Unenhanced multidetector CT (CT KUB) in the initial imaging of suspected acute renal colic: evaluating a new service

To evaluate a new imaging pathway for the investigation of patients presenting with suspected acute renal colic.

A retrospective review of 500 consecutive cases of suspected acute renal colic was undertaken to evaluate the initial results of a new imaging pathway introduced at our institution, which completely replaced the intravenous urogram (IVU) with unenhanced multidetector CT (CT KUB).

The positive rate for urolithiasis was 44% (221/500), the negative rate 46% (229/500) and the rate of other significant findings was 12% (59/500). Female patients had a low positive rate compared with male patients (27.5 versus 57.5%; p<0.001). Urological intervention was required in 28% (61/221) and these patients had a larger average stone size (6.6 versus 3.7 mm; p<0.001) and the stone was located more proximally. Out-of-hours imaging was performed in 37% (186/500), and these patients had a higher positive rate (52 versus 40%; p<0.001). Other findings included a wide range of acute non-urological conditions.

The feasibility of replacing the acute IVU with CT KUB in the initial assessment of suspected acute renal colic was demonstrated in the present study. The technique enables rapid diagnosis of urolithiasis, stratification of patients likely to proceed to urological intervention, and prompt diagnosis of a variety of other acute pathological conditions.