Restorative proctocolectomy has become the surgical treatment of choice in ulcerative colitis. Most commonly, this is performed as a staged procedure which includes formation of a defunctioning loop ileostomy, High output loop ileostomies are associated with both local and systemic complications. We describe two patients with loop ileostomies who developed acute arterial thrombosis, a complication not previously described, thus further emphasizing the importance of careful management and early reversal of high output ileostomies. Eur J Gastroenterol Hepatol 10:795-796 (C) 1998 Lippincott Williams & Wilkins.