Differential Diagnosis for a 12-Month-Old Female with Bloody Diarrhea and Acute Renal Failure

• Single Most Likely Diagnosis

  • Hemolytic Uremic Syndrome (HUS): This condition is characterized by the triad of hemolytic anemia, acute kidney injury, and thrombocytopenia, often following a diarrheal illness caused by E. coli O157:H7 or other Shiga toxin-producing bacteria. The patient's presentation with bloody diarrhea, subsequent acute renal failure, and signs of hemolytic anemia (icteric sclera) and thrombocytopenia (petechiae and ecchymoses) makes HUS the most likely diagnosis.

• Other Likely Diagnoses

  • Shiga toxin-producing E. coli (STEC) infection: Although the patient was initially treated for a suspected E. coli infection, the development of HUS suggests that the infection was indeed caused by a STEC. This diagnosis is closely related to HUS but focuses on the infectious cause rather than the syndrome.
  • Thrombotic Thrombocytopenic Purpura (TTP): TTP is another condition characterized by thrombocytopenia, microangiopathic hemolytic anemia, renal failure, and neurological symptoms. While less common in children and often associated with a more complex presentation, TTP could be considered given the patient's thrombocytopenia and renal failure.

• Do Not Miss Diagnoses

  • Meningococcemia: This condition, caused by Neisseria meningitidis, can present with petechiae, ecchymoses, and shock, and can lead to renal failure. Although the primary presentation is usually with fever and signs of sepsis, the skin findings and potential for renal involvement make it a "do not miss" diagnosis due to its high mortality rate if not promptly treated.
  • Disseminated Intravascular Coagulation (DIC): DIC can occur in the context of severe infection or other systemic conditions, leading to both thrombosis and bleeding. The presence of petechiae, ecchymoses, and renal failure could suggest DIC, especially if there's an underlying severe infection or other predisposing condition.

• Rare Diagnoses

  • Atypical HUS (aHUS): This is a rare form of HUS not typically associated with diarrheal illness or STEC infection. It is caused by complement system dysregulation and can present similarly to STEC-HUS but without a clear infectious trigger.
  • Systemic Vasculitis (e.g., Henoch-Schönlein Purpura): While more commonly presenting with palpable purpura, abdominal pain, and arthritis, systemic vasculitis could be considered in the differential diagnosis, especially if there are other systemic symptoms or if the diagnosis of HUS or STEC infection is not confirmed.