Hemolytic uremic syndrome (HUS) is a condition that can occur when small blood vessels become damaged and inflamed. This damage can cause clots to form in the vessels all through the body. The clots can damage the kidneys and other organs. Hemolytic uremic syndrome can lead to kidney failure, which can be life-threatening.

Anyone can get hemolytic uremic syndrome. But it's most common in young children. Most often, infection with certain strains of Escherichia coli (E. coli) bacteria is the cause.

Other infections, certain medicines or conditions such as pregnancy, cancer or autoimmune diseases can cause hemolytic uremic syndrome. It also can be the result of certain gene changes.

Hemolytic uremic syndrome is serious. But treating it in time leads to a full recovery for most people, especially young children.

The symptoms of hemolytic uremic syndrome vary, depending on the cause. The first symptoms of hemolytic uremic syndrome caused by E. coli bacteria might include:

• Diarrhea, which is often bloody.
• Pain, cramping or bloating in the stomach area.
• Fever.
• Vomiting.

All forms of hemolytic uremic syndrome damage blood vessels. This damage causes red blood cells to break down, called anemia. The condition also causes blood clots to form in the blood vessels and, in turn, damage the kidneys.

Symptoms of these changes include:

• Loss of color in the skin.
• Extreme tiredness.
• Easy bruising.
• Unusual bleeding, such as bleeding from the nose and mouth.
• Decreased urinating or blood in the urine.
• Swelling, called edema, of the legs, feet or ankles. Swelling occurs less often in the face, hands, feet or entire body.
• Confusion, seizures or stroke.
• High blood pressure.

When to see a doctor

See a member of your health care team right away if you or your child has bloody diarrhea or several days of diarrhea followed by:

• Urinating less.
• Swelling.
• Bruising.
• Unusual bleeding.
• Extreme tiredness.

Seek emergency care if you or your child doesn't urinate for 12 hours or more.

The most common cause of hemolytic uremic syndrome is infection with certain strains of E. coli bacteria. This is especially true for children under age 5. Some of the E. coli strains make a toxin called Shiga toxin. These strains are called Shiga toxin-producing E. coli (STEC).

Most of the hundreds of types of E. coli are typical and harmless. But some strains of E. coli can lead to hemolytic uremic syndrome.

Other causes of hemolytic uremic syndrome can include:

• Other infections. This can include infection with pneumococcal bacteria, human immunodeficiency virus (HIV) or a flu virus.
• Certain medicines. These can include some of the medicines used to treat cancer and some medicines used to keep people who receive donor organs from rejecting the organs.
• Complications of other conditions. Rarely, these conditions can include pregnancy or conditions such as autoimmune disease or cancer.

An uncommon type of hemolytic uremic syndrome, called atypical, can be passed down through families. People who inherit the gene that causes this form of hemolytic uremic syndrome don't always get the condition. But an infection, the use of certain medicines or ongoing health conditions can start hemolytic uremic syndrome in people with the gene.

Hemolytic uremic syndrome caused by E.coli can occur if you:

• Eat meat, fruit or vegetables with the bacteria.
• Swim in pools or lakes that have feces with the bacteria.
• Have close contact with an infected person.

The risk of getting hemolytic uremic syndrome is highest for:

• Children 5 or younger.
• People who have weakened immune systems.
• People with certain gene changes.

Hemolytic uremic syndrome can cause life-threatening complications, including:

• Kidney failure, which can be sudden, called acute, or happen over time, called chronic.
• High blood pressure.
• Stroke or seizures.
• Coma.
• Clotting problems, which can lead to bleeding.
• Heart problems.
• Digestive tract problems, such as problems with the intestines, gallbladder or pancreas.

Meat or produce that has E. coli won't always look, feel or smell bad. To protect against E. coli infection and other illnesses from foods:

• Don't drink milk, juice or cider that isn't processed to make it safe to drink, called pasteurized.
• Wash hands well before eating and after using the restroom and changing diapers.
• Clean utensils and food surfaces often.
• Cook meat to an inside temperature of at least 160 degrees Fahrenheit (71 degrees Celsius).
• Defrost meat in the microwave or refrigerator, not on the counter.
• Keep raw foods separate from other foods. Don't put cooked meat on plates that had raw meat on them.
• Store meat below produce in the refrigerator to cut the risk of liquids such as blood dripping on produce.
• Avoid unclean swimming areas. Don't swim if you have diarrhea.

A physical exam and lab tests can confirm a diagnosis of hemolytic uremic syndrome. Lab tests might include:

• Blood tests. These tests can show if the red blood cells are damaged. Blood tests also can show a low platelet count, low red blood cell count or a higher than usual level of a waste product usually removed by the kidneys, called creatinine.
• Urine test. This test can find unusual levels of protein and blood and signs of infection in urine.
• Stool sample. This test might find E. coli and other bacteria in stool.

If the cause of hemolytic uremic syndrome isn't clear, other tests might help find the cause.

Hemolytic uremic syndrome needs treatment in the hospital. Treatment involves replacing lost fluids and minerals to make up for the kidneys not removing fluids and waste as well as usual. It also might involve getting nutrition through a vein.

Transfusions

In the hospital, you might receive red blood cells or platelets through a vein, a process called a transfusion.

• Red blood cells can help reverse symptoms of anemia.
• Platelets can help blood clot better in people who are bleeding or bruising easily.

Medicines

Lasting kidney damage from hemolytic uremic syndrome might be treated with a medicine to lower blood pressure. This medicine might prevent or slow more kidney damage.

For complications or the atypical form of hemolytic uremic syndrome, treatment might include a medicine called eculizumab (Soliris) to help prevent more damage to the blood vessels.

Anyone taking eculizumab needs to have a vaccination to prevent meningitis, a possible serious side effect of the medicine.

Surgery and other procedures

Depending on the symptoms, the cause of hemolytic uremic syndrome and whether there are complications, treatment might include:

• Kidney dialysis. Dialysis removes waste and extra fluid from the blood. Dialysis is often done only until the kidneys begin working well again. But people with a lot of kidney damage might need long-term dialysis.
• Plasma exchange. Plasma is the fluid part of blood that helps blood cells and platelets circulate. Sometimes a machine is used to clear the blood of its own plasma and replace it with fresh or frozen donor plasma.
• Kidney transplant. Some people who have severe kidney damage from hemolytic uremic syndrome need a kidney transplant.

If you or your child has diarrhea for several days, call someone on your care team right away. Be ready to answer these questions:

• Have you seen blood in the diarrhea?
• Have you or your child had a fever, swelling or decreased urine output?
• How long have you or your child been having these symptoms?
• How long has it been since you or your child urinated?

What you can do in the meantime

If you or your child has an illness that causes vomiting or diarrhea, try to replace lost fluids with an oral rehydrating solution, such as Ceralyte, Pedialyte or Oralyte.