Hemolytic uremic syndrome

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Background

  • Abbreviation: HUS
  • Similar to TTP (which is more common in adults), but associated with less central nervous system and more renal involvement.
  • Most cases occur in children <10yr (⅔ of cases in < 5yr)
  • 80-90% cases due to E. coli O157:H7 infection
  • Shiga toxin may induce autoantibody to CD36 (found on endothelial cells and platelets)
  • May also be caused by shigella, yersinia, campylobacter, salmonella

Types

  1. Typical
    • Occurs 2-14d after development of infectious diarrhea (bloody, no fever)
  2. Atypical
    • Occurs in older children and adults
    • Extrarenal involvement is common (difficult to distinguish from TTP)
    • May be caused by atypical pathogens (EBV, S. pneumo) or immunosuppression

Clinical Features

Triad

  1. Acute renal failure
  2. Thrombocytopenia
  3. Microangiopathic Hemolytic Anemia (MAHA)

Other Associated Conditions

  • Enteritis
  • Nausea/vomiting, diarrhea (usually bloody), +/- fever
  • Hyperglycemia
  • Pancreatic beta-cell dealth due to microthrombi within pancreas

Differential Diagnosis

Causes of Glomerulonephritis

Microangiopathic Hemolytic Anemia (MAHA)

Thrombocytopenia

Decreased production

  • Marrow infiltration (tumor or infection)
  • Viral infections (rubella, HIV)
  • Marrow Suppression (commonly chemotherapy or radiation)
  • Congentital thrombocytopenia
    • Fanconi anemia
    • Alport syndrome
    • Bernand Soulier
  • Vitamin B12 and/or folate deficiency

Increased platelet destruction or use

Drug Induced

  • sulfa antibiotics, ETOH, ASA, thiazides/furosemide

Evaluation

  • CBC
    • Anemia
    • Thrombocytopenia
    • Peripheral smear checking for schistocytes, burr cells, helmet cells, spherocytes and segmented red blood cells
  • LDH (elevated)
  • Haptoglobin (decreased)
  • Reticulocyte count (appropriate)
  • PT/PTT/INR (normal; differentiates from DIC)
  • Stool tests
    • Shiga toxin, E. coli O157:H7 test
  • Urinalysis
    • Hematuria, casts
  • LFT
    • Increased bilirubin
  • Chemistry
    • Creatinine, hyperkalemia (renal failure)

Management

  • Plasma exchange (plasmapheresis)
    • Usually performed if Anuria
  • Eculizumab
  • Transfusion of RBCs(only severe bleeding)
    • Generally only indicated if plasma exchange cannot be performed immediately
  • Platelet Transfusion is AVOIDED
    • Only used for life-threatening bleeding or intracranial hemorrhage under guidance from hematologist
    • Platelet infusion may lead to acutely worsened thrombosis, renal failure, and death
  • Hemodialysis/Hemoperfusion
    • Often needed for renal failure and hyperkalemia treatment
  • AVOID Antibiotics
    • May lead to worsening lysis of bacteria and further toxin release
  • AVOID Antimotility agents
    • Leads to prolonged gut exposure to toxins

Disposition

  • Admit

See Also

References

  • Corrigan J. Boineau FG. Hemolytic-uremic syndrome. Pediatr Rev. Nov 2001;22(11):365-9
  • George J. Clinical practice. Thrombotic thrombocytopenic purpura. N Engl J Med 2006; 354:1927