Mesenteric ischemia pathophysiology: Difference between revisions

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__NOTOC__
__NOTOC__
{{Mesenteric ischemia}}
{{Mesenteric ischemia}}
{{CMG}} {{AE}} {{FT}}
{{CMG}}; {{AE}} {{FT}}
==Overview==
==Overview==
The factors that regulate the [[intestinal]] blood flow play a vital role in the development of mesenteric ischemia. [[Mucosa]] of the [[intestines]] has a high metabolic activity and accordingly a high blood flow requirement. The majority of blood supply of the [[intestine]] comes from the [[superior mesenteric artery]], with a collateral blood supply from superior and inferior [[Pancreaticoduodenal artery|pancreaticoduodenal arteries]] (branches of the [[celiac artery]]) as well as the [[inferior mesenteric artery]]. The [[splanchnic]] circulation ([[arteries]] supplying the [[viscera]]) receives 15-35% of the [[cardiac output]], making it sensitive to the effects of decreased [[perfusion]]. Mesenteric ischemia occurs when [[intestinal]] blood supply is compromised by more than 50% of the original blood flow without activation of adaptive responses. This can lead to disruption of [[mucosal]] barrier, allowing the release of [[Bacterial toxin|bacterial toxins]] (present in the [[intestinal]] lumen) and [[vasoactive]] mediators which ultimately lead to complete [[necrosis]] (cell death) of the intestinal mucosa. This can further progress to  depression in [[myocardial]] activity, [[sepsis]], [[multiorgan failure]], and without prompt intervention, even death.
The factors that regulate the [[intestinal]] blood flow play a vital role in the development of mesenteric ischemia. [[Mucosa]] of the [[intestines]] has high metabolic activity and therefore requires high blood flow. The majority of blood supply of the [[intestine]] comes from the [[superior mesenteric artery]], with a collateral blood supply from superior and inferior [[Pancreaticoduodenal artery|pancreaticoduodenal arteries]] (branches of the [[celiac artery]]) as well as the [[inferior mesenteric artery]]. The [[splanchnic]] circulation ([[arteries]] supplying the [[viscera]]) receives 15-35% of the [[cardiac output]], making it sensitive to the effects of decreased [[perfusion]]. Mesenteric ischemia occurs when [[intestinal]] blood supply is compromised by more than 50% of the original blood flow without activation of adaptive responses. This can lead to disruption of [[mucosal]] barrier, allowing the release of [[Bacterial toxin|bacterial toxins]] (present in the [[intestinal]] lumen) and [[vasoactive]] mediators which ultimately lead to complete [[necrosis]] (cell death) of the intestinal mucosa. This can further progress to  depression in [[myocardial]] activity, [[sepsis]], [[multiorgan failure]], and without prompt intervention, death.


==Pathophysiology==
==Pathophysiology==
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==== Factors contributing in the pathogenesis of mesenteric ischemia:<ref name="pmid6101568">{{cite journal| author=Granger DN, Richardson PD, Kvietys PR, Mortillaro NA| title=Intestinal blood flow. | journal=Gastroenterology | year= 1980 | volume= 78 | issue= 4 | pages= 837-63 | pmid=6101568 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=6101568  }} </ref><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> ====
==== Factors contributing in the pathogenesis of mesenteric ischemia:<ref name="pmid6101568">{{cite journal| author=Granger DN, Richardson PD, Kvietys PR, Mortillaro NA| title=Intestinal blood flow. | journal=Gastroenterology | year= 1980 | volume= 78 | issue= 4 | pages= 837-63 | pmid=6101568 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=6101568  }} </ref><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> ====
*(a) Mesenteric blood supply (General circulation)
* Mesenteric blood supply (general circulation)
*(b) Collateral circulation
 
*(c) Response of [[mesenteric]] vasculature to [[ischemia]]
*Collateral circulation
*(d) [[Vasoactive]] and [[humoral]] factors
*Response of [[mesenteric]] vasculature to [[ischemia]]
*[[Vasoactive]] and [[humoral]] factors


===(A) Mesenteric blood supply (General circulation)===
===(A) Mesenteric blood supply (General circulation)===
* The [[mesenteric]] circulation recevies approximately 25% of the resting and 35% of the [[postprandial]] [[cardiac output]].
* The [[mesenteric]] circulation receives approximately 25% of the resting and 35% of the [[postprandial]] [[cardiac output]].
* Mucosal and [[submucosal]] layers of the [[intestine]] receive 70% of the [[mesenteric]] blood flow, with the rest supplying the [[muscularis]] and serosal layers.
* Mucosal and [[submucosal]] layers of the [[intestine]] receive 70% of the [[mesenteric]] blood flow, with the rest supplying the [[muscularis]] and serosal layers.


