Difference between revisions of "Small intestine"

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Small intestine (view source)

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[[Image:Small intestine low mag.jpg|thumb|250px|right|Small bowel mucosa. [[H&E stain]].]]
The '''small intestine''', also '''small bowel''', is a relatively well-behaved piece of machinery from the perspective of [[pathology]].  It is uncommonly affected by malignancies, relative to its length when compared to the [[colon]] and [[rectum]].   
The '''small intestine''', also '''small bowel''', is a relatively well-behaved piece of machinery from the perspective of [[pathology]].  It is uncommonly affected by malignancies, relative to its length when compared to the [[colon]] and [[rectum]].   


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The later two parts keep ''general surgeons'' awake at night (quite literally) 'cause they get obstructed and need urgent operations.
The later two parts keep ''general surgeons'' awake at night (quite literally) 'cause they get obstructed and need urgent operations.
====Length====
*Normal length of small bowel = 3-8 metres.<ref name=pmid10422101>{{Cite journal  | last1 = Nightingale | first1 = JM. | title = Management of patients with a short bowel. | journal = Nutrition | volume = 15 | issue = 7-8 | pages = 633-7 | month =  | year =  | doi =  | PMID = 10422101 }}</ref>
"Short":
*Less than 200 cm = ''short bowel syndrome''.<ref name=pmid20709285>{{Cite journal  | last1 = Donohoe | first1 = CL. | last2 = Reynolds | first2 = JV. | title = Short bowel syndrome. | journal = Surgeon | volume = 8 | issue = 5 | pages = 270-9 | month = Oct | year = 2010 | doi = 10.1016/j.surge.2010.06.004 | PMID = 20709285 }}</ref><ref name=pmid16207689>{{Cite journal  | last1 = Matarese | first1 = LE. | last2 = O'Keefe | first2 = SJ. | last3 = Kandil | first3 = HM. | last4 = Bond | first4 = G. | last5 = Costa | first5 = G. | last6 = Abu-Elmagd | first6 = K. | title = Short bowel syndrome: clinical guidelines for nutrition management. | journal = Nutr Clin Pract | volume = 20 | issue = 5 | pages = 493-502 | month = Oct | year = 2005 | doi =  | PMID = 16207689 }}</ref>
**Less than 100 cm usu. requires parenteral nutrition.<ref name=pmid11873098>{{Cite journal  | last1 = Sundaram | first1 = A. | last2 = Koutkia | first2 = P. | last3 = Apovian | first3 = CM. | title = Nutritional management of short bowel syndrome in adults. | journal = J Clin Gastroenterol | volume = 34 | issue = 3 | pages = 207-20 | month = Mar | year = 2002 | doi =  | PMID = 11873098 }}</ref>


===Histology===
===Histology===
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===Sign out===
===Sign out===
<pre>
Small Bowel, Biopsy:
- Small bowel mucosa within normal limits.
</pre>
<pre>
Terminal Ileum, Biopsy:
- Small bowel mucosa within normal limits.
</pre>
<pre>
Terminal Ileum, Biopsy:
- Small bowel mucosa with morphologically benign lymphoid aggregates, negative for significant pathology.
</pre>
====Roux-en-Y gastric bypass====
{{Main|Obese}}
{{Main|Roux-en-Y gastric bypass}}
====Block letters====
<pre>
<pre>
SMALL BOWEL, BIOPSY:
SMALL BOWEL, BIOPSY:
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TERMINAL ILEUM, BIOPSY:
TERMINAL ILEUM, BIOPSY:
- SMALL BOWEL MUCOSA WITHIN NORMAL LIMITS.
- SMALL BOWEL MUCOSA WITHIN NORMAL LIMITS.
</pre>
<pre>
TERMINAL ILEUM, BIOPSY:
- SMALL BOWEL MUCOSA WITH MORPHOLOGICAL BENIGN LYMPHOID AGGREGATES, NO SIGNIFICANT PATHOLOGY.
</pre>
</pre>


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==Ileum==
==Ileum==
*This is seen occasionally -- often in the context of IBD and more specifically [[Crohn's disease]].
*This is seen occasionally -- often in the context of [[IBD]] and more specifically [[Crohn's disease]].
*Crohn's disease (and [[ulcerative colitis]]) is discussed in the ''[[colon]]'' article.
**[[Crohn's disease]] and[[ulcerative colitis]] are discussed in their respective articles.


