Difference between revisions of "Colon"

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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.   


==Common clinical problems==
It commonly comes to pathologists because there is a suspicion of [[colorectal cancer]] or a known history of [[inflammatory bowel disease]] (IBD).
 
An introduction to gastrointestinal pathology is found in the ''[[gastrointestinal pathology]]'' article.  The ''[[anus]]'' and ''[[ileocecal valve]]'' are dealt with in separate articles.
 
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''.
 
=Anatomy=
*The [[rectum]] has several definition. These are discussed in the ''[[rectum]]'' article.
*The large bowel may be submitted with segment names or with the distance to the anal verge.
 
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>
{| class="wikitable sortable"
!Named segment
!Distance to anal verge (cm)
|-
|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=
===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/AIDS.
**[[HIV|HIV/AIDS]].


==Inflammatory bowel disease (IBD)==
Images:
Exists in two main flavours:
<gallery>
*Crohn's disease (CD).
Image:CMV_colitis_-_high_mag_-_cropped.jpg | CMV colitis - high. mag. (WC/Nephron)
*Ulcerative colitis (UC).
Image:CMV_colitis_-_intermed_mag.jpg | CMV colitis - intermed. mag. (WC/Nephron)
</gallery>


===Clinical===
=Grossing=
*It is important to differentiate UC and CD as the management is different.  
==Types of specimens==
*UC patients get pouches... CD patients do not.
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.


Epidemiology:
===Images===
*NOD2/CARD15 variants are assoc. with stricturing CD, early need for surgery and recurrence.<ref name=pmid16244543 >{{cite journal |author=Alvarez-Lobos M, Arostegui JI, Sans M, ''et al.'' |title=Crohn's disease patients carrying Nod2/CARD15 gene variants have an increased and early need for first surgery due to stricturing disease and higher rate of surgical recurrence |journal=Ann. Surg. |volume=242 |issue=5 |pages=693–700 |year=2005 |month=November |pmid=16244543 |pmc=1409853 |doi= |url=}}</ref>
<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>


Notes:
===Images===
# Microscopic features can be remembered by [[mnemonic]] ''CPP'': Crypts (abnormal), Plasmacytosis, Paneth cells where they don't belong.
<gallery>
# If you see architectural distortion (e.g. crypt branching) in the left colon, look for Paneth cells.
Image: Rectum - lateral view.jpg | Sigmoid and rectum. APR specimen. (WC)
# The hepatic flexure is considered the divider for normal paneth cells and abnormal paneth cells, i.e. paneth cells proximal to the hepatic flexure are normal; paneth cells distal to the hepatic flexure are abnormal.<ref>STC. 14 December 2009.</ref>
</gallery>


===Crohn's disease vs. ulcerative colitis===
==Lymph nodes==
UC features:<ref>PBoD P.850.</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>
*Mucosal involvement --sometimes submucosa.
*No skip lesions.
*Colon/rectum only.
** UC may have 'ileal backwash' -- mild ileal inflammation due to backwash of inflammatory soup from colon.
*"No granulomas".
**Superficial granulomas in the mucosa are non-specific, especially if they are beside an inflammed crypt, i.e. they may be present in UC.<ref name=pmid12147095>{{Cite journal | last1 = Shepherd | first1 = NA. | title = Granulomas in the diagnosis of intestinal Crohn's disease: a myth exploded? | journal = Histopathology | volume = 41 | issue = 2 | pages = 166-8 | month = Aug | year = 2002 | doi = | PMID = 12147095 }}</ref><ref name=pmid12121237>{{Cite journal  | last1 = Mahadeva | first1 = U. | last2 = Martin | first2 = JP. | last3 = Patel | first3 = NK. | last4 = Price | first4 = AB. | title = Granulomatous ulcerative colitis: a re-appraisal of the mucosal granuloma in the distinction of Crohn's disease from ulcerative colitis. | journal = Histopathology | volume = 41 | issue = 1 | pages = 50-5 | month = Jul | year = 2002 | doi =  | PMID = 12121237 }}</ref>
***Deep granulomas are specific for Crohn's disease.


