Objective To elucidate the correlation between the enhancement degree of renal clearcell carcinoma (RCC) on dynamic contrast-enhanced CT and multiple vascular morphometric characteristics including microvessels and mature vessels.Methods A retrospective review was carried out on the records of 37 patients pathologically diagnosed with RCC who underwent plain and triphasic contrast-enhanced CT.The absolute (enhancement attenuation-pre-enhancement attenuation) and relative(absolute enhancement value÷cortex enhancement attenuation) enhancement values of RCC were measured in arterial,venous and delayed phases.And all lesions were divided into hypervascular and hypovascular groups.The number,mean area,perimeter and diameter,shape factor (4π*area/perimeter2) and the total area of microvessels and mature vessels were obtained by CD34 or a-SMA immunohistochemical staining.Then the correlation of radiographic parameters and various vascular morphometric parameters were analyzed.Results In arterial,venous and delayed phases,the absolute enhancement values were positively correlated with the number and the total area of microvessels and mature vessels (P<0.05),meanwhile the relative enhancement values were positively correlated with the number of microvessels and mature vessels(P<0.05).In venous and delayed phases,there were negative correlations of the relative enhancement values with mean area,perimeter and diameter of mature vessels(P<0.05).However, no correlations were found between other enhancement and vascular parameters (P>0.05).In addition, the significant differences in the number of microvessels and mature vessels between hypervascular and hypovascular groups were found (P<0.05).Conclusion CT enhancement degrees of RCC are related to multiple vascular morphometric indicators,which gives us more insights in the mechanism of RCC enhancement on CT.