Abstract: Objective To compare contrast- enhanced ultrasonography (CEUS), contrast- enhanced CT (CECT) and combined detection of two methods in the diagnosis of small renal masses, and differential diagnosis of different types of small renal masses by CEUS. Methods In 95 cases of small renal masses, there were 79 patients with small renal cell carcinoma and 16 patients with benign tumor. The diagnostic results of the three methods were compared based on the pathological results, which were used as the "gold standard" for the diagnostic efficacy. The ROC curve was drawn, and the area under the curve (AUC) was compared. The characteristics of the two groups were analyzed and compared by Q-Lab software in CEUS. The angiographic parameters included arrival time (AT), time to peak (TTP) and peak intensity (PI). CEUS patterns for several pathologic types of renal tumors with larger sample sizes were compared. The characteristic manifestations of small renal masses under CEUS were analyzed. Results The accuracy, sensitivity, specificity, positive predictive value, negative predictive value and AUC of CEUS were 87.37%, 93.67%, 56.25%, 91.36%, 64.29% and 0.750, the values for CECT were 88.42%, 93.67%, 62.50%, 92.50%, 66.67% and 0.775, and the values for combined detection of two methods were 95.79%, 98.73%, 81.25%, 96.30%, 92.86% and 0.869 respectively. The sensitivities of the three methods were high, but the specificities were the same. The combined detection showed better diagnostic efficacy than that of single diagnostic method. The AT and TTP of CEUS were earlier in small renal carcinoma group than those of benign nephrotic group, and PI was higher than that of benign nephrotic group (P＜0.05). There were significant differences in the contrasts of contrast enhancement methods between clear cell carcinoma, papillary cell carcinoma, chromophobe cell carcinoma, and angiomyolipoma (P＜0.01). There was little difference in contrast enhancement between the other types of carcinoma. False envelope can be observed by CEUS.‘Cystic area’of the detection rate was increased significantly by CEUS than that of conventional ultrasound. Conclusion Combined detection of CEUS and CECT can improve the diagnostic accuracy of small renal tumors. CEUS has great clinical value in the differential diagnosis of small renal masses, which is worthy of clinical promoting.

Key words: kidney neoplasms, tomography, spiral computed, diagnosis, differential, sensitivity and specificity, ROC curve, contrast-enhanced ultrasonography, contrast-enhanced CT