The epithelial damage may result from toxins released by bacteria or viruses. In both, the platelet and fibrin microthrombi within the renal microvasculature are accompanied by thrombocytopenia and a microangiopathic hemolytic anemia. Older children and adults have poorer prognoses. HUS is reported less often in adults. Most adult patients are women who have been taking oral contraceptives, are postpartum, or are suffering obstetric complications including preeclampsia and eclampsia.
Children usually present following an acute diarrheal illness.
Urine output is reduced or absent. Neurologic symptoms may be observed in some patients and may result from uremia. Findings reflect those of the inciting prodromal illness. Hypertension and oliguria may be observed. As in TTP, HUS is primarily a clinical diagnosis coupled with consistent laboratory findings.