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: Radiology
Investigation of choice for hydronephrosis – 
Select and explain. 
A. Excretory Urography, B. USG, C. MRI, D. Cystourethrography
B: USG
Answer: B: USG 
Explanation: "Ultrasonography is the initial modality of choice in the investigation of hydronephrosis". —Imaging for students.