The Role Of Multiphasic Multidetector CT In Diagnosing Small Renal Masses

Objectives:To explore the possibility that if we can predict the histopathology types of small renal masses(SRMs) by analyzing the way of enhancement with multiphasic multidetector computed tomography of SRMs (diameter≤<4cm),in order to provide basis for clinical therapy.Methods:The CT imaging of107cases diagnosed as SMRs proven by pathology were analyzed retrospectively,including70clear cell renal cell carcinoma(CCRCC),13papillary renal cell carcinoma(PRCC),10chromophobe renal cell carcinoma(CRCC), renal oncocytoma(RO) and of renal angiomyolipoma absent of fat(RAML). There are59lesions on the left kidney and the others are on the right kidney, and each of the patients had one lesion. All of the cases were performed with multiphasic multidetector CT scanning,including plain scan, corticomedullary phase(CMP), nephrographic phase(NP) and excretory phases(EP).Details:1. Evaluating the density of tumor, presence of calcification and fat in plain scan, as well as the degree and pattern of the tumor in the contrast CT.2. Measuring actual CT value of the solid parts of tumor in each phase respectively.3. Measuring CT value of aorta in each phase and calculating the ratio with the actual CT value of tumor in the same phase. The CT findings were analyzed and processed by SPSS16.0software. P<0.05were considered significant. At the same time, STATA11.0were used to describe the receive operating characteristic curve(ROC) so that we can depict the area under the curve(AUC) as well as the sensitivity and specificity of every threshold.Result:46CCRCCs were homogeneous density and3of them has calcification in plain scan. CCRCCs were enhanced in contrast scan with the present of "fast-in and fast-out"enhancement in general.11PRCCs were homogeneous density and2PRCCs were visualized as calcification. Slight-homogeneous enhancement and "delayed enhancemenf"was performed in PRCCs.6CRCCs were homogeneous density and2were calcified,2CRCCs were heterogeneous density with low-density area. CRCCs presented as slight or moderate enhancement and5CRCCs were homogeneous enhancement while1CRCC was "spoke-wheel-like enhancement", which has the trend of "delayed enhancement". ROs were detected as homogeneous density in plain scan and significant enhanced in contrast CT, of which4were homogeneous and2were heterogeneous enhancement. The peak value in1of6appeared in CMP while the others were in NP. RAMLs were tested heterogeneous density in plain scan and5of them can detected the density of fat. The enhancement showed the tumor were heterogeneous enhancement and appeared enhancement pattern as "fast-in and fast-out". The peak value of3RAMLs appeared at NP. Statistically significant differences were revealed among the actual enhanced CT value, the ratio of enhanced CT value to aorta CT value in all enhancement phases between CCRCCs and non-CCRCCs, CCRCCs and benign tumors respectively. There are no statistically significant differences of actual enhanced CT values of tumor between CCRCCs and benign lesions in NP and EP (P=1.000, P=0.185).The actual contrast threshold value of CCRCCs in three phases was larger than84.2HU,96.5HU,77.5HU differentially comparing with non-CCRCCs. The ratio of actual enhanced CT value and aorta CT value at the same phase was calculated as larger than0.315in CMP,0.776in NP and0.89in EP distinctively, which had a high sensitivity and specificity to identify the CCRCCs and non-CCRCCs. All of the6indications showed statistically significant differences between the two groups. To CCRCCs and benign tumors,if the actual enhanced CT value of tumor was larger than134.5HU,the sensitivity and specificity was48.5%and92.86%. Sensitivity was61.43%、41.43%、70%respectively while the specificity was92.86%、92.86%、78.57%respectively when it comes to distinguish CCRCCs to benign tumors if the ratio of actual enhanced CT value of tumor to aorta CT value at the same phase reached larger than0.487in CMP,0.946in NP and0.905in EP. All the4indications has statistically significant differences in the two groups.Conclusion:Multiphasic multidetector CT examination plays an important role in diagnosis and differential diagnosis of SRMs.Analyzing the way and degree of enhancement,calcification of the tumor and density of fat to some extent helps in diagnosing the different pathology types of SMRs. The actual enhanced CT value of tumor in CMP lager than84.2HU,the ratio of actual enhanced CT value to aorta CT value at the same phase in CMP larger than0.315were used to be the standard to diagnose CCRCCs and exclude non-CCRCCs are of highest value.The ratio of actual enhanced CT value of tumor to aorta CT value in CMP lager than0.487and0.905in EP were applied to be the standard to diagnose CCRCCs and exclude benign renal tumors are of higher value.