Example of a superficial granuloma that is non-specific, i.e. this could be UC or CD:
==Quirke method==
*[http://commons.wikimedia.org/wiki/File:Colitis_with_granuloma_low_mag.jpg Colitis with a superficial granuloma (wikimedia.org)].
*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>


==Ulcerative colitis==
==Standard method==
===General===
*Bowel is prep'ed by [[opening]] it along the antimesenteric side.
*Often abbreviated as ''UC''.
*Dimensions - length, circumference at both [[margins]].
*Radial margin/circumferential margin - should be painted.
**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.


===Epidemiology===
Note:
*Associated with ''[[sclerosing cholangitis]]''.
*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>
*Appendicitis is considered protective against UC.<ref name=pmid19685454>{{Cite journal  | last1 = Beaugerie | first1 = L. | last2 = Sokol | first2 = H. | title = Appendicitis, not appendectomy, is protective against ulcerative colitis, both in the general population and first-degree relatives of patients with IBD. | journal = Inflamm Bowel Dis | volume = | issue = | pages = | month = Aug | year = 2009 | doi = 10.1002/ibd.21064 | PMID = 19685454 }}</ref><ref name=pmid19273505>{{Cite journal  | last1 = Timmer | first1 = A. | last2 = Obermeier | first2 = F. | title = Reduced risk of ulcerative colitis after appendicectomy. | journal = BMJ | volume = 338 | issue =  | pages = b225 | month =  | year = 2009 | doi =  | PMID = 19273505 }}</ref>
**In a survey of surgeons:
*Smoking is protective; the opposite is true for Crohn's disease.<ref name=pmid19273505/>
**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.


===Gross===
=Common non-neoplastic disease=
*Conventionally considered to be contiguous, i.e. no "skip lesions", with rectal involvement being most severe.
==Colorectal polyps==
*Dependent on the study one reads... rectal sparing may be seen in 15% of UC patients.<ref>{{cite journal |author=Bernstein CN, Shanahan F, Anton PA, Weinstein WM |title=Patchiness of mucosal inflammation in treated ulcerative colitis: a prospective study |journal=Gastrointest. Endosc. |volume=42 |issue=3 |pages=232-7 |year=1995 |month=September |pmid=7498688 |doi= |url=}}</ref>
{{main|Intestinal polyps}}
Polyps are the bread & butter of [[GI pathology]]. They are very common.


===Microscopic===
Main types:
*Lack of granulomas.
*Hyperplastic - most common, benign.
*No full wall-thickness inflammation.
*Adenomatous - quite common, pre-malignant.
*[[Hamartomatous polyps|Hamartomatous]] - rare, weird & wonderful.
*Inflammatory, [[AKA]] inflammatory pseudopolyps - associated with [[IBD]].


==Crohn's disease==
Most common (images):
===General===
<gallery>
*Often abbreviated as ''CD''.
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}}


===Gross===
==Diverticular disease==
*Transmural inflammation, i.e. full thickness of bowel wall.
{{Main|Diverticular disease}}
*Creeping fat.
*Cobblestone appearance -- may be described as such on endoscopy.
*Serpiginous ulcers.
** Image: [http://en.wikipedia.org/wiki/File:CD_serpiginous_ulcer.jpg Serpiginous ulcer (endoscopy) - wikipedia.org].


===Microscopic===
==Pseudomembranous colitis==
Features:<ref name=pmid10048734/>
{{Main|Pseudomembranous colitis}}
*Segmental crypt architectural abnormalities,
*Mucin depletion,
*Mucin preservation at the active sites, and
*Focal chronic inflammation without crypt atrophy.


==Bowel ischemia==
==Volvulus==
===Radiologic correlate===
{{Main|Volvulus}}
*Bowel wall thickening.


===Gross===
=Inflammatory diseases=
Features:<ref>PBoD P.852.</ref>
==Inflammatory bowel disease==
*Luminal part (mucosa & submucosa) affected.
{{main|Inflammatory bowel disease}}
*Splenic flexture of colon commonly affected (vascular watershed).


Note:
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).
*May have pseudomembranes (classically assoc. with ''C. difficle'' colitis), i.e. mimics an infectious process.
*DDx for pseudomembranes:<ref>PBoD P.837-8.</ref>
**C. difficle induced pseudomembranous colitis,
**Ischemic colitis,
**Volvulus,
**Necrotizing infections,
**... anything that causes severe mucosal injury.  


