Hemolyticuremic

Hemolytic-uremic syndrome, commonly abbreviated HUS, is a form of thrombotic microangiopathy characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. It is generally categorized into typical (Shiga toxin–associated) HUS and atypical HUS, the latter often arising from dysregulated complement activation. Typical HUS most often follows a diarrheal illness and is especially common in children.

Pathophysiology involves injury to endothelial cells in small blood vessels, leading to formation of microthrombi, red blood cell destruction as they pass through narrowed vessels, and consumption of platelets. Shiga toxin–producing bacterial infections, notably Escherichia coli O157:H7, commonly trigger typical HUS, whereas atypical HUS results from genetic or acquired abnormalities in the alternative complement pathway. Kidney vasculature damage underlies the principal sign of acute kidney injury.

Clinical presentation typically includes sudden onset of pallor from hemolysis, bruising or bleeding due to low platelets, decreased urine output or swelling from kidney injury, and often a recent diarrheal illness. Laboratory findings show schistocytes on peripheral smear, elevated lactate dehydrogenase, low haptoglobin, increased bilirubin, thrombocytopenia, and impaired kidney function. ADAMTS13 activity testing helps distinguish HUS from thrombotic thrombocytopenic purpura.

Management is mainly supportive: careful fluid and electrolyte management, blood pressure control, and renal replacement therapy if needed. Antibiotics are generally avoided in suspected Shiga-toxin–mediated disease because they may increase toxin release. Atypical HUS may respond to complement-directed therapy such as eculizumab. Prognosis varies; children typically recover with supportive care, but atypical or severe cases can lead to lasting kidney damage or require ongoing dialysis. Prevention focuses on food safety and outbreak control, including avoiding undercooked meat and contaminated foods.