A balloon catheter system for draining and/or supplying fluid from/into hollow organs, body cavities or cysts, comprising - a conduit catheter with an open distal end for draining fluids from hollow organs, body cavities or cysts and/or for supplying medication, - a hollow needle guided in a separate guide duct which is formed in the lumen of the conduit catheter and fluidtightly sealed from the lumen of the conduit catheter, - a balloon surrounding a catheter stem at the distal end of the conduit catheter, characterised in that - the conduit catheter with the hollow needle guided in the separate guide duct is configured to be inserted from outside into the hollow organ, body cavity or cyst via a guide catheter that is provided in the conduit catheter, - the balloon is filled with filling medium and provided in the lumen of the balloon via the hollow needle through an opening formed in the guide duct to fix the conduit catheter in the hollow organ, body cavity or cyst, - the hollow needle is removed from the guide duct of the conduit catheter after filling of the balloon with the filling medium, whereas the balloon and the conduit catheter remain in the hollow organ, body cavity or cyst, and - the balloon neck of the balloon and/or the guide duct of the conduit catheter is provided with a non-return valve. - a conduit catheter with an open distal end for draining fluids from hollow organs, body cavities or cysts and/or for supplying medication, - a hollow needle guided in a separate guide duct which is formed in the lumen of the conduit catheter and fluidtightly sealed from the lumen of the conduit catheter, - a balloon surrounding a catheter stem at the distal end of the conduit catheter, characterised in that - the conduit catheter with the hollow needle guided in the separate guide duct is configured to be inserted from outside into the hollow organ, body cavity or cyst via a guide catheter that is provided in the conduit catheter, - the balloon is filled with filling medium and provided in the lumen of the balloon via the hollow needle through an opening formed in the guide duct to fix the conduit catheter in the hollow organ, body cavity or cyst, - the hollow needle is removed from the guide duct of the conduit catheter after filling of the balloon with the filling medium, whereas the balloon and the conduit catheter remain in the hollow organ, body cavity or cyst, and - the balloon neck of the balloon and/or the guide duct of the conduit catheter is provided with a non-return valve. - the conduit catheter with the hollow needle guided in the separate guide duct is configured to be inserted from outside into the hollow organ, body cavity or cyst via a guide catheter that is provided in the conduit catheter, - the balloon is filled with filling medium and provided in the lumen of the balloon via the hollow needle through an opening formed in the guide duct to fix the conduit catheter in the hollow organ, body cavity or cyst, - the hollow needle is removed from the guide duct of the conduit catheter after filling of the balloon with the filling medium, whereas the balloon and the conduit catheter remain in the hollow organ, body cavity or cyst, and - the balloon neck of the balloon and/or the guide duct of the conduit catheter is provided with a non-return valve.