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Hemolytic uremic syndrome (HUS)

Overview

Hemolytic uremic syndrome (HUS) is a condition caused by the abnormal destruction of red blood cells. The damaged red blood cells clog the filtering system in the kidneys, which can lead to life-threatening kidney failure.

HUS usually develops in children after five to 10 days of diarrhea — often bloody — caused by infection with certain strains of Escherichia coli (E. coli) bacteria. Adults also can develop HUS due to E. coli or other types of infection, certain medications, or pregnancy.

HUS is a serious condition. But timely and appropriate treatment leads to a full recovery for most people, especially young children.

Symptoms

Signs and symptoms of HUS can include:

  • Bloody diarrhea
  • Decreased urination or blood in the urine
  • Abdominal pain, vomiting and occasionally fever
  • Pallor
  • Small, unexplained bruises or bleeding from the nose and mouth
  • Fatigue and irritability
  • Confusion or seizures
  • High blood pressure
  • Swelling of the face, hands, feet or entire body

When to see a doctor

See your doctor immediately if you or your child experiences bloody diarrhea or several days of diarrhea followed by:

  • Decreased urine output
  • Unexplained bruises
  • Unusual bleeding
  • Extreme fatigue

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

Causes

The most common cause of HUS — particularly in children under the age of 5 — is infection with E. coli bacteria that produce certain toxins (shiga toxin-producing E. coli or STEC). One such strain of E. coli is known as E. coli O157:H7. Other strains of E. coli have also been linked to HUS.

E. coli refers to a group of bacteria normally found in the intestines of healthy humans and animals. Most of the hundreds of types of E. coli are normal and harmless. But some strains of E. coli — including those that cause HUS — are responsible for serious foodborne infections.

E. coli can be found in:

  • Contaminated meat or produce
  • Swimming pools or lakes contaminated with feces

Sometimes, E. coli infection is spread through close contact with an infected person, such as within a family or at a day care center.

Most people who are infected with E. coli, even the more dangerous strains, don't develop HUS.

Other causes of HUS can include:

  • The use of certain medications, such as quinine sulfate (Qualaquin), some chemotherapy medications, medications containing the immunosuppressant cyclosporine (Neoral, Sandimmune, Gengraf) and anti-platelet medications
  • Certain infections, such as HIV/AIDS or an infection with the pneumococcal bacteria
  • Rarely, pregnancy

Susceptibility to an uncommon type of HUS — known as atypical HUS, primary HUS or complement-mediated HUS — can be passed down genetically to children. People who have inherited the mutated gene that causes atypical HUS won't necessarily develop the condition. The mutated gene might be activated after an upper respiratory or abdominal infection.

Risk factors

The risk of developing HUS is highest for:

  • Children under 5 years of age
  • People over 75
  • People with certain genetic changes that make them more susceptible

Complications

HUS can cause life-threatening complications, including:

  • Kidney failure, which can be sudden (acute) or develop over time (chronic)
  • High blood pressure
  • Stroke
  • Coma
  • Intestinal problems, such as inflammatory colitis
  • Heart problems

Diagnosis

To confirm a diagnosis of HUS, your doctor is likely to recommend lab tests, including:

  • Blood tests. These tests can determine if your red blood cells are damaged. Blood tests can also reveal a low platelet count, low red blood cell count or a higher than normal level of creatinine, a waste product normally removed by your kidneys.
  • Urine test. This test can detect abnormal levels of protein, blood and signs of infection in your urine.
  • Stool sample. This test might detect toxin-producing E. coli and other bacteria that can cause HUS.

Treatment

HUS requires treatment in the hospital. To ease signs and symptoms and to prevent further problems, treatment might include:

  • Fluid replacement. Lost fluid and electrolytes must be carefully replaced because the kidneys aren't removing fluids and waste as efficiently as normal.
  • Red blood cell transfusions. Red blood cells, transfused through an intravenous (IV) needle, can help reverse signs and symptoms of HUS including chills, fatigue, shortness of breath, rapid heart rate, yellow skin and dark urine.
  • Platelet transfusions. IV transfusions of platelets can help your blood clot more normally if you're bleeding or bruising easily.
  • Plasma exchange. Plasma is the part of blood that supports the circulation of blood cells and platelets. Sometimes a machine is used to clear the blood of its own plasma and replace it with fresh or frozen donor plasma.
  • Kidney dialysis. Sometimes dialysis is needed to filter waste and excess fluid from the blood. Dialysis is usually a temporary treatment until the kidneys begin functioning adequately again. But if you have significant kidney damage, you might need long-term dialysis.

Appropriate treatment leads to a full recovery for most people with HUS, especially young children.

If you have lasting kidney damage from HUS, your doctor might recommend a medication to lower your blood pressure, to prevent or delay further kidney damage. Your doctor might also recommend follow-up visits to evaluate your kidney function every year for five years.

Atypical HUS

This uncommon type of HUS is generally treated with plasma exchange. Your doctor might also recommend a medication — eculizumab (Soliris) — that can prevent the continued destruction of healthy cells. To prevent serious infection, you or your child might have a meningococcal vaccine before receiving this medication.

Preparing for an appointment

If you or your child is experiencing symptoms of HUS after several days of diarrhea, call your doctor immediately and be prepared to answer these questions:

  • Have you noticed blood in the diarrhea?
  • Have you or your child had fever, swelling or decreased urine output?
  • How long have you or your child been experiencing 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, it's a good idea to try to replace the fluids that have been lost with an oral rehydrating solution, such as CeraLyte70, Pedialyte or Oralyte.

Prevention

Meat or produce contaminated with E. coli won't necessarily look, feel or smell bad. To protect against E. coli infection and other foodborne illnesses:

  • Avoid unpasteurized milk, juice and cider.
  • Wash hands well before eating and after using the restroom and changing diapers.
  • Clean utensils and food surfaces often.
  • Cook meat to an internal temperature of at least 160 degrees Fahrenheit.
  • Defrost meat in the microwave or refrigerator.
  • Keep raw foods separate from ready-to-eat foods. Don't place cooked meat on plates previously contaminated by raw meat.
  • Store meat below produce in the refrigerator to reduce the risk of liquids such as blood dripping on produce.
  • Avoid unclean swimming areas. Don't swim if you have diarrhea.

Last updated: July 2nd, 2016

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