In gastrointestinal anatomy, which are considered watershed areas?

Watershed areas in gastrointestinal anatomy refer to regions of the bowel that are at the farthest extent of blood supply from two major arteries, making them susceptible to ischemia. The splenic flexure and rectosigmoid junction are classic examples of these watershed areas.

These areas receive blood supply from the superior mesenteric artery (SMA) and the inferior mesenteric artery (IMA), but lie at the boundaries of their respective territories. During situations where blood flow is compromised, such as in severe hypotension or atherosclerosis, these regions are the most likely to suffer from ischemic injury due to their relatively poor blood supply compared to other parts of the intestine.

In contrast, the other options presented do not represent true watershed areas. The ileocolic junction and sigmoid colon receive rich blood supply from both the SMA and IMA without significant areas of compromise. The duodenum and jejunum are supplied primarily by branches of the SMA and do not represent watershed regions. Finally, the ascending and descending colon have significant blood supply from both the ileocolic and left colic arteries, which also prevents them from being categorized as watershed areas.

Thus, identifying the splenic flexure and rectosigmoid junction as watershed areas