Risk Stratification of Patients with STEC Infection

Once a laboratory report confirms STEC, the next step is to determine whether the child is at high risk for progression to HUS. Risk stratification hinges on three key variables: the presence of bloody diarrhea, the duration of illness, and the toxin type if known.⁶ A child with STEC infection, bloody diarrhea, and less than 10 days of symptoms should be presumed high risk for HUS until proven otherwise. HUS develops a median of seven days after diarrhea onset. Children whose diarrhea has persisted for more than 10 days without signs of microangiopathy are generally considered low risk. If toxin typing identifies Stx2 or O157:H7, the child remains high risk regardless of symptom duration.⁶  

Not all laboratories provide toxin typing or serotyping results within a clinically useful timeframe. Emergency physicians should be familiar with their laboratory’s reporting practices and if needed, communicate directly with the lab to clarify whether toxin typing is performed, and when results are expected. In many cases, toxin typing may require an additional 24 hours beyond initial PCR detection.

Management of High-Risk Patients

Management of a high-risk child centers on close monitoring and hydration. Literature suggests that intravascular volume depletion at the onset of HUS is associated with worse renal outcomes, including higher rates of dialysis and increased mortality.⁷ Preventing dehydration is a cornerstone of management. Children identified as high risk should undergo daily reassessment of hydration status, urine output monitoring, and serial laboratory testing, including complete blood count, creatinine, LDH (to identify hemolysis), and electrolytes.

The platelet count is the earliest laboratory marker of evolving HUS.² A declining platelet count, even within the normal range, may indicate developing microangiopathy. For example, a drop from 400 to 275 x10⁹/L over 24 hours, although technically still normal, may represent early progression toward HUS in the context of STEC infection. Identifying such trends allows for early hospital admission and monitoring before the onset of overt renal failure or neurologic complications.

Children diagnosed with HUS require hospitalization, ideally in a center with pediatric nephrology expertise. Management includes careful attention to hydration, avoidance of nephrotoxic agents, monitoring for electrolyte disturbances and hypertension, and early recognition of neurologic complications such as seizures or altered mental status. Peritoneal dialysis is typically the preferred modality for renal replacement therapy in pediatric patients. Neurologic complications, including stroke and cerebral edema, are the most serious sequelae and the leading cause of mortality in HUS.⁸