What is the appropriate management for a child under 5 with suspected Hemolytic Uremic Syndrome (HUS) following a diarrheal illness?

Management of Suspected HUS in Children Under 5 Following Diarrheal Illness

Immediately evaluate for dehydration and initiate aggressive intravenous fluid resuscitation while avoiding antibiotics, antimotility agents, narcotics, and NSAIDs—this is the single most critical intervention to prevent progression to oligoanuric renal failure. 1

Immediate Assessment and Stabilization

Hydration Status Evaluation

• Assess skin turgor, mucous membranes, mental status, pulse, and capillary refill time to determine dehydration severity 2
• Administer IV fluids during the diarrhea phase—this reduces the risk of oligoanuric renal failure in children who subsequently develop HUS 1
• Dehydration at admission is associated with increased need for dialysis in post-diarrheal HUS 1

Critical Medications to AVOID

• Do not administer antibiotics—they may worsen outcomes and potentially increase HUS risk in STEC infections 3, 4, 5
• Avoid antimotility agents, narcotics, and NSAIDs during acute phase 4, 6, 5

Diagnostic Workup

Immediate Laboratory Testing

When anemia plus thrombocytopenia presents in the emergency setting, immediately obtain: 1

• Haptoglobin (reduced in hemolysis)
• Indirect bilirubin (elevated)
• LDH (elevated)
• Direct Coombs test (negative in HUS)
• Peripheral blood smear for schistocytes

Establish HUS Diagnosis

The diagnostic triad consists of: 1

• Platelet consumption: platelets <150,000/mm³ or 25% reduction from baseline
• Microangiopathic hemolysis: non-immune hemolytic anemia with negative Coombs, elevated LDH, reduced haptoglobin, schistocytes present
• Renal involvement: hematuria and/or proteinuria and/or elevated creatinine

Distinguish STEC-HUS from Atypical HUS

The timing of diarrhea onset is critical for differentiation: 1, 3

• STEC-HUS typically appears 4-5 days after diarrhea onset
• Simultaneous onset of diarrhea and HUS suggests atypical HUS
• Short diarrhea prodrome or concomitant appearance should raise suspicion for atypical HUS

Essential Pathogen Testing

When clinical history suggests Shiga toxin-producing organism, apply diagnostic approaches that detect Shiga toxin (or genes encoding them) and distinguish E. coli O157:H7 from other STEC in stool 1

• Test for both STEC O157 culture AND Shiga toxin/genes 1
• If available, distinguish between Shiga toxin 1 and Shiga toxin 2 (stx2 is more potent and associated with higher HUS risk) 1
• Consider Shigella dysenteriae type 1, especially with international travel history 1

Rule Out TTP

• Urgently measure ADAMTS13 activity (severely deficient <10 IU/dL indicates TTP, not HUS) 1
• This must be done as an urgent test when TMA is evident 1

Monitoring for HUS Progression

For diagnosed or suspected STEC infection (especially O157 or stx2-producing strains), perform frequent monitoring to detect early HUS manifestations: 1

• Daily hemoglobin and platelet counts during days 1-14 of diarrheal illness
• Daily electrolytes, BUN, and creatinine
• Examine peripheral blood smear for red blood cell fragmentation when HUS suspected
• A single normal CBC is insufficient—patients with decreasing platelet count trend are at greater risk 1
• Continue daily monitoring until platelet count increases or stabilizes with resolved symptoms 1

Age-Specific Considerations

First Year of Life

When atypical HUS presents in infants <1 year old, consider mutations in complement-unrelated genes (DGKE, WT1) 1, 3

• Also consider methylmalonic acidemia with homocystinuria cblC type (MMACHC)—an ultra-rare metabolism-associated HUS from cobalamin deficiency 1, 3

Supportive Management

Renal Support

• Approximately 46-67% of HUS cases require dialysis 4, 6
• For dialysis indication, peritoneal dialysis should be first-choice treatment 4
• Monitor for volume overload, hypertension, and rising creatinine 1

Neurological Monitoring

• Neurological involvement occurs in 10-20% of patients and is the first cause of death 1, 4
• If neurological symptoms suspected (seizures, encephalopathy, motor symptoms, vision changes, generalized weakness), obtain: 1
  • Neurological consultation
  • EEG
  • Brain MRI

Multidisciplinary Approach

This condition should be treated as a medical emergency with immediate supportive measures 1

• Many patients require ICU admission at presentation 1
• Early recognition, appropriate treatment, and multidisciplinary approach are critical to reduce risk of irreversible organ damage or death 1

Prognosis and Follow-Up

Acute Outcomes

• Overall mortality ranges 1-5% 4
• Immediate outcome is most often favorable with supportive care 7, 8

Long-Term Sequelae

• One-third of patients suffer long-term renal morbidity (proteinuria, hypertension, decreased GFR) 4
• The longer the duration of anuria, the greater the risk of sequelae 4
• Any patient with HUS history needs long-term renal follow-up 4
• Regular follow-up recommended until laboratory and clinical parameters normalize 1

Atypical HUS Prognosis

• Represents 5-10% of all HUS cases 3, 7
• Has relapsing course with >50% progressing to chronic renal dysfunction 3
• 10% mortality rate 3
• Complement inhibitors (eculizumab) have considerably improved prognosis 8