Prostacyclin in diarrhoea-associated haemolytic uraemic syndrome

The role of prostacyclin (PGI2) in the pathogenesis of haemolytic uraemic syndrome (HUS) is controversial. In part, confusion has been caused by failure to distinguish between two main sub-types of the syndrome: extrinsic, diarrhoea-associated HUS (D+ HUS), usually caused by infection with verocytotoxin-producing Escherichia coli or Shigella dysenteriae, and the heterogeneous group of non-prodromal forms where intrinsic factors predominate (D- HUS). This paper critically reviews data confined to D+ HUS. Two methods have been used to assess PGI2 synthesis; the generation of PGI2 from endothelium in the presence of HUS plasma in vitro and the measurement of stable metabolites in body fluids. No concensus could be reached with regard to the former. The reported increase of PGI2 stable metabolites in plasma may represent reduced clearance or increased carriage by plasma lipids. Apparent differences between studies of urinary excretion of PGI2 metabolites may reflect the way excretion was expressed. If the metabolite concentration is factored for urinary creatinine, it appears that renal excretion and thus renal synthesis of PGI2 is reduced. However, these are insufficient data on which to attribute the pathogenesis of D+ HUS to disordered PGI2 metabolism.