* The arterial supply of the [[intestine]] originates from three major arteries which include [[superior mesenteric artery]], [[inferior mesenteric artery]] and [[celiac artery]]:<ref name="pmid11759648">{{cite journal| author=Kumar S, Sarr MG, Kamath PS| title=Mesenteric venous thrombosis. | journal=N Engl J Med | year= 2001 | volume= 345 | issue= 23 | pages= 1683-8 | pmid=11759648 | doi=10.1056/NEJMra010076 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=11759648  }} </ref><ref name="pmid19491858">{{cite journal| author=Ha C, Magowan S, Accortt NA, Chen J, Stone CD| title=Risk of arterial thrombotic events in inflammatory bowel disease. | journal=Am J Gastroenterol | year= 2009 | volume= 104 | issue= 6 | pages= 1445-51 | pmid=19491858 | doi=10.1038/ajg.2009.81 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=19491858  }} </ref><ref name="pmid6101568">{{cite journal| author=Granger DN, Richardson PD, Kvietys PR, Mortillaro NA| title=Intestinal blood flow. | journal=Gastroenterology | year= 1980 | volume= 78 | issue= 4 | pages= 837-63 | pmid=6101568 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=6101568  }} </ref>
* The arterial supply of the [[intestine]] originates from three major arteries which include [[superior mesenteric artery]], [[inferior mesenteric artery]], and [[celiac artery]]:<ref name="pmid11759648">{{cite journal| author=Kumar S, Sarr MG, Kamath PS| title=Mesenteric venous thrombosis. | journal=N Engl J Med | year= 2001 | volume= 345 | issue= 23 | pages= 1683-8 | pmid=11759648 | doi=10.1056/NEJMra010076 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=11759648  }} </ref><ref name="pmid19491858">{{cite journal| author=Ha C, Magowan S, Accortt NA, Chen J, Stone CD| title=Risk of arterial thrombotic events in inflammatory bowel disease. | journal=Am J Gastroenterol | year= 2009 | volume= 104 | issue= 6 | pages= 1445-51 | pmid=19491858 | doi=10.1038/ajg.2009.81 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=19491858  }} </ref><ref name="pmid6101568">{{cite journal| author=Granger DN, Richardson PD, Kvietys PR, Mortillaro NA| title=Intestinal blood flow. | journal=Gastroenterology | year= 1980 | volume= 78 | issue= 4 | pages= 837-63 | pmid=6101568 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=6101568  }} </ref>
{| class="wikitable"
{| class="wikitable"
!Arterial  
! align="center" style="background:#4479BA; color: #FFFFFF;" | Arterial supply
!Region supplied
! align="center" style="background:#4479BA; color: #FFFFFF;" | Region supplied
|-
|-
|[[Superior mesenteric artery]] (SMA)
|[[Superior mesenteric artery]] ([[SMA]])
|[[Small intestine]], [[proximal]] and mid [[colon]] upto the [[splenic flexure]].
|[[Small intestine]], [[proximal]] and mid [[colon]] up to the [[splenic flexure]].
|-
|-
|[[Inferior mesenteric artery|Inferior mesenteric artery (IMA)]]
|[[Inferior mesenteric artery|Inferior mesenteric artery (IMA)]]
|Hind gut starting from the [[splenic flexure]] to the [[rectum]].
|[[Hindgut]] starting from the [[splenic flexure]] to the [[rectum]].
|-
|-
|[[Celiac artery|Celiac artery (CA)]]
|[[Celiac artery|Celiac artery (CA)]]
|[[Foregut]], [[hepatobiliary system]] and [[spleen]].
|[[Foregut]], [[hepatobiliary system]] and [[spleen]].
|-
|-
! colspan="2" |Venous supply
! colspan="2" style="background:#4479BA; color: #FFFFFF;" |Venous drainage
|-
|-
| colspan="2" |The venous system parallels the arterial branches and drains into the [[portal venous system]].
| colspan="2" |The venous system parallels the arterial branches and drains into the [[portal venous system]].
|}
|}
'''Commonly affected arteries:'''
 
[[Image: Colonic blood supply1.gif|thumb|center|300px|Blood supply to the intestines includes the celiac artery, superior mesenteric artery (SMA), inferior mesenteric artery (IMA), and branches of the internal iliac artery (IIA). <br>Source: By Anpol42 (Own work) [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons]]
 
'''Commonly affected arteries:'''<ref name="Wyers2010">{{cite journal|last1=Wyers|first1=Mark C.|title=Acute Mesenteric Ischemia: Diagnostic Approach and Surgical Treatment|journal=Seminars in Vascular Surgery|volume=23|issue=1|year=2010|pages=9–20|issn=08957967|doi=10.1053/j.semvascsurg.2009.12.002}}</ref>
 
* [[Embolus]] can typically lodge into points of normal [[anatomic]] narrowing.  
* [[Embolus]] can typically lodge into points of normal [[anatomic]] narrowing.  
* This makes [[superior mesenteric artery]] the most vulnerable site because of its relatively larger diameter (more blood flow) and low take off angle (more likely to from the aorta.
* This makes [[superior mesenteric artery]] the most vulnerable site because of its relatively larger diameter (more blood flow) and low take off angle (more likely to from the [[aorta]].
*The majority of [[emboli]] lodge 3-10cm distal to the origin of [[superior mesenteric artery]], classically sparing the proximal [[jejunum]] and [[colon]].
*The majority of [[emboli]] lodge 3-10 cm distal to the origin of [[superior mesenteric artery]], classically sparing the proximal [[jejunum]] and [[colon]].
 
