Abstract: Objective　To investigate the clinical value of microRNA-21 (miR-21) expression in urine combined with three-dimensional ultrasound imaging (3D-US) in the diagnosis of urinary urothelial carcinoma (BUC). Methods　The urine samples of 78 BUC patients (the case group) and 80 patients with benign urinary tract diseases (the control group) were collected. The expression level of miR-21 in urine was detected by real-time quantitative PCR (qPCR). The relationship between miR-21 level and clinicopathological characteristics was analyzed. The 3D-US examination was performed, and receiver operating characteristic (ROC) curve was used to analyze the clinical value of urine miR-21 and miR-21 combined with 3D-US for BUC diagnosis. Results　The relative expression level of miR-21 in urine was significantly higher in case group than that of control group (P＜0.01). The content of urine miR-21 was significantly higher in the infiltrating group than that in the non-infiltrating group, and the expression of urine miR-21 was significantly higher in the high-grade group than that in the low-grade group (P＜0.05). ROC curve analysis showed that the sensitivity and specificity of urine miR-21 expression combined with 3D-US were 94.87% and 96.25% in the diagnosis of urothelial carcinoma, and Youden index was close to the result of cystoscopy. Conclusion　The upregulated expression of miR-21 in urine of BUC patients may be related to tumor progression. Urine miR-21 combined with 3D-US can be used as an effective and non-invasive diagnostic method for screening BUC.

Key words: urine, microRNAs, urinary bladder neoplasms, microRNA-21, three-dimensional ultrasonography, urothelium carcinoma