Hi jlm52
Unless your condition has improved, then you do not have to inform the DWP of any hospital treatment. If you are hospitalised for four weeks or more then you will need to inform PIP, your claim will stop, when you come out of hospital your claim will restart.
If your condition has deteriorated and you do not inform DWP of a change in your circumstances, you will loose any benefit increase entitlement as a change of circumstances is from when you notify DWP.
Gary
Nothing on this board constitutes legal advice - always consult a professional about specific problems