About hemolytic uremic syndrome

What is hemolytic uremic syndrome?

What is hemolytic uremic syndrome (HUS)?

Hemolytic uremic syndrome (HUS) is a disease of two body systems, the blood stream and the kidney. Hemolysis describes the destruction of red blood cells. In hemolytic uremic syndrome, blood within capillaries, the smallest blood vessels in the body, begins to clot abnormally. When red blood cells pass through the clogged capillaries, they are sheared apart and broken. (hemo=blood +lysis=destruction). The second failed system, kidney failure (uremia), occurs when urea and other waste products build up in the bloodstream because the kidneys cannot filter and dispose of them. (urea=a waste chemical + emia= in the blood).

HUS is also related to another disease caused by a similar normal clotting process within the capillaries called thrombotic thrombocytic purpura (TTP). Within the medical literature, these two conditions are often considered together. HUS is more widely known, however, because it has been discussed in the press because of its relationship to a special type of E. Coli (Escherichia coli) infection associated with food poisoning.

HUS can be classified as typical or atypical. The typical type is associated with gastrointestinal (GI) signs and symptoms including vomiting and diarrhea. Atypical HUS is not associated with GI symptoms.

What are the symptoms for hemolytic uremic syndrome?

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.

What are the causes for hemolytic uremic syndrome?

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.

What are the treatments for hemolytic uremic syndrome?

What is the treatment for hemolytic uremic syndrome?

Typical HUS in children tends to be self-limiting, and supportive care is often all that is needed. This may include intravenous fluids for rehydration and rebalancing of electrolytes like sodium and potassium, which can be lost with the diarrhea.

Blood transfusions are only used for the most severe cases of anemia in which the hemoglobin falls below 6 or 7 g/dL (depending on age, the normal value is 11-16).

Kidney failure may be managed expectantly (by observation and supportive care), and dialysis is not often required.

Adults with atypical HUS tend to become more ill and need more aggressive therapy than children with the condition. In addition to the supportive care discussed above, plasmapheresis or plasma exchange may be required. Since it is thought there is an abnormal chemical in the plasma stimulating the abnormal clot formation, removing the plasma and replacing it with donor plasma is helpful in treating adult HUS.

Dialysis may be needed while awaiting recovery of the kidneys from the illness.

Eculizumab (Soliris) has been approved by the FDA for the treatment of atypical HUS. It is a monoclonal antibody that decreases the blood clotting in the capillary blood vessels, decreasing the potential destruction of cells. This type of therapy decreases the body's immune capabilities, and the risk of infection increases.

What is the prognosis of hemolytic uremic syndrome?

Typical HUS in children tends to be self-limiting, and full recovery is most likely.

Adults do less well. Without aggressive therapy like plasmapheresis and dialysis, up to 25% of those affected with atypical HUS may die in the acute phase of the disease, and 50% may have developed long-term kidney impairment.

Patients with HUS not related to a diarrheal illness have a worse prognosis than those whose illness is due to gastrointestinal infection.

In those patients with genetically caused HUS, relapsing illness is common as are kidney failure requiring dialysis and death.

What are the risk factors for hemolytic uremic syndrome?

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

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