Comparative evaluation of previously reported contralateral testicular length cutoffs for predicting nonviable testes...

In boys with unilateral nonpalpable testis (NPT), contralateral testicular hypertrophy (CTH) is a reportedly useful indicator for predicting viability of the affected testis. However, the cutoff values of contralateral testicular length (longitudinal diameter) used for defining CTH vary considerably among reports. To date, no consensus has been established regarding which previously reported cutoff value provides the most balanced diagnostic performance. We aimed to evaluate and compare the diagnostic performance of previously reported cutoff values in our institutional cohort.

We retrospectively reviewed data of 26 prepubertal boys who underwent surgical exploration for unilateral NPT at Nagasaki University Hospital between October 2013 and September 2025. The patients were intraoperatively allocated into nonviable testis (NVT) and viable testis (VT) groups. Clinical characteristics and contralateral testicular length were compared between the groups. Logistic regression analysis was performed to identify factors associated with NVT. Six previously reported cutoff values were applied to our cohort, and diagnostic performances were compared in terms of sensitivity, specificity, positive predictive value, negative predictive value, and the Youden index.

Among the 26 patients, 17 (65.4%) and 9 (34.6%) were classified as NVT and VT, respectively. The median contralateral testicular length was significantly greater in the NVT group than in the VT group (17.6 vs. 13.7 mm, p = 0.013). Contralateral testicular length was significantly associated with NVT (p = 0.004). Among previously reported cutoff values, 16.55 mm yielded the highest Youden index of 0.654 (95% CI 0.252-0.820).

Contralateral testicular length is a simple, noninvasive, and potential preoperative indicator of testicular viability in boys with unilateral NPT. Among previously reported cutoff values, 16.55 mm demonstrated a favorable balance between sensitivity and specificity in this cohort.