Final answer:
The likely diagnosis is Hemolytic uremic syndrome (HUS) caused by Shiga toxin-producing E. coli, which presents with oliguria, petechiae, and jaundice following bloody diarrhea due to the damage caused by the toxin to the kidney endothelial cells, resulting in acute renal failure and hemolysis.
Step-by-step explanation:
The most likely diagnosis for a four-year-old child presenting with oliguria, petechiae, and jaundice following an illness with bloody diarrhea is Hemolytic uremic syndrome (HUS) caused by Shiga toxin-producing Escherichia coli (STEC). This condition is characterized by the triad of acute renal failure, hemolytic anemia, and thrombocytopenia. The presentation of bloody diarrhea preceding the renal and hematological symptoms can often be attributed to infection with EHEC, which is a common cause of HUS in children.
STEC infection typically leads to symptoms such as bloody diarrhea without fever, cramping, and eventually may progress to more severe complications like HUS. The Shiga toxin produced by certain strains of Escherichia coli can cause significant damage to the endothelial cells in the blood vessels of the kidneys, leading to acute renal failure and other systemic manifestations such as petechiae due to thrombocytopenia and jaundice as a result of hemolysis.