Difference between revisions of "Colon"

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*Bowel wall thickening.
*Bowel wall thickening.


==Microscopic==
===Microscopic===
Features:<ref>Kirsch, R. 8 August 2011.</ref>
Features:<ref>Kirsch, R. 8 August 2011.</ref>
*Crypt loss.
*Crypt loss.

Revision as of 23:26, 15 August 2011

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 colorectal cancer or a known history of inflammatory bowel disease (IBD).

An introduction to gastrointestinal pathology is found in the gastrointestinal pathology article.

Surgery

Introduction to colorectal surgery:

  1. Colonic resection - remove a piece of large bowel.
  2. Total colectomy - leaves rectum and anus.[1]
  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).

Grossing

Identifying the piece

  • 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. (???)

Lymph nodes

Quirke method

  • Bowel is not opened - it is fixed... then sliced.[3], [4].

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.

Common clinical problems

Obstruction

Top three (in adults):[5]

  • Neoplasia.
  • Volvulus (cecal, sigmoid).
  • Diverticular disease + stricture formation.

Bleeding

Mnemonic CHAND:[6]

  • Colitis (radiation, infectious, ischemic, IBD (UC >CD), iatrogenic (anticoagulants)).
  • Hemorrhoids.
  • Angiodysplasia.
  • Neoplastic.
  • Diverticular disease.

Infectious colitis with bleeding - causes:

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

Infectious colitis in the immunosuppressed:

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:[9]

  • 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[10] - 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.[11]

Bowel ischemia

General

Gross

Features:[12]

  • Luminal part (mucosa & submucosa) affected.
  • Splenic flexture of colon commonly affected (vascular watershed).

Note:

  • May have pseudomembranes (classically assoc. with C. difficile colitis), i.e. mimics an infectious process.
  • DDx for pseudomembranes:[13]
    • C. difficile induced pseudomembranous colitis.
    • Ischemic colitis.
    • Volvulus.
    • Necrotizing infections.
    • ... anything that causes severe mucosal injury.

Radiologic correlate

  • Bowel wall thickening.

Microscopic

Features:[14]

  • Crypt loss.
  • Lamina propria fibrosis.
  • Submucosa fibrosis.

Pseudomembranes (microscopic):[13]

  • Loss of surf. epithelium.
  • PMNs in lamina propria.
  • +/- capillary fibrin thrombi.

Note:

  • Pseudomembranes arise from the crypts.

Images:

DDx:

  • IBD.
  • Radiation.
  • Toxins/drugs.

Angiodysplasia

General

  • Causes (lower) GI haemorrhage.
  • Generally, not a problem pathologists see.
  • May be associated with aortic stenosis; known as Heyde syndrome.[15]

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.[16]

Pseudomelanosis coli

  • AKA melanosis coli.[17]

General

  • Not melanin as the name melanosis coli suggests; it is actually lipofuscin (in macrophages).[18]
  • 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.[18]

Gross

  • Brown pigmentation of the mucosa.

Image:

Microscopic

Features:

  • Brown granular pigment - in the lamina propria.
    • Typically more prominent in the cecum and proximal colon.[18]

Images:

Notes:

  • DDx of brown pigment:
    • Lipofuscin - comes with age (can be demonstrated with a PAS stain[19] or Kluver-Barrera stain[20]).
      • Melanosis coli.
    • Old haemorrhage, i.e. hemosiderin-laden macrophages (may be demonstrated with Prussian blue stain[21]).
    • Melanin (from melanocytes) - rare in colon (may be demonstrated with a Fontana-Masson stain[22] -- though not so useful in the GI tract).
    • Foreign material (e.g. tattoo pigment) - not seen in GI tract.

Stains

Microscopic colitis

General

Definition:

  • As the name suggests, they are microscopic, i.e. endoscopic examination is normal.

Presentation:

  • Chronic diarrhea, non-bloody.[24]

Notes:

Microscopic colitis - types

  • Lymphocytic colitis (LC).
  • Collagenous colitis (CC).

Some believe that LC and CC are different time points in the same process-- but this is unproven.[24]

Epidemiology

  • Age: a disease of adults - usually 50s.
  • Sex:
    • LC males ~= females,[24]
    • CC females:males = 20:1.[24]
  • 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.[25]
  • No increased risk of colorectal carcinoma.[25]

Treatment

  • Sometimes just follow-up.
  • Steroids - budesonide -- short-term treatment.[25]

Characteristics

Lymphocytic colitis

  • Lots of intraepithelial lymphocytes (>=20/100 lymphocytes/surface epithelial cells[25]) and
  • lymphocytes in the lamina propria.
  • NEGATIVES:[26]
    • No PMNs.
    • No crypt distortion.

