Difference between revisions of "Small intestine"

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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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===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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==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]] are discussed their respective articles.
**[[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'':
*Strictures (think [[IBD]]).
*Hernias.
*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>
* Adhesions > hernias > neoplasms.
 
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.
 
===Radiology===
*Air-fluid levels.
 
===Gross===
*+/-Adhesions.
*+/-Bowel contorted.
*+/-Luminal narrowing +/-proximal dilation.
*+/-Serosal exudate.
**Suggestive of perforation.


===Microscopic===
===Microscopic===
Features:
Features:
*+/-Adhesions (serosal).
*Intraepithelial [[neutrophil]]s.
**Dense fibrous tissue replaces the adipose tissue.
**+/-Increased vascularity.
*+/-Submucosal fibrosis.
*+/-[[Serositis]] - seen in small bowel perforation.
*+/-Foreign body-type granuloma - due to previous surgical intervention.


DDx:
DDx:
*Small bowel [[adenocarcinoma]] - most important differential diagnosis.
*[[Crohn's disease]].
*Metastatic adenocarcinoma - classically on the serosal aspect.
*Infectious ileitis.
*[[Signet ring cell carcinoma]].
**[[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>
 
====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>


===Sign out===
===Sign out===
<pre>
<pre>
SMALL BOWEL, RESECTION:
Terminal Ileum, Biopsy:
- SMALL BOWEL WITH FIBROUS ADHESIONS (EXTENSIVE) ASSOCIATED WITH FOCAL LUMINAL
- Small bowel with moderate active inflammation, marked villous blunting, basal plasmacytosis
   NARROWING.
   and prominent eosinophils, see comment.
- NEGATIVE FOR DYSPLASIA AND NEGATIVE FOR MALIGNANCY.
- NEGATIVE for granulomas.
</pre>
- NEGATIVE for dysplasia.


<pre>
Comment:
SMALL BOWEL, RESECTION:
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.
- SMALL BOWEL WITH FIBROUS ADHESIONS (EXTENSIVE), FOCAL LUMINAL NARROWING AND A
  FOREIGN BODY-TYPE GRANULOMA.
- NEGATIVE FOR DYSPLASIA AND NEGATIVE FOR MALIGNANCY.
</pre>
</pre>


====Ischemic changes====
==Small bowel obstruction==
<pre>
*Abbreviated ''SBO''.
SMALL BOWEL, RESECTION:
{{Main|Small bowel obstruction}}
- SMALL BOWEL WITH ISCHEMIC CHANGES, FIBROUS ADHESIONS, FOCAL SEROSITIS AND MURAL
  MICROABSCESS FORMATION.
- NO SIGNIFICANT VASCULAR PATHOLOGY APPARENT.
- NEGATIVE FOR MALIGNANCY.
</pre>


==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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===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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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 changes]].
*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=

Latest revision as of 16:07, 18 November 2022

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.

Small bowel mucosa. H&E stain.

Normal small bowel

  • AKA normal small intestine.

Anatomy

Consists of three segments:

  • Duodenum - can be divided into four parts.
  • Jejunum.
  • Ileum.

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.[1]

"Short":

  • Less than 200 cm = short bowel syndrome.[2][3]
    • Less than 100 cm usu. requires parenteral nutrition.[4]

Histology

Main article: Gastrointestinal pathology

The Gastrointestinal pathology article covers basic histology of the GI tract.

Immunohistochemistry

  • Normal small intestine is CK20 +ve... while adenocarcinoma of the small bowel may be CK20 -ve.[5]

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Small Bowel, Biopsy:
- Small bowel mucosa within normal limits.

Terminal Ileum, Biopsy:
- Small bowel mucosa within normal limits.

Terminal Ileum, Biopsy:
- Small bowel mucosa with morphologically benign lymphoid aggregates, negative for significant pathology.

Roux-en-Y gastric bypass

Main article: Obese
Main article: Roux-en-Y gastric bypass

Block letters

SMALL BOWEL, BIOPSY:
- SMALL BOWEL MUCOSA WITHIN NORMAL LIMITS.

TERMINAL ILEUM, BIOPSY:
- SMALL BOWEL MUCOSA WITHIN NORMAL LIMITS.

TERMINAL ILEUM, BIOPSY:
- SMALL BOWEL MUCOSA WITH MORPHOLOGICAL BENIGN LYMPHOID AGGREGATES, NO SIGNIFICANT PATHOLOGY.

The segments

Duodenum

Main article: Duodenum

The duodenum is often biopsied by gastroenterologists.

Common reasons for biopsy:

  • Suspected giardia.
  • Suspected celiac sprue.
  • Is this cancer?
  • Looks normal... want to dot the i's and cross the t's.

Jejunum

  • Uncommonly seen by pathologists.
  • May be seen in the context of a resection done for a bowel obstruction.

Ileum

Specific diagnoses

Ileitis

Active ileitis and acute ileitis redirect here.
This deals with nonspecific ileitis.

General

  • Common.

Microscopic

Features:

DDx:

Images

  • Ileitis - very low mag. (WC)

  • Ileitis - low mag. (WC)

  • Ileitis - intermed. mag. (WC)

  • Ileitis - high mag. (WC)

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Terminal Ileum, Biopsy:
- Small bowel with moderate active inflammation, marked villous blunting, basal plasmacytosis 
  and prominent eosinophils, see comment.
- NEGATIVE for granulomas.
- NEGATIVE for dysplasia.

Comment: 
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.

