Non-contrast computed tomography (CT) abdomen has emerged as a first line investigation in suspected upper urinary tract obstruction. Underlying causes can usually be ascertained on computed tomography of kidneys, ureters and bladder (CT KUB). However, further investigations may be required to delineate/confirm underlying pathology like ureteropelvic junction obstruction (UPJ), differentiation between obstruction and residual dilatation. Actual protocol of CT KUB for evaluation of stone disease and haematuria vary on institutional guidelines. CT KUB is not only extremely sensitive and specific in the diagnosis of stone; it is now used in the pre-operative nomograms in predicting success of various endourological interventions like percutaneous nephrolithotomy (PCNL) and shock wave lithotripsy (SWL). Determination of stone density, stone volume, stone composition, skin to stone distance, presence of ureteral wall oedema, perinephric oedema are highly predictive of stone free rate. CT recognition of various anomalies, presence of retro-renal colon, horse-shoe kidney, malrotation, etc. can help in better planning to avoid complications. One of the major limitations of CT is the radiation dose, besides cost and availability. Modification in technique and technological innovation has resulted in significant dose reduction from 4.5 to about 1 mSv.
Part of the book: Computed Tomography