Watershed areas

[panmit]

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Why are watershed areas, splenic flexure and rectosigmoid areas prone to ischemia when they have dual blood supplies (i.e. SMA and IMA for splenic flexure). Doesn't it seem counter intuitive?

 

[Ven0m]

Watershed areas are at the most distal tips of arteries, like this:
===(artery)===> splenic flexure <===(artery)===
And this means perfusion pressure is kind of low to them (because they're at the most distal tips), so if there's a systemic drop in BP (shock) they won't get perfused enough = ischemia

and yes it seems counter intuitive, quality over quantity i guess

 

[panmit]

Watershed areas are at the most distal tips of arteries, like this:
===(artery)===> splenic flexure <===(artery)===
And this means perfusion pressure is kind of low to them (because they're at the most distal tips), so if there's a systemic drop in BP (shock) they won't get perfused enough = ischemia

and yes it seems counter intuitive, quality over quantity i guess

Ahh kk. I see. So in hypoperfusion they are prone to ischemia, however, let’s say in a rare occlusive event anastomoses will redirect blood flow and still perfuse the area. So during thrombotic events it’s good, and events like shock watershed sucks.

 

[Ven0m]

Actually the splenic flexure (although its supplied by branches of the IMA and SMA) will become ischemic even if just one supply fails (because the other supply doesn't perfuse strong enough).

Idk if this is the case for other watershed areas

 

[panmit]

Actually the splenic flexure (although its supplied by branches of the IMA and SMA) will become ischemic even if just one supply fails (because the other supply doesn't perfuse strong enough).

Idk if this is the case for other watershed areas

Okay cool thanks bro. Yeah seems counter intuitive. Like first aid and other resources stress the importance of dual blood supply and in the end it doesn’t matter - it will still be ischemic

 

[Ven0m]

Okay cool thanks bro. Yeah seems counter intuitive. Like first aid and other resources stress the importance of dual blood supply and in the end it doesn’t matter - it will still be ischemic

There are other areas that resist infarction more than others because of their dual blood supply, e.g the lungs (bronchial a + pulmonary a)

also some parts of the colon (thanks to the marginal artery and all the arcades)