===(B) Collateral circulation===
===(B) Collateral circulation===
The role of collateral circulation in the development of mesenteric ischemia is as follows:<ref name="pmid9146714">{{cite journal| author=McKinsey JF, Gewertz BL| title=Acute mesenteric ischemia. | journal=Surg Clin North Am | year= 1997 | volume= 77 | issue= 2 | pages= 307-18 | pmid=9146714 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=9146714  }} </ref><ref name="pmid21326561">{{cite journal| author=Walker TG| title=Mesenteric vasculature and collateral pathways. | journal=Semin Intervent Radiol | year= 2009 | volume= 26 | issue= 3 | pages= 167-74 | pmid=21326561 | doi=10.1055/s-0029-1225663 | pmc=3036491 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21326561  }} </ref><ref name="pmid3554567">{{cite journal| author=Fisher DF, Fry WJ| title=Collateral mesenteric circulation. | journal=Surg Gynecol Obstet | year= 1987 | volume= 164 | issue= 5 | pages= 487-92 | pmid=3554567 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=3554567  }} </ref><ref name="pmid4025549">{{cite journal| author=Bulkley GB, Womack WA, Downey JM, Kvietys PR, Granger DN| title=Characterization of segmental collateral blood flow in the small intestine. | journal=Am J Physiol | year= 1985 | volume= 249 | issue= 2 Pt 1 | pages= G228-35 | pmid=4025549 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=4025549  }} </ref><ref name="pmid: 3738747">{{cite journal| author=Bulkley GB, Womack WA, Downey JM, Kvietys PR, Granger DN| title=Collateral blood flow in segmental intestinal ischemia: effects of vasoactive agents. | journal=Surgery | year= 1986 | volume= 100 | issue= 2 | pages= 157-66 | pmid=: 3738747 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=3738747 }} </ref><ref name="pmid4025549">{{cite journal| author=Bulkley GB, Womack WA, Downey JM, Kvietys PR, Granger DN| title=Characterization of segmental collateral blood flow in the small intestine. | journal=Am J Physiol | year= 1985 | volume= 249 | issue= 2 Pt 1 | pages= G228-35 | pmid=4025549 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=4025549 }} </ref>
The role of collateral circulation in the development of mesenteric ischemia is as follows:<ref name="pmid9146714">{{cite journal| author=McKinsey JF, Gewertz BL| title=Acute mesenteric ischemia. | journal=Surg Clin North Am | year= 1997 | volume= 77 | issue= 2 | pages= 307-18 | pmid=9146714 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=9146714  }} </ref><ref name="pmid21326561">{{cite journal| author=Walker TG| title=Mesenteric vasculature and collateral pathways. | journal=Semin Intervent Radiol | year= 2009 | volume= 26 | issue= 3 | pages= 167-74 | pmid=21326561 | doi=10.1055/s-0029-1225663 | pmc=3036491 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21326561  }} </ref><ref name="pmid3554567">{{cite journal| author=Fisher DF, Fry WJ| title=Collateral mesenteric circulation. | journal=Surg Gynecol Obstet | year= 1987 | volume= 164 | issue= 5 | pages= 487-92 | pmid=3554567 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=3554567  }} </ref><ref name="pmid4025549">{{cite journal| author=Bulkley GB, Womack WA, Downey JM, Kvietys PR, Granger DN| title=Characterization of segmental collateral blood flow in the small intestine. | journal=Am J Physiol | year= 1985 | volume= 249 | issue= 2 Pt 1 | pages= G228-35 | pmid=4025549 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=4025549  }} </ref><ref name="pmid: 3738747">{{cite journal| author=Bulkley GB, Womack WA, Downey JM, Kvietys PR, Granger DN| title=Collateral blood flow in segmental intestinal ischemia: effects of vasoactive agents. | journal=Surgery | year= 1986 | volume= 100 | issue= 2 | pages= 157-66 | pmid=: 3738747 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=3738747  }} </ref>
* [[Intestines]] receive collateral blood supply at all levels from the superior and inferior pancreaticoduodenal arteries, branches of the [[celiac artery]], which provide protection from [[ischemia]].  
* [[Intestines]] receive collateral blood supply at all levels from the superior and inferior pancreaticoduodenal arteries, branches of the [[celiac artery]], which provide protection from [[ischemia]].  
* These arteries can compensate for 75% reduction in [[mesenteric]] blood flow for upto 12 hours, without substanial injury.
* These arteries can compensate for 75% reduction in [[mesenteric]] blood flow for up to 12 hours, without substanial injury.
*  An extensive [[collateral circulation]] protects the [[intestines]] from transient periods of inadequate [[perfusion]]. However, prolonged reduction in [[splanchnic]] blood flow leads to [[vasoconstriction]] in the affected [[vascular bed]], and eventually reduces collateral blood flow.  
*  An extensive [[collateral circulation]] protects the [[intestines]] from transient periods of inadequate [[perfusion]]. However, prolonged reduction in [[splanchnic]] blood flow leads to [[vasoconstriction]] in the affected [[vascular bed]], and eventually reduces collateral blood flow.  
* The [[Superior mesenteric artery|SMA]] and [[Inferior mesenteric artery|IMA]] communicate via the [[marginal artery]] of Drummond and the meandering [[mesenteric artery]].  
* The [[Superior mesenteric artery|SMA]] and [[Inferior mesenteric artery|IMA]] communicate via the marginal artery of Drummond and the meandering [[mesenteric artery]].  
* [[Collateralization]] between the [[Inferior mesenteric artery|IMA]] and [[systemic circulation]] occurs in the [[rectum]] as the [[Superior rectal plexus|superior rectal]] ([[Hemorrhoidal plexus|hemorrhoidal]]) vessels merge with the [[Middle rectal plexus|middle rectal]] vessels from the [[internal iliac arteries]].
* [[Collateralization]] between the [[Inferior mesenteric artery|IMA]] and [[systemic circulation]] occurs in the [[rectum]] as the [[Superior rectal plexus|superior rectal]] ([[Hemorrhoidal plexus|hemorrhoidal]]) vessels merge with the [[Middle rectal plexus|middle rectal]] vessels from the [[internal iliac arteries]].
* The areas lacking this [[collateralization]] are prone towards [[ischemia]].
* The areas lacking this [[collateralization]] are prone to [[ischemia]].
===(C) Response of mesenteric vasculature to ischemia===
===(C) Response of mesenteric vasculature to ischemia===
* Mesenteric ischemia occurs when the blood supply to [[mesentery]] is reduced leading to disruption of [[cellular metabolism]] owing to [[oxygen]] and [[nutrient]] deficiency.<ref name="pmid26909235">{{cite journal| author=Mastoraki A, Mastoraki S, Tziava E, Touloumi S, Krinos N, Danias N et al.| title=Mesenteric ischemia: Pathogenesis and challenging diagnostic and therapeutic modalities. | journal=World J Gastrointest Pathophysiol | year= 2016 | volume= 7 | issue= 1 | pages= 125-30 | pmid=26909235 | doi=10.4291/wjgp.v7.i1.125 | pmc=4753178 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=26909235  }} </ref><ref name="CorcosNuzzo2013">{{cite journal|last1=Corcos|first1=Olivier|last2=Nuzzo|first2=Alexandre|title=Gastro-Intestinal Vascular Emergencies|journal=Best Practice & Research Clinical Gastroenterology|volume=27|issue=5|year=2013|pages=709–725|issn=15216918|doi=10.1016/j.bpg.2013.08.006}}</ref>
* Mesenteric ischemia occurs when the blood supply to [[mesentery]] is reduced leading to disruption of [[cellular metabolism]] owing to [[oxygen]] and [[nutrient]] deficiency.<ref name="pmid26909235">{{cite journal| author=Mastoraki A, Mastoraki S, Tziava E, Touloumi S, Krinos N, Danias N et al.| title=Mesenteric ischemia: Pathogenesis and challenging diagnostic and therapeutic modalities. | journal=World J Gastrointest Pathophysiol | year= 2016 | volume= 7 | issue= 1 | pages= 125-30 | pmid=26909235 | doi=10.4291/wjgp.v7.i1.125 | pmc=4753178 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=26909235  }} </ref><ref name="CorcosNuzzo2013">{{cite journal|last1=Corcos|first1=Olivier|last2=Nuzzo|first2=Alexandre|title=Gastro-Intestinal Vascular Emergencies|journal=Best Practice & Research Clinical Gastroenterology|volume=27|issue=5|year=2013|pages=709–725|issn=15216918|doi=10.1016/j.bpg.2013.08.006}}</ref>
Line 88: Line 94:


