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==Overview==
==Overview==
Ischemic colitis is the result of a sudden reduction in [[blood]] flow that is insufficient to meet the [[Metabolism|metabolic]] demands of the region of [[Colon (anatomy)|colon]]. [[Ischemia|Ischemic]] change will subsequently extend from the [[Mucous membrane|mucosa]] to the [[Serous membrane|serosa]]. [[Mucous membrane|Mucosal]] injury will develop in 20 minutes to 1 hour, and transmural infarction occurs within 8 to 16 hours. [[Reperfusion injury]] can occur with the release of [[reactive oxygen species]], which cause [[lipid peroxidation]] within [[Cell membrane|cell membranes]], causing [[Cell (biology)|cell]] [[necrosis]].
Ischemic colitis is the result of a sudden reduction in [[blood flow]] that is insufficient to meet the [[Metabolism|metabolic]] demands of the region of the [[Colon (anatomy)|colon]]. [[Ischemia|Ischemic]] changes will subsequently extend from the [[Mucous membrane|mucosa]] to the [[Serous membrane|serosa]]. [[Mucous membrane|Mucosal]] injury will develop in 20 minutes to 1 hour and transmural infarction occurs within 8 to 16 hours. [[Reperfusion injury]] can occur with the release of [[reactive oxygen species]], which cause [[lipid peroxidation]] within [[Cell membrane|cell membranes]], causing [[Cell (biology)|cell]] [[necrosis]].


==Physiology==
==Physiology==
===Colonic Blood Supply===
===Colonic Blood Supply===
*The physiology of blood supply is as follows:<ref name="pmid9146713">{{cite journal| author=Rosenblum JD, Boyle CM, Schwartz LB| title=The mesenteric circulation. Anatomy and physiology. | journal=Surg Clin North Am | year= 1997 | volume= 77 | issue= 2 | pages= 289-306 | pmid=9146713 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=9146713  }} </ref>
*The physiology of blood supply is as follows:<ref name="pmid9146713">{{cite journal| author=Rosenblum JD, Boyle CM, Schwartz LB| title=The mesenteric circulation. Anatomy and physiology. | journal=Surg Clin North Am | year= 1997 | volume= 77 | issue= 2 | pages= 289-306 | pmid=9146713 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=9146713  }} </ref>
* [[Colon (anatomy)|Colon]] receives [[blood]] from the [[superior mesenteric artery|superior]] and [[inferior mesenteric artery|inferior mesenteric arteries]].  
** [[Colon (anatomy)|Colon]] receives [[blood]] from the [[superior mesenteric artery|superior]] and [[inferior mesenteric artery|inferior mesenteric arteries]].  
*[[Blood]] supply from these [[Artery|arteries]] overlap, with abundant collateral [[Circulatory system|circulation]].
**[[Blood]] supply from these [[Artery|arteries]] overlap, with abundant collateral [[Circulatory system|circulation]].
*There are weak points, or "[[Watershed Area (medical)|watershed]]" areas, at the borders of the territory supplied by each of these [[Artery|arteries]].  
**There are weak points, or "[[Watershed Area (medical)|watershed]]" areas, at the borders of the territory supplied by each of these [[Artery|arteries]]. and are vulnerable to [[ischemia]] when [[blood]] flow decrease due to hypotension.  
**These [[Watershed Area (medical)|watershed]] areas are most vulnerable to [[ischemia]] when [[blood]] flow decreases, as they have the fewest [[vascular]] collaterals.


* [[Rectum]] receives [[blood]] from the [[inferior mesenteric artery]] and the [[internal iliac artery]]
* [[Rectum]] receives [[blood]] from the [[inferior mesenteric artery]] and the [[internal iliac artery]] which is rarely affected by colonic [[ischemia]] due to its dual [[blood]] supply.
**[[Rectum]] is rarely involved by colonic [[ischemia]] due to this dual [[blood]] supply.


==Pathophysiology==
==Pathophysiology==
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===Development of Ischemia===
===Development of Ischemia===
* [[Colon (anatomy)|Colon]] receives between 10% and 35% of the total [[cardiac output]].
* The [[Colon (anatomy)|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.
*If [[blood]] flow to the colon drops by more than about 50%, [[ischemia]] will develop.
* The [[Artery|arteries]] feeding the [[Colon (anatomy)|colon]] are very sensitive to [[vasoconstrictors]]
* The [[Artery|arteries]] feeding the [[Colon (anatomy)|colon]] are very sensitive to [[vasoconstrictors]] and during periods of [[hypotension|low blood pressure]] the [[Artery|arteries]] will collapse.
** During periods of [[hypotension|low blood pressure]], the [[Artery|arteries]] will collapse.
* [[Vasoconstriction|Vasoconstricting]] drugs such as [[ergotamine]], [[cocaine]], or [[vasopressor]]s can also cause colonic [[ischemia]] which results in non-occlusive [[Ischemia|ischemic]] colitis.
* [[Vasoconstriction|Vasoconstricting]] drugs such as [[ergotamine]], [[cocaine]], or [[vasopressor]]s can also cause colonic [[ischemia]] with results in non-occlusive [[Ischemia|ischemic]] colitis.


===Microscopic Pathology===
===Microscopic Pathology===
* 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.
** Mildest form, [[Mucous membrane|mucosal]] and [[Submucosa|submucosal]] [[hemorrhage]] and [[edema]] are seen, possibly with mild [[necrosis]] or [[ulceration]].
** In the mildest form [[Mucous membrane|mucosal]] and [[Submucosa|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.
** 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.
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{{WS}}
{{WS}}
[[Category:Gastroenterology]]
[[Category:Gastroenterology]]
[[Category:Surgery]]
[[Category:Medicine]]
[[Category:Disease]]
[[Category:Disease]]
[[Category:Cardiology]]
[[Category:Emergency medicine]]
[[Category:Emergency medicine]]
[[Category:Up-To-Date]]
[[Category:Up-To-Date]]

Latest revision as of 14:12, 5 February 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]

Overview

Ischemic colitis is the result of a sudden reduction in blood flow that is insufficient to meet the metabolic demands of the region of the colon. Ischemic changes will subsequently extend from the mucosa to the serosa. Mucosal injury will develop in 20 minutes to 1 hour and transmural infarction occurs within 8 to 16 hours. Reperfusion injury can occur with the release of reactive oxygen species, which cause lipid peroxidation within cell membranes, causing cell necrosis.

Physiology

Colonic Blood Supply

Pathophysiology

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

Development of Ischemia

Microscopic Pathology

Images

By Nephron Micrograph of a colonic pseudomembrane, a finding that may be associated with ischemic colitis. H&E stain.Source: Own work, CC BY-SA 3.0

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{{#ev:youtube|LCwMQU7ylYg}}

References

  1. Rosenblum JD, Boyle CM, Schwartz LB (1997). "The mesenteric circulation. Anatomy and physiology". Surg Clin North Am. 77 (2): 289–306. PMID 9146713.
  2. Granger DN, Rutili G, McCord JM (1981). "Superoxide radicals in feline intestinal ischemia". Gastroenterology. 81 (1): 22–9. PMID 6263743.
  3. Brandt LJ, Boley SJ, Goldberg L, et al: Colitis in the elderly. Am J Gastroenterol 76:239, 1981.
  4. Washington, Christopher; Carmichael, Joseph (2012). "Management of Ischemic Colitis". Clinics in Colon and Rectal Surgery. 25 (04): 228–235. doi:10.1055/s-0032-1329534. ISSN 1531-0043.

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