the less common causes of sudden kidney problems in children, and it affects only a small number of people each year. Because it is rare, many parents and even some general clinicians may not have seen it before. That is why knowing the warning signs is useful.

The most common type usually affects children under 5 years old, but older children, teenagers and adults can also get it. A less common type, caused by a problem in the immune system, can affect people of any age and sometimes runs in families. HUS can affect anyone, but it is more often seen in young children after a bout of diarrhoea.

Symptoms

Common symptoms

• Feeling very tired, weak or lacking energy
• Pale skin, lips or gums (a sign of low red blood cells)
• Passing much less urine than usual, or no urine at all
• Bruises or tiny red or purple dots on the skin (a sign of low platelets)
• Bleeding that is harder to stop than usual, such as nosebleeds or bleeding gums
• Swelling in the face, hands, feet or legs
• Feeling sick, being sick, or having a swollen, uncomfortable tummy

Symptoms in children

• Often starts with diarrhoea that may become bloody, with tummy pain and vomiting
• Becoming unusually sleepy, floppy or hard to wake
• Fewer wet nappies or much less urine than usual
• Pale, grey-ish skin colour
• Irritability or crying more than usual
• Refusing feeds or drinks
• Small bruises or pinprick red spots appearing on the skin

Symptoms in older adults

• Marked tiredness and breathlessness with everyday tasks
• Less urine, or needing to pass urine much less often
• Confusion or feeling more muddled than usual
• Bruising or unusual bleeding
• Swelling in the legs or ankles
• Loss of appetite and feeling generally unwell
• Symptoms after a recent bout of diarrhoea or a tummy infection

Causes

Main causes

• The most common cause is an infection of the gut by certain types of bacteria, often picked up from contaminated food or water. These bacteria make a toxin (a poison) that damages small blood vessels. This is sometimes called 'typical' HUS.
• A less common cause is a problem with the body's complement system — part of the immune system that usually fights infection. When this system is overactive, it can damage blood vessel walls. This is sometimes called 'atypical' HUS.
• More rarely, HUS can be linked to certain medicines, some infections such as pneumonia, pregnancy-related problems, transplant, or conditions affecting the immune system.
• Some cases are linked to genes that affect how the complement system works, which is why HUS can sometimes run in families.

Risk factors

• Being a young child, especially under 5 years old
• Recent diarrhoea or a tummy infection, particularly bloody diarrhoea
• Eating undercooked meat, unpasteurised dairy products, or food washed in contaminated water
• Drinking or swallowing contaminated water, or swallowing water while swimming in lakes or pools
• Close contact with farm animals or an infected person, such as in a household or nursery
• Having a family history of atypical HUS or certain immune system conditions
• Having a weakened immune system or another serious illness

When to see a doctor

See a doctor urgently if:

• You or your child has bloody diarrhoea
• There is much less urine than usual, or a baby has fewer wet nappies
• You notice unusual paleness, extreme tiredness or sleepiness
• New bruising or tiny red or purple spots on the skin
• Swelling of the face, hands or legs that has come on quickly
• Vomiting that means drinks cannot be kept down

Book a routine appointment if:

• You are recovering from a tummy infection and want advice about what to watch for
• You have had HUS before and need a routine kidney check-up
• You have a family history of atypical HUS and want to discuss your risk
• You have ongoing high blood pressure or protein in the urine after a previous kidney problem

Diagnosis

HUS is diagnosed in hospital using blood and urine tests. Doctors look for the three key signs: red blood cells that are breaking down, a low platelet count, and kidneys that are not filtering properly. They will also ask about recent diarrhoea, food and travel, and any family history. Sometimes a small sample of kidney tissue is taken to look at under a microscope, but this is not always needed. If the less common immune-related type is suspected, extra blood tests may be done to check the complement system and, in some cases, genetic testing.

Tests that may be done

• Full blood count — checks red cells and platelets
• Blood film — a look at the blood cells under a microscope to spot damaged red cells
• Kidney blood tests (urea and creatinine) — show how well the kidneys are filtering
• Tests for broken-down red blood cells, such as lactate dehydrogenase and haptoglobin
• Urine tests — check for blood and protein in the urine
• Stool sample — looks for the bacteria that can cause the common type of HUS
• Blood pressure measurement and monitoring of urine output
• In some cases, kidney imaging, a kidney biopsy, or tests of the complement system and genes

What to expect at your appointment

If HUS is suspected, you or your child will usually be admitted to hospital. There will be regular blood tests, often several times a day at first, and staff will keep a close eye on how much urine is being passed. This can feel busy and worrying, especially for parents, but it is how the team spots changes early and acts on them. Many people need to stay in hospital for days or sometimes longer. Ask questions whenever you want to — the team expects it and it helps you feel more in control.

Treatment

There is no single cure for HUS. Treatment focuses on supporting the body while it recovers, protecting the kidneys, and preventing complications. Most people need to be in hospital so that fluids, blood counts and kidney function can be watched closely. The right approach depends on which type of HUS is causing the illness and how unwell the person is.

