Testicular Two-Dimensional Shear Wave Elastography, Peak Systolic Velocity, Volume and Epididymal Thickness: Establishment of Normal Reference Values and Discrimination From Orchitis in Adult Patients Presenting With Acute Scrotal Pain

Abstract

Aim

To establish normal testicular stiffness reference values using two-dimensional shear wave elastography (2D-SWE) and together with volume, PSV and epididymal thickness to discriminate from inflammatory pathology, specifically orchitis, in adult patients presenting with acute scrotal symptoms.

Materials and Methods

Retrospective analysis of patients referred for scrotal ultrasonography for investigation of scrotal pain or discomfort. Evaluation of 494 testes included B-Mode, colour and pulsed wave (PW) Doppler, testicular volume, peak systolic velocity (PSV) and the median elasticity (SWE). Statistical evaluation was performed to identify stiffness threshold values to rule in normal.

Results

In normal testes, the median volume, PSV and SWE were 13.8 mL (10.3–17.2 mL), 6.3 cm/s (4.9–7.7 cm/s) and 2.5 kPa (2.15–2.85 kPa). The right testes were larger (right 14.4 mL, left 13.2 mL, p < 0.05) with both decreasing in size and increasing in stiffness with increasing age (> 60 years, p < 0.05). In patients with normal testes but extra-testicular pathology, the median volume, PSV and SWE were 13.3 mL (9.75–16.8 mL), 6.3 cm/s (4.55–8.05 cm/s) and 2.8 kPa (2.3–3.3 kPa), respectively. In patients with orchitis, the median volume, PSV and SWE were 18.1 mL (11.5–24.7 mL), 7.9 cm/s (2.8–13 cm/s) and 5.4 kPa (3.4–7.4 kPa), respectively. The PSV and SWE values in this group were age- and side-independent. Differentiating normal testes from orchitis using SWE had AUC, accuracy, sensitivity and specificity of 0.91, 0.801, 0.892 and 0.792.

Conclusion

Normal adult testes have a median stiffness of 2.5 kPa. A threshold cut-off median value of 3.6 kPa suggests the diagnosis of an inflammatory testicular pathology such as orchitis, with AUC, accuracy, sensitivity and specificity of 0.922, 0.840, 0.928 and 0.831. Caution is required in the presence of extra-testicular pathology, where there is a wider range of SWE and other parameters.