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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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'':
*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.


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) AND FOCAL LUMINAL NARROWING.
- Small bowel with moderate active inflammation, marked villous blunting, basal plasmacytosis
- NEGATIVE FOR DYSPLASIA AND NEGATIVE FOR MALIGNANCY.
  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>
</pre>
==Small bowel obstruction==
*Abbreviated ''SBO''.
{{Main|Small bowel obstruction}}


==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 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

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

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

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

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

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.

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

Ischemic enteritis

Weird stuff

Autoimmune enteropathy

  • Abbreviated as AIE.

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.