Difference between revisions of "Colon"

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

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>

=Common clinical problems=

*[[Volvulus]] (cecal, sigmoid).

*Colitis ([[radiation colitis|radiation]], [[infectious colitis|infectious]], [[ischemic colitis|ischemic]], [[IBD]] (UC >CD), iatrogenic (anticoagulants)).  

*[[Hemorrhoids]].

*[[Angiodysplasia]].  

[[Infectious colitis]] in the immunosuppressed:

Image:CMV_colitis_-_intermed_mag.jpg | CMV colitis - intermed. mag. (WC/Nephron)

# 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.

#* 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.

===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>

==Identifying the specimen==

*Ascending colon - usu. comes with [[ileocecal valve]] and a bit of ileum.

*Rectum - has adventitia.

**Pathologists define it as starting where the adventitia starts/the serosal surface no longer completely surrounds the large intestine.<ref>{{Ref Lester3|339}}</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>

===Images===

<gallery>

Image: Rectum - lateral view.jpg | Sigmoid and rectum. APR specimen. (WC)

</gallery>

*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>

==Quirke method==

*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>

==Standard method==

*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.<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>

**In a survey of surgeons:

***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.

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

Main types:

*Hyperplastic - most common, benign.

*Adenomatous - quite common, pre-malignant.

*[[Hamartomatous polyps|Hamartomatous]] - rare, weird & wonderful.

*Inflammatory, [[AKA]] inflammatory pseudopolyps - associated with [[IBD]].

Most common (images):

*[[AKA]] ''colonic ischemia''.

*[[AKA]] ''ischemia of the colon''.

==Diverticular disease==

{{Main|Diverticular disease}}

==Inflammatory bowel disease==

{{main|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).

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>

*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'' 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|Lymphocytic colitis}}

{{Main|Collagenous colitis}}

==Diversion colitis==

{{Main|Diversion colitis}}

*Abbreviated ''EC''.

=Infectious=

==Infectious colitis==

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

*Common.

*Diarrhea - typical symptom.

*+/-Erythema on endoscopy.

*Neutrophils predominant - '''key feature'''.<ref name=Ref_GLP324>{{Ref GLP|324}}</ref>

DDx:

*[[Inflammatory bowel disease]] - lymphoplasmacytic infiltrate predominant,<ref name=Ref_GLP324>{{Ref GLP|324}}</ref> usually has chronic changes.

*[[Ischemic colitis]].

*Medications - focal neutrophils.

*[[Lymphocytic colitis]] - lymphocytes with a squiggly nucleus, may be confused with neutrophils.

*Specific causes of infective colitis - with a distinctive morphology.

**[[CMV colitis]] - esp. in the immunodeficient.

**[[Pseudomembranous colitis]] - usu. due to ''C. difficle'', has characteristic gross & microscopic appearance.

**[[Amebiasis]].

**[[Strongyloidiasis]].

**[[Cryptosporidiosis]].

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

*[[CMV]].

*HSV-1.

*[[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>

===Sign out===

- MILD ACTIVE COLITIS, SEE COMMENT.

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

present.

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>

==Cytomegalovirus colitis==

{{Main|CMV}}

*Abbreviated ''CMV colitis''.

{{Main|Cytomegalovirus colitis}}

{{Main|Intestinal spirochetosis}}

*May also be spelled ''amoebiasis''.

{{Main|Amebiasis}}

==Solitary rectal ulcer==

*''[[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|Rectal prolapse}}

==Neuroendocrine tumour==

{{Main|Neuroendocrine neoplasms#GI tract}}

*[[AKA]] ''carcinoid''.

:Described in detail in the ''[[appendix]]'' article.

*Biphasic tumour; features of ''carcinoid tumour'' and ''adenocarcinoma''.

=Other=

==Colonic pseudo-obstruction==

{{Main|Colonic pseudo-obstruction}}

==Pseudomelanosis coli==

*[[AKA]] ''melanosis coli''.

==Drugs==

===Sodium polystyrene sulfonate===

*AKA ''Kayexalate''.

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

====Microscopic====

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>  

Image:Cecal_adenocarcinoma.jpg | Adenocarcinoma and sodium polystyrene crystals (WC/Nephron)

==Graft-versus host disease==

==Bowel transplant==

*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 }}

General differential diagnosis for constipation:

*Neuropathy.<ref name=pmid21382578/>

**[[Parkinson disease]].

*Congenital defect ([[Hirschsprung's disease]]).

 

 

 

Work-up if no tumour is identified:<ref>IAV. 15 December 2009.</ref><ref name=pmid19360428/>

*Smooth muscle actin - confirm myocyte loss.

*Gomori trichrome - examine connective tissue.

===Sign out===

*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>

**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.

Tau: no abnormalities apparent.

=See also=

=References=