31. REPORT 4 CASE STUDY OF URETEROPELVIC JUNCTION OBSTRUCTION BY RETROPERITONEAL LAPAROSCOPIC SURGERY AT TRANSPORT HOSPITAL 4/2024 - 4/2025. YHCĐ. 2026;66(CĐ14-HNKH BV Giao thông Vận tải). doi:10.52163/yhc.v66iCD14.3137