{| class="wikitable"
{| class="wikitable"
! colspan="2" |'''Post [[ischemic]] cellular changes''':
! colspan="2" style="background:#4479BA; color: #FFFFFF;" |'''Post [[ischemic]] cellular changes''':
|-
|-
!Time duration since [[ischemia]]
! style="background:#4479BA; color: #FFFFFF;" |Time duration since [[ischemia]]
!Pathological changes in the [[small intestine]]
! style="background:#4479BA; color: #FFFFFF;" |Pathological changes in the [[small intestine]]
|-
|-
|3-4 hours
|3-4 hours
Line 105: Line 111:
* Restoration of blood flow to the area of [[ischemic]] insult results in [[reperfusion]] injury.
* Restoration of blood flow to the area of [[ischemic]] insult results in [[reperfusion]] injury.
* This leads to release of [[oxygen free radicals]], toxic byproducts of [[ischemic]] injury and [[neutrophil]] activation.
* This leads to release of [[oxygen free radicals]], toxic byproducts of [[ischemic]] injury and [[neutrophil]] activation.
* [[Immune]] cells remove dead and damaged cells releasing [[cytokines]] such as [[TNF-alpha]]
* [[Immune]] cells remove dead and damaged cells releasing [[cytokines]] such as [[TNF-alpha]].
* Blood vessels become more permeable leading to [[edema]] of the [[small intestine]].
* Blood vessels become more permeable leading to [[edema]] of the [[small intestine]].
* As the [[ischemia]] progresses from [[mucosa]] to all the layers beneath (transmural), it leads to breaks in the [[epithelial]] lining.
* As the [[ischemia]] progresses from [[mucosa]] to all the layers beneath (transmural), it leads to breaks in the [[epithelial]] lining.
Line 112: Line 118:


===(D) Vasoactive and humoral factors regulating the mesenteric blood flow===
===(D) Vasoactive and humoral factors regulating the mesenteric blood flow===
* [[Vasoactive]] and [[humoral]] factors control the regulation of [[vascular]] tone of [[mesenteric]] circulation in response to periods of stress such as [[systemic hypotension]] or [[postprandial]] state.
* [[Vasoactive]] and [[humoral]] factors control the regulation of [[vascular]] tone of [[mesenteric]] circulation in response to periods of stress such as [[systemic hypotension]] or [[postprandial]] state.