Histology of pseudomembranes:<ref>PBoD P.837-8.</ref>
===Microscopic===
*Loss of surf. epithelium,  
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>
*PMNs in lamina propria,  
*Basal, i.e. crypt base, plasmacytosis with severe chronic inflammation,
*+/- capillary fibrin thrombi.
*Crypt architectural abnormalities, and
NB: Pseudomembranes arise from the crypts.
*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.
Image:
**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>
*[http://commons.wikimedia.org/wiki/File:Colonic_pseudomembranes_low_mag.jpg Micrograph of pseudomembranes - low mag. (wikimedia.org)].
*[http://commons.wikimedia.org/wiki/File:Colonic_pseudomembranes_intermed_mag.jpg Micrograph of pseudomembranes - intermed. mag. (wikimedia.org)].
 
==Angiodysplasia==
===General===
*Causes (lower) GI haemorrhage.
*Generally, not a problem pathologists see.
 
===Location===
*Cecum.
 
===Epidemiology===
*Older people.
 
===Etiology===
*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>PBoD P.854</ref>
 
==Melanosis coli==
*AKA ''Pseudomelanosis coli''.<ref>[http://www.medicinenet.com/melanosis_coli/article.htm http://www.medicinenet.com/melanosis_coli/article.htm]</ref>
*''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===
*Classically associated with anthracene containing laxative (e.g. Senokot) use and herbal remedies.<ref name=pmid18666316/>
 
===Features===
*Brown pigmentation of the mucosa.
*Typically more prominent in the cecum and proximal colon.<ref name=pmid18666316/>
 
DDx of brown pigment:
*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.


==Microscopic colitis==
==Microscopic colitis==
Definition:
:''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.
*As the name suggests, they are microscopic, i.e. endoscopic examination is normal.
{{Main|Lymphocytic colitis}}
{{Main|Collagenous colitis}}


Presentation:
==Diversion colitis==
*Chronic diarrhea, non-bloody.<ref name=medscape180664>http://emedicine.medscape.com/article/180664-overview</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>
*NEGATIVES<ref name=hopkins_cc_lc/>
**No [[PMN]]s.
**No crypt distortion.


Notes: CC is typically more prominent in the proximal colon - may reflect concentration gradient of offending causitive agents.<ref name=pmid19109861/>
===Sign out===
<pre>
ASCENDING COLON, BIOPSY:
- MILD ACTIVE COLITIS, SEE COMMENT.


==Spirochetes==
COMMENT:
*Very rare cause of diarrhea.
There is are no granulomas. The crypt architecture is normal. A benign lymphoid nodule 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>
present.
*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>


===Histology===
The differential diagnosis includes infective etiologies, early inflammatory
*Hyperchromatic fuzz on luminal aspect of epithelial cells; at brush border.
bowel disease and ischemia.  The histomorphology is more in keeping with an infective
etiology as neutrophils are a predominant feature; however, clinical correlation is
required.
</pre>


Special stain:
==Cytomegalovirus colitis==
*Silver stains highlight 'em (e.g. Warthin-Starry stain).
{{Main|CMV}}
*Abbreviated ''CMV colitis''.
{{Main|Cytomegalovirus colitis}}


==Polyps==
==Intestinal spirochetosis==
{{main|Intestinal polyps}}
*[[AKA]] ''intestinal spirochetes''; more specifically ''colonic spirochetes'', ''colonic spirochetosis''.
Polyps are the bread & butter of GI pathology.  They are very common.
{{Main|Intestinal spirochetosis}}


Main types:
==Amebiasis==
*Hyperplastic (most common)
*May also be spelled ''amoebiasis''.
*Adenomatous (quite common, pre-malignant)
{{Main|Amebiasis}}
*Hamartomatous (rare, weird & wonderful)
*Inflammatory (associated with IBD)


Most common (images):
==Cryptosporidiosis==
*[http://en.wikipedia.org/wiki/File:Hyperplastic_polyp1.jpg Hyperplastic polyp image - intermed. mag. (wikipedia.org)].
{{Main|Cryptosporidiosis}}
*[http://commons.wikimedia.org/wiki/File:Hyperplastic_polyp2.jpg Hyperplastic polyp image - low mag. (wikipedia.org)].
===General===
*Usually in immune incompetent individuals, e.g. [[HIV|HIV/AIDS]].


==Colorectal Tumours==
===Microscopic===
===Epidemiology===
Features:
Very common type of cancer.
*Uniform spherical nodules 2-4 micrometres in diameter, typical location - GI tract brush border.
 
