Difference between revisions of "Vermiform appendix"

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The appendix is a vestigial structure that is thought to have arisen from a larger cecum.  Larger cecae are often seen in herbivores and thought to facilitate better digestion of plant matter.<ref>{{cite book |author=Dawkins, R. |title=The Greatest Show on Earth: The Evidence for Evolution |publisher=Free Press |location= |year=2009 |pages=115 |edition=1st |isbn=978-1416594789 |oclc= |doi= |accessdate=}}</ref>  
The appendix is a vestigial structure that is thought to have arisen from a larger cecum.  Larger cecae are often seen in herbivores and thought to facilitate better digestion of plant matter.<ref>{{cite book |author=Dawkins, R. |title=The Greatest Show on Earth: The Evidence for Evolution |publisher=Free Press |location= |year=2009 |pages=115 |edition=1st |isbn=978-1416594789 |oclc= |doi= |accessdate=}}</ref>  


=Inflammatory pathologies=
=Normal=
==Acute appendicitis==
==Normal vermiform appendix==
===General===
===General===
*Bread 'n butter of general surgery.
*Seen in:
*Interesting factoid: appendicitis is considered protective against [[ulcerative colitis]].<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>
**Right hemicolectomies.
 
***[[colorectal carcinoma|Colon cancer]].
Short clinical DDx:
***[[Crohn's disease]].
*GI tract:
**Surgeries for ovarian mucinous tumours.
**Symptomatic [[Meckel diverticulum]].
**Epiploic appendagitis.
*Gynecologic tract:
**Ectopic pregnancy.
**Ruptured ovarian cyst.
**Ovarian torsion.
***Pelvic inflammatory disease.


===Gross===
===Gross===
Features:
*Shiny serosal surface.
*Serosal surface dull.
**No exudate.
*May be perforated (best determined on gross).
*Normal diameter.
*+/-Fibrinous exudate.
**6.6 +/- 1.5 mm -- based on CT.<ref name=pmid21344807>{{Cite journal  | last1 = Charoensak | first1 = A. | last2 = Pongpornsup | first2 = S. | last3 = Suthikeeree | first3 = W. | title = Wall thickness and outer diameter of the normal appendix in adults using 64 slices multidetector CT. | journal = J Med Assoc Thai | volume = 93 | issue = 12 | pages = 1437-42 | month = Dec | year = 2010 | doi =  | PMID = 21344807 }}</ref>


===Microscopic===
===Microscopic===
Features:
Features:
* Neutrophils in the muscularis propria - '''key feature'''.
*+/-Lymphoid hyperplasia - mucosa or submucosa.
* +/- Vascular [[thrombosis]] (and [[necrosis]]) - known as ''gangrenous appendicitis''.<ref>URL: [http://emedicine.medscape.com/article/363818-overview http://emedicine.medscape.com/article/363818-overview]. Accessed on: 21 June 2010.</ref>
*Normal colorectal-type mucosa.
* +/- Findings suggestive of etiology - usu. absent:
*Fatty submucosa.
** +/- Fecalith.
*Benign smooth muscle.
** +/- Viral inclusions (extremely rare)
*Serosa.
*** See ''[[adenovirus appendicitis]]''.


Images:
Negatives:
*[http://commons.wikimedia.org/wiki/File:Appendicitis_-_low_mag.jpg Appendicitis - low mag. (WC)].
*No [[neutrophil]]s in the muscularis propria.
*[http://commons.wikimedia.org/wiki/File:Appendicitis_-_very_high_mag.jpg Appendicitis - very high mag. (WC)].
*No lesion in appendiceal tip.
*No serosal inflammation ([[periappendicitis]]).
*No organisms in the appendiceal lumen, e.g. [[Enterobius vermicularis]].


====DDx====
DDx:
*Mucinous tumour.
*[[Adenovirus appendicitis]].
*[[Neuroendocrine tumour]].
*[[Cryptosporidiosis]].
*[[Granulomatous appendicitis]].
*Mild colitis.
*[[Crohn's disease]] of the appendix.


