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Key Features

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Essentials of Diagnosis
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  • Bloody diarrhea is the usual presenting complaint, followed by hemolysis, thrombocytopenia, and renal failure

  • Circulating toxin causes endothelial damage, which leads to platelet deposition/consumption, and microvascular occlusion with subsequent hemolysis

  • Similar microvascular endothelial activation may also be triggered by

    • Drugs (eg, cyclosporine)

    • Viruses (HIV)

    • Pneumococcal infections

  • Rare cases are caused by genetic factors causing complement dysregulation (eg, factor H deficiency)

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General Considerations
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  • Most common glomerulovascular cause of acute renal failure in childhood

  • Diarrhea-associated form

    • Usually the result of infection with Shiga toxin–producing strains of Shigella or Escherichia coli

    • Ingestion of undercooked ground beef or unpasteurized foods is a common source

  • There are many serotypes, but the most common pathogen in the United States is E coli O157:H7

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Clinical Findings

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  • HUS due to Shigella or E coli

    • Begins with a prodrome of abdominal pain, diarrhea, and vomiting

    • Oliguria, pallor, and bleeding manifestations (principally gastrointestinal) occur next

  • Pneumococcal-associated HUS typically presents with

    • Documented pneumococcal pneumonia

    • Sepsis

    • Meningitis

  • Atypical HUS associated with complement dysregulation

    • An episode of HUS often develops following intercurrent illness

    • Presents with malaise and pallor

  • Hypertension and seizures develop in some children—especially those in whom severe renal failure and fluid overload develop

  • There may also be significant endothelial involvement in the central nervous system (CNS), heart, and pancreas

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Diagnosis

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  • Anemia may be profound

  • Red blood cell (RBC) fragments are seen on blood smears

  • Thrombocytopenia is often severe, but other coagulation abnormalities are less consistent

  • Serum fibrin split products are often present, but fulminant disseminated intravascular coagulation is rare

  • Hematuria and proteinuria are often present

  • Hemoglobinuria is occasionally observed due to marked RBC hemolysis

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Treatment

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  • Meticulous attention to fluid and electrolyte status is crucial

  • Antimotility agents and antibiotics for HUS caused by gastrointestinal infection should be avoided because antibiotics may cause release of large amounts of Shiga toxin

  • Timely dialysis improves the prognosis

  • RBC transfusions are often necessary

  • Platelet transfusions should be avoided unless there is active bleeding

  • Erythropoietin (epoetin alfa)

    • May reduce RBC transfusion needs

    • Indicated for patients with renal failure

  • Atypical HUS due to complement dysregulation

    • May benefit from plasmapheresis or plasma infusion

    • However, eculizumab has replaced these therapies

  • Plasma therapy should be avoided in pneumococcal HUS because it drives the HUS process by providing the anti–Thomsen-Friedenreich antibody

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Outcome

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Follow-Up
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  • Includes serial determinations of renal function with frequency dictated by the etiology, course, and subsequent findings and routine monitoring of blood pressure

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Complications
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  • Complications of acute kidney injury occur

  • Neurologic problems, particularly seizures, may result from hyponatremia, hypertension, or CNS vascular disease

  • Despite thrombocytopenia, many children are thrombophilic due to the underlying endothelial damage

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Prognosis
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  • Most commonly, children recover from ...

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