Hemolytic uremic syndrome

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 (â…” 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 death due to microthrombi within pancreas

Differential Diagnosis

Causes of Glomerulonephritis

Microangiopathic Hemolytic Anemia (MAHA)

Thrombocytopenia

Decreased production

Increased platelet destruction or use

Drug Induced

Comparison by Etiology
ITP TTP HUS HIT DIC
↓ PLT YesYesYesYesYes
↑PT/INR NoNoNo+/-Yes
MAHA NoYesYesNoYes
↓ Fibrinogen NoNoNoNoYes
Ok to give PLT YesNoNoNoYes

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
  • LFTs
    • Increased bilirubin
  • Chemistry

Management
  • Initial management largely supportive with early fluid resuscitation
  • Insulin therapy if hyperglycemic and ketones (pancreatic insufficiency complication)
  • Antihypertensives
    • NifedipineER (0.25-0.5 mg/kg/day oral)
    • Labetalol 1-3 mg/kg/day, divided into twice daily dosing (12 mg/kg/day up to 1200 mg/day)
    • Nitroprusside 0.3-0.5 ug/kg/min IV (max 10 ug/kg/min)
  • Plasma exchange (plasmapheresis)
    • Usually performed if anuria or neurologic sequela
  • Eculizumab
    • Monoclonal anti-C5 antibody that interrupts complement cascade
  • 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
    • Usually reserved for symptomatic uremia, azotemia (BUN >80 mg/dL), fluid overload or electrolyte abnormalities refractory to medical therapy[1]
  • AVOID Antibiotics
    • May lead to worsening lysis of bacteria and further shiga toxin release
  • AVOID Antimotility agents

Disposition
  • Admit

See Also
  • TTP

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
  1. Niaudet P, Boyer OG. Overview of hemolytic uremic syndrome in children. Post TW, ed. UpToDate. UpToDate Inc. Accessed February 1st, 2021.
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