The aetiologies of computed tomography-diagnosed acute colitis remain surprisingly unknown. Moreover, no diagnostic tool or clinical score allow to quickly determine or at least stratify the exact cause of colitis in patients admitted at an Emergency Ward and to direct them to the appropriate therapeutic care. The aims of the present study are to describe the presentation and aetiologies of acute colitis, and to develop diagnostic methods to guide patients admitted for acute colitis to the appropriate therapeutic care, particularly colonoscopy.