**Bluish staining of brush border '''key feature''' - low power.
===Classification===
*Colon & rectum, most common --by far-- is [[adenocarcinoma]].<ref>PBoD P.864.</ref>
 
Other tumours - many (incomplete list):<ref>WMSP P.198.</ref>
*Mucinous carcinoma.
*Adenosquamous carcinoma.
*Signet-ring carcinoma.
*Squamous carcinoma.
*Neuroendocrine neoplasms (carcinoid tumours).
*Lipoma.
*Leiomyoma.
*[[GIST]].
*Angiosarcoma.
*Lymphoma (Non-Hodgkin's lymphoma).
 
===Grading===
*"adenocarcinoma in situ" and "high-grade dysplasia" is used interchangeably by many in the colon and rectum.
**splitting hairs - ''adenocarcinoma in situ'' is ''invasion into the lamina propria'', high-grade dysplasia does not have lamina propria invasion. Ergo, the difference (in my opinion) amounts to seeing a [[desmoplastic stroma]] (adenocarcinoma) or not seeing one (dysplasia).
 
Grading of tumours:
*Tis - in situ (intramucosal),
*T1 - into submucosa (through mucularis mucosae),
**this is different than elsewhere,
*T2 - into muscularis propria,
*T3 - into fat beyond musclaris propria,
*T4 - into something else.
 
Nodes:
*N0 - no positive nodes,
*N1 - 1-3 positive nodes,
*N2 - 4+ positive nodes.
 
===Staging of colorectal cancer===
====Simple version====
Tumour/node grade for stage:<ref>TN 2006 GS27</ref>
*Stage I - '''T1 or T2''' N0 M0.
*Stage II - '''T3 or T4''' N0 M0.
*Stage III - Tx '''N1 or N2''' M0.
*Stage IV - Tx Nx '''M1'''.
 
====Complex version====
Detailed tumour/node grade for stage:<ref>[http://www.cancer.org/docroot/CRI/content/CRI_2_4_3X_How_is_colon_and_rectum_cancer_staged.asp http://www.cancer.org/docroot/CRI/content/CRI_2_4_3X_How_is_colon_and_rectum_cancer_staged.asp]</ref>
*Stage I - T1 or T2.
*Stage IIA - T3.
*Stage IIB - T4.
*Stage IIIA - T1 N1 or T2 N1.
*Stage IIIB - T3 N1 or T4 N1.
*Stage IIIC - Tx N2.
*Stage IV - Tx Nx M1.
 
===Surgery===
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==
*Lymph nodes - should get at least 12.<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''
*Bowel is not opened.
**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>.
 
''Standard method''
*Bowel is prep'ed by opening it along the antimesenteric side.
*Dimensions - length, circumference at both margins.
*Radial margin/circumferential margin - should be painted.
**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.


=Rectal pathology=
==Solitary rectal ulcer==
==Solitary rectal ulcer==
===General===
*[[AKA]] ''solitary ulcer syndrome of the rectum'', abbreviated ''SUS''.
*Clinically may be suspected to a malignancy - biopsied routinuely.
*[[AKA]] ''solitary rectal ulcer syndrome''.
*Mucosal ulceration.
*''[[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>
*"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>  
{{Main|Solitary rectal ulcer}}
# 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.
==Rectal prolapse==
{{Main|Rectal prolapse}}


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


===Clinical===
==Neuroendocrine tumour==
*Usually presents as BRBPR ~ 85% of cases.<ref name=pmid17139403/>
{{Main|Neuroendocrine neoplasms#GI tract}}
*Abdominal pain present in approx. 1/3.<ref name=pmid17139403/>
*[[AKA]] ''carcinoid''.
**May be very painful.


===Histology===
==Goblet cell carcinoid==
Features:<ref name=pmid18271667/>
:Described in detail in the ''[[appendix]]'' article.
*Fibrosis of the lamina propria - should be obliterated.
*AKA ''crypt cell carcinoma''.
*Thickened muscularis mucosa - abnormally extends to the lumen.
*Biphasic tumour; features of ''carcinoid tumour'' and ''adenocarcinoma''.


