The role of gastrointestinal microflora in the pathogenesis of complications of mesenteric ischemia.

Mesenteric ischemia is a catastrophic event, which has a mortality due to florid sepsis that approaches 100%. The demography of the bacterial changes has not been documented. After 72 hr of colonic ischemia in the dog, the total number of anaerobic organisms increased while the number of aerobic organisms decreased. After 24 hr of ischemia, anaerobic bacteria appeared only in the portal vein and persisted. Cultures of peritoneal fluid and aortic blood became positive for the same anaerobic organisms after 48 hr. Acute colonic ischemia promotes a relative overgrowth of intraluminal anaerobic bacteria, which progressively invade the portal vein and later the systemic circulation.