Is there an optimal contralateral testicular cut-off size that predicts monorchism in boys with nonpalpable testicles?

ObjectiveTo identify a contralateral testicular cut-off size that would predict monorchism (intra-abdominal vanishing testis or inguinal/scrotal nubbin) in boys with unilateral nonpalpable testis (NPT).Materials and methodsBoys with cryptorchidism, treated by a single surgeon at a tertiary care center from 2009 to 2013, were grouped based on intra-operative findings: boys with a solitary gonad (monorchism group, M) and two control groups: intra-abdominal testis (IAT) and palpable undescended testis (pUDT). Immediately before the procedures, the contralateral descended testes were measured using callipers. Boys with NPT underwent diagnostic laparoscopy. Sensitivity, specificity, positive and negative predictive values, likelihood ratios and receiver operating characteristic (ROC) curves were calculated.ResultsOut of the 324 boys with cryptorchidism, 58 were found to have pUDT and 85 had NPT. Of these 85 boys with NPT, 50 had an IAT and 35 had monorchism. Mean ages at surgery for groups M, IAT and pUDT were similar (28.0, 31.3 and 30.4 months, respectively; P = 0.4). Mean length of the contralateral descended testes in groups M, IAT and pUDT was 24.3, 16.5 and 18.8 mm, respectively. Contralateral testicular cut-off lengths of 18, 19 and 20 mm had positive likelihood ratios (LR+) of 6.5, 7.4 and 10.1, respectively. The area under the ROC curve was 95% (95% CI: 91–100%).ConclusionA contralateral testicular cut-off length of 19–20 mm had the best accuracy in predicting monorchism in boys aged 11–30 months with unilateral NPT.