To assess the accuracy of contralateral testis hypertrophy for predicting the fate of nonpalpable testis in Chinese boys at different ages.

The data of patients who presented with unilateral impalpable testis and who underwent laparoscopy at the Children's Hospital of Chongqing Medical University between January 1, 2000 and January 1, 2018 were reviewed. The boys were divided into four groups: age-matched volunteers with no testicular abnormalities represented the control group (group I), boys with palpable undescended testis (group II), boys with nonpalpable testis (NPT)/viable testis (VT) (group III), and boys with NPT/non-viable testis (NVT) group (group IV). Scrotal testes were prospectively measured by ultrasonography for volume and size, and diagnostic laparoscopy was performed to determine the state of the cryptorchid testis.

The mean contralateral testicular volume and length in the boys with an absent testis was 0.78mL and 17mm compared with 0.67mL and 15mm in the boys with a testis present and 0.63mL and 15mm in the controls, respectively (P<0.05). The predictive accuracy, sensitivity, and specificity for an absent testis were 64.9%, 75%, and 49%, respectively, for volume and 64.2%, 56.3%, and 76.4%, respectively for length at the optimal cutoff value of 0.65mL volume and 16.55mm length. Contralateral testis volume was the most accurate in predicting monorchism in 0–2-year-olds (sensitivity: 75%, specificity: 70%, accuracy: 73.1%) and the contralateral testicular length was most accurate for 4–6-years-old (sensitivity: 68.6%; specificity: 77.8%; accuracy: 72.2%). We also included 29 patients with bilateral undescended testis (UDT) and with unilateral nonpalpable. Cutoff values for testicular volume and length were 0.6mL (sensitivity: 81.8%, specificity: 88.9%, accuracy: 86.2%) and 13.5mm (sensitivity: 63.6%, specificity: 77.8%, accuracy: 77.8%).

The present results exclusively obtained from laparoscopic exploration suggest that a testis volume of>0.65mL or a testis length of>16.55mm could predict monarchism with an accuracy of about 65%. In younger patients aged 0–2 years and 4–6 years, the overall predictive accuracy increases to about 73% but laparoscopic exploration is still required.