* Physiologically [[mesenteric]] circulation is affected by:<ref name="pmid10052599">{{cite journal| author=Hansen MB, Dresner LS, Wait RB| title=Profile of neurohumoral agents on mesenteric and intestinal blood flow in health and disease. | journal=Physiol Res | year= 1998 | volume= 47 | issue= 5 | pages= 307-27 | pmid=10052599 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10052599  }} </ref><ref name="pmid8370303">{{cite journal| author=Schoenberg MH, Beger HG| title=Reperfusion injury after intestinal ischemia. | journal=Crit Care Med | year= 1993 | volume= 21 | issue= 9 | pages= 1376-86 | pmid=8370303 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=8370303  }} </ref><ref name="PatelKaleya1992">{{cite journal|last1=Patel|first1=Amit|last2=Kaleya|first2=Ronald N.|last3=Sammartano|first3=Robert J.|title=Pathophysiology of Mesenteric Ischemia|journal=Surgical Clinics of North America|volume=72|issue=1|year=1992|pages=31–41|issn=00396109|doi=10.1016/S0039-6109(16)45626-4}}</ref><ref name="pmid8703630">{{cite journal| author=Takala J| title=Determinants of splanchnic blood flow. | journal=Br J Anaesth | year= 1996 | volume= 77 | issue= 1 | pages= 50-8 | pmid=8703630 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=8703630  }} </ref><ref name="pmid7386643">{{cite journal| author=Granger HJ, Norris CP| title=Intrinsic regulation of intestinal oxygenation in the anesthetized dog. | journal=Am J Physiol | year= 1980 | volume= 238 | issue= 6 | pages= H836-43 | pmid=7386643 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=7386643  }} </ref><ref name="pmid4684756">{{cite journal| author=Granger HJ, Shepherd AP| title=Intrinsic microvascular control of tissue oxygen delivery. | journal=Microvasc Res | year= 1973 | volume= 5 | issue= 1 | pages= 49-72 | pmid=4684756 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=4684756  }} </ref>
* Physiologically [[mesenteric]] circulation is affected by:<ref name="pmid10052599">{{cite journal| author=Hansen MB, Dresner LS, Wait RB| title=Profile of neurohumoral agents on mesenteric and intestinal blood flow in health and disease. | journal=Physiol Res | year= 1998 | volume= 47 | issue= 5 | pages= 307-27 | pmid=10052599 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10052599  }} </ref><ref name="pmid8370303">{{cite journal| author=Schoenberg MH, Beger HG| title=Reperfusion injury after intestinal ischemia. | journal=Crit Care Med | year= 1993 | volume= 21 | issue= 9 | pages= 1376-86 | pmid=8370303 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=8370303  }} </ref><ref name="PatelKaleya1992">{{cite journal|last1=Patel|first1=Amit|last2=Kaleya|first2=Ronald N.|last3=Sammartano|first3=Robert J.|title=Pathophysiology of Mesenteric Ischemia|journal=Surgical Clinics of North America|volume=72|issue=1|year=1992|pages=31–41|issn=00396109|doi=10.1016/S0039-6109(16)45626-4}}</ref><ref name="pmid8703630">{{cite journal| author=Takala J| title=Determinants of splanchnic blood flow. | journal=Br J Anaesth | year= 1996 | volume= 77 | issue= 1 | pages= 50-8 | pmid=8703630 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=8703630  }} </ref><ref name="pmid7386643">{{cite journal| author=Granger HJ, Norris CP| title=Intrinsic regulation of intestinal oxygenation in the anesthetized dog. | journal=Am J Physiol | year= 1980 | volume= 238 | issue= 6 | pages= H836-43 | pmid=7386643 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=7386643  }} </ref><ref name="pmid4684756">{{cite journal| author=Granger HJ, Shepherd AP| title=Intrinsic microvascular control of tissue oxygen delivery. | journal=Microvasc Res | year= 1973 | volume= 5 | issue= 1 | pages= 49-72 | pmid=4684756 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=4684756  }} </ref>
Line 121: Line 127:
'''(a) Metabolic factors:'''   
'''(a) Metabolic factors:'''   
* Reduction in blood supply to the [[mesentery]] causes adaptive changes in the [[splanchnic]] circulation.   
* Reduction in blood supply to the [[mesentery]] causes adaptive changes in the [[splanchnic]] circulation.   
* A discrepancy between tissue oxyegn demand and supply raises the concentration of local [[metabolites]] such as [[hydrogen]], [[potassium]], [[carbon dioxide]], and [[adenosine]], resulting in [[vasodilation]] and [[hyperemia]].  
* A discrepancy between tissue oxyegn demand and supply raises the concentration of local [[metabolites]] such as [[hydrogen]], [[potassium]], [[carbon dioxide]], and [[adenosine]], resulting in [[vasodilation]], and [[hyperemia]].  
'''(b) Myogenic factors:'''  
'''(b) Myogenic factors:'''  
* Myogenic theory suggests that arteriolar tension [[receptors]] act to regulate [[vascular resistance]] in accordance with the transmural pressure.  
* Myogenic theory suggests that arteriolar wall tension [[receptors]] act to regulate [[vascular resistance]] in accordance with the transmural pressure.  
* An [[acute]] decrease in [[perfusion pressure]] is compensated for by a reduction in arteriolar wall tension, thereby maintaining [[splanchnic]] blood flow.
* An [[acute]] decrease in [[perfusion pressure]] is compensated for by a reduction in arteriolar wall tension, thereby maintaining [[splanchnic]] blood flow.
'''<u>Extrinsic regulation:</u>'''
'''<u>Extrinsic regulation:</u>'''
Line 130: Line 136:
* The extrinsic [[neural]] component of [[splanchnic]] [[circulatory]] regulation comprises the alpha-activated [[vasoconstrictor]] fibers.  
* The extrinsic [[neural]] component of [[splanchnic]] [[circulatory]] regulation comprises the alpha-activated [[vasoconstrictor]] fibers.  
* Intense activation of [[vasoconstrictor]] fibers through alpha-[[adrenergic]] stimulation results in [[vasoconstriction]] of small vessels and a decrease in [[mesenteric]] blood flow.  
* Intense activation of [[vasoconstrictor]] fibers through alpha-[[adrenergic]] stimulation results in [[vasoconstriction]] of small vessels and a decrease in [[mesenteric]] blood flow.  
* After periods of prolonged alpha-[[adrenergic]] [[vasoconstriction]], blood flow increases, presumably through β-adrenergic stimulation, which acts as a protective response.  
* After periods of prolonged [[Alpha adrenergic|alpha-adrenergic]] [[vasoconstriction]], blood flow increases, presumably through β-adrenergic stimulation, which acts as a protective response.  
* Although numerous types of neural stimulation (e.g. [[vagal]], [[cholinergic]], histaminergic, and [[sympathetic]]) can affect the blood supply of the gut, the [[adrenergic]] limb of the [[autonomic nervous system]] is the predominant neural influence on [[splanchnic]] circulation.
* Although numerous types of neural stimulation (e.g. [[vagal]], [[cholinergic]], histaminergic, and [[sympathetic]]) can affect the blood supply of the gut, the [[adrenergic]] limb of the [[autonomic nervous system]] is the predominant neural influence on [[splanchnic]] circulation.


