The goal of this observational study is to learn about the performance of the drainova® ArgentiC Catheter in clinical routine, which is used to treat fluid accumulations in hollow body structures. The device is already on the market and participants receive the catheter as part of their regular treatment. The main questions of this study are: * Does the device function as intended? * Are there any other safety risks that have not been identified? * Does it lower the symptoms of the patients as intended? Doctors and patients will answer questions regarding the improvement of the patients´ symptoms and if there were any problems with the catheter.