Hemolytic Uremic Syndrome (HUS)

  • Medical Author:
    Benjamin Wedro, MD, FACEP, FAAEM

    Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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What are the signs and symptoms of hemolytic uremic syndrome?

In typical HUS, gastroenteritis occurs with abdominal cramping, vomiting and profuse bloody, watery diarrhea, as a symptom up to a week before the onset of HUS. This may cause significant dehydration, weakness and lethargy, as well as electrolyte imbalances because of the loss of sodium, potassium, and chloride in the vomit and diarrhea. These symptoms may resolve before the onset of anemia and the kidney failure symptoms of HUS.

The anemia and uremia usually present with weakness, lethargy, and sleepiness. Seizures may occur. Purpura or small areas of bleeding in the skin may be seen because of low platelet counts (thrombocytopenia).

How is hemolytic uremic syndrome diagnosed?

The health care professional will have a suspicion of the disease based on the history and physical examination, especially in a small child who has had the typical bloody diarrhea. Abnormal laboratory tests help confirm the diagnosis. These abnormal findings may include:

  • Hemolytic anemia: the red blood cell count is low and a peripheral blood smear, in which blood is examined under a microscope, will show that the red cells have been damaged and destroyed. This differentiates hemolysis (hemo=blood + lysis=destruction) from anemia caused by decreased production of blood cells in the bone marrow.
  • Thrombocytopenia: a low platelet count
  • Uremia: Kidney function can be measured by testing the level of waste products in the blood normally filtered by the kidney. BUN (blood urea nitrogen) and creatinine are measures of this kidney function. When levels rise, it is an indication of kidney failure or uremia in which the kidneys cannot clear the waste products of metabolism from the body.
  • Abnormal urine findings: Blood and protein may be found in the urine when normally they are not present.
  • Stool cultures: Since E. coli O157:O7 is the most common cause of HUS in children; attempts are made to culture the bacteria from stool samples. The body usually clears the bacteria from the stool within a week, so a negative test does not exclude the disease. A positive test helps confirm HUS and will be reported to public health authorities to try to determine the source of the infection. In 2011, outbreaks in Europe were traced by public health authorities to tainted sprouts.

In atypical HUS, history is very important to search for other potential causes of the disease. Unfortunately, the case may not be found in up to half of cases of atypical HUS.

One of the distinguishing findings between HUS and TTP is a normal neurologic examination. The brain function is normal in HUS.

Medically Reviewed by a Doctor on 4/8/2015

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