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The '''colon''' and '''rectum''' smell like poo... 'cause that's where poo comes from.  It commonly comes to pathologists because there is a suspicion of cancer or a known history of inflammatory bowel disease (IBD).
[[Image:Blausen_0603_LargeIntestine_Anatomy.png|thumb|right|Anatomy of the colon and rectum. (WC)]]
The '''colon''' is section of the large bowel.  This article also covers the '''rectum''' and '''cecum''' as both have a similar mucosa.   


An introduction to gastrointestinal pathology is found in the ''[[gastrointestinal pathology]]'' article.
It commonly comes to pathologists because there is a suspicion of [[colorectal cancer]] or a known history of [[inflammatory bowel disease]] (IBD).


==Surgery==
An introduction to gastrointestinal pathology is found in the ''[[gastrointestinal pathology]]'' article. The ''[[anus]]'' and ''[[ileocecal valve]]'' are dealt with in separate articles.
Introduction to colorectal surgery:
# Colonic resection - remove a piece of large bowel.
# Total colectomy - leaves rectum and anus.<ref>[http://www.allaboutbowelsurgery.com/shared/stoma_care/stoma_surgery/procedures/surgery_colon/subtotal.htm http://www.allaboutbowelsurgery.com/shared/stoma_care/stoma_surgery/procedures/surgery_colon/subtotal.htm]</ref>
# Subtotal colectomy - part of colon removed --or-- some of the rectum remains.
# Right hemicolectomy - right colon + distal ileum.
# Lower anterior resection (LAR) - proximal rectum +/- sigmoid (for proximal rectal malignancies).
# Abdominoperineal resection (APR) - anus + rectum - results in a permanent stoma (for distal rectal malignancies).


==Grossing==
Technically, the rectum and cecum are ''not'' part of the colon. Thus, inflammation of the rectum should be ''proctitis'' and inflammation of the cecum should be ''cecitis''.
*Lymph nodes - should get at least 12 - if it is cancer.<ref name=pmid18780863>{{cite journal |author=Bilimoria KY, Bentrem DJ, Stewart AK, ''et al.'' |title=Lymph node evaluation as a colon cancer quality measure: a national hospital report card |journal=J. Natl. Cancer Inst. |volume=100 |issue=18 |pages=1310–7 |year=2008 |month=September |pmid=18780863 |doi=10.1093/jnci/djn293 |url=http://www.medscape.com/viewarticle/581463}}</ref>


''Quirke method''
=Anatomy=
*Bowel is not opened.
*The [[rectum]] has several definition. These are discussed in the ''[[rectum]]'' article.
**References: <ref name=pmid18667357>{{cite journal |author=West NP, Morris EJ, Rotimi O, Cairns A, Finan PJ, Quirke P |title=Pathology grading of colon cancer surgical resection and its association with survival: a retrospective observational study |journal=Lancet Oncol. |volume=9 |issue=9 |pages=857–65 |year=2008 |month=September |pmid=18667357 |doi=10.1016/S1470-2045(08)70181-5 |url=}}</ref>, <ref name=pmid18541901>{{cite journal |author=West NP, Finan PJ, Anderin C, Lindholm J, Holm T, Quirke P |title=Evidence of the oncologic superiority of cylindrical abdominoperineal excision for low rectal cancer |journal=J. Clin. Oncol. |volume=26 |issue=21 |pages=3517–22 |year=2008 |month=July |pmid=18541901 |doi=10.1200/JCO.2007.14.5961 |url=}}</ref>.
*The large bowel may be submitted with segment names or with the distance to the anal verge.


''Standard method''
A conversion between named segments and distance - as per NCI of the United States:<ref>URL: [https://training.seer.cancer.gov/colorectal/anatomy/figure/figure1.html]https://training.seer.cancer.gov/colorectal/anatomy/figure/figure1.html]. Accessed on: 8 February 2018.</ref>
*Bowel is prep'ed by opening it along the antimesenteric side.
{| class="wikitable sortable"
*Dimensions - length, circumference at both margins.
!Named segment
*Radial margin/circumferential margin - should be painted.
!Distance to anal verge (cm)
**Rectum starts/sigmoid ends @ place where serosa ends on the posterior aspect of the bowel.
|-
***The proximal, anterior aspect of the rectum has serosa, i.e. it is not painted.
|Anus
|0-4
|-
|[[Rectum]]
|4-16
|-
|Rectosigmoid
|15-17
|-
|Sigmoid
|17-57
|-
|Descending
|57-82
|-
|Transverse
|82-132
|-
|Ascending
|132-147
|-
|Cecum
|150
|}


==Common clinical problems==
=Common clinical problems=
===Obstruction===
===Obstruction===
Top three (in adults):<ref>[http://www.emedicine.com/EMERG/topic65.htm http://www.emedicine.com/EMERG/topic65.htm]</ref>
Top three (in adults):<ref>URL: [http://www.emedicine.com/EMERG/topic65.htm http://www.emedicine.com/EMERG/topic65.htm]. Accessed on: 28 June 2011.</ref>
*Neoplasia,
*Neoplasia.
*Volvulus (cecal, sigmoid),
*[[Volvulus]] (cecal, sigmoid).
*Diverticular disease + stricture formation.
*[[Diverticular disease]] + stricture formation.


===Bleeding===
===Bleeding===
Mnemonic ''CHAND'':<ref>TN 2007 G29.</ref>
Mnemonic ''CHAND'':<ref>TN 2007 G29.</ref>
*Colitis (radiation, infectious, ischemic, IBD (UC >CD), iatrogenic (anticoagulants)),
*Colitis ([[radiation colitis|radiation]], [[infectious colitis|infectious]], [[ischemic colitis|ischemic]], [[IBD]] (UC >CD), iatrogenic (anticoagulants)).
*Hemorrhoids,
*[[Hemorrhoids]].
*Angiodysplasia,
*[[Angiodysplasia]].
*Neoplastic,
*Neoplastic.
*Diverticular disease.
*[[Diverticular disease]].