===Histologic DDx===
=Other=
*Rectal prolapse. (?)
==Colonic pseudo-obstruction==
{{Main|Colonic pseudo-obstruction}}


===Treatment===
==Pseudomelanosis coli==
*Usually conservative, i.e. non-surgical.
*[[AKA]] ''melanosis coli''.
*Resection - may be done for fear of malignancy.
{{Main|Pseudomelanosis coli}}


==Rectal prolapse==
==Angiodysplasia==
===Histopathology===
{{Main|Angiodysplasia}}
Features:<ref>NEED REF.</ref>
*"Fibromuscular hyperplasia":
**Fibrosis,
**Muscularis mucosae is "too superficial".
*Surface ulceration + inflammation (neutrophils).
*+/-Serration of epithelium at the surface.
*NEGATIVES:
**No nuclear atypia.


==Mucosal prolapse syndrome==
==Drugs==
*Similar to rectal prolapse???
{{Main|Drug toxicity}}
===Sodium polystyrene sulfonate===
*AKA ''Kayexalate''.
====General====
*Used to treat hyperkalemia - as may be seen in renal failure.


==Weird stuff==
====Microscopic====
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>
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>  
*Used to treat hyperkalemia.
*Purple blobs on H&E stain - look somewhat like [[calcium phosphate]].
*Purple blobs on H&E stain - look somewhat like [[calcium phosphate]].
*Can cause focal necrosis.
*Can cause focal [[necrosis]].


Image: [http://commons.wikimedia.org/wiki/File:Cecal_adenocarcinoma.jpg Sodium polystyrene crystals - commons.wikimedia.org].
=====Image=====
<gallery>
Image:Cecal_adenocarcinoma.jpg | Adenocarcinoma and sodium polystyrene crystals (WC/Nephron)
</gallery>
==Graft-versus host disease==
{{Main|Graft-versus-host disease}}
*Abbreviated as ''GVHD''.
*Seen in the context of bone marrow transplants.
 
==Bowel transplant==
The histology of bowel transplant rejection is identical to GVHD - see ''[[GVHD]]''.


==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 cell of Cajal''.
*CD117 - to look for the ''interstitial cells of Cajal''.
*HU - neuronal marker.<ref name=pmid8586967>PMID 8586967.</ref>
**<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>


==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]]

Latest revision as of 14:46, 5 October 2023

The colon is section of the large bowel. This article also covers the rectum and cecum as both have a similar mucosa.

Anatomy of the colon and rectum. (WC)

It commonly comes to pathologists because there is a suspicion of colorectal cancer or a known history of inflammatory bowel disease (IBD).

An introduction to gastrointestinal pathology is found in the gastrointestinal pathology article. The anus and ileocecal valve are dealt with in separate articles.

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.

Anatomy

  • The rectum has several definition. These are discussed in the rectum article.
  • The large bowel may be submitted with segment names or with the distance to the anal verge.

A conversion between named segments and distance - as per NCI of the United States:[1]

Named segment Distance to anal verge (cm)
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

Obstruction

Top three (in adults):[2]

Bleeding

Mnemonic CHAND:[3]

Infectious colitis with bleeding - causes:

  • Enterohemorrhagic Escherichia coli (EHEC) -- commonly 0157:H7.
  • Campylobacter jejuni.
  • Clostridium difficile.
  • Shigella.

Infectious colitis in the immunosuppressed:

  • Cytomegalovirus (CMV).[4]
    • May afflict patients with IBD and lead to colectomy... as IBD patients are put on immunosuppression.[5]
    • Organ transplant recipients.
    • HIV/AIDS.

Images:

  • CMV colitis - high. mag. (WC/Nephron)

  • CMV colitis - intermed. mag. (WC/Nephron)

Grossing

Types of specimens

Introduction to colorectal surgery:

  1. Colonic resection - remove a piece of large bowel.
  2. Total colectomy - leaves rectum and anus.[6]
  3. Subtotal colectomy - part of colon removed --or-- some of the rectum remains.
  4. Right hemicolectomy - right colon + distal ileum.
  5. Lower anterior resection (LAR) - proximal rectum +/- sigmoid (for proximal rectal malignancies).
  6. Abdominoperineal resection (APR) - anus + rectum - results in a permanent stoma (for distal rectal malignancies).
  7. Stoma - these are often done emergently and then get cut-out after the patient's condition has settled.
  8. Doughnuts (also donuts) from an end-to-end anastomosis stapler.
    • Often accompany lower anterior resections.

