Colonoscopy was done for a patient who was suffering from recurrent episodes of abdominal pain and low volume diarrhea since six months. Colonoscopy showed many areas of mucosal edema and ulceration and some areas appeared normal. Microscopy of biopsy specimen from an ulcerated ared showed patchy acute and chronic inflammatory infiltrate , crypt abscesses and non caseating granulomas . What could be the probable diagnosis ?