laboratory features

Last reviewed 06/2021

Haematological abnormalities:

  • red cells:
    • anaemia, usual values 7-9 gHb/dL
    • fragmented red blood cells - schistocytes, helmet cells, triangle forms - in peripheral blood smear
    • normocytic, normochromic
    • marked reticulocytosis; occasional nucleated red cell
    • haemolysis - increased serum indirect bilirubin, LDH, and serum haemoglobin; absent haptoglobin
    • negative Coomb's test
  • platelets - usually around 50x10^9/L - reduced by consumption in microthrombi
  • leucocytes:
    • neutrophil leucocytosis
    • a poor prognosis is associated with leucocyte counts of greater than 20x10^9/L
  • kaolin clotting time and prothrombin time are usually normal; a clotting abnormality is suggestive of septicaemia

Biochemical abnormalities:

  • uraemia, out of proportion to the mild degree of apparent dehydration
  • hyponatraemia is common, which may be a consequence of diarrhoea and vomiting, or a result of endothelial damage causing capillary leak.
  • hypoalbuminaemia occurs in severe cases


  • generally HUS presents with oliguria but patients can present with polyuria - a proteinuria of typically, 1-2g of protein per day