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Hemolytic Uremic Syndrome (HUS)

Quick Review

Child develops bloody diarrhea (sometimes it's not bloody) and abdominal pain and is given antibiotics which help with the diarrhea. Then about a week later is overly tired with pale skin and petechiae. They also often have reduced urine output (oliguria) and swelling (edema). CBC shows low hemoglobin (anemia), normal MCV (normocytic), low platelets (thrombocytopenia). Serum chemistry shows elevated BUN and Cr (renal damage). Liver function testing shows elevated bilirubin (suggests hemolysis). Peripheral blood smear shows schistocytes. Diagnosis is based on history and above laboratory tests. Treatment is supportive (fluids, electrolytes, blood transfusions, dialysis).

The cause is Shiga toxin producing bacteria, usually E. coli O157:H7 which is a strain of enterohemorrhagic E. coli (EHEC). The toxin destroys the epithelial lining of the colon leading to abdominal pain and bloody diarrhea. Once in the blood the toxin damages endothelium leading to platelet microthrombi which are especially problematic in small blood vessels. This used up platelets (thrombocytopenia) and RBCs are damaged by microthrombi in small vessels such as the glomeruli in the kidney. This leads to fragmented RBCs (shistocytes) and damaged small vessel areas (e.g. glomerular damage --> elevated BUN and Cr, edema, oliguria). This also results in microangiopathic hemolytic anemia (destruction/ fragmentation of RBCs) --> elevated bilirubin (jaundice, scleral icterus) and decreased haptoglobin.





Additional Notes

  • most often seen in children < 10 years old
  • history of diarrhea and antibiotic use for the diarrhea
  • exposure to E. coli O157:H7 via undercooked, contaminated ground beef; person-to-person; daycare center; raw unpasturized milk; sewage contaminated water


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