Detection of monorchidism in boys with unilateral undescended testes: clinical benefits and limitations of contralateral testicular size

Abstract

Contralateral testicular size was recommended as an effective measurement in prediction of monorchidism in some previous studies but a few argued it as invalid. Further investigation was demanded. To investigate the effectiveness of contralateral testicular size in prediction of monorchidism in patients with unilateral non-palpable undescended testes (NPT) aged between 9 and 48 months. Total of 707 patients aged between 9 and 48 months and diagnosed with unilateral undescended testes (UDT) between January 2016 and December 2018at the study department were enrolled. In accordance with physical examinations and surgical findings, patients were divided into three groups: palpable UDT (group A, n=609), non-palpable but viable testes (group B, n=57) and monorchidism (group C, n=41). Contralateral testicular length and volume were evaluated with ultrasonography. Comparison of contralateral testicular size between three groups and calculation of optimal cut-off value and diagnostic performance of it among NPT were performed. The length and volume of contralateral testes of group C were larger than of group A (P<0.01) and group B (P<0.01), whereas these differences between groups were small. Among patients with NPT, a receiver operating characteristic curvewas used to determine the optimal cut-off value. It revealed that both a testicular length of 17.5mm and a volume of 1.05ml provided the highest Youden's index for prediction of monorchidism. The sensitivity and specificity for testicular length were 34.1% and 94.7%, and volume were 34.1% and 93%, respectively. The predictive accuracy for testicular length and volume were 69.4% and 65.7%, respectively. Even though the negative predictive valuewas merely 66.6% (54/81) and 66.2% (53/80), the positive predictive value (PPV) reaches to 82.3% (14/17) and 77.7% (14/18) for testicular length and volume. Several factors including choosing of measurement tools, age range, ethnicity, and selection bias of cohorts may be accounted for the huge differences among cut-off values and predictive accuracy. The diagnostic performance of contralateral testicular size in prediction of monorchidism in patients with NPT was poor. But the PPV was relatively promising. Contralateral testicular hypertrophy can provide information for surgical planning. The overall diagnostic performance of contralateral testicular size in prediction of monorchidism in poatients with UDTaged between 9 and 48 months was poor. But the efficiency of cut-off value predicting absence of viable testes was relatively higher. This value should be objectively applied but only as a reference which would not be a complete replacement of laparoscopy exploration.