Ischemic colitis pathophysiology: Difference between revisions

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{{Ischemic colitis}}
{{Ischemic colitis}}
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==Pathophysiology==
==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 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==
===Colonic Blood Supply===
===Colonic Blood Supply===
* The colon receives blood from both the [[superior mesenteric artery|superior]] and [[inferior mesenteric artery|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.
*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]].  
**[[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]]. and are vulnerable to [[ischemia]] when [[blood]] flow decrease due to hypotension.
 
* [[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.


* The [[rectum]] receives blood from both the [[inferior mesenteric artery]] and the [[internal iliac artery]]; the rectum is rarely involved by colonic ischemia due to this dual blood supply.
==Pathophysiology==
The [[pathophysiology]] of ischemic colitis is as follows:<ref name="pmid6263743">{{cite journal| author=Granger DN, Rutili G, McCord JM| title=Superoxide radicals in feline intestinal ischemia. | journal=Gastroenterology | year= 1981 | volume= 81 | issue= 1 | pages= 22-9 | pmid=6263743 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=6263743  }} </ref><ref>Brandt LJ, Boley SJ, Goldberg L, et al: Colitis in the elderly. Am J Gastroenterol 76:239, 1981.</ref><ref name="WashingtonCarmichael2012">{{cite journal|last1=Washington|first1=Christopher|last2=Carmichael|first2=Joseph|title=Management of Ischemic Colitis|journal=Clinics in Colon and Rectal Surgery|volume=25|issue=04|year=2012|pages=228–235|issn=1531-0043|doi=10.1055/s-0032-1329534}}</ref>


===Development of Ischemia===
===Development of Ischemia===
* Under ordinary conditions, the colon receives between 10% and 35% of the total cardiac output.<ref name="uptodate">UpToDate, ''Colonic ischemia'', accessed 2 September 2006.</ref> If blood flow to the colon drops by more than about 50%, ischemia will develop.
* The [[Colon (anatomy)|colon]] receives between 10% and 35% of the total [[cardiac output]].
* 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.<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> As a result, during periods of [[hypotension|low blood pressure]], the arteries feeding the colon clamp down vigorously.
*If [[blood]] flow to the colon drops by more than about 50%, [[ischemia]] will develop.
* A similar process can result from vasoconstricting drugs such as [[ergotamine]], [[cocaine]], or [[vasopressor]]s. This vasoconstriction can result in non-occlusive ischemic colitis.
* 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.
* [[Vasoconstriction|Vasoconstricting]] drugs such as [[ergotamine]], [[cocaine]], or [[vasopressor]]s can also cause colonic [[ischemia]] which 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.
** In its mildest form, mucosal and 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.<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 mucosae|muscularis]] propria may be replaced by [[Fibrous connective tissue|fibrous tissue]], resulting in a [[stricture]].
** Following restoration of normal blood flow, [[reperfusion injury]] may also contribute to the damage to the colon.<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>
** Following restoration of normal blood flow, [[reperfusion injury]] may contribute to the damage to the [[Colon (anatomy)|colon]].


====Images====
====Images====
[[File:230px-Colonic pseudomembranes intermed mag.jpg|thumb|center|By Nephron - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=8171438]]
[[File:230px-Colonic pseudomembranes intermed mag.jpg|thumb|center|By Nephron Micrograph of a colonic pseudomembrane, a finding that may be associated with ischemic colitis. H&E stain.[https://commons.wikimedia.org/w/index.php?curid=8171438 Source: Own work, CC BY-SA 3.0]]]
 
[[Micrograph]] of a colonic [[pseudomembranous colitis|pseudomembrane]], a finding that may be associated with ischemic colitis. [[H&E stain]].


====Videos====
====Videos====
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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

Videos

{{#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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