Line 155: Line 161:
** [[Glucagon]]
** [[Glucagon]]
{| class="wikitable"
{| class="wikitable"
! colspan="4" |Factors regulating mesenteric blood flow
! colspan="4" style="background:#4479BA; color: #FFFFFF;" |Factors regulating mesenteric blood flow
|-
|-
! colspan="4" |'''Extrinsic reguatory system'''
! colspan="4" style="background:#4479BA; color: #FFFFFF;" |'''Extrinsic reguatory system'''
|-
|-
! colspan="2" |'''Humoral (endogenous and exogenous)'''
! colspan="2" style="background:#4479BA; color: #FFFFFF;" |'''Humoral (endogenous and exogenous)'''
! colspan="2" |'''Neural component'''
! colspan="2" style="background:#4479BA; color: #FFFFFF;" |'''Neural component'''
|-
|-
|'''Decrease blood flow'''
! align="center" style="background:#4479BA; color: #FFFFFF;" |'''Decrease blood flow'''
|'''Increase blood flow'''
! align="center" style="background:#4479BA; color: #FFFFFF;" |'''Increase blood flow'''
|''Decrease blood flow''
! align="center" style="background:#4479BA; color: #FFFFFF;" |'''Decrease blood flow'''
|'''Increase blood flow'''
! align="center" style="background:#4479BA; color: #FFFFFF;" |'''Increase blood flow'''
|-
|-
|
|
* Epinephrine (high dose)
* [[Epinephrine]] (high dose)
* Norepinephrine (moderate to high dose)
* [[Norepinephrine]] (moderate to high dose)
* Dopamine (high dose)
* [[Dopamine]] (high dose)
* Phenylephrine
* [[Phenylephrine]]
* Vasopressin
* [[Vasopressin]]
* Angiotensin  
* [[Angiotensin]]
* Digoxin  
* [[Digoxin]]
|
|
* Epinephrine (low dose)
* [[Epinephrine]] (low dose)
* Norepinephrine (low dose)
* [[Norepinephrine]] (low dose)
* Dopamine (low dose)
* [[Dopamine]] (low dose)
* Dobutamine
* [[Dobutamine]]
* Sodium nitroprusside
* [[Sodium nitroprusside]]
* Papaverine
* [[Papaverine]]
* Nitric oxide
* [[Nitric oxide]]
* Acetylcholine  
* [[Acetylcholine]]
* Histamine
* [[Histamine]]
|
|
* Alpha-adrenergic receptors
* [[Alpha adrenergic|Alpha-adrenergic]] receptors
* Dopamenergic receptors
* [[Dopaminergic]] receptors
|
|
* Beta adrenergic receptors
* Beta [[adrenergic]] receptors
|-
|-
! colspan="4" |'''Intrinsic regulatory component'''
! colspan="4" style="background:#4479BA; color: #FFFFFF;" |'''Intrinsic regulatory component'''
|-
|-
| colspan="2" |'''Decrease blood flow'''
| colspan="2" style="background:#4479BA; color: #FFFFFF;" |'''Decrease blood flow (Myogenic factors)'''
| colspan="2" |'''Increase blood flow'''
| colspan="2" style="background:#4479BA; color: #FFFFFF;" |'''Increase blood flow (Metabolic factors)'''
|-
|-
| colspan="2" |
| colspan="2" |
* Arteriolar tension receptors
* Arteriolar tension receptors
| colspan="2" |
| colspan="2" |
* Hydrogen
* [[Hydrogen]]
* Potasssium
* [[Potassium]]
* Carbon dioxide
* [[Carbon dioxide]]
* Adenosine  
* [[Adenosine]]
|}
|}
'''Areas prone to ischemia:'''
===Areas prone to ischemia===


{| class="wikitable"
{| class="wikitable"
!Areas prone to ischemia  
! align="center" style="background:#4479BA; color: #FFFFFF;" | Areas prone to ischemia  
! colspan="3" |Blood supply
! style="background:#4479BA; color: #FFFFFF;" | Blood supply
|-
|-
|Splenic flexure
|[[Splenic flexure]]
| colspan="3" |End arteries of superior mesenteric artery
|End arteries of [[superior mesenteric artery]]
|-
|-
|Rectosigmoid junction
|Rectosigmoid junction
| colspan="3" |End arteries of inferior mesenteric artery
|End arteries of [[inferior mesenteric artery]]
|-
|Middle segment of [[jejunum]]
|
|}
|}
* The watershed areas that lack collateralization are as follows:


* Splenic flexure
==== Watershed areas lacking collateralization: ====
** Supplied by the end arteries of SMA with no collateral circulation.
* [[Splenic flexure]]
** Supplied by the end arteries of [[Superior mesenteric artery|SMA]] with no collateral circulation.
* Rectosigmoid junction
* Rectosigmoid junction
Supplied by the end arteries of IMA with no collateral circulation.
** Supplied by the end arteries of [[Inferior mesenteric artery|IMA]] with no collateral circulation.
* Middle segment of jejunum<ref name="pmid9890114">{{cite journal| author=Cappell MS| title=Intestinal (mesenteric) vasculopathy. I. Acute superior mesenteric arteriopathy and venopathy. | journal=Gastroenterol Clin North Am | year= 1998 | volume= 27 | issue= 4 | pages= 783-825, vi | pmid=9890114 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=9890114  }} </ref>
 
** This area is the farthest from collateral circulation and hence prone to ischemia as compared to other segments of jejunum.
* Middle segment of [[jejunum]]<ref name="pmid9890114">{{cite journal| author=Cappell MS| title=Intestinal (mesenteric) vasculopathy. I. Acute superior mesenteric arteriopathy and venopathy. | journal=Gastroenterol Clin North Am | year= 1998 | volume= 27 | issue= 4 | pages= 783-825, vi | pmid=9890114 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=9890114  }} </ref>
** This area is the farthest from collateral circulation and hence prone to [[ischemia]] as compared to other segments of [[jejunum]].


===Pathogenesis of occlusive mesenteric ischemia:===
===Pathogenesis of occlusive mesenteric ischemia:===
Line 229: Line 239:


{{familytree/start|summary=Sample 1}}
{{familytree/start|summary=Sample 1}}
{{familytree| | | | | | | | | |B01| | | | | | | | |B01= Vascular occlusion|}}
{{familytree| | | | | | | | | |B01| | | | | | | | |B01= [[Vascular]] [[occlusion]]|}}
{{familytree| | | | | | | | | | |!| | | | | | | | |}}
{{familytree| | | | | | | | | | |!| | | | | | | | |}}
{{familytree| | | | | | | | | |C01| | | | | | | | |C01= Blood flow<metabolic demand|}}
{{familytree| | | | | | | | | |C01| | | | | | | | |C01= Blood flow<metabolic demand|}}
{{familytree| | | |,|-|-|-|-|-|-|+|-|-|-|-|-|-|-|.| |}}
{{familytree| | | |,|-|-|-|-|-|-|+|-|-|-|-|-|-|-|.| |}}
{{familytree| | |D01| | | | |D02| | | | | | |D03|D01= Mucosal barrier disruption and bacterial translocation into the circulation|D02= Anerobic glycolysis in mucosa and lactate production|D03= Activation of vascular and humoral factors leading to vasoconstriction|}}
{{familytree| | |D01| | | | |D02| | | | | | |D03|D01= [[Mucosal]] barrier disruption and [[bacterial]] translocation into the circulation|D02= Anaerobic [[glycolysis]] in [[mucosa]] and [[lactate]] production|D03= Activation of [[vascular]] and [[humoral]] factors leading to [[vasoconstriction]]|}}
{{familytree| | | |!| | | | | | |!| | | | | | | |!|}}
{{familytree| | | |!| | | | | | |!| | | | | | | |!|}}
{{familytree| | |E01| | | | |E02| | | | | | |E03|E01= Systemic activation of inflammatory response|E02= Lactic acidosis|E03= Intestinal necrosis|}}
{{familytree| | |E01| | | | |E02| | | | | | |E03|E01= Systemic activation of [[inflammatory]] response|E02= [[Lactic acidosis]]|E03= [[Intestinal]] [[necrosis]]|}}
{{familytree| | | |`|-|-|-|-|-|-|+|-|-|-|-|-|-|-|'| |}}
{{familytree| | | |`|-|-|-|-|-|-|+|-|-|-|-|-|-|-|'| |}}
{{familytree| | | | | | | | | | |!| | | | | | | | |}}
{{familytree| | | | | | | | | | |!| | | | | | | | |}}
{{familytree| | | | | | | | | |F01| | | | | | | | |F01= Multiorgan failure|}}
{{familytree| | | | | | | | | |F01| | | | | | | | |F01= [[Multiorgan failure]]|}}
{{familytree/end}}
{{familytree/end}}