==Adenovirus appendicitis==
===Sign out===
===General===
<pre>
*Rare type of appendicitis in children.
VERMIFORM APPENDIX WITHIN NORMAL LIMITS.
*Presents as run-of-the-mill acute appendicitis.
</pre>


===Microscopic===
Note:
Features:<ref name=pmid17990936>{{cite journal |author=Grynspan D, Rabah R |title=Adenoviral appendicitis presenting clinically as acute appendicitis |journal=Pediatr. Dev. Pathol. |volume=11 |issue=2 |pages=138–41 |year=2008 |pmid=17990936 |doi=10.2350/07-06-0299.1 |url=}}</ref>
*This is for a normal appendix within a larger operation. The article ''[[negative appendectomy]]'' deals with a normal appearing appendix that was removed for presumed appendicitis.
*Lymphoid hyperplasia - key feature.
*+/-Adenovirus inclusions; "smudge cells".


Notes:
==Negative appendectomy==
*The classic finding of appendicitis (neutrophils infiltrating into the muscularis propria) may be absent.<ref name=pmid17990936/>
{{Main|Negative appendectomy}}
An appendectomy done for presumed [[acute appendicitis]] that is pathologically within normal limits


Image:
=Inflammatory pathologies=
*[http://wiki.medpedia.com/Image:Ab14.jpg?filetimestamp=20091014175858 Smudge cell (medpedia.com)].
==Acute appendicitis==
{{Main|Acute appendicitis}}


===IHC===
==Adenovirus appendicitis==
*Adenovirus +ve = '''diagnostic'''.
{{Main|Adenovirus appendicitis}}


==Enterobius vermicularis==
==Enterobius vermicularis==
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*May be found in the appendix.
*May be found in the appendix.
*The incidence is higher in normal appendices than inflamed ones.<ref name=pmid1853157>{{Cite journal  | last1 = Wiebe | first1 = BM. | title = Appendicitis and Enterobius vermicularis. | journal = Scand J Gastroenterol | volume = 26 | issue = 3 | pages = 336-8 | month = Mar | year = 1991 | doi =  | PMID = 1853157 }}</ref><ref name=pmid7945067/>
*The incidence is higher in normal appendices than inflamed ones.<ref name=pmid1853157>{{Cite journal  | last1 = Wiebe | first1 = BM. | title = Appendicitis and Enterobius vermicularis. | journal = Scand J Gastroenterol | volume = 26 | issue = 3 | pages = 336-8 | month = Mar | year = 1991 | doi =  | PMID = 1853157 }}</ref><ref name=pmid7945067/>
*Clinically mimics appendicitis.<ref>{{cite journal |author=Ariyarathenam AV, Nachimuthu S, Tang TY, Courtney ED, Harris SA, Harris AM |title=Enterobius vermicularis infestation of the appendix and management at the time of laparoscopic appendectomy: case series and literature review |journal=Int J Surg |volume=8 |issue=6 |pages=466–9 |year=2010 |pmid=20637320 |doi=10.1016/j.ijsu.2010.06.007 |url=}}</ref>


===Microscopic===
===Microscopic===
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*Usu. the appendiceal wall has no inflammation, i.e. there is no appendicitis.<ref name=pmid1853157/><ref name=pmid7945067>{{Cite journal  | last1 = Dahlstrom | first1 = JE. | last2 = Macarthur | first2 = EB. | title = Enterobius vermicularis: a possible cause of symptoms resembling appendicitis. | journal = Aust N Z J Surg | volume = 64 | issue = 10 | pages = 692-4 | month = Oct | year = 1994 | doi =  | PMID = 7945067 }}</ref>
*Usu. the appendiceal wall has no inflammation, i.e. there is no appendicitis.<ref name=pmid1853157/><ref name=pmid7945067>{{Cite journal  | last1 = Dahlstrom | first1 = JE. | last2 = Macarthur | first2 = EB. | title = Enterobius vermicularis: a possible cause of symptoms resembling appendicitis. | journal = Aust N Z J Surg | volume = 64 | issue = 10 | pages = 692-4 | month = Oct | year = 1994 | doi =  | PMID = 7945067 }}</ref>
*''[[Enterobius vermicularis]]'' organisms.
*''[[Enterobius vermicularis]]'' organisms.
====Image====
<gallery>
Image:Enterobius_-_very_low_mag.jpg | Enterobius - very low mag. (WC/Nephron)
Image:Enterobius_-_high_mag.jpg | Enterobius - high mag. (WC/Nephron)
Image:Pinworms_in_the_Appendix_%281%29.jpg | Pinworm (WC/Uthman)
</gallery>