Infectious colitis with bleeding - causes:  
Infectious colitis with bleeding - causes:  
*Enterohemorrhagic Escherichia coli (EHEC) -- commonly 0157:H7,
*Enterohemorrhagic Escherichia coli (EHEC) -- commonly 0157:H7.
*Campylobacter jejuni,
*Campylobacter jejuni.
*Clostridium difficile,
*[[Clostridium difficile]].
*Shigella.
*Shigella.


Infectious colitis in the immunosuppressed:
[[Infectious colitis]] in the immunosuppressed:
*Cytomegalovirus (CMV).<ref name=pmid7934809>{{cite journal |author=Golden MP, Hammer SM, Wanke CA, Albrecht MA |title=Cytomegalovirus vasculitis. Case reports and review of the literature |journal=Medicine (Baltimore) |volume=73 |issue=5 |pages=246–55 |year=1994 |month=September |pmid=7934809 |doi= |url=}}</ref>
*[[Cytomegalovirus]] (CMV).<ref name=pmid7934809>{{cite journal |author=Golden MP, Hammer SM, Wanke CA, Albrecht MA |title=Cytomegalovirus vasculitis. Case reports and review of the literature |journal=Medicine (Baltimore) |volume=73 |issue=5 |pages=246–55 |year=1994 |month=September |pmid=7934809 |doi= |url=}}</ref>
**May afflict patients with IBD and lead to colectomy... as IBD patients are put on immunosuppression.
**May afflict patients with IBD and lead to colectomy... as IBD patients are put on immunosuppression.<ref name=pmid17026558>{{cite journal |author=Kandiel A, Lashner B |title=Cytomegalovirus colitis complicating inflammatory bowel disease |journal=Am. J. Gastroenterol. |volume=101 |issue=12 |pages=2857–65 |year=2006 |month=December |pmid=17026558 |doi=10.1111/j.1572-0241.2006.00869.x |url=}}</ref>
**Organ transplant recipients.
**Organ transplant recipients.
**[[HIV|HIV/AIDS]].
**[[HIV|HIV/AIDS]].


==Inflammatory bowel disease==
Images:
{{main|Inflammatory bowel disease}}
<gallery>
Image:CMV_colitis_-_high_mag_-_cropped.jpg | CMV colitis - high. mag. (WC/Nephron)
Image:CMV_colitis_-_intermed_mag.jpg | CMV colitis - intermed. mag. (WC/Nephron)
</gallery>
 
=Grossing=
==Types of specimens==
Introduction to colorectal surgery:
# Colonic resection - remove a piece of large bowel.
# Total colectomy - leaves rectum and anus.<ref>[http://www.allaboutbowelsurgery.com/shared/stoma_care/stoma_surgery/procedures/surgery_colon/subtotal.htm http://www.allaboutbowelsurgery.com/shared/stoma_care/stoma_surgery/procedures/surgery_colon/subtotal.htm]</ref>
# Subtotal colectomy - part of colon removed --or-- some of the rectum remains.
# Right hemicolectomy - right colon + distal ileum.
# [[Lower anterior resection]] (LAR) - proximal rectum +/- sigmoid (for proximal rectal malignancies).
#* Specimens have should have intact mesorectum - ''[[total mesorectal excision]]'' (TME) - reduces local recurrence.<ref name=pmid8665198>{{Cite journal  | last1 = Arbman | first1 = G. | last2 = Nilsson | first2 = E. | last3 = Hallböök | first3 = O. | last4 = Sjödahl | first4 = R. | title = Local recurrence following total mesorectal excision for rectal cancer. | journal = Br J Surg | volume = 83 | issue = 3 | pages = 375-9 | month = Mar | year = 1996 | doi =  | PMID = 8665198 }}</ref>
# [[Abdominoperineal resection]] (APR) - anus + rectum - results in a permanent [[stoma]] (for distal rectal malignancies).
# [[Stoma]] - these are often done emergently and then get cut-out after the patient's condition has settled.
#[[Doughnuts]] (also ''donuts'') from an end-to-end anastomosis stapler.
#*Often accompany lower anterior resections.


The bread 'n butter of gastroenterology. A detailed discussion of '''IBD''' is in the ''[[inflammatory bowel disease]]'' article.
===Images===
<gallery>
Image:Rectum - anterior view.jpg | APR specimen - anterior (WC)
Image: Rectum - lateral view.jpg | APR specimen - lateral (WC)
Image: Rectum - anterior and lateral - inked.jpg | APR specimen - inked (WC)
</gallery>


===Microscopic===
==Identifying the specimen==
Features helpful for the diagnosis of IBD - as based on a study:<ref name=pmid10048734>{{cite journal |author=Tanaka M, Riddell RH, Saito H, Soma Y, Hidaka H, Kudo H |title=Morphologic criteria applicable to biopsy specimens for effective distinction of inflammatory bowel disease from other forms of colitis and of Crohn's disease from ulcerative colitis |journal=Scand. J. Gastroenterol. |volume=34 |issue=1 |pages=55–67 |year=1999 |month=January |pmid=10048734 |doi= |url=}}</ref>
*Transverse colon - has [[omentum]].
*Basal, i.e. crypt base, plasmacytosis with severe chronic inflammation,
*Ascending colon - usu. comes with [[ileocecal valve]] and a bit of ileum.
*Crypt architectural abnormalities, and
*Descending colon - has a bare area.
*Distal Paneth cell metaplasia.
*Rectum - has adventitia.
**Paneth cells should ''not'' be in the left colon<ref name=pmid11851832>{{cite journal |author=Tanaka M, Saito H, Kusumi T, ''et al'' |title=Spatial distribution and histogenesis of colorectal Paneth cell metaplasia in idiopathic inflammatory bowel disease |journal=J. Gastroenterol. Hepatol. |volume=16 |issue=12 |pages=1353–9 |year=2001 |month=December |pmid=11851832 |doi= |url=http://www3.interscience.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0815-9319&date=2001&volume=16&issue=12&spage=1353}}</ref> - if you see 'em think of IBD and other long-standing injurious processes.
**Pathologists define it as starting where the adventitia starts/the serosal surface no longer completely surrounds the large intestine.<ref>{{Ref Lester3|339}}</ref>  
**Some claim that (friendly right colonic) paneth cells and paneth cell metaplasia look quite different and can be distinguished.<ref name=pmid12655793>{{cite journal |author=Rubio CA, Nesi G |title=A simple method to demonstrate normal and metaplastic Paneth cells in tissue sections |journal=In Vivo |volume=17 |issue=1 |pages=67–71 |year=2003 |pmid=12655793 |doi= |url=}}</ref>
**Anatomists define it in relation to the third sacral vertebra.<ref>URL: [http://www.bartleby.com/107/249.html http://www.bartleby.com/107/249.html]. Accessed on: 19 October 2012.</ref>