=Specific conditions=
=Specific diagnoses=
==Small bowel obstruction==
==Ileitis==
*Abbreviated ''SBO''.
:''Active ileitis'' and ''acute ileitis'' redirect here.
:This deals with nonspecific ileitis.
===General===
===General===
*Radiologic/[[clinical diagnosis]].
*Common.


The usual causes of bowel obstruction (large & small) are (mnemonic) ''SHAVING'':
===Microscopic===
*Strictures (think [[IBD]]).
Features:
*Hernias.
*Intraepithelial [[neutrophil]]s.
*Adhesions.
*[[Volvulus]].
*Intussusception.
*Neoplasia.
*Gallstone ileus.


The top three are:<ref>URL: [http://www.emedicine.com/EMERG/topic66.htm http://www.emedicine.com/EMERG/topic66.htm]. Accessed on: 19 April 2011.</ref><ref>TN 2007 GS21</ref>
DDx:
* Adhesions > hernias > neoplasms.
*[[Crohn's disease]].
*Infectious ileitis.
**[[Tuberculosis]].
*Benign ileum - may have focal intra-epithelial lymphocytes associated with lamina propria lymphoid nodules.
*[[NSAID enteropathy]].<ref name=pmid20532706>{{Cite journal  | last1 = Dilauro | first1 = S. | last2 = Crum-Cianflone | first2 = NF. | title = Ileitis: when it is not Crohn's disease. | journal = Curr Gastroenterol Rep | volume = 12 | issue = 4 | pages = 249-58 | month = Aug | year = 2010 | doi = 10.1007/s11894-010-0112-5 | PMID = 20532706 }}</ref>


In the context of bowel obstructions and IBD, pathologists often see resected [[stoma]]s (that were put in place emergently). These specimens are usually fairly straight forward.
====Images====
<gallery>
Image: Mild ileitis -- very low mag.jpg | Ileitis - very low mag. (WC)
Image: Mild ileitis -- low mag.jpg | Ileitis - low mag. (WC)
Image: Mild ileitis -- intermed mag.jpg | Ileitis - intermed. mag. (WC)
Image: Mild ileitis -- high mag.jpg | Ileitis - high mag. (WC)
</gallery>


===Gross===
===Sign out===
*+/-Adhesions.
<pre>
*+/-Bowel contorted.
Terminal Ileum, Biopsy:
*+/-Luminal narrowing +/-proximal dilation.
- Small bowel with moderate active inflammation, marked villous blunting, basal plasmacytosis
*+/-Serosal exudate.
  and prominent eosinophils, see comment.
**Suggestive of perforation.
- NEGATIVE for granulomas.
- NEGATIVE for dysplasia.


===Microscopic===
Comment:  
Features:
The inflammation is nonspecific; it could be due to infection, inflammatory bowel disease (especially Crohn's disease), ischemia, or therapy/drugs. Clinical correlation is required.
*+/-Adhesions (serosal).
</pre>
**Dense fibrous tissue replaces the adipose tissue.
**+/-Increased vascularity.
*+/-Submucosal fibrosis.


DDx:
==Small bowel obstruction==
*Small bowel [[adenocarcinoma]] - most important differential diagnosis.
*Abbreviated ''SBO''.
*Metastatic adenocarcinoma - classically on the serosal aspect.
{{Main|Small bowel obstruction}}
*[[Signet ring cell carcinoma]].


