Laparoscopic surgery admits the retroperitoneal approach: the main restriction is the tight manoeuvring space that can be obtained with insufflation. The use of a dilatator balloon in the retroperitoneal cavity offers a solution to this problem. A cutaneous access and a dull parietal path is created, with blind positioning of the apex of the dihedron between the inferior renal pole and the ureter. Peroperative ultrasound control makes it possible to identify the inferior renal pole, to control the position of the apex of the catheter with the balloon and the movements of the retroperitoneal organs in real time. The possibility of following the procedure by ultrasonography have proven usefull in our experience.