**Core Concept**
Hemolytic uremic syndrome (HUS) is a condition characterized by the triad of microangiopathic hemolytic anemia, acute kidney injury, and thrombocytopenia, often following a diarrheal illness caused by Shiga toxin-producing E. coli.

**Why the Correct Answer is Right**
In this scenario, the infant presents with a history of diarrhoea, which is a common precursor to HUS. The laboratory findings of fragmented RBCs (schistocytes) in the peripheral smear, elevated urea and creatinine levels indicating acute kidney injury, and a low platelet count (thrombocytopenia) are consistent with HUS. The presence of Shiga toxin-producing E. coli is suggested by the diarrheal illness, which leads to endothelial damage and subsequent microangiopathic hemolytic anemia.

**Why Each Wrong Option is Incorrect**
* **Option A:** Thrombotic thrombocytopenic purpura (TTP) is a similar condition to HUS, but it typically presents with more severe thrombocytopenia, neurological symptoms, and a lack of a preceding diarrheal illness.
* **Option B:** Acute kidney injury due to other causes such as sepsis or dehydration would not be accompanied by the characteristic microangiopathic hemolytic anemia and thrombocytopenia seen in HUS.
* **Option C:** Hemolytic uremic syndrome is a more likely diagnosis than Goodpasture syndrome, which typically presents with anti-GBM antibodies and renal and pulmonary involvement.
* **Option D:** Sickle cell disease would not typically present with a history of diarrhoea and the laboratory findings seen in this infant.

**Clinical Pearl / High-Yield Fact**
HUS is a medical emergency requiring prompt recognition and treatment to prevent long-term complications such as chronic kidney disease and stroke.

**Correct Answer:** C.