This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genito Urinary System, Subject name: Radiology
Investigation of choice in small renal calculi: 
Select and explain. 
A. Low dose non enhanced CT, B. High dose non enhanced CT, C. Low dose enhanced CT, D. High dose enhanced CT
A: Low dose non enhanced CT
Answer: A: Low dose non enhanced CT 
Explanation: Ans: a) Low dose non enhanced CT Low dose non enhanced CT scans can image renal stones better without much sacrifice in the quality of scanVirtually all stones (including uric acid stones) are radio-opaque on CT, except for stones associated with protease inhibitors used for treating HIV (Indinavir)Even calculi of sub mm size can be easily identified.Most common sites of calculi impaction are:Ureteropelvic junction - 35%Mid ureter - 7%Distal ureter - 33%UV junction -18%