Small bowel obstruction

  • Abbreviated SBO.
Main article: Small bowel obstruction

Small bowel neoplasms

Mechanical small bowel perforation

See mechanical bowel perforation.

Ileal nodular lymphoid hyperplasia

  • AKA nodular lymphoid hyperplasia of the terminal ileum.

General

  • An uncommon diagnosis.
  • May be associated with hypogammaglobulinemia.[8]

Gross

  • Mucosal nodularity.

Microscopic

Features:

  • Lymphoid nodules +/- germinal centre formation.

Note:

  • Tingible body macrophages suggest an aggregate is benign.

DDx:

IHC

  • CD20 and CD3 - mixed population of lymphocytes.
  • CD23 - follicular dendritic cells.
  • Cyclin D1 -ve.

Note:

  • IHC should be used if there is:
    • Clinical suspicion.
    • Histologic suspicion - either:

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TERMINAL ILEUM, BIOPSY:
- SMALL BOWEL MUCOSA WITH LYMPHOID NODULES WITH GERMINAL CENTRE
  FORMATION -- NO SIGNIFICANT PATHOLOGY.
- NEGATIVE FOR ILEITIS.

TERMINAL ILEUM, BIOPSY:
- SMALL BOWEL MUCOSA WITH LYMPHOID HYPERPLASIA -- NO SIGNIFICANT PATHOLOGY.

Micro

The sections show small bowel mucosa with lymphoid hyperplasia.

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.

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

  • Abbreviated MLP.
  • AKA lymphomatous polyposis.

General

Microscopic

Features:

  • Lymphoid nodules consisting of (small) atypical lymphocytes with an abnormal architecture.

IHC

See small cell lymphomas.

Small bowel diaphragm disease

  • AKA diaphragm disease.

General

  • Strictures associated with chronic NSAID use.[11]
  • Usu. mid to distal ileum.

Microscopic

Features:[11]

  • Focal submucosal fibrosis.
    • +/-Distortion of adjacent muscularis propria.
    • +/-Adjacent mucosal erosions/granulation tissue.

DDx:

Meckel diverticulum

Main article: Meckel diverticulum

Ischemic enteritis

Main article: Ischemic enteritis

Weird stuff

Autoimmune enteropathy

  • Abbreviated as AIE.
Main article: Autoimmune enteropathy

See also

References

  1. ↑ Nightingale, JM.. "Management of patients with a short bowel.". Nutrition 15 (7-8): 633-7. PMID 10422101.
  2. ↑ Donohoe, CL.; Reynolds, JV. (Oct 2010). "Short bowel syndrome.". Surgeon 8 (5): 270-9. doi:10.1016/j.surge.2010.06.004. PMID 20709285.
  3. ↑ Matarese, LE.; O'Keefe, SJ.; Kandil, HM.; Bond, G.; Costa, G.; Abu-Elmagd, K. (Oct 2005). "Short bowel syndrome: clinical guidelines for nutrition management.". Nutr Clin Pract 20 (5): 493-502. PMID 16207689.
  4. ↑ Sundaram, A.; Koutkia, P.; Apovian, CM. (Mar 2002). "Nutritional management of short bowel syndrome in adults.". J Clin Gastroenterol 34 (3): 207-20. PMID 11873098.
  5. ↑ Chen ZM, Wang HL (October 2004). "Alteration of cytokeratin 7 and cytokeratin 20 expression profile is uniquely associated with tumorigenesis of primary adenocarcinoma of the small intestine". Am. J. Surg. Pathol. 28 (10): 1352–9. PMID 15371952.
  6. ↑ Dilauro, S.; Crum-Cianflone, NF. (Aug 2010). "Ileitis: when it is not Crohn's disease.". Curr Gastroenterol Rep 12 (4): 249-58. doi:10.1007/s11894-010-0112-5. PMID 20532706.
  7. ↑ Levy AD, Quiles AM, Miettinen M, Sobin LH (March 2005). "Gastrointestinal schwannomas: CT features with clinicopathologic correlation". AJR Am J Roentgenol 184 (3): 797–802. PMID 15728600. http://www.ajronline.org/cgi/content/full/184/3/797.
  8. ↑ Yamaue H, Tanimura H, Ishimoto K, Morikawa Y, Kakudo K (1996). "Nodular lymphoid hyperplasia of the terminal ileum: report of a case and the findings of an immunological analysis". Surg. Today 26 (6): 431-4. PMID 8782302.
  9. ↑ Ruskoné-Fourmestraux, A.; Audouin, J. (Feb 2010). "Primary gastrointestinal tract mantle cell lymphoma as multiple lymphomatous polyposis.". Best Pract Res Clin Gastroenterol 24 (1): 35-42. doi:10.1016/j.bpg.2009.12.001. PMID 20206107.
  10. ↑ URL: http://www.pathmax.com/gilymph.html. Accessed on: 1 April 2012.
  11. ↑ 11.0 11.1 McCune KH, Allen D, Cranley B (October 1992). "Small bowel diaphragm disease--strictures associated with non-steroidal anti-inflammatory drugs". Ulster Med J 61 (2): 182–4. PMC 2448949. PMID 1481311. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2448949/.
  12. ↑ Chung, SH.; Jo, Y.; Ryu, SR.; Ahn, SB.; Son, BK.; Kim, SH.; Park, YS.; Hong, YO. (Jun 2011). "Diaphragm disease compared with cryptogenic multifocal ulcerous stenosing enteritis.". World J Gastroenterol 17 (23): 2873-6. doi:10.3748/wjg.v17.i23.2873. PMID 21734797.
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