==Bowel ischemia==
===Images===
===Radiologic correlate===
<gallery>
*Bowel wall thickening.
Image: Rectum - lateral view.jpg | Sigmoid and rectum. APR specimen. (WC)
</gallery>


===Gross===
==Lymph nodes==
Features:<ref name=Ref_PBoD852>{{Ref PBoD|852}}</ref>
*One should get at least 12 [[lymph nodes]] if it is cancer.<ref name=pmid18780863>{{cite journal |author=Bilimoria KY, Bentrem DJ, Stewart AK, ''et al.'' |title=Lymph node evaluation as a colon cancer quality measure: a national hospital report card |journal=J. Natl. Cancer Inst. |volume=100 |issue=18 |pages=1310–7 |year=2008 |month=September |pmid=18780863 |doi=10.1093/jnci/djn293 |url=http://www.medscape.com/viewarticle/581463}}</ref>
*Luminal part (mucosa & submucosa) affected.
*Splenic flexture of colon commonly affected (vascular watershed).


Note:
==Quirke method==
*May have pseudomembranes (classically assoc. with ''C. difficle'' colitis), i.e. mimics an infectious process.
*Bowel is not opened - it is fixed... then sliced.<ref name=pmid18667357>{{cite journal |author=West NP, Morris EJ, Rotimi O, Cairns A, Finan PJ, Quirke P |title=Pathology grading of colon cancer surgical resection and its association with survival: a retrospective observational study |journal=Lancet Oncol. |volume=9 |issue=9 |pages=857–65 |year=2008 |month=September |pmid=18667357 |doi=10.1016/S1470-2045(08)70181-5 |url=}}</ref><ref name=pmid18541901>{{cite journal |author=West NP, Finan PJ, Anderin C, Lindholm J, Holm T, Quirke P |title=Evidence of the oncologic superiority of cylindrical abdominoperineal excision for low rectal cancer |journal=J. Clin. Oncol. |volume=26 |issue=21 |pages=3517–22 |year=2008 |month=July |pmid=18541901 |doi=10.1200/JCO.2007.14.5961 |url=}}</ref>
*DDx for pseudomembranes:<ref name=Ref_PBoD837-8>{{Ref PBoD|837-8}}</ref>
**C. difficle induced pseudomembranous colitis.
**Ischemic colitis.
**Volvulus.
**Necrotizing infections.
**... anything that causes severe mucosal injury.


Histology of pseudomembranes:<ref name=Ref_PBoD837-8>{{Ref PBoD|837-8}}</ref>
==Standard method==
*Loss of surf. epithelium.  
*Bowel is prep'ed by [[opening]] it along the antimesenteric side.
*PMNs in lamina propria.  
*Dimensions - length, circumference at both [[margins]].
*+/- capillary fibrin thrombi.  
*Radial margin/circumferential margin - should be painted.
NB: Pseudomembranes arise from the crypts.
**Rectum starts/sigmoid ends @ place where serosa ends on the posterior aspect of the bowel.
***The proximal, anterior aspect of the rectum has serosa, i.e. it is not painted.


Image:  
Note:
*[http://commons.wikimedia.org/wiki/File:Colonic_pseudomembranes_low_mag.jpg Micrograph of pseudomembranes - low mag. (wikimedia.org)].
*There are several definitions for the rectum.<ref name=pmid24130630>{{Cite journal  | last1 = Kenig | first1 = J. | last2 = Richter | first2 = P. | title = Definition of the rectum and level of the peritoneal reflection - still a matter of debate? | journal = Wideochir Inne Tech Maloinwazyjne | volume = 8 | issue = 3 | pages = 183-6 | month = Sep | year = 2013 | doi = 10.5114/wiitm.2011.34205 | PMID = 24130630 }}</ref>
*[http://commons.wikimedia.org/wiki/File:Colonic_pseudomembranes_intermed_mag.jpg Micrograph of pseudomembranes - intermed. mag. (wikimedia.org)].
**In a survey of surgeons:
**67% defined it by an anatomical landmark
***35% of all respondants considered the peritoneal reflection the proximal boundary of the rectum.
**30% defined the proximal boundary as a distance from the anal verge.


==Angiodysplasia==
=Common non-neoplastic disease=
===General===
==Colorectal polyps==
*Causes (lower) GI haemorrhage.
{{main|Intestinal polyps}}
*Generally, not a problem pathologists see.
Polyps are the bread & butter of [[GI pathology]]. They are very common.
*May be associated with aortic stenosis; known as ''Heyde syndrome''.<ref name=pmid19652242>{{cite journal |author=Hui YT, Lam WM, Fong NM, Yuen PK, Lam JT |title=Heyde's syndrome: diagnosis and management by the novel single-balloon enteroscopy |journal=Hong Kong Med J |volume=15 |issue=4 |pages=301–3 |year=2009 |month=August |pmid=19652242 |doi= |url=http://www.hkmj.org/abstracts/v15n4/301.htm}}</ref>


===Location===
Main types:
*Cecum.
*Hyperplastic - most common, benign.
*Adenomatous - quite common, pre-malignant.
*[[Hamartomatous polyps|Hamartomatous]] - rare, weird & wonderful.
*Inflammatory, [[AKA]] inflammatory pseudopolyps - associated with [[IBD]].