==Granulomatous appendicitis==
==Granulomatous appendicitis==
Most common cause:
{{Main|Granulomatous appendicitis}}
*Yersinia appendicitis.<ref name=pmid11257626>{{cite journal |author=Lamps LW, Madhusudhan KT, Greenson JK, ''et al.'' |title=The role of Yersinia enterocolitica and Yersinia pseudotuberculosis in granulomatous appendicitis: a histologic and molecular study |journal=Am. J. Surg. Pathol. |volume=25 |issue=4 |pages=508–15 |year=2001 |month=April |pmid=11257626 |doi= |url=}}</ref>
 
DDx:<ref>[http://granuloma.homestead.com/appendicitis.html http://granuloma.homestead.com/appendicitis.html]</ref>
*Yersinia appendicitis.<ref name=pmid11257626>{{cite journal |author=Lamps LW, Madhusudhan KT, Greenson JK, ''et al.'' |title=The role of Yersinia enterocolitica and Yersinia pseudotuberculosis in granulomatous appendicitis: a histologic and molecular study |journal=Am. J. Surg. Pathol. |volume=25 |issue=4 |pages=508–15 |year=2001 |month=April |pmid=11257626 |doi= |url=}}</ref>
**Yersinia = gram negative rod (red on [[Gram stain]]).
**"Safety pin"-like appearance<ref>URL: [http://www.cdc.gov/ncidod/dvbid/plague/p1.htm http://www.cdc.gov/ncidod/dvbid/plague/p1.htm]. Accessed on: 30 June 2011.</ref> - approximately 0.5 micrometers diameter x 2 micrometers length.
*Other micro-organism ([[TB]], fungus).
*[[Crohn's disease]].
*[[Sarcoidosis]].
*Foreign body reaction.
*Interval (delayed) appendectomy.
 
===Microscopic===
Features:
*[[Granulomas]].
*+/-"Safety pin"-like organisms (Yersinia).
 
Image(s):
*[http://www.cdc.gov/ncidod/dvbid/plague/p1.htm Yersinia (CDC)].


==Inflammatory bowel disease==
==Inflammatory bowel disease==
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*Acute inflammation of the serosa.
*Acute inflammation of the serosa.
**[[Neutrophil]]s in the serosa.
**[[Neutrophil]]s in the serosa.
DDx:
*[[Acute appendicitis]].


=Tumours of the appendix=
=Tumours of the appendix=
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*Like ''colorectal adenocarcinoma'' - see ''[[colorectal tumours]]''.
*Like ''colorectal adenocarcinoma'' - see ''[[colorectal tumours]]''.


==Mucinous tumour==
==Mucinous tumours of the appendix==
General
{{Main|Mucinous tumours of the appendix}}
*classification is controversial.
This grouping includes ''mucinous cystadenoma'' and ''mucinous cystadenocarcinoma''.
**the controversy centres on whether to call all mucinous tumours outside of the appendix adenocarcinoma - regardless of whether they have atypia & show invasion.
*in women - an ovarian primary must be excluded.
**concurrent ''bilateral'' ovarian tumours suggests the tumour originated from the appendix and spread to the ovaries.
 
