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
Which one of the following is the most common cause of abdominal mass in neonates – 
Select and explain. 
A. Neuroblastoma, B. Wilm's tumour, C. Distended bladder, D. Multicystic dysplastic kidneys
D: Multicystic dysplastic kidneys
Answer: D: Multicystic dysplastic kidneys 
Explanation: "Multicystic dysplastic kidney is the most common cause of an abdominal mass in the newborn"  - Nelson

A most common abdominal mass is a neonate → Multicystic renal dysplasia.
A Most common abdominal mass in 1 month to 3 years → Wilms a tumour or multicystic renal dysplasia.
A most common renal problem in 3 to 6 years → Minimal change disease-causing nephrotic syndrome.
A most common renal problem in 6 to 14 years → Acute post-streptococcal GN.