===Epidemiology===
Most common (images):
*Older people.
<gallery>
Image:Hyperplastic_polyp1.jpg | Hyperplastic polyp image - intermed. mag. (WC/Nephron)
Image:Hyperplastic_polyp2.jpg | Hyperplastic polyp image - low mag. (WC/Nephron)
</gallery>
==Ischemic colitis==
*[[AKA]] ''colonic ischemia''.
*[[AKA]] ''ischemia of the colon''.
{{Main|Ischemic colitis}}


===Etiology===
==Diverticular disease==
*Thought to be caused by the higher wall tension of cecum (due to larger diameter) and result from (intermittent) venous occulsion/focal dilation of vessels.<ref name=Ref_PBoD854>{{Ref PBoD|854}}</ref>
{{Main|Diverticular disease}}


==Melanosis coli==
==Pseudomembranous colitis==
*AKA ''Pseudomelanosis coli''.<ref>[http://www.medicinenet.com/melanosis_coli/article.htm http://www.medicinenet.com/melanosis_coli/article.htm]</ref>
{{Main|Pseudomembranous colitis}}
*''Not melanin'' as the name suggests; it is actually lipofuscin (in macrophages).<ref name=pmid18666316>{{cite journal |author=Freeman HJ |title="Melanosis" in the small and large intestine |journal=World J. Gastroenterol. |volume=14 |issue=27 |pages=4296-9 |year=2008 |month=July |pmid=18666316 |doi= |url=http://www.wjgnet.com/1007-9327/14/4296.asp}}</ref>
*Endoscopist may see brown pigmentation of mucosa and suspect the diagnosis.


===Epidemiology===
==Volvulus==
*Classically associated with anthracene containing laxative (e.g. Senokot) use and herbal remedies.<ref name=pmid18666316/>
{{Main|Volvulus}}


===Features===
=Inflammatory diseases=
*Brown pigmentation of the mucosa.
==Inflammatory bowel disease==
*Typically more prominent in the cecum and proximal colon.<ref name=pmid18666316/>
{{main|Inflammatory bowel disease}}


DDx of brown pigment:
The bread 'n butter of gastroenterology.  A detailed discussion of '''IBD''' is in the ''[[inflammatory bowel disease]]'' article. It comes in two main flavours (Crohn's disease, ulcerative colitis).
*Lipofuscin - comes with age (can be demonstrated with a ''Kluver-Barrera stain''<ref>URL: [http://education.vetmed.vt.edu/curriculum/VM8054/labs/Lab2/Examples/exkluvbarr.htm http://education.vetmed.vt.edu/curriculum/VM8054/labs/Lab2/Examples/exkluvbarr.htm]. Accessed on: 5 May 2010.</ref>).
**Melanosis coli.
*Old haemorrhage, i.e. hemosiderin-laden macrophages (may be demonstrated with ''Prussian blue stain''<ref>URL: [http://education.vetmed.vt.edu/curriculum/VM8054/labs/Lab2/Examples/exprussb.htm http://education.vetmed.vt.edu/curriculum/VM8054/labs/Lab2/Examples/exprussb.htm]. Accessed on: 5 May 2010.</ref>).
*Melanin (from melanocytes) - rare in colon (may be demonstrated with a ''Fontana-Masson stain''<ref>URL: [http://education.vetmed.vt.edu/curriculum/VM8054/labs/Lab2/Examples/exfontana.htm http://education.vetmed.vt.edu/curriculum/VM8054/labs/Lab2/Examples/exfontana.htm]. Accessed on: 5 May 2010.</ref> -- though not so useful in the GI tract).
*Foriegn material (e.g. tattoo pigment) - not seen in GI tract.


Images:
===Microscopic===
*[http://commons.wikimedia.org/wiki/File:Melanosis_coli_high_mag.jpg Melanosis coli - high mag. (WC)].
Features helpful for the diagnosis of IBD - as based on a study:<ref name=pmid10048734>{{cite journal |author=Tanaka M, Riddell RH, Saito H, Soma Y, Hidaka H, Kudo H |title=Morphologic criteria applicable to biopsy specimens for effective distinction of inflammatory bowel disease from other forms of colitis and of Crohn's disease from ulcerative colitis |journal=Scand. J. Gastroenterol. |volume=34 |issue=1 |pages=55–67 |year=1999 |month=January |pmid=10048734 |doi= |url=}}</ref>
*[http://commons.wikimedia.org/wiki/File:Melanosis_coli_low_mag.jpg Melanosis coli - low mag. (WC)].
*Basal, i.e. crypt base, plasmacytosis with severe chronic inflammation,
*Crypt architectural abnormalities, and
*Distal [[Paneth cell]] metaplasia.
**Paneth cells should ''not'' be in the left colon<ref name=pmid11851832>{{cite journal |author=Tanaka M, Saito H, Kusumi T, ''et al'' |title=Spatial distribution and histogenesis of colorectal Paneth cell metaplasia in idiopathic inflammatory bowel disease |journal=J. Gastroenterol. Hepatol. |volume=16 |issue=12 |pages=1353–9 |year=2001 |month=December |pmid=11851832 |doi= |url=http://www3.interscience.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0815-9319&date=2001&volume=16&issue=12&spage=1353}}</ref> - if you see 'em think of IBD and other long-standing injurious processes.
**Some claim that (friendly right colonic) paneth cells and paneth cell metaplasia look quite different and can be distinguished.<ref name=pmid12655793>{{cite journal |author=Rubio CA, Nesi G |title=A simple method to demonstrate normal and metaplastic Paneth cells in tissue sections |journal=In Vivo |volume=17 |issue=1 |pages=67–71 |year=2003 |pmid=12655793 |doi= |url=}}</ref>


==Microscopic colitis==
==Microscopic colitis==
===General===
:''Microscopic colitis'' may refer to a microscopic manifestation of an unspecified disease process that can be apparent macroscopically. This section links to a pair of diseases (''lymphocytic colitis'' and ''collagenous colitis'') that are considered to only have microscopic manifestations and characteristic clinical presentation.
Definition:
{{Main|Lymphocytic colitis}}
*As the name suggests, they are microscopic, i.e. endoscopic examination is normal.
{{Main|Collagenous colitis}}


Presentation:
==Diversion colitis==
*Chronic diarrhea, non-bloody.<ref name=medscape180664>URL: [http://emedicine.medscape.com/article/180664-overview http://emedicine.medscape.com/article/180664-overview]. Accessed on: 31 May 2010.</ref>
{{Main|Diversion colitis}}


===Microscopic colitis - types===
==Eosinophilic colitis==
*Lymphocytic colitis (LC).
*Abbreviated ''EC''.
*Collagenous colitis (CC).
{{Main|Eosinophilic colitis}}


Some believe that LC and CC are different time points in the same process-- but this is unproven.<ref name=medscape180664/>
=Infectious=
==Infectious colitis==
:This section covers non-specific colitides that appear to have an infective etiology.
===General===
*Common.
*Diarrhea - typical symptom.


