Hemolytic Uremic Syndrome (HUS)

Pathophysiology/Presentation

• Bloody diarrhea, abdominal cramping, may have fever

• As diarrhea resolves: bloody urine, oliguria, HTN, edema

• May become critically ill quickly

• Commonly involved other systems:

  • CNS (mental status change, seizures)

  • GI (severe colitis with necrosis and perforation)

  • Pancreatitis

Workup/Diagnosis

• KFP – signs of AKI - high: BUN, Cr, K; low: Ca, HCO3

• CBC – low Hb, low Plts, may have high WBCs

• Signs of hemolysis: high LDH, schistocytes on blood smear, low haptoglobin

• Urine: many RBCs, moderate to severe proteinuria

• Normal/neg: complements, ANA, ADAMTS13, Coombs

• Stool test for E. Coli and toxin: best to test while having diarrhea (at time of kidney disease, stool may be negative)

• Kidney biopsy not needed

Treatment

• Supportive: diuretics, manage HTN, may need dialysis

• PRBCs: avoid (will hemolyze), give if Hb<6 or symptomatic

• Plts: avoid (promote microthrombi formation), give for procedures or active bleeding

• Plasma exchange (PE): may use in very sick patients

• Eculizumab: may use in very sick patients

• If caught early in the few days window between diarrhea and HUS development, give generous IV hydration – may reduce thrombus formation and ischemic organ damage (monitor for fluid overload as this done)

Prognosis/Follow up

• May fully self-resolve as toxin cleared

• 5% mortality rate in acute phase

• Toxin effects in acute phase may leave sequelae:

  • Chronic kidney disease (CKD)

  • pancreatic insufficiency/IDDM

  • CNS deficits

  • HTN

  • colonic strictures

• Poor prognostic factors: high WBCs, fever, oligoanuria > 14 days, younger age (<5 yrs)

• Higher risk of more severe STEC+HUS: early use of antimotility agents (retain toxin in colon) and antibiotics (more toxin release)

• Needs ongoing follow-up with nephrology as may develop CKD and HTN later in life

• Make sure atypical HUS (due to complement dysregulation via autoimmune or genetic mechanisms) is not missed, if not convincing STEC+HUS