BACKGROUND AND OBJECTIVE: The objective of our study is to examine the impact of monorchism on contralateral testicular size in children with non-palpable testis (NPT). Enhanced contralateral testicular volume or longitudinal diameter (length) serves as a predictor of monorchism. In the present study, we assessed the ability of ultrasound measured enlarged contralateral testicular length for predicting monorchism (and hence a testicular nubbin) in children with NPT. Furthermore, we evaluated the general prevalence of viable versus non-viable testes in patients referred to our institution with unilateral undescended testis between 2005 and 2020.

STUDY DESIGN: We analysed the records of 54 patients who underwent diagnostic laparoscopy for NPT between 2005 and 2020 in a European tertiary care centre. Testicular lengths (longitudinal diameter) and testicular volume of the contralateral testis, as well as surgeon (surgeon 1 vs surgeon 2 vs others) and age at surgery (months) were assessed and stratified according to intraoperative findings (presence or absence of a testicular nubbin). Testicular length and volume were evaluated by ultrasound examination in office prior to surgery. Chi-square and t-test for descriptive analyses as well as uni- and multivariable logistic regression analyses were performed using R Version 3.1.0 (R Project for Statistical Computing, www.R-project.org).

RESULTS: A total of 15 children presented with viable testes and 39 patients with testicular nubbin. Mean age was 20.5 months in the overall cohort and 22.6 vs 19.7 months in children with viable testis vs testicular nubbin (p = 0.4). In patients with presence of a testicular nubbin, the contralateral testis was larger (median length 17 mm (16-19.2)) as compared to patients with a viable testis (median length 15 mm (14-17), p = 0.001). Similarly, contralateral testicular volume was lower in patients with a present viable testis (0.6 ccm vs 0.8 ccm; p < 0-001). This effect remained statistically significant when logistic regression analyses were adjusted for age and weight at surgery, year of surgery, surgeon, and laterality. OR (odds ratio) for presence of a testicular nubbin was 1.6 (per mm) [95% CI (confidence interval) 1.13-2.17; p = 0.007].

CONCLUSION: Patients with preoperative increased length and volume of the contralateral testis in the ultrasound examination are at significantly higher risk of monorchism than their counterparts with lower testicular length. This should be emphasized during counselling of the parents prior to surgery. In our experience parents cope more easily with the diagnosis of monorchism, once this has already been discussed and explained thoroughly prior to surgery.