Collagenous colitis

  • Intraepithelial lymphocytes, and
  • lymphocytes in the lamina propria.
  • Collagenous material in the lamina propria (pink on H&E) -- key feature.
    • Can be demonstrated with a trichrome stain -- collagen = green on trichrome.
    • Subepithelial collagen needs to be >= 10 micrometres thick for Dx.[25]
      • 8 micrometres is the diameter of a RBC.
      • The normal thickness of the subepithelial collagen is 3 micrometres.[25]
    • Thickening "follows the crypts from the surface" - useful for differentiating from tangential sections of the basement membrane.[27]
    • Collagen may envelope capillaries - useful to discern from basement membrane.[28]

Images:

Notes:

  • CC is typically more prominent in the proximal colon - may reflect concentration gradient of offending causitive agents.[25]
  • Significant negative findings:[26]
    • No PMNs.
    • No crypt distortion.

Intestinal spirochetosis

  • AKA intestinal spirochetes; more specifically colonic spirochetes, colonic spirochetosis.

General

  • Caused by spirochetes[29][30] - specifically Brachyspira piloicoli[31] (previously Serpulina pilosicoli[32]) and Brachyspira aalborgi.
  • Very rare cause of diarrhea, associated with male homosexual behaviour.

Symptoms:[30]

  • Watery diarrhea, abdominal pain, +/-blood per rectum.

Treatment:[33]

  • Metronidazole.

Microscopic

Features:

  • Hyperchromatic fuzz on luminal aspect of epithelial cells; at brush border.

Images:

Special stains

  • Silver stains highlight 'em (e.g. Warthin-Starry stain).

Amebiasis

General

  • Infection with Entamoeba histolytica.[34]
  • May also be spelling amoebiasis.
  • May mimic colon cancer.[35]

May cause:[36]

  • Dysentery (diarrhea containing mucus and/or blood in the feces).
  • Colitis.
  • Liver abscess.

Microscopy

Features:

  • Entamoeba histolytica are round/ovoid eosinophilic bodies ~ 40-60 micrometers in maximal dimension.
    • Found in bowel lumen.
    • Ingest RBCs.

Image:

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.

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):

Colorectal Tumours

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

Solitary rectal ulcer

General

  • Clinically may be suspected to a malignancy - biopsied routinuely.
  • Mucosal ulceration.
  • "Three-lies disease":[37]
  1. May not be solitary.
  2. May not be rectal -- can be in left colon.
  3. May not be ulcerating -- non-ulcerated lesions: polypoid and/or erythematous.

Note: Each of the words in solitary rectal ulcer is a lie.

Epidemiology

  • Typically younger patients - average age of presentation ~30 years in one study.[38]
  • Rare.

Clinical

  • Usually presents as BRBPR ~ 85% of cases.[38]
  • Abdominal pain present in approx. 1/3.[38]
    • May be very painful.

Microscopic

Features:[37]

  • Fibrosis of the lamina propria - should be obliterated.
  • Thickened muscularis mucosa - abnormally extends to the lumen.

Histologic DDx

Treatment

  • Usually conservative, i.e. non-surgical.
  • Resection - may be done for fear of malignancy.

Rectal prolapse

Generally

  • Usually close to the anal verge.
  • Rare forms can occasionally be confused with cancer.[39]

Microscopic

Features:[40]

  • "Fibromuscular hyperplasia" - key feature:
    • Fibrosis (submucosa, lamina propria).
    • Muscularis mucosae is "too superficial" (muscle in the lamina propria).
  • Surface ulceration + inflammation (neutrophils).
  • +/-Serration of epithelium at the surface.

Notes:

  • Important NEGATIVE: no nuclear atypia.

Images:

Mucosal prolapse syndrome

  • Similar to rectal prolapse???

Weird stuff

Drugs

Kayexalate (sodium polystyrene sulfonate):[41]

Image: Sodium polystyrene crystals (WC).

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 is occasionally an indication for colectomy.

Causes:

  • Tumour.
  • Adhesions - due to previous surgery.
  • Neuropathy.
  • Congenital defect (Hirschsprung's disease).
  • Medications/substance use.
  • Idiopathic.

Work-up if no tumour is identified:[42]

  • Routine H&E.
  • Pan-actin.
  • Gomori trichrome.
  • CD117 - to look for the interstitial cells of Cajal.
  • HU - neuronal marker.[43]

Neuroendocrine tumour

Goblet cell carcinoid

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

Stoma

These are often done emergently and then get cut-out after the patient's condition has settled.

See also

References

  1. http://www.allaboutbowelsurgery.com/shared/stoma_care/stoma_surgery/procedures/surgery_colon/subtotal.htm
  2. 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.
  3. 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.
  4. 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.
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  8. 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.
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  41. 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.
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