Small bowel ischemia and infarction
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Small bowel ischemia and infarction
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Small bowel refers to the small intestine and infarction is when ischemia, which is an inadequate blood supply, causes necrosis, or tissue death.
So, a small bowel infarction happens when there’s a reduced blood supply to the small intestine causing parts of the intestinal wall to necrose or die which can be life threatening.
Now, the small intestine is made of several layers.
The innermost layer is the mucosal layer and it’s composed of a few of its own layers.
The first layer is the epithelial lining and it faces the lumen; next is the lamina propria, which is rich with blood and lymph vessels; and finally the muscularis mucosae, which has smooth muscle.
Deep to this mucosal layer is the submucosal layer, which has connective tissue with proteins like collagen and elastin, as well as glands, and additional blood vessels.
The submucosal layer also contains the Meissner plexus which is a part of the enteric nervous system.
Below the submucosal layer is the muscularis propria which is basically two layers of smooth muscle with the myenteric plexus, another part of the enteric nervous system, sandwiched between them.
These muscles are particularly important in helping to move food through the bowel.
Finally, there’s the serosal layer which is the outermost layer of the small intestines that faces the abdominal cavity.
The superior mesenteric artery is the main supplier of blood to the small intestine.
Branches of the artery spread through the mesentery - called mesenteric arteries - and penetrate the serosa layer and travel to the submucosa where they branch further into arterioles.
Because the small intestine has a high demand for oxygen and nutrients to sustain digestion, it is highly susceptible to tissue injury from ischemia.
To reduce the risk of that happening, the mesenteric arteries branch and reconnect at points forming collateral circulation.
That’s protective because if blood flow is reduced in one pathway, then the tissue can still receive blood through another pathway.
Once the small intestines have gotten oxygenated blood, that blood leaves through the superior mesenteric vein.
Summary
Small bowel ischemia and infarction refer to a medical condition characterized by reduced blood flow and tissue death in the small intestine. It often results from something like a blood clot or a nearby tumor, a hernia, a volvulus, or intussusception, which blocks blood vessels supplying the small intestine. It may also be due to low blood pressure, or a decrease in the overall amount of blood flowing into the area.
Small bowel ischemia and infarction can complicate into an ileus in which food lingers and doesn't get pushed along, or even peritonitis and sepsis. Symptoms include severe abdominal pain( out of proportion to the physical examination), nausea, vomiting, diarrhea, and fever. Treatment typically involves addressing the underlying cause and restoring blood flow to the affected area, using medications or surgery. Treatment involves IV fluids, pain management, antibiotics, and surgery if needed.
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