This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genitourinary radiology, 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: Excretory Urography Also known as IVP Used to evaluate pelvic and calyceal system USG: IOC for fluid anywhere in the body Investigation of choice for Hydronephrosis MRI: Multiplanar imaging Good soft tissue resolution IOC for Neurological diseases IOC for Brain tumors: CE - MRI IOC for spinal metastasis: MRI IOC for ventricular function: CINE-MRI Preferred for Bone Marrow evaluation Cystourethrography: Also known as voiding cystourethrography IOC for Vesicoureteral reflex Also used to evaluate posterior urethra