The Authors report one case of uretero-pelvic junction obstruction in which the endopyelotomy was preceded by intrapelvic invagination of the proximal ureter. After a standard percutaneous access a guide wire is passed down into the ureter through the nephroscope to let a 6 Fr. dilatation balloon catheter be slid just below the junction; a slight traction is exerted on the catheter, so that the proximal ureter is invaginated and drawn toward the pelvis. Both ureter and pelvis receive longitudinal and simultaneous incision. Finally, a double-J ureteral stent is inserted, to be left indwelling for 4 weeks.
