Is long term use of baclofen truly bad 4 kidneys? could it cause mass or cyst on or above kidneyafter 5yrs daily use?

No: It does not have effect on kidneys. It does not cause mass or cyst.

Need to see M.D.: Any long-term use of medication can cause problems though though I am not specifically aware of masses or cysts in the kidney. Any long-term use of medications needs to be reassessed by a physician to make sure it is indicated and is not causing problems. A simple blood tests would determine any problems with the kidneys.