===Epidemiology===
===Gross===
*Age: a disease of adults - usually 50s.
*+/-Erythema on endoscopy.
*Sex:
**LC males ~= females,<ref name=medscape180664/>
**CC females:males = 20:1.<ref name=medscape180664/>
*Drugs are associated with LC and CC.
**NSAIDs - posulated association/weak association,
**SSRIs (used primarily for depression) - moderate association, dependent on specific drug.
*Associated with autoimmune disorders - celiac disease, diabetes mellitus, thyroid disorders and arthritis.<ref name=pmid19109861>{{cite journal |author=Tysk C, Bohr J, Nyhlin N, Wickbom A, Eriksson S |title=Diagnosis and management of microscopic colitis |journal=World J. Gastroenterol. |volume=14 |issue=48 |pages=7280-8 |year=2008 |month=December |pmid=19109861 |doi= |url=http://www.wjgnet.com/1007-9327/14/7280.asp}}</ref>
*No increased risk of colorectal carcinoma.<ref name=pmid19109861/>


===Treatment===
===Microscopic===
*Sometimes just follow-up.
Features:
*Steroids - budesonide -- short-term treatment.<ref name=pmid19109861/>
*Neutrophils predominant - '''key feature'''.<ref name=Ref_GLP324>{{Ref GLP|324}}</ref>
**The neutrophils are often superficial - they go to were the bad guys are.
*No architectural distortion - if acute.


===Characteristics===
DDx:
====Lymphocytic colitis====
*[[Inflammatory bowel disease]] - lymphoplasmacytic infiltrate predominant,<ref name=Ref_GLP324>{{Ref GLP|324}}</ref> usually has chronic changes.
*Lots of intraepithelial lymphocytes (>=20/100 lymphocytes/surface epithelial cells<ref name=pmid19109861>{{cite journal |author=Tysk C, Bohr J, Nyhlin N, Wickbom A, Eriksson S |title=Diagnosis and management of microscopic colitis |journal=World J. Gastroenterol. |volume=14 |issue=48 |pages=7280-8 |year=2008 |month=December |pmid=19109861 |doi= |url=http://www.wjgnet.com/1007-9327/14/7280.asp}}</ref>) and
*[[Ischemic colitis]].
*lymphocytes in the lamina propria.
*Medications - focal neutrophils.
*NEGATIVES:<ref name=hopkins_cc_lc>[http://hopkins-gi.nts.jhu.edu/pages/latin/templates/index.cfm?pg=disease1&disease=29&organ=6&lang_id=1 http://hopkins-gi.nts.jhu.edu/pages/latin/templates/index.cfm?pg=disease1&disease=29&organ=6&lang_id=1]</ref>
*[[Lymphocytic colitis]] - lymphocytes with a squiggly nucleus, may be confused with neutrophils.
**No PMNs.
*Specific causes of infective colitis - with a distinctive morphology.
**No crypt distortion.
**[[CMV colitis]] - esp. in the immunodeficient.
**[[Pseudomembranous colitis]] - usu. due to ''C. difficle'', has characteristic gross & microscopic appearance.
**[[Intestinal spirochetes]].
**[[Amebiasis]].
**[[Strongyloidiasis]].
**[[Cryptosporidiosis]].


====Collagenous colitis====
===IHC===
*Intraepithelial lymphocytes, and
Done if the patient is immunosuppressed, or there is clinical or morphological suspicion:
*lymphocytes in the lamina propria.
*[[CMV]].
*Collagenous material in the lamina propria (pink on H&E) -- '''key feature'''.
*HSV-1.
**Can be demonstrated with a trichrome stain -- collagen = green on trichrome.
*HSV-2.
**Subepithelial collagen needs to be >= 10 micrometres thick for Dx.<ref name=pmid19109861/>
*[[EBV]] - may mimic IBD.<ref name=pmid21119609>{{Cite journal  | last1 = Karlitz | first1 = JJ. | last2 = Li | first2 = ST. | last3 = Holman | first3 = RP. | last4 = Rice | first4 = MC. | title = EBV-associated colitis mimicking IBD in an immunocompetent individual. | journal = Nat Rev Gastroenterol Hepatol | volume = 8 | issue = 1 | pages = 50-4 | month = Jan | year = 2011 | doi = 10.1038/nrgastro.2010.192 | PMID = 21119609 }}</ref>
***8 micrometres is the diameter of a RBC.
***The normal thickness of the subepithelial collagen is 3 micrometres.<ref name=pmid19109861/>
**Thickening "follows the crypts from the surface" - useful for differentiating from tangential sections of the basement membrane.<ref>BEC 4 Mar 2009</ref>
**Collagen may envelope capillaries - useful to discern from basement membrane.<ref>BEC 4 Mar 2009</ref>


Images:
===Sign out===
*[http://commons.wikimedia.org/wiki/File:Collagenous_colitis_-_intermed_mag.jpg Collagenous colitis - intermed mag. (WC)].
<pre>
*[http://commons.wikimedia.org/wiki/File:Collagenous_colitis_-_high_mag.jpg Collagenous colitis - high mag. (WC)].
ASCENDING COLON, BIOPSY:
- MILD ACTIVE COLITIS, SEE COMMENT.


Notes:  
COMMENT:
*CC is typically more prominent in the proximal colon - may reflect concentration gradient of offending causitive agents.<ref name=pmid19109861/>
There is are no granulomas. The crypt architecture is normal. A benign lymphoid nodule is
*Significant negative findings:<ref name=hopkins_cc_lc/>
present.
**No [[PMN]]s.
**No crypt distortion.


