A mother brings her 3-year-old daughter to the emergency department because she is having trouble urinating. The child is not feverish. She has otherwise been healthy except for a bout of diarrhea about 10 days ago. Laboratory test results are as follows:

TEST RESULT
RBC 4.30 x 1012/L (moderate schistocytes present on peripheral blood smear)
WBC 5.00 x 109/L
PLT 28 x 109/L
HGB 13.0 g/dL
HCT 39%
MCV 89 fl
MCH 28 pg
MCHC 33%
BUN 85 mg/dL (RR: 8 - 24 mg/dL)
CREAT 3.3 mg/dL (RR: 0.2 - 1.3 mg/dL)

Based on the history and the laboratory results, what is the most likely diagnosis?
a. DIC
b. Bartonella sp. infection
c. HUS
d. Previous Clostridium sp. infection

Correct Answer: C