Pseudomelanosis and colitis

Unfortunately I seem to have posted my comment (question) to the wrong place - so I try it here again:
I have colitis ulcerosa for 9 years now (I'm 30 years old). Yesterday I had another colonoscopy to have it checked once again: The colitis was not found anymore,  instaed of my doctor approved the suspicion of colon irritabile and found a pseudomelanosis too. Because of my colitis I have never taken laxatives! (I really don't need it at all!!) - Only for preparing the colonoscopies in 2001, 2003 and yesterday. Because I also have an sorbitol-intollerancy I used Glauber salt this time (for two days). What about other reasons for pseudomelanosis and is it really reversible? Can this be because of the (short use) of the Glauber salt?
Thank you very much for your answer!