In a small group of cases ischemia progresses to necrosis and frank gangrene. These patients are quite toxic and ill, with evidence of sepsis, hemodynamic instability, and eventual shock. This mandates emer­gent laparotomy. The goals of surgery are (1) to assess the extent of ischemia by evaluating mesen­teric fl ow (palpation, Doppler, intravenous fl uores­cein dye combined with a Wood’s lamp) and by endoscopic evaluation of mucosal viability; and (2) to resect all nonviable, compromised bowel. Normal mucosa must be present at the margins of the resec­tion. In general, an end-colostomy and a Hartmann’s pouch or mucous fi stula should be created (the latter has the unique advantage of allowing direct evalua­tion of the mucosa for evidence of ongoing isch­emia); in the rare hemodynamically stable, low-risk patient, intraoperative cleansing of the proximal large bowel can be followed by a primary anastomo­sis. Another option is extension of the resection to include a subtotal colectomy with an ileorectal anas­tomosis. If the involvement is confi ned to the right colon, a primary anastomosis is feasible, provided there has been no major contamination and the patient is hemodynamically stable. If a primary anas­tomosis has been fashioned but there are doubts about intestinal viability, a planned second-look lapa­rotomy is scheduled within 24 hours.