Images

  • APR specimen - anterior (WC)

  • APR specimen - lateral (WC)

  • APR specimen - inked (WC)

Identifying the specimen

  • Transverse colon - has omentum.
  • Ascending colon - usu. comes with ileocecal valve and a bit of ileum.
  • Descending colon - has a bare area.
  • Rectum - has adventitia.
    • Pathologists define it as starting where the adventitia starts/the serosal surface no longer completely surrounds the large intestine.[8]
    • Anatomists define it in relation to the third sacral vertebra.[9]

Images

  • Sigmoid and rectum. APR specimen. (WC)

Lymph nodes

Quirke method

  • Bowel is not opened - it is fixed... then sliced.[11][12]

Standard method

  • Bowel is prep'ed by opening it along the antimesenteric side.
  • Dimensions - length, circumference at both margins.
  • Radial margin/circumferential margin - should be painted.
    • 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.

Note:

  • There are several definitions for the rectum.[13]
    • 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.

Common non-neoplastic disease

Colorectal polyps

Main article: Intestinal polyps

Polyps are the bread & butter of GI pathology. They are very common.

Main types:

  • Hyperplastic - most common, benign.
  • Adenomatous - quite common, pre-malignant.
  • Hamartomatous - rare, weird & wonderful.
  • Inflammatory, AKA inflammatory pseudopolyps - associated with IBD.

Most common (images):

  • Hyperplastic polyp image - intermed. mag. (WC/Nephron)

  • Hyperplastic polyp image - low mag. (WC/Nephron)

Ischemic colitis

  • AKA colonic ischemia.
  • AKA ischemia of the colon.
Main article: Ischemic colitis

Diverticular disease

Main article: Diverticular disease

Pseudomembranous colitis

Main article: Pseudomembranous colitis

Volvulus

Main article: Volvulus

Inflammatory diseases

Inflammatory bowel disease

Main article: Inflammatory bowel disease

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).

Microscopic

Features helpful for the diagnosis of IBD - as based on a study:[14]

  • 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[15] - 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.[16]

Microscopic colitis

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.
Main article: Lymphocytic colitis
Main article: Collagenous colitis

Diversion colitis

Main article: Diversion colitis

Eosinophilic colitis

  • Abbreviated EC.
Main article: Eosinophilic colitis

Infectious

Infectious colitis

This section covers non-specific colitides that appear to have an infective etiology.

General

  • Common.
  • Diarrhea - typical symptom.

Gross

  • +/-Erythema on endoscopy.

Microscopic

Features:

  • Neutrophils predominant - key feature.[17]
    • The neutrophils are often superficial - they go to were the bad guys are.
  • No architectural distortion - if acute.

DDx:

IHC

Done if the patient is immunosuppressed, or there is clinical or morphological suspicion:

Sign out

ASCENDING COLON, BIOPSY:
- MILD ACTIVE COLITIS, SEE COMMENT.

COMMENT:
There is are no granulomas.  The crypt architecture is normal.  A benign lymphoid nodule is
present.

The differential diagnosis includes infective etiologies, early inflammatory
bowel disease and ischemia.  The histomorphology is more in keeping with an infective
etiology as neutrophils are a predominant feature; however, clinical correlation is
required.

Cytomegalovirus colitis

Main article: CMV
  • Abbreviated CMV colitis.
Main article: Cytomegalovirus colitis

Intestinal spirochetosis

  • AKA intestinal spirochetes; more specifically colonic spirochetes, colonic spirochetosis.
Main article: Intestinal spirochetosis

Amebiasis

  • May also be spelled amoebiasis.
Main article: Amebiasis

Cryptosporidiosis

Main article: Cryptosporidiosis

General

  • Usually in immune incompetent individuals, e.g. HIV/AIDS.

Microscopic

Features:

  • Uniform spherical nodules 2-4 micrometres in diameter, typical location - GI tract brush border.
    • Bluish staining of brush border key feature - low power.

Rectal pathology

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.[19]
Main article: Solitary rectal ulcer

Rectal prolapse

Main article: Rectal prolapse

Neoplastic disease

Colorectal Tumours

Main article: Colorectal tumours

These are very common. The are covered in a separate article entitled colorectal tumours.

