Structure not forming watershed area

Watershed area is the medical term referring to regions of the body that receive dual blood supply from the most distal branches of two large aeries, such as the splenic flexure of the large intestine. Watershed areas are found in the brain, where areas are perfused by both the anterior and middle cerebral aeries, and in the intestines, where areas are perfused by both the superior and inferior mesenteric aeries (i.e., splenic flexure). Additionally, the sigmoid colon and rectum form a watershed zone with blood supply from inferior mesenteric, pudendal and iliac circulations. Hypoperfusion in watershed areas can lead to mural and mucosal infarction in the case of ischemic bowel disease. When watershed stroke occurs in the brain, it produces unique focal neurologic symptoms that aid clinicians in diagnosis and localization.