According to UpToDate (https://www.uptodate.com/contents/colonic-ischemia), "Nonocclusive or low blood flow ischemia is the predominant mechanism (95 percent of cases) causing colonic ischemia". The FA image on this card states for colonic ischemia: "Reduction in intestinal blood flow causes ischemia". B&B (GI - GI Blood Supply - Watershed Areas), regarding colonic ischemia, only describes non-occlusive ischemia of watershed areas. Sketchy (SketchyPath - GI - Intestinal Ischemia & Angiodysplasia) states "NON-occlusive intestinal ischemia usually occurs in the COLON because of watershed areas (therefore termed ACUTE COLONIC ISCHEMIA". Although Pathoma (2019, p. 111) states that for ischemic colitis "atherosclerosis of SMA is the most common cause", it is firmly in the minority. This card doesn't seem to be tagged to any UWorld questions either so I don't think this change would contradict UWorld either.