Line 244: Line 254:
<br><br>
<br><br>
{{familytree/start|summary=Sample 1}}
{{familytree/start|summary=Sample 1}}
{{familytree| | | | X01 | | | | | | | | | | | X02 |X01=Hypovolemia|X02= Cardiac failure|}}
{{familytree| | | | X01 | | | | | | | | | | | X02 |X01=[[Hypovolemia]]|X02= [[Cardiac failure]]|}}
{{familytree| | | |`|-|-|-|-|-|-|v|-|-|-|-|-|-|-|'| |}}
{{familytree| | | |`|-|-|-|-|-|-|v|-|-|-|-|-|-|-|'| |}}
{{familytree| | | | | | | | | |A01| | | | | | | | |A01= Endogenous vasoconstriction|}}
{{familytree| | | | | | | | | |A01| | | | | | | | |A01= [[Endogenous]] [[vasoconstriction]]|}}
{{familytree| | | | | | | | | | |!| | | | | | | | |}}
{{familytree| | | | | | | | | | |!| | | | | | | | |}}
{{familytree| | | | | | | | | |B01| | | | | | | | |B01= Splanchnic vasoconstriction|}}
{{familytree| | | | | | | | | |B01| | | | | | | | |B01= [[Splanchnic]] [[vasoconstriction]]|}}
{{familytree| | | | | | | | | | |!| | | | | | | | |}}
{{familytree| | | | | | | | | | |!| | | | | | | | |}}
{{familytree| | | | | | | | | |C01| | | | | | | | |C01= Gut mucosal hypoperfusion|}}
{{familytree| | | | | | | | | |C01| | | | | | | | |C01= Gut mucosal hypoperfusion|}}
{{familytree| | | |,|-|-|-|-|-|-|^|-|-|-|-|-|-|-|.| |}}
{{familytree| | | |,|-|-|-|-|-|-|^|-|-|-|-|-|-|-|.| |}}
{{familytree| | |D01| | | | | | | | | | | | | |D02|D01= Restoration of blood by vasodialtion of collaterals|D02= Gut mucosal barrier disruption|}}
{{familytree| | |D01| | | | | | | | | | | | | |D02|D01= Restoration of blood by [[vasodilation]] of collaterals|D02= Gut [[mucosal]] barrier disruption|}}
{{familytree| | | |!| | | | | | | | | | | | | | |!|}}
{{familytree| | | |!| | | | | | | | | | | | | | |!|}}
{{familytree| | |E01| | | | | | | | | | | | | |E02|E01= Ischemia-reperfusion injury|E02= Increased mucosal perfusion to bacterial toxins|}}
{{familytree| | |E01| | | | | | | | | | | | | |E02|E01= [[Ischemia]]-reperfusion injury|E02= Increased [[mucosal]] [[perfusion]] to [[bacterial]] [[toxins]]|}}
{{familytree| | | |`|-|-|-|-|-|-|v|-|-|-|-|-|-|-|'| |}}
{{familytree| | | |`|-|-|-|-|-|-|v|-|-|-|-|-|-|-|'| |}}
{{familytree| | | | | | | | | | |!| | | | | | | | |}}
{{familytree| | | | | | | | | | |!| | | | | | | | |}}
{{familytree| | | | | | | | | |F01| | | | | | | | |F01= Activation of inflammatory response|}}
{{familytree| | | | | | | | | |F01| | | | | | | | |F01= Activation of [[inflammatory]] response|}}
{{familytree/end}}
{{familytree/end}}


==Gross Pathology==
==Gross Pathology==
Gross pathology shows following changes:
Gross pathology shows following changes:
*Early stage of ischemia: Intestinal wall in congested.
*Early stage of [[ischemia]]
*Late stage of ischemia: Edematous, friable and hemorrhagic bowel wall.
**[[Intestinal wall]] in [[congested]].
*Late stage of [[ischemia]]
**[[Edema|Edematous]], friable and [[hemorrhagic]] [[bowel]] wall.
 
== Microscopic pathology ==
Mesenteric ischemia is classified histopathologically into five grades:<ref name="pmid16332482">{{cite journal| author=Rosow DE, Sahani D, Strobel O, Kalva S, Mino-Kenudson M, Holalkere NS et al.| title=Imaging of acute mesenteric ischemia using multidetector CT and CT angiography in a porcine model. | journal=J Gastrointest Surg | year= 2005 | volume= 9 | issue= 9 | pages= 1262-74; discussion 1274-5 | pmid=16332482 | doi=10.1016/j.gassur.2005.07.034 | pmc=3807105 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16332482  }} </ref>
* Grade 1. Normal. [[Vascular]] [[congestion]] is absent, and both the villous architecture and [[Muscle|muscular]] layer are preserved. 
 
* Grade 2. Villous architecture is preserved, with some mucosal congestion and dilated [[Capillary|capillaries]]. 
 
* Grade 3. There is [[congestion]] of mucosa with loss of superficial [[Gland|glandular]] architecture, but deep villous architecture is preserved.
 
* Grade 4. [[Muscle|Muscular]] layer is preserved, but the mucosa is completely involved, with loss of all superficial and deep [[Gland|glandular]] architecture. 
 