Self-care at home

• Drink fluids as advised by the medical team — follow their guidance on how much, because both too little and too much can be a problem in kidney illness
• Rest as much as your body needs and build activity back up slowly
• Keep all follow-up appointments, even when you feel well again
• Wash hands well with soap and water, especially after the toilet and before preparing food
• Keep a simple note of how often you pass urine if the team asks you to
• Avoid anti-diarrhoea medicines and don't take any new medicines or supplements without checking with a pharmacist or doctor first
• Tell any healthcare professional you see that you have had HUS, especially before scans or new treatments

Medical treatments

Treatment in hospital usually includes careful control of fluids given into a vein, close monitoring of blood tests and urine output, and support for the kidneys. Some people need blood transfusions because their red blood cell count is low, and some need platelets. If the kidneys stop working well, dialysis is used — this is a machine that cleans the blood while the kidneys recover. For the immune-related (atypical) type, specialists may use treatments that calm the overactive complement system, or a procedure called plasma exchange, where the liquid part of the blood is filtered and replaced. Antibiotics and some other medicines may be avoided in the common diarrhoea-linked type, as they can sometimes make things worse — your medical team will decide what is safe. Because treatment choices vary so much between people, your doctors will explain what they recommend and why.

When is surgery considered?

Surgery is not usually part of treating HUS. In rare cases, a kidney transplant may be considered later for someone whose kidneys have not recovered, usually after careful specialist assessment. Occasionally a small procedure is needed to place a tube for dialysis. Your kidney team will discuss any procedure with you in detail.

Living with this condition

Many people recover fully from HUS and return to normal life. Others need ongoing checks because the kidneys can be left with some scarring. This usually means regular blood pressure checks, urine tests and blood tests, often at a kidney clinic. In the months after HUS, some people feel more tired than usual and need to pace themselves. Children often bounce back faster than adults. It helps to keep a simple record of appointments and any symptoms you notice, and to tell your clinic about any changes rather than waiting for the next visit.

Lifestyle tips

• Eat a balanced diet — if you have kidney changes, your team may suggest some adjustments, such as watching salt
• Stay active in a way that suits you, building up gradually after illness
• Keep blood pressure healthy through diet, activity and any treatment your doctor recommends
• Avoid smoking and keep alcohol within sensible limits
• Practice good food hygiene — cook meat thoroughly, wash hands, and avoid unpasteurised dairy or untreated water
• Tell your doctor about any new medicines, including over-the-counter ones, so your kidneys can be protected
• Keep up routine vaccinations as advised by your GP or kidney team

Diet and exercise

There is no special HUS diet, but eating well supports recovery. A balanced mix of vegetables, fruit, whole grains, beans and lean protein is a good starting point. If your kidneys are not working at full strength, your team may advise on salt, potassium, phosphate or fluid. Exercise is encouraged once you feel ready — short walks and gentle activity first, then more as energy returns. Ask your team if you are unsure what is safe for you.

Mental health and emotional wellbeing

A sudden illness like HUS can be frightening, both for the person affected and for family members. It is very common to feel anxious afterwards, to worry when a child gets a tummy bug, or to feel low for a while. These feelings usually ease, but they deserve attention. Talk to your GP or kidney team if worry, low mood or disturbed sleep is affecting daily life — support such as talking therapy is available and helps. If you or someone you care for has thoughts of harming themselves or feels unable to cope, contact your local emergency number or a crisis line in your country straight away, or go to the nearest emergency department. You do not have to manage alone.

Prevention

The most common type of HUS cannot always be prevented, but you can lower the chance of the gut infection that often comes first. Wash hands well with soap and water after using the toilet, changing nappies, handling animals and before cooking or eating. Cook meat thoroughly, keep raw and cooked foods apart, wash fruit and vegetables, and avoid unpasteurised milk and untreated water. Don't swallow water while swimming in lakes, rivers or pools. If someone in the household has diarrhoea, keep towels and utensils separate and clean surfaces carefully. The immune-related type of HUS cannot be prevented through hygiene, but knowing your family history can help your doctors monitor you.

Vaccines

There is no vaccine that prevents HUS. Keeping up with routine vaccinations is still worthwhile, because other infections can be harder on the body during and after kidney illness. Ask your GP or kidney team which vaccinations are right for you.

Screening programmes

There is no general screening programme for HUS. If you have a family history of the immune-related type, or a known gene change linked to it, specialist teams may offer counselling and testing for relatives. After any episode of HUS, regular blood pressure and urine checks act as a form of monitoring so that kidney changes are picked up early.

Complications

If left untreated

• Worsening kidney failure, which may need dialysis
• Dangerously low red blood cells (anaemia) causing severe tiredness and breathlessness
• Low platelets leading to bleeding problems
• High blood pressure
• Fluid building up in the lungs, causing breathlessness
• Seizures, confusion or stroke-like symptoms if the brain is affected
• Long-term kidney damage or scarring, sometimes developing years later
• Bowel problems, or inflammation of the pancreas in rare cases

Long-term outlook

The outlook is encouraging for most people, especially children with the common diarrhoea-linked type — many recover fully and go on to live normal, healthy lives. Some people are left with mild kidney changes and need regular check-ups, and a small number need longer-term kidney care. The immune-related type needs ongoing specialist management, and modern treatments have improved outcomes a great deal. Whatever your situation, regular follow-up gives your team the best chance to catch problems early and support you well.

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