This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
A 2-year-old child with severe dehydration has sudden-onset Gross Hematuria with a unilateral flank mass. The most likely diagnosis is 
Select and explain. 
A. Renal vein thrombosis, B. Hemolytic syndrome, C. Wilm's tumor, D. Hydronephrosis
A: Renal vein thrombosis
Answer: A: Renal vein thrombosis 
Explanation: None