Difference between revisions of "Small intestine"

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The '''small bowel''' is a relatively well-behaved piece of machinery from the perspective of pathology.  It is uncommonly affected by malignancies.   
[[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]].   


==Anatomy==
=Normal small bowel=
*[[AKA]] ''normal small intestine''.
===Anatomy===
Consists of three segments:
Consists of three segments:
*Duodenum (which can be divided into four parts).
*[[Duodenum]] - can be divided into four parts.
*Jejunum.
*Jejunum.
*Ileum.
*Ileum.
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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.


The usual causes of bowel obstruction (large & small) are (mnemonic) ''SHAVING'':
====Length====
*Strictures (think IBD).
*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>
*Hernias.
*Adhesions.
*Volvulus.
*Intussusception.
*Neoplasia.
*Gallstone ileus.


The top three are:<ref>[http://www.emedicine.com/EMERG/topic66.htm http://www.emedicine.com/EMERG/topic66.htm]</ref><ref>TN 2007 GS21</ref>
"Short":
* Adhesions > hernias > neoplasms.
*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>


In the context of bowel obstructions and IBD, pathologists often see resected stomas (that were put in place emergently). These specimens are usually fairly straight forward.
===Histology===
{{main|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.<ref>{{cite journal |author=Chen ZM, Wang HL |title=Alteration of cytokeratin 7 and cytokeratin 20 expression profile is uniquely associated with tumorigenesis of primary adenocarcinoma of the small intestine |journal=Am. J. Surg. Pathol. |volume=28 |issue=10 |pages=1352–9 |year=2004 |month=October |pmid=15371952 |doi= |url=}}</ref>
 
===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}}


==Histology==
====Block letters====
{{main|Gastrointestinal pathology}}
<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 MORPHOLOGICAL BENIGN LYMPHOID AGGREGATES, NO SIGNIFICANT PATHOLOGY.
</pre>


=The segments=
==Duodenum==
==Duodenum==
{{main|Duodenum}}
{{main|Duodenum}}
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Common reasons for biopsy:
Common reasons for biopsy:
*Suspected giardia.
*Suspected giardia.
*Suspected celiac sprue.
*Suspected [[celiac sprue]].
*Is this cancer?
*Is this [[cancer]]?
*Looks normal... want to dot the i's and cross the t's.
*Looks normal... want to dot the i's and cross the t's.


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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.


===Nodular lymphoid hyperplasia===
=Specific diagnoses=
General
==Ileitis==
*An uncommon diagnosis
:''Active ileitis'' and ''acute ileitis'' redirect here.
*Prominent lymphoid follicles
:This deals with nonspecific ileitis.
*May be assoc. with hypogammaglobulinemia.<ref name=pmid8782302>{{cite journal |author=Yamaue H, Tanimura H, Ishimoto K, Morikawa Y, Kakudo K |title=Nodular lymphoid hyperplasia of the terminal ileum: report of a case and the findings of an immunological analysis |journal=Surg. Today |volume=26 |issue=6 |pages=431-4 |year=1996 |pmid=8782302 |doi= |url=}}</ref>
===General===
*Common.
 
===Microscopic===
Features:
*Intraepithelial [[neutrophil]]s.
 
DDx:
*[[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>
 
====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===
<pre>
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.
</pre>
 
==Small bowel obstruction==
*Abbreviated ''SBO''.
{{Main|Small bowel obstruction}}


==Small bowel neoplasms==
==Small bowel neoplasms==
*Adenocarcinoma - like colonic.
*Adenocarcinoma - like colonic.
*Adenosquamous carcinoma.
*[[Adenosquamous carcinoma]].
*Neuroendocine tumour.
*[[Neuroendocrine tumour]].
*[[GIST]].
*[[GIST]].
*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>
 
==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.<ref name=pmid8782302>{{cite journal |author=Yamaue H, Tanimura H, Ishimoto K, Morikawa Y, Kakudo K |title=Nodular lymphoid hyperplasia of the terminal ileum: report of a case and the findings of an immunological analysis |journal=Surg. Today |volume=26 |issue=6 |pages=431-4 |year=1996 |pmid=8782302 |doi= |url=}}</ref>
 
===Gross===
*Mucosal nodularity.
 
===Microscopic===
Features:
*Lymphoid nodules +/- germinal centre formation.
 
Note:
*Tingible body macrophages suggest an aggregate is benign.
 
DDx:
*[[MALT lymphoma]].
*[[Mantle cell lymphoma]].
*Other lymphomas.
 
===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:
***Sheets of lymphocytes without apparent germinal centre formation in a larger area (~ 2 mm).
***[[Lymphoepithelial lesion]]s.
 
===Sign out===
<pre>
TERMINAL ILEUM, BIOPSY:
- SMALL BOWEL MUCOSA WITH LYMPHOID NODULES WITH GERMINAL CENTRE
  FORMATION -- NO SIGNIFICANT PATHOLOGY.
- NEGATIVE FOR ILEITIS.
</pre>
 
<pre>
TERMINAL ILEUM, BIOPSY:
- SMALL BOWEL MUCOSA WITH LYMPHOID HYPERPLASIA -- NO SIGNIFICANT PATHOLOGY.
</pre>
 
====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===
*MLP is classically due to ''[[mantle cell lymphoma]]''.<ref name=pmid20206107>{{Cite journal  | last1 = Ruskoné-Fourmestraux | first1 = A. | last2 = Audouin | first2 = J. | title = Primary gastrointestinal tract mantle cell lymphoma as multiple lymphomatous polyposis. | journal = Best Pract Res Clin Gastroenterol | volume = 24 | issue = 1 | pages = 35-42 | month = Feb | year = 2010 | doi = 10.1016/j.bpg.2009.12.001 | PMID = 20206107 }}</ref>
**May be due to other lymphomas, e.g. [[follicular lymphoma]].<ref>URL: [http://www.pathmax.com/gilymph.html http://www.pathmax.com/gilymph.html]. Accessed on: 1 April 2012.</ref>
 
===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.<ref name=pmid1481311>{{cite journal |author=McCune KH, Allen D, Cranley B |title=Small bowel diaphragm disease--strictures associated with non-steroidal anti-inflammatory drugs |journal=Ulster Med J |volume=61 |issue=2 |pages=182–4 |year=1992 |month=October |pmid=1481311 |pmc=2448949 |doi= |url=}}</ref>
*Usu. mid to distal ileum.
 
===Microscopic===
Features:<ref name=pmid1481311/>
*Focal submucosal fibrosis.
**+/-Distortion of adjacent muscularis propria.
**+/-Adjacent mucosal erosions/granulation tissue.
 
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]].
 
==Meckel diverticulum==
{{Main|Meckel diverticulum}}
 
==Ischemic enteritis==
{{Main|Ischemic enteritis}}
 
=Weird stuff=
==Autoimmune enteropathy==
*Abbreviated as ''AIE''.
{{Main|Autoimmune enteropathy}}


==See also==
=See also=
*[[Stomach]].
*[[Stomach]].
*[[Gastrointestinal pathology]].
*[[Gastrointestinal pathology]].
*[[Colon]].
*[[Colon]].


==References==
=References=
{{reflist|2}}
{{reflist|2}}


[[Category:Gastrointestinal pathology]]
[[Category:Gastrointestinal pathology]]

Latest revision as of 16:07, 18 November 2022

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.

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]

Sign out

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)

Sign out

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:

Sign out

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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