<prompt> Investigation of choice in small renal calculi:Low dose non enhanced CTHigh dose non enhanced CTLow dose enhanced CTHigh dose enhanced CT  <response>: 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 IndinavirEven calculi of sub mm size can be easily identified.Most common sites of calculi impaction are:Ureteropelvic junction - 35Mid ureter - 7Distal ureter - 33UV junction -18 