What Causes Pain In Right Side Of The Back?

Hello! My mother (54) has been having these bad pains on her right side sort of towards her back. She said they are very painful. She also said it doesn`t feel like muscle it feel like its deep inside like a organ or something. Shes tried going to the doctor but nothing they have done helps. She cant walk to the kitchen and back to her chair in the den with out screaming in pain. She said shes had gal stones before and this isn`t what that feels like. I`m at a total loss and so are her doctors. If anyone could help I would greatly appreciate it. Thank you!