Classification:<ref name=pmid12883241>{{cite journal |author=Misdraji J, Yantiss RK, Graeme-Cook FM, Balis UJ, Young RH |title=Appendiceal mucinous neoplasms: a clinicopathologic analysis of 107 cases |journal=Am. J. Surg. Pathol. |volume=27 |issue=8 |pages=1089–103 |year=2003 |month=August |pmid=12883241 |doi= |url=http://meta.wkhealth.com/pt/pt-core/template-journal/lwwgateway/media/landingpage.htm?issn=0147-5185&volume=27&issue=8&spage=1089}}</ref>
*Benign - ''low grade mucinous tumour''.
*Borderline - ''mucinous tumour of uncertain malignant potential'' or ''borderline mucinous tumour''.
*Balignant - ''mucinous adenocarcinoma''.
 
Five year survival (in a series of 107 cases):<ref name=pmid12883241/>
{| class="wikitable sortable"
!Tumour
!Five year survival
|-
|LAMN
|100%
|-
|LAMN ex-appy spread
|86%
|-
|MACA
|44%
|-
|}
*LAMN = low-grade appendiceal mucinous neoplasm.
*LAMN ex-appy = LAMN with extra-appendiceal spread.
*MACA = mucinous adenocarcinoma.
 
===Benign mucinous tumour===
Microscopic:
*Epithelium forms ''tufts'' - vaguely resemble ''serrations'', i.e. the ''saw-tooth'' pattern in hyperplastic polyps.
*Single layer of epithelium.
*Mucin contained (inside appendix only).
 
Negatives:
*No marked nuclear atypia.
*No invasion into the lamina propria.
 
===Borderline mucinous tumour===
Microscopic:
*Same as benign, but mucin outside of the appendix.
*Cells in mucin, i.e. cellular mucin.
 
===Malignant mucinous tumour===
Microscopic:
*Marked nuclear pleomorphism.
*Invasion into the wall.
 
==Goblet cell carcinoid==
===General===
*[[AKA]] '''crypt cell carcinoma''',<ref name=pmid18042066>{{cite journal |author=van Eeden S, Offerhaus GJ, Hart AA, ''et al.'' |title=Goblet cell carcinoid of the appendix: a specific type of carcinoma |journal=Histopathology |volume=51 |issue=6 |pages=763–73 |year=2007 |month=December |pmid=18042066 |doi=10.1111/j.1365-2559.2007.02883.x |url=}}</ref> '''neuroendocrine tumour with goblet cell differentiation.
*Rare appendiceal tumour that typically has an aggressive course vis-a-vis other appendiceal carcinoids.<ref name=pmid18042066>{{cite journal |author=van Eeden S, Offerhaus GJ, Hart AA, ''et al.'' |title=Goblet cell carcinoid of the appendix: a specific type of carcinoma |journal=Histopathology |volume=51 |issue=6 |pages=763–73 |year=2007 |month=December |pmid=18042066 |doi=10.1111/j.1365-2559.2007.02883.x |url=}}</ref>
*Mixed (biphasic) tumour with endocrine and exocrine features.
 
===Microscopic===
Features:<ref name=pmid15967038>{{cite journal |author=Pahlavan PS, Kanthan R |title=Goblet cell carcinoid of the appendix |journal=World J Surg Oncol |volume=3 |issue= |pages=36 |year=2005 |month=June |pmid=15967038 |pmc=1182398 |doi=10.1186/1477-7819-3-36 |url=http://wjso.com/content/3/1/36}}</ref>
*Mixed neuroendocrine-nonneuroendocrine tumour;<ref name=pmid17684764>{{cite journal |author=Volante M, Righi L, Asioli S, Bussolati G, Papotti M |title=Goblet cell carcinoids and other mixed neuroendocrine/nonneuroendocrine neoplasms |journal=Virchows Arch. |volume=451 Suppl 1 |issue= |pages=S61–9 |year=2007 |month=August |pmid=17684764 |doi=10.1007/s00428-007-0447-y |url=}}</ref> features of both ''carcinoid'' and ''adenocarcinoma.<ref name=pmid15967038>PMID 15967038.</ref>
**Archictecture: cells arranged in nests or clusters without a lumen.
**Location: deep to the intestinal crypts (crypts of Lieberkühn); usually do not involve the mucosa.
**Cytoplasm distended with mucin.
**DNA: crescentic nucleus (similar to in signet-ring cells).
***+/-Multinucleation.
***+/-High mitotic rate.
***Usually minimal nuclear atypia.
 
