Prospective comparison of nonenhanced helical computerized tomography and Doppler ultrasonography for the diagnosis of renal colic.

PURPOSE: We evaluate the accuracy of nonenhanced helical computerized tomography (CT) and Doppler ultrasonography for the diagnosis of renal colic.
MATERIALS AND METHODS: Our study includes 109 patients, with 218 kidneys, who presented with unilateral flank pain. All patients underwent nonenhanced helical CT, Doppler ultrasonography and excretory urography (IVP). CT was evaluated for the presence of ureteral stones and manifestation of ureteral obstruction. For Doppler ultrasonography the renal resistive index was measured for the left and right kidneys in each patient, and change in resistive index between ipsilateral and contralateral kidneys was calculated and considered positive for ureteral obstruction with values 0.04 or greater. As a reference standard, absence of obstruction was considered if IVP was negative and the cause of flank pain was confirmed not to be urological. Obstruction was diagnosed not only by positive IVP, but also by patient followup until passage or retrieval of ureteral stones. Results of CT and change in resistive index were compared with those of the reference standard.
RESULTS: Unilateral ureteral obstruction was confirmed in 52 patients, while no obstruction was found in 57. Of the 57 patients without ureterolithiasis the change in resistive index results was negative in all patients with a specificity of 100%, while CT was negative in 55 with a specificity of 96%. Of the 52 patients with ureteral obstruction CT was positive in 50, and change in resistive index was positive in 47 with a sensitivity of 96% and 90%, respectively, with a difference of no significant value.
CONCLUSIONS: Nonenhanced helical CT and change in resistive index are sensitive and specific tests that can contribute significantly to the diagnosis of acute unilateral renal obstruction. They can replace IVP, particularly in situations in which it is undesirable.