Transverse testicular ectopia with fused vas deferens: A systematic review.
BACKGROUND: Transverse testicular ectopia (TTE) with fused vas deferens is an extremely rare anomaly, often diagnosed intraoperatively. Current TTE classifications do not address internal ductal variations, limiting surgical guidance. OBJECTIVE: To systematically review cases of TTE with fused vas deferens, summarize presentation, operative strategies, outcomes and identify patterns that highlight the need for classification refinement. METHODS: A PRISMA 2020-compliant systematic review (PROSPERO; CRD420251247785) was performed across PubMed, ScienceDirect and citation of included articles through December 2025. Case reports and series confirming fused vas deferens were included. Data extracted comprised demographics, presentation, imaging, surgical approach, and outcomes. Quality assessment used JBI checklists. RESULTS: 12 studies (16 patients) were included. Most presented with unilateral inguinal hernia (62%) and contralateral undescended testis (68%); 81% were diagnosed intraoperatively. Anatomical patterns included common/proximal fused vas (87%), Y-shaped fusion (6%), and long-loop vas (6%). Trans-septal orchidopexy was the preferred approach, with preservation of vas integrity. Postoperative outcomes were favorable; long-term follow-up was limited. CONCLUSION: TTE with fused vas deferens represents a distinct variant requiring careful intraoperative recognition. We propose a Type IV TTE category for internal ductal fusion to guide surgical planning and classification refinement. Further accumulation of case-based evidence may help clarify its anatomical patterns and operative implications.