Images:
*[http://commons.wikimedia.org/wiki/File:Goblet_cell_carcinoid_-2-_very_high_mag.jpg GCC - very high mag. (WC)].
*[http://commons.wikimedia.org/wiki/File:Goblet_cell_carcinoid_-_very_low_mag.jpg GCC - very low mag. (WC)].
 
===Stains===
*Mucin stains +ve:
**Mucicarmine, perodic acid-Schiff diastase (PAS-D), alician blue.


====IHC====
==Goblet cell adenocarcinoma==
*Classic neuroendocrine markers:
{{Main|Goblet cell adenocarcinoma}}
**Synaptophysin +ve.
*Previously known as ''goblet cell carcinoid''.
**Chromogranin +ve.
*S100 +ve.
*NSE +ve.
*Serotonin +ve.
 
Keratins:
*Usually CK20 +ve > CK7 +ve.
 
*CEA +ve (membrane).
 
Notes:
*Nice review of stains in Pahlavan and Kanthan.<ref name=pmid15967038>{{cite journal |author=Pahlavan PS, Kanthan R |title=Goblet cell carcinoid of the appendix |journal=World J Surg Oncol |volume=3 |issue= |pages=36 |year=2005 |month=June |pmid=15967038 |pmc=1182398 |doi=10.1186/1477-7819-3-36 |url=http://wjso.com/content/3/1/36}}</ref>


==Neuroendocrine tumour of the appendix==
==Neuroendocrine tumour of the appendix==
{{Main|Neuroendocrine tumour}}
*Previously known as ''appendiceal carcinoid''.
*Previously known as ''appendiceal carcinoid''.
===General===
*[[AKA]] ''appendiceal neuroendocrine tumour'', abbreviated ''appendiceal NET''.
*Most common tumour of the appendix.<ref name=PCPBoD8_435>{{Ref PCPBoD8|435}}</ref>
{{Main|Neuroendocrine tumour of the appendix}}
 
Size matters in ''appendiceal NETs'':<ref name=pmid12569593>{{Cite journal  | last1 = Modlin | first1 = IM. | last2 = Lye | first2 = KD. | last3 = Kidd | first3 = M. | title = A 5-decade analysis of 13,715 carcinoid tumors. | journal = Cancer | volume = 97 | issue = 4 | pages = 934-59 | month = Feb | year = 2003 | doi = 10.1002/cncr.11105 | PMID = 12569593 }}</ref>
*<1.0 cm - do not metastasize.
*1.0-2.0 cm - rarely metastasize.
 
===Microscopic===
Features:
*See ''[[neuroendocrine tumours]]''.
 
===IHC===
Features:
*See ''[[neuroendocrine tumours]]''.


=See also=
=See also=
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[[Category:Gastrointestinal pathology]]
[[Category:Gastrointestinal pathology]]
[[Category:Vermiform appendix]]

Latest revision as of 15:11, 4 December 2023

The vermiform appendix, usually just appendix, is a little thingy that is attached to the cecum. Taking it out is the bread 'n butter of general surgery.

The appendix is a vestigial structure that is thought to have arisen from a larger cecum. Larger cecae are often seen in herbivores and thought to facilitate better digestion of plant matter.[1]

Normal

Normal vermiform appendix

General

Gross

  • Shiny serosal surface.
    • No exudate.
  • Normal diameter.
    • 6.6 +/- 1.5 mm -- based on CT.[2]

Microscopic

Features:

  • +/-Lymphoid hyperplasia - mucosa or submucosa.
  • Normal colorectal-type mucosa.
  • Fatty submucosa.
  • Benign smooth muscle.
  • Serosa.

