My mum is aged 78, she had an operation on her back - she had a plate inserted, 2 baskets and also some fusion work, When she came out of hospital she was doing well, starting to get her balance and learning to work unaided. In the last few weeks she has become extremely tired, constantly drinking water and no energy, She has had several blood tests and chest xray which have come back clear, Do you have any idea what could be wrong.