This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urology, Subject name: Surgery
A 18 year old with pain and tenderness in left scrotum, and normal right scrotum, what should be the investigation done ? 
Select and explain. 
A. B mode USG, B. Color doppler, C. CT scan, D. MRI
B: Color doppler
Answer: B: Color doppler 
Explanation: Colour doppler should be done to look for the testicular aery pulsation as this is most probably a case of torsion testis on left side.Reference : page 1082 SRB's manual of surgery 5th edition