Neuroendocrine tumour

Main article: Neuroendocrine neoplasms#GI tract

Goblet cell carcinoid

Described in detail in the appendix article.
  • AKA crypt cell carcinoma.
  • Biphasic tumour; features of carcinoid tumour and adenocarcinoma.

Other

Colonic pseudo-obstruction

Main article: Colonic pseudo-obstruction

Pseudomelanosis coli

  • AKA melanosis coli.
Main article: Pseudomelanosis coli

Angiodysplasia

Main article: Angiodysplasia

Drugs

Main article: Drug toxicity

Sodium polystyrene sulfonate

  • AKA Kayexalate.

General

  • Used to treat hyperkalemia - as may be seen in renal failure.

Microscopic

Features:[20]

Image

  • Adenocarcinoma and sodium polystyrene crystals (WC/Nephron)

Graft-versus host disease

Main article: Graft-versus-host disease
  • Abbreviated as GVHD.
  • Seen in the context of bone marrow transplants.

Bowel transplant

The histology of bowel transplant rejection is identical to GVHD - see GVHD.

Chronic constipation

This section deals with chronic constipation that has no apparent cause.

General

General differential diagnosis for constipation:

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.[22]

Negatives:

  • No significant vascular disease.
  • No fibrosis.
  • No loss of muscle.

Stains & IHC

Work-up if no tumour is identified:[23][24]

  • Routine H&E.
  • Smooth muscle actin - confirm myocyte loss.
  • Gomori trichrome - examine connective tissue.
  • CD117 - to look for the interstitial cells of Cajal.
    • <50% the expected = abnormal.[24]
      • Normal numbers not defined.
  • HU - neuronal marker.[25]

Sign out

  • A long list of things to report is contained the recommendation of a working group.[24]
    • Most pathology practises do not report much.
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.

