Abstract: Objective:To determine preliminarily the feasibility and a one-stop strategy of CT urography and angiography in one scanning acquisition using 4-slice MDCT. Materials and methods:Seventy-five consecutive patients (41 men and 34 women; mean age 52 years; age range, 22 to 86 years) without evident hydronephrosis who asked for CT urography (CTU) examination received the new technique of CTUA using by 4-MDCT. Twice-bolus protocol consisted of 50 mL of contrast material (300 mg per milliliter of iodine) immediately after urinating at 2~2.5 mL/sec at 0 seconds and 50 mL at 3.5~4 mL/sec at 20 minutes through the forearm vein. CT scanning (CTUA) started with one breath-hold 20 seconds after the second injection with 10 mm of slice thick, 0.75:1 of pitch and 15 mm/rot of speed. Five minutes after the second injection, CT scanning started again using the same parameters for routine CTU. After thin-slice reconstruction of 5 mm thick and 2.5 mm interval, all the images data were then transferred to an ADW 4.2 workstation to post-process by 3D VR software. Excellent rate of visualization of renal parenchyma, urinary tracts, and main arteries on CTUA and CTU images were reviewed and assessed independently first and interpreted agreeably by two experienced radiologists. Statistical analysis was performed using variance analysis (ANOVA) to evaluate the difference, and P<0.05 is considered statistically significant. Results:The technique success rate of CTUA was 100%, and excretory-corticomedullary phase source images were acquired, which the good rate of distinguishing the renal cortex from the medulla and calices was 100% (148/148), while the CTU source images were not well depicted the renal cortex, medulla and calicessimultaneously (P=0.000). The good opacification of the renal calices, ureter, bladder, and the renal artery, the aorta and iliac artery was achieved in 95.94% (142/148), 94.59% (140/148), 95.95% (71/74), and 87.16% (129/148), 96% (72/75), 81.33% (122/150) of segments, respectively in CTUA, and 100% (148/148), 97.97% (145/148), 98.65% (73/74), 0%, 0%, 0% of segments, respectively in CTU. Urinary tracts were shown slightly better in CTU than in CTUA (P>0.05), but the arteries were shown significantly better in CTUA than in CTU (P=0.000), and the CTUA could accurately reveal the tumor, stones, inflammation, prostatic hyperplasia, atherosclerosis and all kinds of deformities of urinary tract and vessels. Conclusion:It is technically adequate for a one-stop CTUA to achieve by using a single excretory-corticomedullary phase CT scanning after twice-bolus contrast injection with routine concentration and volume with once venepuncture. It three-dimensionally reveals renal parenchyma, urinary tract and main arteries simultaneously and the renal cortex, medulla and calices are also distinguished clearly.