What Is The Ileum, What Causes A Thickening Of The Ileum?

Hi , I am 26, female and been suffering with what my consultant believes is most likely Irritable Bowel Syndrome . I get stomach discomfort, at time very severe pain, changes to my bowel movements and weight loss . I have had lots of investigations MR scan, 2 x camera procedures, lots of blood tests and also I think chrones disease has been ruled out. I am being sent to a dietision. I have just received a letter that was also sent to my GP from my consultant. This was not discussed with me but mentions that he has noticed when reviewing my notes a thickening of a section of the ileum (just beyond the ileo-caecal valve) and will be discussing this at a x-ray meeting. Can anyone tell me please what is the ileum, what causes a thickening of the ileum? Also what, if any effects does this have? Is it a common thing with IBS or something which can just be a normal in a person. Any information would be appreciated as my next consultation is not for a few months and I am unsure if this is something I should be concerned about or not. Thankyou for taking the time to read this. Sarah