Polygenic Risk Score for Adult Idiopathic Hydrocele Testis: Susceptibility and Severity in a Japanese Cohort

This exploratory study evaluated whether a polygenic risk score (PRS) derived from a European genome-wide association study is transferable to a Japanese cohort, for both susceptibility to and severity of adult idiopathic hydrocele testis. Surgically confirmed hydrocele cases were compared with two independently ascertained control groups: prostate cancer patients with intraoperatively confirmed absence of hydrocele fluid (Control 1), and urolithiasis patients without malignancy (Stone Control). Multivariable logistic regression evaluated disease occurrence; multiple linear regression restricted to hydrocele cases evaluated the association between PRS and fluid volume. A higher PRS was associated with increased susceptibility to hydrocele when cases were compared with Stone Controls (strictest threshold: odds ratio 1.98, 95% CI 1.01–3.88, p = 0.048; AUC 0.733), though this was not observed using Control 1. Among cases, PRS showed a consistent inverse association with fluid volume across all three thresholds tested (standardized β = −0.54, p = 0.010 at ≥10 mL). Given the modest sample size and limited statistical power, these findings should be regarded as preliminary and hypothesis-generating. They nonetheless suggest that genetic susceptibility to hydrocele and its severity may show different associations with polygenic risk, a pattern requiring confirmation in larger, independent, ideally East Asian-derived cohorts.