See also

References

  1. ↑ URL: [1]https://training.seer.cancer.gov/colorectal/anatomy/figure/figure1.html]. Accessed on: 8 February 2018.
  2. ↑ URL: http://www.emedicine.com/EMERG/topic65.htm. Accessed on: 28 June 2011.
  3. ↑ TN 2007 G29.
  4. ↑ Golden MP, Hammer SM, Wanke CA, Albrecht MA (September 1994). "Cytomegalovirus vasculitis. Case reports and review of the literature". Medicine (Baltimore) 73 (5): 246–55. PMID 7934809.
  5. ↑ Kandiel A, Lashner B (December 2006). "Cytomegalovirus colitis complicating inflammatory bowel disease". Am. J. Gastroenterol. 101 (12): 2857–65. doi:10.1111/j.1572-0241.2006.00869.x. PMID 17026558.
  6. ↑ http://www.allaboutbowelsurgery.com/shared/stoma_care/stoma_surgery/procedures/surgery_colon/subtotal.htm
  7. ↑ Arbman, G.; Nilsson, E.; Hallböök, O.; Sjödahl, R. (Mar 1996). "Local recurrence following total mesorectal excision for rectal cancer.". Br J Surg 83 (3): 375-9. PMID 8665198.
  8. ↑ Lester, Susan Carole (2010). Manual of Surgical Pathology (3rd ed.). Saunders. pp. 339. ISBN 978-0-323-06516-0.
  9. ↑ URL: http://www.bartleby.com/107/249.html. Accessed on: 19 October 2012.
  10. ↑ Bilimoria KY, Bentrem DJ, Stewart AK, et al. (September 2008). "Lymph node evaluation as a colon cancer quality measure: a national hospital report card". J. Natl. Cancer Inst. 100 (18): 1310–7. doi:10.1093/jnci/djn293. PMID 18780863. http://www.medscape.com/viewarticle/581463.
  11. ↑ West NP, Morris EJ, Rotimi O, Cairns A, Finan PJ, Quirke P (September 2008). "Pathology grading of colon cancer surgical resection and its association with survival: a retrospective observational study". Lancet Oncol. 9 (9): 857–65. doi:10.1016/S1470-2045(08)70181-5. PMID 18667357.
  12. ↑ West NP, Finan PJ, Anderin C, Lindholm J, Holm T, Quirke P (July 2008). "Evidence of the oncologic superiority of cylindrical abdominoperineal excision for low rectal cancer". J. Clin. Oncol. 26 (21): 3517–22. doi:10.1200/JCO.2007.14.5961. PMID 18541901.
  13. ↑ Kenig, J.; Richter, P. (Sep 2013). "Definition of the rectum and level of the peritoneal reflection - still a matter of debate?". Wideochir Inne Tech Maloinwazyjne 8 (3): 183-6. doi:10.5114/wiitm.2011.34205. PMID 24130630.
  14. ↑ Tanaka M, Riddell RH, Saito H, Soma Y, Hidaka H, Kudo H (January 1999). "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". Scand. J. Gastroenterol. 34 (1): 55–67. PMID 10048734.
  15. ↑ Tanaka M, Saito H, Kusumi T, et al (December 2001). "Spatial distribution and histogenesis of colorectal Paneth cell metaplasia in idiopathic inflammatory bowel disease". J. Gastroenterol. Hepatol. 16 (12): 1353–9. PMID 11851832. http://www3.interscience.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0815-9319&date=2001&volume=16&issue=12&spage=1353.
  16. ↑ Rubio CA, Nesi G (2003). "A simple method to demonstrate normal and metaplastic Paneth cells in tissue sections". In Vivo 17 (1): 67–71. PMID 12655793.
  17. ↑ 17.0 17.1 Iacobuzio-Donahue, Christine A.; Montgomery, Elizabeth A. (2005). Gastrointestinal and Liver Pathology: A Volume in the Foundations in Diagnostic Pathology Series (1st ed.). Churchill Livingstone. pp. 324. ISBN 978-0443066573.
  18. ↑ Karlitz, JJ.; Li, ST.; Holman, RP.; Rice, MC. (Jan 2011). "EBV-associated colitis mimicking IBD in an immunocompetent individual.". Nat Rev Gastroenterol Hepatol 8 (1): 50-4. doi:10.1038/nrgastro.2010.192. PMID 21119609.
  19. ↑ Abid, S.; Khawaja, A.; Bhimani, SA.; Ahmad, Z.; Hamid, S.; Jafri, W. (2012). "The clinical, endoscopic and histological spectrum of the solitary rectal ulcer syndrome: a single-center experience of 116 cases.". BMC Gastroenterol 12: 72. doi:10.1186/1471-230X-12-72. PMID 22697798.
  20. ↑ Abraham SC, Bhagavan BS, Lee LA, Rashid A, Wu TT (May 2001). "Upper gastrointestinal tract injury in patients receiving kayexalate (sodium polystyrene sulfonate) in sorbitol: clinical, endoscopic, and histopathologic findings". Am. J. Surg. Pathol. 25 (5): 637-44. PMID 11342776. http://meta.wkhealth.com/pt/pt-core/template-journal/lwwgateway/media/landingpage.htm?issn=0147-5185&volume=25&issue=5&spage=637.
  21. ↑ 21.0 21.1 21.2 Knowles, CH.; Farrugia, G. (Feb 2011). "Gastrointestinal neuromuscular pathology in chronic constipation.". Best Pract Res Clin Gastroenterol 25 (1): 43-57. doi:10.1016/j.bpg.2010.12.001. PMID 21382578.
  22. ↑ Streutker, CJ.; Huizinga, JD.; Driman, DK.; Riddell, RH. (Jan 2007). "Interstitial cells of Cajal in health and disease. Part I: normal ICC structure and function with associated motility disorders.". Histopathology 50 (2): 176-89. doi:10.1111/j.1365-2559.2006.02493.x. PMID 17222246. http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2559.2006.02493.x/pdf.
  23. ↑ IAV. 15 December 2009.
  24. ↑ 24.0 24.1 24.2 Knowles, CH.; De Giorgio, R.; Kapur, RP.; Bruder, E.; Farrugia, G.; Geboes, K.; Gershon, MD.; Hutson, J. et al. (Aug 2009). "Gastrointestinal neuromuscular pathology: guidelines for histological techniques and reporting on behalf of the Gastro 2009 International Working Group.". Acta Neuropathol 118 (2): 271-301. doi:10.1007/s00401-009-0527-y. PMID 19360428.
  25. ↑ Barami K, Iversen K, Furneaux H, Goldman SA (September 1995). "Hu protein as an early marker of neuronal phenotypic differentiation by subependymal zone cells of the adult songbird forebrain". J. Neurobiol. 28 (1): 82–101. doi:10.1002/neu.480280108. PMID 8586967.
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