Hemolytic uremic syndrome - NYSORA

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Hemolytic uremic syndrome

Learning objectives

  • Describe the etiology of hemolytic uremic syndrome
  • Management of hemolytic uremic syndrome

Definition and mechanisms

  • Hemolytic uremic syndrome (HUS) is a triad of renal failure, hemolytic anemia, and thrombocytopenia and is the most common cause of renal failure in infancy and childhood
  • HUS can lead to widespread inflammation and thrombotic microangiopathy, the formation of platelet microthrombi in the walls of small blood vessels
  • Most cases occur after infectious diarrhea due to a specific type of E. coli 
  • Other causes include S. pneumonia, Shigella, Salmonella, and certain medications
  • Two predominant types:
    • Typical HUS
      • Preceded by 4-6 days of diarrhea
      • Most commonly caused by infection with Shiga toxin-producing E. coli (O157:H7)
      • The mortality rate is 3%-5%
      • Approximately two-thirds of children require dialysis although 85% regain normal renal function
    • Atypical HUS
      • 60-50% can be attributed to dysregulation of the alternative complement pathway
      • Involves mutations in factor H, factor I, CD46/MCP, factor B, and C3 components
      • A mortality rate of up to 25% in the acute phase
      • 50% of patients require renal replacement therapy at some point
  • The first symptoms of infection can emerge between 1 to 10 days later, but usually after 3 to 4 days
  • Affects about 1.5 per 100,000 people each year
  • A multisystemic disease affecting:
Cardiovascular system
Congestive heart failure
Severe Hypertension
Respiratory system
Severe respiratory insufficiency
Pulmonary edema
Congestive heart failure
BiochemicalEvidence of Acute kidney injury (AKI)
Acid-base and electrolyte disturbances
Abnormal liver function tests associated with hepatitis
HematologicalHemolysis rapidly appears
Hemoglobin falls to as low as 4 g/L
Renal systemProteinuria, hematuria and oliguria leading to anuria
Gastrointestinal tractHemorrhagic gastritis
ImmunologicalSevere infections: peritonitis, meningitis, osteomyelitis

Signs and symptoms

  • Abdominal pain, cramping, or bloating
  • Bloody diarrhea
  • Fever
  • Vomiting
  • Pale coloring, including loss of pink color in cheeks and inside the lower eyelids
  • Extreme fatigue
  • Shortness of breath
  • Easy bruising or unexplained bruises
  • Unusual bleeding
  • Decreased urination or blood in the urine
  • Edema
  • Confusion, seizures, or stroke
  • High blood pressure
  • Low platelets



  • Travel and dietary history
  • Complete blood count: anemia (Hb < 10 g/dl) and thrombocytopenia
  • Comprehensive metabolic panel (elevated creatinine, elevated indirect bilirubin, and elevated lactate dehydrogenase)
  • Urinalysis
  • Peripheral smear



Hemolytic uremic syndrome, thiopental, rapid sequence induction, isoflurane, desflurane, atracurium, mivacurium, sepsis, hemolytic crisis, hemodialysis

Suggested reading

  • Pollard BJ, Kitchen, G. Handbook of Clinical Anaesthesia. Fourth Edition. CRC Press. 2018. 978-1-4987-6289-2.
  • Noris M, Remuzzi G. Hemolytic uremic syndrome. J Am Soc Nephrol. 2005;16(4):1035-1050.

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