* Grade 5. There is total loss of [[Gland|glandular]] architecture, and the muscularis propria shows degeneration, fragmentation, and [[Skeletal muscle|myocyte]] death, all of which indicate transmural [[infarction]].


==References==
==References==
Line 269: Line 293:
{{Reflist|2}}
{{Reflist|2}}


[[Category:Needs content]]
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Latest revision as of 12:41, 14 April 2021


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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Feham Tariq, MD [2]

Overview

The factors that regulate the intestinal blood flow play a vital role in the development of mesenteric ischemia. Mucosa of the intestines has high metabolic activity and therefore requires high blood flow. The majority of blood supply of the intestine comes from the superior mesenteric artery, with a collateral blood supply from superior and inferior pancreaticoduodenal arteries (branches of the celiac artery) as well as the inferior mesenteric artery. The splanchnic circulation (arteries supplying the viscera) receives 15-35% of the cardiac output, making it sensitive to the effects of decreased perfusion. Mesenteric ischemia occurs when intestinal blood supply is compromised by more than 50% of the original blood flow without activation of adaptive responses. This can lead to disruption of mucosal barrier, allowing the release of bacterial toxins (present in the intestinal lumen) and vasoactive mediators which ultimately lead to complete necrosis (cell death) of the intestinal mucosa. This can further progress to depression in myocardial activity, sepsis, multiorgan failure, and without prompt intervention, death.

Pathophysiology

Pathogenesis

Factors contributing in the pathogenesis of mesenteric ischemia:[7][8]

  • Mesenteric blood supply (general circulation)

(A) Mesenteric blood supply (General circulation)

Arterial supply Region supplied
Superior mesenteric artery (SMA) Small intestine, proximal and mid colon up to the splenic flexure.
Inferior mesenteric artery (IMA) Hindgut starting from the splenic flexure to the rectum.
Celiac artery (CA) Foregut, hepatobiliary system and spleen.
Venous drainage
The venous system parallels the arterial branches and drains into the portal venous system.
Blood supply to the intestines includes the celiac artery, superior mesenteric artery (SMA), inferior mesenteric artery (IMA), and branches of the internal iliac artery (IIA).
Source: By Anpol42 (Own work) [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons

Commonly affected arteries:[11]

(B) Collateral circulation

The role of collateral circulation in the development of mesenteric ischemia is as follows:[12][13][14][15][16]

(C) Response of mesenteric vasculature to ischemia

The sequence of events that take place in the small intestine subsequent to decreased blood flow:



 
 
 
Ischemic insult
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Decreased delivery of oxygen and nutrients
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Disruption in cellular metabolism
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Tissue injury due to hypoxia and reperfusion
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Full thickness necrosis of the bowel
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Perforation of the bowel wall
 
 
 
 


Post ischemic cellular changes:
Time duration since ischemia Pathological changes in the small intestine
3-4 hours Necrosis of the mucosal villi
6 hours Transmural, mural or mucosal infarction
1-4 days Bowel hemorrhage

Reperfusion injury:

(D) Vasoactive and humoral factors regulating the mesenteric blood flow

Intrinsic regulation:

(a) Metabolic factors:

(b) Myogenic factors:

Extrinsic regulation:

(a) Neural component:

(b) Humoral component:

Factors regulating mesenteric blood flow
Extrinsic reguatory system
Humoral (endogenous and exogenous) Neural component
Decrease blood flow Increase blood flow Decrease blood flow Increase blood flow
Intrinsic regulatory component
Decrease blood flow (Myogenic factors) Increase blood flow (Metabolic factors)
  • Arteriolar tension receptors

Areas prone to ischemia

Areas prone to ischemia Blood supply
Splenic flexure End arteries of superior mesenteric artery
Rectosigmoid junction End arteries of inferior mesenteric artery
Middle segment of jejunum

Watershed areas lacking collateralization:

  • Splenic flexure
    • Supplied by the end arteries of SMA with no collateral circulation.
  • Rectosigmoid junction
    • Supplied by the end arteries of IMA with no collateral circulation.
  • Middle segment of jejunum[25]
    • This area is the farthest from collateral circulation and hence prone to ischemia as compared to other segments of jejunum.

Pathogenesis of occlusive mesenteric ischemia:



 
 
 
 
 
 
 
 
 
Vascular occlusion
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Blood flow<metabolic demand
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Mucosal barrier disruption and bacterial translocation into the circulation
 
 
 
 
Anaerobic glycolysis in mucosa and lactate production
 
 
 
 
 
 
Activation of vascular and humoral factors leading to vasoconstriction
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Systemic activation of inflammatory response
 
 
 
 
Lactic acidosis
 
 
 
 
 
 
Intestinal necrosis
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Multiorgan failure
 
 
 
 
 
 
 
 

Pathogenesis of non-occlusive mesenteric ischemia:



 
 
 
Hypovolemia
 
 
 
 
 
 
 
 
 
 
Cardiac failure
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Endogenous vasoconstriction
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Splanchnic vasoconstriction
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Gut mucosal hypoperfusion
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Restoration of blood by vasodilation of collaterals
 
 
 
 
 
 
 
 
 
 
 
 
 
Gut mucosal barrier disruption
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Ischemia-reperfusion injury
 
 
 
 
 
 
 
 
 
 
 
 
 
Increased mucosal perfusion to bacterial toxins
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Activation of inflammatory response
 
 
 
 
 
 
 
 

Gross Pathology

Gross pathology shows following changes:

Microscopic pathology

Mesenteric ischemia is classified histopathologically into five grades:[26]

  • Grade 2. Villous architecture is preserved, with some mucosal congestion and dilated capillaries
  • Grade 3. There is congestion of mucosa with loss of superficial glandular architecture, but deep villous architecture is preserved.
  • Grade 4. Muscular layer is preserved, but the mucosa is completely involved, with loss of all superficial and deep glandular architecture. 
  • Grade 5. There is total loss of glandular architecture, and the muscularis propria shows degeneration, fragmentation, and myocyte death, all of which indicate transmural infarction.

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