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Hemolytic Uremic Syndrome (HUS)

What is Hemolytic Uremic Syndrome (HUS)?

  • It is characterized by the triad of anemia, a low platelet count (thrombocytopenia), and acute renal failure.
  • HUS is the most common cause of acute renal failure in children.
  • HUS is a disease primarily seen in children younger than 4 years.

It develops suddenly after a syndrome complex of fever, vomiting, diarrhea, and abdominal pain. In some cases it may follow a respiratory illness.

What causes HUS in children?

  • The most common cause of HUS is a toxin produced by E coli type O157:H7. Additional agents include Shigella, Salmonella, Yersinia, and Campylobacter species.
  • HUS is also associated with viruses, including varicella, echovirus, and coxsackie A and B, as well as other infectious agents such as Streptococcus pneumoniae and Clostridium difficile.
  • Transmission of E coli O157:H7 appears to be caused by contaminated food, such as
    ground beef and other cattle products that are undercooked, and unpasteurized dairy products.
    Food contaminated with E coli does not look, smell, or taste bad.
  • Person-to-person contact, as well as contamination of public water supplies, may also have a role in the transmission of this bacterium.

E coli is normal flora in the gastrointestinal tracts of some healthy cattle, and children can contract it by petting a cow.

How common is HUS?

  • In individuals aged 5 years and younger, the average annual incidence is 2.65 cases per 100,000; in individuals aged 18 and younger, the average annual incidence is 0.97 cases per 100,000.
  • Incidence tends to parallel the seasonal fluctuation of E coli O157:H7 infections, which
    peaks between June and September.

What are the signs and symptoms of HUS?

  • Children usually present following an acute diarrheal illness or upper respiratory illness a few days to a few weeks before the onset of HUS.
  1. Fever is often absent in these cases.
  2. Lower gastrointestinal bleeding is common.
  3. Urine output is reduced or absent.
  4. Neurologic symptoms such as confusion or seizures may be observed in some patients.
  5. Petechiae may be present as a result of the low platelet count. (SEE PHOTO called Petechiae)
  6. Lethargy, irritability
  7. Pallor (pale) as a result of the low red blood cell count
  8. Cardiac involvement may lead to congestive heart failure (CHF) and arrhythmias.
  9. Hypertension and swelling may be observed 5-10 days after onset of illness.

How is HUS treated?

Management consists of early dialysis for acute renal failure and general supportive care, including treatment of hypertension.

Antibiotics are not effective except for certain forms caused by Shigella dysenteriae. In fact, antibiotic therapy may increase the risk of developing HUS in children with E coli O157:H7 colitis.

What is the prognosis for HUS?

  • Recurrent low platelet and red blood cell counts occur for 1-2 weeks
  • Urine output improves over 2-6 weeks
  • The mortality rate is 5-15%.
  • Older children and adults have poorer prognoses.
  • Approximately 85% of children recover if given supportive care. 15% develop long term kidney problems