Coagulation changes associated with the hemolytic uremic syndrome.

The hemolytic uremic syndrome (HUS) is characterized by hemolytic anemia, acute renal failure, and thrombocytopenia. The pathological correlate is thrombotic microangiopathy of glomerular capillaries and arterioles in the kidneys and almost every other organ. The presence of platelet thrombi without extensive soluble coagulation system activation is a constant feature of HUS and thrombotic thrombocytopenic purpura (TTP). Damage to the endothelial cell seems to be a central event in the pathogenesis of HUS and TTP, resulting in loss of fibrinolytic properties and subsequent thrombotic occlusion of the microvasculature. According to earlier and recent studies, a variety of hemostatic alterations have been described. Among the many findings, low platelet counts, increased von Willebrand's factor (vWF), and normal fibrinogen are almost invariably observed. The dubious long-term outcome, even of postdiarrheal HUS, which is believed to have a more favorable prognosis than HUS of other etiopathogenic origin, necessitates further investigation of the pathophysiology of thrombotic microangiopathy and meticulous reevaluation of treatment strategies aimed at interfering with the process of thrombosis early in the disease course. The intention of this article is to highlight findings possibly relevant for disease management and to give an overview of the putative pathomechanisms involved.