==Small bowel neoplasms==
==Small bowel neoplasms==
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*[[Schwannoma]].
*[[Schwannoma]].
**Classically have a ''peripheral lymphoid cuff''.<ref name=pmid15728600>{{cite journal |author=Levy AD, Quiles AM, Miettinen M, Sobin LH |title=Gastrointestinal schwannomas: CT features with clinicopathologic correlation |journal=AJR Am J Roentgenol |volume=184 |issue=3 |pages=797–802 |year=2005 |month=March |pmid=15728600 |doi= |url=http://www.ajronline.org/cgi/content/full/184/3/797}}</ref>
**Classically have a ''peripheral lymphoid cuff''.<ref name=pmid15728600>{{cite journal |author=Levy AD, Quiles AM, Miettinen M, Sobin LH |title=Gastrointestinal schwannomas: CT features with clinicopathologic correlation |journal=AJR Am J Roentgenol |volume=184 |issue=3 |pages=797–802 |year=2005 |month=March |pmid=15728600 |doi= |url=http://www.ajronline.org/cgi/content/full/184/3/797}}</ref>
==Mechanical small bowel perforation==
:See ''[[mechanical bowel perforation]]''.


==Ileal nodular lymphoid hyperplasia==
==Ileal nodular lymphoid hyperplasia==
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Features:
Features:
*Lymphoid nodules +/- germinal centre formation.
*Lymphoid nodules +/- germinal centre formation.
Note:
*Tingible body macrophages suggest an aggregate is benign.


DDx:
DDx:
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===IHC===
===IHC===
*CD20 and CD3 - mixed population of lymphocytes.
*[[CD20]] and CD3 - mixed population of lymphocytes.
*CD23 - follicular dendritic cells.
*[[CD23]] - follicular dendritic cells.
*Cyclin D1 -ve.
*Cyclin D1 -ve.


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**Histologic suspicion - either:
**Histologic suspicion - either:
***Sheets of lymphocytes without apparent germinal centre formation in a larger area (~ 2 mm).
***Sheets of lymphocytes without apparent germinal centre formation in a larger area (~ 2 mm).
***Lymphoepithelial lesions.
***[[Lymphoepithelial lesion]]s.


===Sign out===
===Sign out===
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The sections show small bowel mucosa with lymphoid hyperplasia.
The sections show small bowel mucosa with lymphoid hyperplasia.


Immunostains for CD3, CD20 show a mixed population of lymphocytes.  CD23 show follicular
Immunostains for CD3 and CD20 show a mixed population of lymphocytes.  A CD23 immunostain shows follicular dendritic cell networks. A cyclin D1 immunostain is negative.
dendritic cells. Cyclin D1 is negative.
 
=====Alternate=====
Immunostains for CD3 and CD20 show a mixed population of lymphocytes, with CD20 cells predominating. A cyclin D1 immunostain is negative. A CD23 immunostain shows follicular dendritic cell networks.


==Multiple lymphomatous polyposis==
==Multiple lymphomatous polyposis==
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DDx:
DDx:
*Cryptogenic multifocal ulcerous stenosing enteritis.<ref>{{Cite journal  | last1 = Chung | first1 = SH. | last2 = Jo | first2 = Y. | last3 = Ryu | first3 = SR. | last4 = Ahn | first4 = SB. | last5 = Son | first5 = BK. | last6 = Kim | first6 = SH. | last7 = Park | first7 = YS. | last8 = Hong | first8 = YO. | title = Diaphragm disease compared with cryptogenic multifocal ulcerous stenosing enteritis. | journal = World J Gastroenterol | volume = 17 | issue = 23 | pages = 2873-6 | month = Jun | year = 2011 | doi = 10.3748/wjg.v17.i23.2873 | PMID = 21734797 }}</ref> (???)
*[[Crohn's disease]].
*[[Crohn's disease]].


==Meckel diverticulum==
==Meckel diverticulum==
===General===
{{Main|Meckel diverticulum}}
*Most common congenital anomaly of the gastrointestinal tract.<ref name=pmid15026601>{{Cite journal  | last1 = Levy | first1 = AD. | last2 = Hobbs | first2 = CM. | title = From the archives of the AFIP. Meckel diverticulum: radiologic features with pathologic Correlation. | journal = Radiographics | volume = 24 | issue = 2 | pages = 565-87 | month =  | year =  | doi = 10.1148/rg.242035187 | PMID = 15026601 }}</ref>
**Remnant of the ''omphalomesenteric duct'' - a connection of the yolk sac and midgut.
 
