ObjectiveTo analyze the relationship between image development types and delay time in computed tomography urography (CTU) examination and to investigate the value of choosing reasonable delay time to get the best images. MethodWe collected the data of 62 patients who underwent multi-slice CTU examination without fully developed images within 8 minutes from January 2010 to May 2014. There were 35 unilateral and 27 bilateral delayed imaging patients with a total of 89 cases. According to the degree of imaging development after the delayed 8 minutes, we divided it into 4 levels as follows:level 0 (no development), levelⅠ (light development), levelⅡ (partial development) and levelⅢ (full development). LevelⅢ was not included in this study. For level 0 to levelⅡ, we delayed scan for 15 to 1 440 minutes. ResultsAs the imaging development degree decreased, the delay time obviously extended. LevelⅡ could be fully displayed after 15 to 150 minutes of delayed scan. LevelⅠ could be fully displayed after 150 to 720 minutes. Level 0 still had no imaging development after 120 minutes, so there was no need to continue scanning. ConclusionsSelecting appropriate delay time of CTU based on the type of delayed imaging development can avoid unnecessary repeated delay scans, get the best development images, and estimate the kidney secretion functions, which is most helpful for accurate diagnosis of urinary system related diseases.