==Spirochetes==
The differential diagnosis includes infective etiologies, early inflammatory
===General===
bowel disease and ischemia. The histomorphology is more in keeping with an infective
*Very rare cause of diarrhea.
etiology as neutrophils are a predominant feature; however, clinical correlation is
*Caused by ''Serpulina pilosicoli'' and ''Brachyspira aalborgi''.<ref name=pmid14718105>{{cite journal |author=Amat Villegas I, Borobio Aguilar E, Beloqui Perez R, de Llano Varela P, Oquiñena Legaz S, Martínez-Peñuela Virseda JM |title=[Colonic spirochetes: an infrequent cause of adult diarrhea] |language=Spanish; Castilian |journal=Gastroenterol Hepatol |volume=27 |issue=1 |pages=21–3 |year=2004 |month=January |pmid=14718105 |doi= |url=}}</ref>
required.
*Tx: metronidazole.<ref name=pmid17914949>{{cite journal |author=Calderaro A, Bommezzadri S, Gorrini C, ''et al.'' |title=Infective colitis associated with human intestinal spirochetosis |journal=J. Gastroenterol. Hepatol. |volume=22 |issue=11 |pages=1772–9 |year=2007 |month=November |pmid=17914949 |doi=10.1111/j.1440-1746.2006.04606.x |url=}}</ref>
</pre>


===Histology===
==Cytomegalovirus colitis==
*Hyperchromatic fuzz on luminal aspect of epithelial cells; at brush border.
{{Main|CMV}}
*Abbreviated ''CMV colitis''.
{{Main|Cytomegalovirus colitis}}


Special stain:
==Intestinal spirochetosis==
*Silver stains highlight 'em (e.g. Warthin-Starry stain).
*[[AKA]] ''intestinal spirochetes''; more specifically ''colonic spirochetes'', ''colonic spirochetosis''.
{{Main|Intestinal spirochetosis}}


==Amebiasis==
==Amebiasis==
*May also be spelled ''amoebiasis''.
{{Main|Amebiasis}}
==Cryptosporidiosis==
{{Main|Cryptosporidiosis}}
===General===
===General===
*Infection with ''Entamoeba histolytica''.<ref>URL: [http://www.health.state.ny.us/diseases/communicable/amebiasis/fact_sheet.htm http://www.health.state.ny.us/diseases/communicable/amebiasis/fact_sheet.htm]. Accessed on: 17 June 2010.</ref>
*Usually in immune incompetent individuals, e.g. [[HIV|HIV/AIDS]].
*May also be spelling ''amoebiasis''.
*May mimic colon cancer.<ref name=pmid19332922>{{Cite journal  | last1 = Fernandes | first1 = H. | last2 = D'Souza | first2 = CR. | last3 = Swethadri | first3 = GK. | last4 = Naik | first4 = CN. | title = Ameboma of the colon with amebic liver abscess mimicking metastatic colon cancer. | journal = Indian J Pathol Microbiol | volume = 52 | issue = 2 | pages = 228-30 | month =  | year =  | doi =  | PMID = 19332922 | url=http://www.ijpmonline.org/article.asp?issn=0377-4929;year=2009;volume=52;issue=2;spage=228;epage=230;aulast=Fernandes }}</ref>


May cause:<ref name=pmid20303955>{{Cite journal  | last1 = Mortimer | first1 = L. | last2 = Chadee | first2 = K. | title = The immunopathogenesis of Entamoeba histolytica. | journal = Exp Parasitol | volume =  | issue =  | pages =  | month = Mar | year = 2010 | doi = 10.1016/j.exppara.2010.03.005 | PMID = 20303955 }}</ref>
===Microscopic===
*Dysentery (diarrhea containing mucus and/or blood in the feces).
*Colitis.
*Liver abscess.
 
===Microscopy===
Features:
Features:
*Round/Ovoid eosinophilic bodies ~ 40-60 micrometers in maximal dimension.  
*Uniform spherical nodules 2-4 micrometres in diameter, typical location - GI tract brush border.
*Found in bowel lumen.
**Bluish staining of brush border '''key feature''' - low power.
*Ingest RBCs.


Image:
=Rectal pathology=
*[http://commons.wikimedia.org/wiki/File:Amoebic_dysentery_in_colon_biopsy_%281%29.jpg Amebiasis (WC)].
==Solitary rectal ulcer==
*[[AKA]] ''solitary ulcer syndrome of the rectum'', abbreviated ''SUS''.
*[[AKA]] ''solitary rectal ulcer syndrome''.
*''[[Mucosal prolapse syndrome]]'' may be used as a synonym; however, it encompasses other entities.<ref name=pmid22697798>{{Cite journal  | last1 = Abid | first1 = S. | last2 = Khawaja | first2 = A. | last3 = Bhimani | first3 = SA. | last4 = Ahmad | first4 = Z. | last5 = Hamid | first5 = S. | last6 = Jafri | first6 = W. | title = The clinical, endoscopic and histological spectrum of the solitary rectal ulcer syndrome: a single-center experience of 116 cases. | journal = BMC Gastroenterol | volume = 12 | issue =  | pages = 72 | month =  | year = 2012 | doi = 10.1186/1471-230X-12-72 | PMID = 22697798 }}</ref>
{{Main|Solitary rectal ulcer}}


==Polyps==
==Rectal prolapse==
{{main|Intestinal polyps}}
{{Main|Rectal prolapse}}
Polyps are the bread & butter of GI pathology.  They are very common.
 
Main types:
*Hyperplastic (most common)
*Adenomatous (quite common, pre-malignant)
*Hamartomatous (rare, weird & wonderful)
*Inflammatory (associated with IBD)
 
Most common (images):
*[http://en.wikipedia.org/wiki/File:Hyperplastic_polyp1.jpg Hyperplastic polyp image - intermed. mag. (wikipedia.org)].
*[http://commons.wikimedia.org/wiki/File:Hyperplastic_polyp2.jpg Hyperplastic polyp image - low mag. (wikipedia.org)].


=Neoplastic disease=
==Colorectal Tumours==
==Colorectal Tumours==
{{main|Colorectal tumours}}
{{main|Colorectal tumours}}
These are very common.  The are covered in a separate article entitled ''[[colorectal tumours]]''.
These are very common.  The are covered in a separate article entitled ''[[colorectal tumours]]''.


