Case02

A 62-year-old patient complains of rapid onset of severe left abdominal pain that has been increasing over the past 3 hours. The patient indicates they has had nausea and vomiting associated with the pain. On examination, their abdomen has normal bowel sounds. Blood is present in a stool specimen. Bloodwork shows a pronounced low bicarbonate level with a matching increase in serum lactate level. They has a history of myocardial ischemia and vascular disease, including extensive calcifications of their aorta and a thoracic aortic aneurysm repair several years ago.

Question 3/3 - Which watershed region of the gastrointestinal tract is most sensitive to ischemic colitis?

Incorrect. This region is a watershed between the esophageal vascular supply (esophageal branches directly from the aorta) and the celiac artery foregut territory. There is sufficient anastomotic supply to make this a minimal initial risk area.

Incorrect. This area is well vascularized at the boundary between the celiac artery foregut and superior mesenteric artery midgut territories. There is ample anastomotic coverage in this area and the celiac artery is large easily able to cover the territory, so this area is rarely a clinical concern for ischemia.

Incorrect. This region is a junction between small intestine (ileum) and large intestine (cecum), supplied entirely by branches of the superior mesenteric artery (specifically, the ileocolic artery)

Incorrect. The right colic flexure (aka, hepatic flexure) is entirely within the supply territory of the superior mesenteric artery and is not a watershed area.

Correct! The left colic flexure (aka, splenic flexure) is the watershed territory between the superior mesenteric artery and the inferior mesenteric artery. This is the most vulnerable point for generalized ischemic colitis due to distal distribution between the SMA and IMA territory.

If both vessels have diminished flow or oxygen availability this territory can rapidly become ischemic. Prognosis is poor with high mortality in such patients.

The past history of atherosclerotic vascular disease affecting the aorta with history of aneurysm suggests there could be a generalized reduction of flow through the SMA/IMA or arterial occlusion from rupture of an atherosclerotic plaque along the abdominal aorta causing bloodflow reduction.

Incorrect. This point is the boundary between the last sigmoidal branch of the sigmoid colon and the first rectal branch of the superior rectal artery. There is controversy on the importance of this point, but the overall frequency of anastomosis through this region appears sufficient for the middle and inferior rectal artery supply (from the internal iliac vasculature) to provide blood to this region in most cases of diminished IMA flow.