What Causes Abusive Behaviour After A Rectum Surgery?

Sir , my father of age 64 undergone CR Rectum operation in 2007 and from last few years we observed changes in his behaviour such as , he abuses my mother saying that she had a illegal connection with other man and she will kill him , he also doubts that we r mixing some medicne in his food to kill him , he gets irritated for petty matters and quarrels with family members and he behaves normally with ousiders. I had took him to Dr Ramesh psycartist , after using mediciens my father goes into sleep and mean while the bag at laterine discharge fills & spoils his dress and bed and so, my father is not co-operating to take medicines. Now his behaviour changed drastically and neighbours are also complaning abt him Sir ,on job purpose i stay at Bhubaneswar and my brother stay at Mumbai . my mother suffers a lot who only is with my father at Vizag. my parents r not willing to leave vizag. Please suggest me how to save my mom & dad G.Gurunadha Rao