Haemolytic Uraemic Syndrome in Children
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Direct answer
Pallor, oliguria and a preceding week of bloody diarrhoea in a toddler — with fragmented red cells and thrombocytopenia on the smear and a rising creatinine — is the triad of haemolytic uraemic syndrome: microangiopathic haemolytic anaemia, thrombocytopenia and acute kidney injury from endothelial injury, most often triggered by Shiga toxin-producing organisms after dysentery. In Indian outbreaks the classical trigger is Shigella dysenteriae type 1; globally Escherichia coli O157:H7 dominates. Management is meticulous supportive care — fluids, controlled transfusion, nutrition, dialysis when indicated — with two prohibitions: antibiotics and antimotility agents in bloody diarrhoea (both increase toxin exposure), and no routine steroids or plasma exchange in typical disease.
What you must remember
- The triad: microangiopathic haemolytic anaemia (haemoglobin often 5-8 g/dL with schistocytes and helmet cells, negative direct antiglobulin test), thrombocytopenia (typically 20,000-100,000/cumm, disproportionately mild relative to the anaemia), and acute kidney injury with oligoanuria.
- Typical (diarrhoea-associated) HUS: Shiga toxin from E. coli O157:H7 or Shigella dysenteriae type 1; children under five, summer outbreaks, prodrome of watery then bloody diarrhoea with abdominal pain; the Indian experience is Shigella-driven, with institutional and slum outbreaks.
- Why antibiotics are withheld: antimicrobial lysis of bacteria releases Shiga toxin and antimotility drugs retain it in the gut — both increase the risk and severity of HUS.
- Atypical HUS: complement-mediated (factor H and related mutations) or pneumococcal (neuraminidase exposes the T antigen — Coombs positive, unlike typical HUS) and drug or cobalamin C disease; no diarrhoea, relapsing, responds to eculizumab.
- Supportive care package: strict input-output with daily weight, correct hyperkalaemia and acidosis, treat hypertension (nifedipine acutely), transfuse packed cells slowly for symptomatic anaemia, avoid platelet transfusion unless bleeding, maintain nutrition.
- Dialysis indications: uraemia (encephalopathy or pericarditis), refractory hyperkalaemia, severe acidosis, fluid overload with hypertension or pulmonary oedema, and prolonged anuria — peritoneal dialysis is the usual Indian modality in small children.
- Complications and course: most children survive the acute phase with supportive care; mortality and chronic kidney disease concentrate in those with anuria over a week, hypertension and central nervous system involvement (seizures, stroke); long-term follow-up of blood pressure, proteinuria and renal function is mandatory for years.
- Infection-control reality: the index child sheds organisms; hand hygiene, exclusion from daycare during diarrhoea, safe water and food (avoid raw milk, undercooked meat) are the prevention stack — no vaccine exists.
How to work through it
A three-year-old, one week after bloody diarrhoea treated with "an antibiotic and a red suspension", is pale, puffy and anuric for a day. Assess volume and hypertension; send haemoglobin with smear (schistocytes), platelets, creatinine, electrolytes and lactate dehydrogenase. Fluid management is the tightrope — a child who is oligoanuric gets restriction to insensible losses plus output, not boluses, unless clearly hypovolaemic; hyperkalaemia gets calcium, salbutamol or glucose-insulin and a dialysis plan. Transfuse slowly for symptomatic anaemia, treat hypertension, and start peritoneal dialysis when uraemia, fluid overload or hyperkalaemia demand it. Counsel on the weeks-long course, dialysis as a bridge, and yearly renal follow-up.
The contrast case is the afebrile six-year-old with the same smear but no diarrhoea, a positive direct antiglobulin test and pneumococcal pneumonia: pneumococcal, complement-mediated territory — avoid plasma (it delivers complement), consider eculizumab, and think of the hereditary forms in any child with recurrent HUS or a family history.
How the exam frames it
Three testable rules lead. One, the triad plus the smear: fragmented cells with a negative Coombs test (typical HUS) versus positive in pneumococcal atypical HUS — a discriminating detail that separates the well-prepared. Two, the prohibitions: no antibiotics, no antimotility agents in bloody diarrhoea — the Indian vignette usually hides them in the treatment history and rewards the candidate who spots the harm. Three, the system: thrombotic thrombocytopenic purpura is the adult, brain-dominant relative with severe ADAMTS13 deficiency, while childhood typical HUS is kidney-dominant with only mildly low platelets. Programme-level Indian facts include Shigella outbreaks in crowded settings and rational drug use in dysentery.
Frequently asked questions
What is the diagnostic triad of haemolytic uraemic syndrome?
Microangiopathic haemolytic anaemia with fragmented red cells, thrombocytopenia, and acute kidney injury — classically following bloody diarrhoea from Shiga toxin-producing organisms.
Why are antibiotics avoided in diarrhoea-associated HUS?
Antibiotics lyse Shiga toxin-producing bacteria, releasing more toxin, and antimotility agents prolong gut exposure — both are associated with increased risk and severity of HUS.
Which organisms cause typical HUS in India?
Shigella dysenteriae type 1 in outbreaks, alongside Shiga toxin-producing Escherichia coli such as O157:H7 from contaminated food and water.
When is dialysis indicated in HUS?
Refractory hyperkalaemia, severe metabolic acidosis, fluid overload with hypertension or pulmonary oedema, symptomatic uraemia, and prolonged anuria — peritoneal dialysis is standard in small children.
How does atypical HUS differ and what is its specific therapy?
It occurs without diarrhoea, is complement- or pneumococcal (Coombs-positive)-mediated, tends to relapse, and is treated with eculizumab — with plasma therapy avoided in pneumococcal disease.