Inflammatory bowel disease (IBD) is a chronic intestinal disorder comprising 2 distinct but often overlapping diseases: Crohn's disease and ulcerative colitis. Although much research to identify the etiology of IBD has focused on genetic constitution, infectious causes, and immune dysregulation, its exact cause and pathogenesis remain incompletely understood. Mesenteric blood flow, the intestinal microcirculation, and intestinal ischemia also have been proposed as etiologic, although they remain less-explored themes despite evidence suggesting a contributory role in IBD pathogenesis. The anatomy, architecture, and function of the splanchnic microcirculation will be reviewed here with regard to the development of intestinal microvascular ischemia, a pathologic process that appears to precede the classic changes that characterize IBD.