==Solitary rectal ulcer==
==Neuroendocrine tumour==
===General===
{{Main|Neuroendocrine neoplasms#GI tract}}
*Clinically may be suspected to a malignancy - biopsied routinuely.
*[[AKA]] ''carcinoid''.
*Mucosal ulceration.
*"Three-lies disease":<ref name=pmid18271667>{{cite journal |author=Crespo Pérez L, Moreira Vicente V, Redondo Verge C, López San Román A, Milicua Salamero JM |title=["The three-lies disease": solitary rectal ulcer syndrome] |language=Spanish; Castilian |journal=Rev Esp Enferm Dig |volume=99 |issue=11 |pages=663–6 |year=2007 |month=November |pmid=18271667 |doi= |url=http://www.grupoaran.com/mrmUpdate/lecturaPDFfromXML.asp?IdArt=459864&TO=RVN&Eng=1}}</ref>
# May not be solitary,
# May not be rectal -- can be in left colon,
# May not be ulcerating -- non-ulcerated lesions: polypoid and/or erythematous.


Note: Each of the words in ''solitary rectal ulcer'' is a lie.
==Goblet cell carcinoid==
:Described in detail in the ''[[appendix]]'' article.
*AKA ''crypt cell carcinoma''.
*Biphasic tumour; features of ''carcinoid tumour'' and ''adenocarcinoma''.


===Epidemiology===
=Other=
*Typically younger patients - average age of presentation ~30 years in one study.<ref name=pmid17139403>{{cite journal |author=Chong VH, Jalihal A |title=Solitary rectal ulcer syndrome: characteristics, outcomes and predictive profiles for persistent bleeding per rectum |journal=Singapore Med J |volume=47 |issue=12 |pages=1063–8 |year=2006 |month=December |pmid=17139403 |doi= |url=http://www.sma.org.sg/smj/4712/4712a7.pdf}}</ref>
==Colonic pseudo-obstruction==
*Rare.
{{Main|Colonic pseudo-obstruction}}


===Clinical===
==Pseudomelanosis coli==
*Usually presents as BRBPR ~ 85% of cases.<ref name=pmid17139403/>
*[[AKA]] ''melanosis coli''.
*Abdominal pain present in approx. 1/3.<ref name=pmid17139403/>
{{Main|Pseudomelanosis coli}}
**May be very painful.


===Histology===
==Angiodysplasia==
Features:<ref name=pmid18271667/>
{{Main|Angiodysplasia}}
*Fibrosis of the lamina propria - should be obliterated.
*Thickened muscularis mucosa - abnormally extends to the lumen.


===Histologic DDx===
==Drugs==
*Rectal prolapse. (?)
{{Main|Drug toxicity}}
===Sodium polystyrene sulfonate===
*AKA ''Kayexalate''.
====General====
*Used to treat hyperkalemia - as may be seen in renal failure.


===Treatment===
====Microscopic====
*Usually conservative, i.e. non-surgical.
Features:<ref name=pmid11342776>{{cite journal |author=Abraham SC, Bhagavan BS, Lee LA, Rashid A, Wu TT |title=Upper gastrointestinal tract injury in patients receiving kayexalate (sodium polystyrene sulfonate) in sorbitol: clinical, endoscopic, and histopathologic findings |journal=Am. J. Surg. Pathol. |volume=25 |issue=5 |pages=637-44 |year=2001 |month=May |pmid=11342776 |doi= |url=http://meta.wkhealth.com/pt/pt-core/template-journal/lwwgateway/media/landingpage.htm?issn=0147-5185&volume=25&issue=5&spage=637}}</ref>  
*Resection - may be done for fear of malignancy.
*Purple blobs on H&E stain - look somewhat like [[calcium phosphate]].
 
*Can cause focal [[necrosis]].
==Rectal prolapse==
===Generally===
*Usually close to the anal verge.
*Rare forms can occasionally be confused with cancer.<ref name=pmid19861563>{{cite journal |author=Brosens LA, Montgomery EA, Bhagavan BS, Offerhaus GJ, Giardiello FM |title=Mucosal prolapse syndrome presenting as rectal polyposis |journal=J. Clin. Pathol. |volume=62 |issue=11 |pages=1034–6 |year=2009 |month=November |pmid=19861563 |pmc=2853932 |doi=10.1136/jcp.2009.067801 |url=}}</ref>


===Histopathology===
=====Image=====  
Features:<ref name=pmid3234303>{{cite journal |author=Schneider A, Fritze C, Bosseckert H, Machnik G |title=[Primary clinical, endoscopic and histologic findings in solitary rectal ulcer] |language=German |journal=Dtsch Z Verdau Stoffwechselkr |volume=48 |issue=3-4 |pages=183–9 |year=1988 |pmid=3234303 |doi= |url=}}</ref>
<gallery>
*"Fibromuscular hyperplasia" - '''key feature''':
Image:Cecal_adenocarcinoma.jpg | Adenocarcinoma and sodium polystyrene crystals (WC/Nephron)
**Fibrosis,
</gallery>
**Muscularis mucosae is "too superficial".
==Graft-versus host disease==
*Surface ulceration + inflammation (neutrophils).
{{Main|Graft-versus-host disease}}
*+/-Serration of epithelium at the surface.
*Abbreviated as ''GVHD''.
*NEGATIVES:
*Seen in the context of bone marrow transplants.
**No nuclear atypia.


==Mucosal prolapse syndrome==
==Bowel transplant==
*Similar to rectal prolapse???
The histology of bowel transplant rejection is identical to GVHD - see ''[[GVHD]]''.
 
==Weird stuff==
Kayexalate (sodium polystyrene sulfonate):<ref name=pmid11342776>{{cite journal |author=Abraham SC, Bhagavan BS, Lee LA, Rashid A, Wu TT |title=Upper gastrointestinal tract injury in patients receiving kayexalate (sodium polystyrene sulfonate) in sorbitol: clinical, endoscopic, and histopathologic findings |journal=Am. J. Surg. Pathol. |volume=25 |issue=5 |pages=637-44 |year=2001 |month=May |pmid=11342776 |doi= |url=http://meta.wkhealth.com/pt/pt-core/template-journal/lwwgateway/media/landingpage.htm?issn=0147-5185&volume=25&issue=5&spage=637}}</ref>
*Used to treat hyperkalemia.
*Purple blobs on H&E stain - look somewhat like [[calcium phosphate]].
*Can cause focal necrosis.
 
