Haemolytic uraemic syndrome (HUS)

Haemolytic uraemic syndrome is generally seen in young children and produces a triad of:

1. acute kidney injury
2. microangiopathic haemolytic anaemia (MAHA)
3. thrombocytopenia

Most cases are secondary (termed 'typical HUS'):

• classically Shiga toxin-producing Escherichia coli (STEC) 0157:H7
  • 'verotoxigenic', 'enterohaemorrhagic'
  • this is the most common cause in children, accounting for over 90% of cases
• pneumococcal infection
• HIV
• rare: systemic lupus erythematosus, drugs, cancer

Primary HUS ('atypical') is due to complement dysregulation.

Investigations

• a blood film is the most useful initial diagnostic test
  • remember that in HUS there is a ΜΑНΑ (i.e. Coombs-negative haemolysis) resulting from intravascular red blood cell fragmentation → formation of ѕϲhiѕtοϲytеs
  • anaemia: a haemoglobin level < than 8 g/dL
  • thrombocytopenia
• U&E: acute kidney injury
• stool culture
  • looking for evidence of STEC infection
  • PCR for Shiga toxins

Blood film with schistocytes highlighted

Management

• treatment is supportive e.g. Fluids, blood transfusion and dialysis if required
• there is no role for antibiotics, despite the preceding diarrhoeal illness in many patients
• the indications for plasma exchange in HUS are complicated
  • as a general rule plasma exchange is reserved for severe cases of HUS not associated with diarrhoea