Radiolueent kidney stones -

Ans. is 'b' i.e., Uric acid o Lucent stones on plain x-ray KUB are -Uric acidTriametrineCystineXanthineIndinavir stonePure matrix stoneso Almost all stones are opaque on CT scan, varying considerbly in density, but INDINAVIR and PURE MATRIX stones are usually undetectable on CT.o Non contrast helical CT scan is gold standard investigation for urolithiasis now.o CT signs diffemtiating ureteric calculus and pelvic pblebolith are soft tissue rim sign - soft tissue around stone - ureteric calculus.o Tail sign - soft tissue extending towards calcification - phlebolith.