The rule of 2s:
*2 feet from the terminal ileum
*2% of the population
*2% symptomatic.
*2 inches long.
*2 year old.
*2 types of epithelium - gastric and pancreatic.
 
Main clinical DDx of a symptomatic Meckel diverticulum:
*[[Appendicitis]].
 
===Gross===
*Antimesenteric attachement, i.e. a ''Meckel's diverticulum'' hangs off the side opposite of the mesentery.
 
Image:
*[http://commons.wikimedia.org/wiki/File:Meckel%27s_Diverticulum_AFIP.jpg Meckel diverticulum - (AFIP/WC)].
 
===Microscopic===
Features:<ref name=pmid15026601/>
*Small bowel mucosa.
*+/-Gastric mucosa:
**Foveolar epithelium: champagne flute-like columnar epithelium.
**Oxyntic mucosa: parietal cells (pink) and chief cells (purple).
*+/-Pancreatic epithelium:
**Pancreatic acini.
 
Images:
*[http://radiographics.rsna.org/content/24/2/565/F12.expansion.html Gastric foveolar epithelium in a MD (radiographics.rsna.org)].
*[http://radiographics.rsna.org/content/24/2/565/F15.expansion.html Gastric glands in a MD (radiographics.rsna.org)].
*[http://radiographics.rsna.org/content/24/2/565.long Pancreatic glands in a MD (radiographics.rsna.org)].


==Ischemic enteritis==
==Ischemic enteritis==
===General===
{{Main|Ischemic enteritis}}
*Typically elderly and due to [[atherosclerosis]].
*Rare.
*High mortality.<ref name=pmid18616124>{{Cite journal  | last1 = Nakase | first1 = H. | title = [Ischemic enteritis]. | journal = Nihon Rinsho | volume = 66 | issue = 7 | pages = 1330-4 | month = Jul | year = 2008 | doi =  | PMID = 18616124 }}</ref>
*May occur together with ischemia of the colon, i.e. ''[[ischemic colitis]]'', in which case it is known as ''ischemic enterocolitis''.
 
Etiologies:
*[[Atherosclerosis]].
*[[Vasculitis]].
*Embolism.
*Thrombosis.
 
===Microscopic===
Features:
*See ''[[ischemic colitis]]''.
 
DDx:
*Infection.
*[[Crohn's disease]].
*Radiation.
*Drugs/toxins.


=Weird stuff=
=Weird stuff=
==Autoimmune enteropathy==
==Autoimmune enteropathy==
*Abbreviated as ''AIE''.
*Abbreviated as ''AIE''.
===General===
{{Main|Autoimmune enteropathy}}
*Considered a pediatric disease.
*Super rare in adults - there are only ~11 reported cases in the literature.<ref name=pmid17683994>{{Cite journal  | last1 = Akram | first1 = S. | last2 = Murray | first2 = JA. | last3 = Pardi | first3 = DS. | last4 = Alexander | first4 = GL. | last5 = Schaffner | first5 = JA. | last6 = Russo | first6 = PA. | last7 = Abraham | first7 = SC. | title = Adult autoimmune enteropathy: Mayo Clinic Rochester experience. | journal = Clin Gastroenterol Hepatol | volume = 5 | issue = 11 | pages = 1282-90; quiz 1245 | month = Nov | year = 2007 | doi = 10.1016/j.cgh.2007.05.013 | PMID = 17683994 | PMC = 2128725 | URL = http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2128725/ }}</ref>
 
Diagnosis is clinico-pathologic:<ref name=pmid17683994/>
#Intact immune system.
#Autoantibodies.
#*Anti-enterocyte antibody.
#*Anti-goblet antibody.
#Lack of response to gluten-free diet.
 
===Microscopic===
Features:<ref name=pmid17683994/>
*+/-Loss of goblet cells.
*+/-Loss of paneth cells.
*Villous blunting.
 
DDx:
*[[Celiac disease]].


=See also=
=See also=
Michael
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