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==Pathophysiology==
==Pathophysiology==
The pathophysiology of ischemic colitis is as follows:<ref name="uptodate">UpToDate, ''Colonic ischemia'', accessed 2 September 2006.</ref><ref>{{cite journal | author = Rosenblum J, Boyle C, Schwartz L | title = The mesenteric circulation. Anatomy and physiology. | journal = Surg Clin North Am | volume = 77 | issue = 2 | pages = 289-306 | year = 1997 | id = PMID 9146713}}</ref><ref>{{cite journal | author = Granger D, Rutili G, McCord J | title = Superoxide radicals in feline intestinal ischemia. | journal = Gastroenterology | volume = 81 | issue = 1 | pages = 22-9 | year = 1981 | id = PMID 6263743}}</ref>
The pathophysiology of ischemic colitis is as follows:<ref name="uptodate">UpToDate, ''Colonic ischemia'', accessed 2 September 2006.</ref><ref>{{cite journal | author = Rosenblum J, Boyle C, Schwartz L | title = The mesenteric circulation. Anatomy and physiology. | journal = Surg Clin North Am | volume = 77 | issue = 2 | pages = 289-306 | year = 1997 | id = PMID 9146713}}</ref><ref>{{cite journal | author = Granger D, Rutili G, McCord J | title = Superoxide radicals in feline intestinal ischemia. | journal = Gastroenterology | volume = 81 | issue = 1 | pages = 22-9 | year = 1981 | id = PMID 6263743}}</ref><ref>Brandt LJ, Boley SJ, Goldberg L, et al: Colitis in the elderly. Am J Gastroenterol 76:239, 1981.</ref>


===Colonic Blood Supply===
===Colonic Blood Supply===
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* A range of pathologic findings are seen in ischemic colitis, corresponding to the spectrum of clinical severity.
* A range of pathologic findings are seen in ischemic colitis, corresponding to the spectrum of clinical severity.
** In its mildest form, mucosal and submucosal [[hemorrhage]] and [[edema]] are seen, possibly with mild [[necrosis]] or [[ulceration]].
** In its mildest form, mucosal and submucosal [[hemorrhage]] and [[edema]] are seen, possibly with mild [[necrosis]] or [[ulceration]].
** With more severe ischemia, a pathologic picture resembling [[inflammatory bowel disease]] (i.e. chronic [[ulcerations]], [[crypt abscess]]es and [[pseudopolyps]]) may be seen.<ref>Brandt LJ, Boley SJ, Goldberg L, et al: Colitis in the elderly. Am J Gastroenterol 76:239, 1981.</ref>
** With more severe ischemia, a pathologic picture resembling [[inflammatory bowel disease]] (i.e. chronic [[ulcerations]], [[crypt abscess]]es and [[pseudopolyps]]) may be seen.
** In the most severe cases, transmural [[infarction]] with resulting perforation may be seen.
** In the most severe cases, transmural [[infarction]] with resulting perforation may be seen.
** After recovery, the muscularis propria may be replaced by fibrous tissue, resulting in a [[stricture]].
** After recovery, the muscularis propria may be replaced by fibrous tissue, resulting in a [[stricture]].

Revision as of 12:51, 2 January 2018

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Hamid Qazi, MD, BSc [2] Cafer Zorkun, M.D., Ph.D. [3]

Pathophysiology

The pathophysiology of ischemic colitis is as follows:[1][2][3][4]

Colonic Blood Supply

  • The colon receives blood from both the superior and inferior mesenteric arteries. The blood supply from these two major arteries overlap, with abundant collateral circulation. However, there are weak points, or "watershed" areas, at the borders of the territory supplied by each of these arteries. These watershed areas are most vulnerable to ischemia when blood flow decreases, as they have the fewest vascular collaterals.

Development of Ischemia

  • Under ordinary conditions, the colon receives between 10% and 35% of the total cardiac output.
  • If blood flow to the colon drops by more than about 50%, ischemia will develop.
  • The arteries feeding the colon are very sensitive to vasoconstrictors; presumably this is an evolutionary adaptation to shunt blood away from the bowel and to the heart and brain in times of stress. As a result, during periods of low blood pressure, the arteries feeding the colon clamp down vigorously.
  • A similar process can result from vasoconstricting drugs such as ergotamine, cocaine, or vasopressors. This vasoconstriction can result in non-occlusive ischemic colitis.

Microscopic Pathology

  • A range of pathologic findings are seen in ischemic colitis, corresponding to the spectrum of clinical severity.

Images

By Nephron - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=8171438

Micrograph of a colonic pseudomembrane, a finding that may be associated with ischemic colitis. H&E stain.

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References

  1. UpToDate, Colonic ischemia, accessed 2 September 2006.
  2. Rosenblum J, Boyle C, Schwartz L (1997). "The mesenteric circulation. Anatomy and physiology". Surg Clin North Am. 77 (2): 289–306. PMID 9146713.
  3. Granger D, Rutili G, McCord J (1981). "Superoxide radicals in feline intestinal ischemia". Gastroenterology. 81 (1): 22–9. PMID 6263743.
  4. Brandt LJ, Boley SJ, Goldberg L, et al: Colitis in the elderly. Am J Gastroenterol 76:239, 1981.


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