Severe acute colitis is a serious complication of ulcerative colitis (UC). It can be life-threatening for the patient. Its definition is based on a set of clinico-biological and/or endoscopic criteria. In the event of any outbreak of UC, severe acute colitis must be ruled out. Therapeutic management is multidisciplinary. It must be rapid, first of all eliminating a complication requiring emergency surgical treatment. Several molecules are currently...