Multi-slice CT Urography after diuretic injection: initial results

Purpose: To investigate the feasibility of CT urography (CTU) using a multi -slice (MS) scanner and to find out whether a low-dose diuretic injection i s advantageous for the opacification of the urinary tract. Methods: MS-CTU was performed in 21 patients with urologic diseases. In 5/21 patients, 250 ml of physiologic saline Solution were injected. In 16/21 patients, 10 mg o f furosemide were injected 3-5 min before contrast material administration. A 4 x 2.5 mm collimation with a pitch of 1.25 and a tube curent of 100 - 1 50 mA were used. Scan time was 12 - 16 sec. 3 mm thin axial images with an overlap of 67 % were reconstructed. Multiplanar maximum intensity projectio n (MIP) images were postprocessed to obtain urographic views. Bone structur es were eliminated using the volume-of-interest method. Results: Furosemide -enhanced MS-CTU achieved either near complete or complete opacification in 30/32 (94 %) ureters and in 32/32 (100 %) pelvicaliceal systems up to a se rum creatinine of 150 mu mol/l. In our series, only one CTU scan per patien t was needed to obtain a diagnostic urogram after 10 min of contrast materi al injection. Ureteral compression was not necessary. When physiologic sali ne solution was used instead of furosemide, the radiopacity inside the enha nced pelvicalices was 4 - 5 times higher and more inhomogeneous. Diuretic-e nhanced MS-CTU was more accurate in the depiction of pelvicaliceal details. In combination with furosemide, calculi were well identified inside the op acified urine and were safely differentiated from phleboliths. Postprocessi ng times of up to 20 minutes were problematic as were contrast-enhanced sup erimposing bowel loops on MIP images. Conclusion: Preliminary results demon strate a good feasibility of furosemide-enhanced MS-CTU for obtaining detai led visualization of the entire upper urinary tract.