Image: [http://commons.wikimedia.org/wiki/File:Cecal_adenocarcinoma.jpg Sodium polystyrene crystals - commons.wikimedia.org].


==Chronic constipation==
==Chronic constipation==
This is occasionally an indication for colectomy.
:This section deals with ''chronic constipation'' that has no apparent cause.
===General===
*This is occasionally an indication for [[colectomy]].<ref name=pmid21382578>{{Cite journal  | last1 = Knowles | first1 = CH. | last2 = Farrugia | first2 = G. | title = Gastrointestinal neuromuscular pathology in chronic constipation. | journal = Best Pract Res Clin Gastroenterol | volume = 25 | issue = 1 | pages = 43-57 | month = Feb | year = 2011 | doi = 10.1016/j.bpg.2010.12.001 | PMID = 21382578 }}
</ref>


Causes:
General differential diagnosis for constipation:
*Tumour.
*Tumour.
*Adhesions - due to previous surgery.
*Adhesions - due to previous surgery.
*Neuropathy.
*Neuropathy.<ref name=pmid21382578/>
*Congenital defect (Hirschsprung's disease).
**[[Parkinson disease]].
*Congenital defect ([[Hirschsprung's disease]]).
*Myopathy.<ref name=pmid21382578/>
*Medications/substance use.
*Medications/substance use.
*Idiopathic.
*Idiopathic.


Work-up if no tumour is identified:<ref>IAV. 15 December 2009.</ref>
===Gross===
*No changes.
 
===Microscopic===
Features:
*Colon within normal limits.
**Look for the Ganglion cells (submucosal plexus, myenteric plexus).
**Look for interstitial cells of Cajal (with CD117) - typically most common around the myenteric plexus.<ref name=pmid17222246>{{Cite journal  | last1 = Streutker | first1 = CJ. | last2 = Huizinga | first2 = JD. | last3 = Driman | first3 = DK. | last4 = Riddell | first4 = RH. | title = Interstitial cells of Cajal in health and disease. Part I: normal ICC structure and function with associated motility disorders. | journal = Histopathology | volume = 50 | issue = 2 | pages = 176-89 | month = Jan | year = 2007 | doi = 10.1111/j.1365-2559.2006.02493.x | PMID = 17222246 | url = http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2559.2006.02493.x/pdf }}</ref>
 
Negatives:
*No significant vascular disease.
*No fibrosis.
*No loss of muscle.
 
===Stains & IHC===
Work-up if no tumour is identified:<ref>IAV. 15 December 2009.</ref><ref name=pmid19360428/>
*Routine H&E.
*Routine H&E.
*Pan-actin.
*Smooth muscle actin - confirm myocyte loss.
*Gomori trichrome.
*Gomori trichrome - examine connective tissue.
*CD117 - to look for the ''interstitial cells of Cajal''.
*CD117 - to look for the ''interstitial cells of Cajal''.
**<50% the expected = abnormal.<ref name=pmid19360428/>
***Normal numbers not defined.
*HU - neuronal marker.<ref name=pmid8586967>{{cite journal |author=Barami K, Iversen K, Furneaux H, Goldman SA |title=Hu protein as an early marker of neuronal phenotypic differentiation by subependymal zone cells of the adult songbird forebrain |journal=J. Neurobiol. |volume=28 |issue=1 |pages=82–101 |year=1995 |month=September |pmid=8586967 |doi=10.1002/neu.480280108 |url=}}</ref>
*HU - neuronal marker.<ref name=pmid8586967>{{cite journal |author=Barami K, Iversen K, Furneaux H, Goldman SA |title=Hu protein as an early marker of neuronal phenotypic differentiation by subependymal zone cells of the adult songbird forebrain |journal=J. Neurobiol. |volume=28 |issue=1 |pages=82–101 |year=1995 |month=September |pmid=8586967 |doi=10.1002/neu.480280108 |url=}}</ref>


==Goblet cell carcinoid==
===Sign out===
:Described in detail in the ''[[appendix]]'' article.
*A long list of things to report is contained the recommendation of a working group.<ref name=pmid19360428>{{Cite journal  | last1 = Knowles | first1 = CH. | last2 = De Giorgio | first2 = R. | last3 = Kapur | first3 = RP. | last4 = Bruder | first4 = E. | last5 = Farrugia | first5 = G. | last6 = Geboes | first6 = K. | last7 = Gershon | first7 = MD. | last8 = Hutson | first8 = J. | last9 = Lindberg | first9 = G. | title = Gastrointestinal neuromuscular pathology: guidelines for histological techniques and reporting on behalf of the Gastro 2009 International Working Group. | journal = Acta Neuropathol | volume = 118 | issue = 2 | pages = 271-301 | month = Aug | year = 2009 | doi = 10.1007/s00401-009-0527-y | PMID = 19360428 }}</ref>
*AKA ''crypt cell carcinoma''.
**Most pathology practises do not report much.
*Biphasic tumour; features of ''carcinoid tumour'' and ''adenocarcinoma''.
 
<pre>
TERMINAL ILEUM, CECUM, COLON (ASCENDING, TRANSVERSE AND SIGMOID), COLECTOMY:
- SMALL BOWEL, CECUM, AND COLON WITHIN NORMAL LIMITS.
- FOUR LYMPH NODES NEGATIVE FOR MALIGNANCY ( 0 POSITIVE / 4 ).
- NEGATIVE FOR DYSPLASIA AND NEGATIVE FOR MALIGNANCY.
 
COMMENT:
Several stains were done:
CD117: interstitial cells of Cajal present, no apparent decrease.
SMA: no significant myocyte loss.
Gomori trichrome: no abnormal fibrosis apparent.
Tau: no abnormalities apparent.
</pre>


==See also==
=See also=
*[[GIST]].
*[[GIST]].
*[[Gastrointestinal pathology]].
*[[Gastrointestinal pathology]].
*[[Intestinal polyps]].
*[[Intestinal polyps]].
*[[Small bowel]].
*[[Small bowel]].
*[[Doughnuts]].


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


[[Category:Gastrointestinal pathology]]
[[Category:Gastrointestinal pathology]]
[[Category:Colon|Colon]]
Michael
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