BACKGROUND: The characteristics of testicular viscoelasticity could help identify azoospermia. This study sought to assess the diagnostic value of viscoelasticity for male infertility using high-frequency ultrasound shear wave dispersion (SWD) imaging. METHODS: In this prospective study, 330 consecutive patients with male infertility were allocated to the ultrasound normal group, the varicocele group, the non-obstructive azoospermia (NOA) group, and the obstructive azoospermia (OA) group, and 30 healthy volunteers were allocated to the control group. Two physicians with over 10 years of experience each in andrology ultrasound measured the viscosity coefficient, dispersion slope, and elasticity of each testis, respectively. The testicular viscoelasticity was compared among the patients from the four groups and the control group. The inter-reader variability between the two physicians was assessed. The diagnostic efficacy of viscoelasticity for NOA was evaluated by receiver operating characteristic (ROC) curve analysis. Binary logistic regression was used to analyze the risk factors for NOA. RESULTS: Among the 360 participants, the viscosity coefficient, dispersion slope, and elasticity were all higher in the NOA group than the other groups (P<
0.002). The inter-reader variability was excellent [intraclass correlation coefficient (ICC): 0.87-0.96]. Comparisons between the patient groups categorized by testicular volume (TV) revealed no statistically significant difference in the elasticity of testes with smaller volumes (5-10 mL) between the OA and NOA groups (P=0.130), but differences in the viscosity coefficient and dispersion slope were observed (P=0.009 and P=0.031, respectively). The ROC curve analysis showed that the viscosity coefficient had the highest diagnostic efficacy for NOA, with an area under the curve (AUC) of 0.834. In the logistic regression, the viscosity coefficient [odds ratio (OR) =665
95% confidence interval (CI): 1.62-2,732.64], elasticity (OR =1.35
95% CI: 0.98-1.84), and TV (OR =0.51
95% CI: 0.44-0.61) were identified as independent risk factors for NOA. CONCLUSIONS: The viscosity coefficient, dispersion slope, and elasticity all have diagnostic value for NOA. Unlike elasticity, the differential diagnosis of azoospermia by the viscosity coefficient and dispersion slope is not affected by TV. Testicular viscoelasticity can be effectively used in the differential diagnosis of azoospermia, especially in patients with slightly smaller testicles.