Negatives:

DDx:

Sign out

VERMIFORM APPENDIX WITHIN NORMAL LIMITS.

Note:

  • This is for a normal appendix within a larger operation. The article negative appendectomy deals with a normal appearing appendix that was removed for presumed appendicitis.

Negative appendectomy

Main article: Negative appendectomy

An appendectomy done for presumed acute appendicitis that is pathologically within normal limits

Inflammatory pathologies

Acute appendicitis

Main article: Acute appendicitis

Adenovirus appendicitis

Main article: Adenovirus appendicitis

Enterobius vermicularis

Main article: Enterobius vermicularis

General

  • May be found in the appendix.
  • The incidence is higher in normal appendices than inflamed ones.[3][4]
  • Clinically mimics appendicitis.[5]

Microscopic

Features:

Image

  • Enterobius - very low mag. (WC/Nephron)

  • Enterobius - high mag. (WC/Nephron)

  • Pinworm (WC/Uthman)

Granulomatous appendicitis

Main article: Granulomatous appendicitis

Inflammatory bowel disease

See Inflammatory bowel disease.

Periappendicitis

General

Definition: inflammation of tissues around the (vermiform) appendix.[6]

  • May be seen in association of appendicitis or alone.
    • With appendicitis it is suggestive of perforation.
    • Without concurrent appendicitis it is suggestive of another abdominal pathology.[7][8]

Microscopic

Features:

  • Acute inflammation of the serosa.

DDx:

Tumours of the appendix

Adenocarcinoma

Mucinous tumours of the appendix

Main article: Mucinous tumours of the appendix

This grouping includes mucinous cystadenoma and mucinous cystadenocarcinoma.

Goblet cell adenocarcinoma

Main article: Goblet cell adenocarcinoma
  • Previously known as goblet cell carcinoid.

Neuroendocrine tumour of the appendix

  • Previously known as appendiceal carcinoid.
  • AKA appendiceal neuroendocrine tumour, abbreviated appendiceal NET.
Main article: Neuroendocrine tumour of the appendix

See also

References

  1. ↑ Dawkins, R. (2009). The Greatest Show on Earth: The Evidence for Evolution (1st ed.). Free Press. pp. 115. ISBN 978-1416594789.
  2. ↑ Charoensak, A.; Pongpornsup, S.; Suthikeeree, W. (Dec 2010). "Wall thickness and outer diameter of the normal appendix in adults using 64 slices multidetector CT.". J Med Assoc Thai 93 (12): 1437-42. PMID 21344807.
  3. ↑ 3.0 3.1 Wiebe, BM. (Mar 1991). "Appendicitis and Enterobius vermicularis.". Scand J Gastroenterol 26 (3): 336-8. PMID 1853157.
  4. ↑ 4.0 4.1 Dahlstrom, JE.; Macarthur, EB. (Oct 1994). "Enterobius vermicularis: a possible cause of symptoms resembling appendicitis.". Aust N Z J Surg 64 (10): 692-4. PMID 7945067.
  5. ↑ Ariyarathenam AV, Nachimuthu S, Tang TY, Courtney ED, Harris SA, Harris AM (2010). "Enterobius vermicularis infestation of the appendix and management at the time of laparoscopic appendectomy: case series and literature review". Int J Surg 8 (6): 466–9. doi:10.1016/j.ijsu.2010.06.007. PMID 20637320.
  6. ↑ URL: http://www.medilexicon.com/medicaldictionary.php?t=66889. Accessed on: 1 June 2011.
  7. ↑ Fink, AS.; Kosakowski, CA.; Hiatt, JR.; Cochran, AJ. (Jun 1990). "Periappendicitis is a significant clinical finding.". Am J Surg 159 (6): 564-8. PMID 2349982.
  8. ↑ O'Neil, MB.; Moore, DB. (Sep 1977). "Periappendicitis: Clinical reality or pathologic curiosity?". Am J Surg 134 (3): 356-7. PMID 900337.
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