As a last resort I would suggest a very high fibre diet to include dishes such as pulverised fresh fruit to which organic bran has been added. Likewise pulverised fresh vegetables + bran. Also drink two litres of water per day. No white bread, no junk food, no colas etc etc!!
There have been questions on Medhelp whereby a total colectomy has been mentioned as a treatment of last resort for chronic constipation - obviously you would need to discuss this with your G.I. specialist.
I underwent this operation about seven years ago - not for constipation but for torrential diverticular bleeding. In response to a question from another Medhelp patient's posting I shared my experience of this operation on:-
http://www.medhelp.org/posts/show/523166
and you may like to read through this prior to a discussion with your G.I. specialist.
regards
Morecambe