Difference between revisions of "Small intestine"

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TERMINAL ILEUM, BIOPSY:
TERMINAL ILEUM, BIOPSY:
- SMALL BOWEL MUCOSA WITHIN NORMAL LIMITS.
- SMALL BOWEL MUCOSA WITHIN NORMAL LIMITS.
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TERMINAL ILEUM, BIOPSY:
- SMALL BOWEL MUCOSA WITH MORPHOLOGICAL BENIGN LYMPHOID AGGREGATES, NO SIGNIFICANT PATHOLOGY.
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Revision as of 14:07, 4 November 2013

The small intestine, also small bowel, is a relatively well-behaved piece of machinery from the perspective of pathology. It is uncommonly affected by malignancies, relative to its length when compared to the colon and rectum.

Normal small bowel

  • AKA normal small intestine.

Anatomy

Consists of three segments:

  • Duodenum - can be divided into four parts.
  • Jejunum.
  • Ileum.

The later two parts keep general surgeons awake at night (quite literally) 'cause they get obstructed and need urgent operations.

Histology

The Gastrointestinal pathology article covers basic histology of the GI tract.

Immunohistochemistry

  • Normal small intestine is CK20 +ve... while adenocarcinoma of the small bowel may be CK20 -ve.[1]

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SMALL BOWEL, BIOPSY:
- SMALL BOWEL MUCOSA WITHIN NORMAL LIMITS.
TERMINAL ILEUM, BIOPSY:
- SMALL BOWEL MUCOSA WITHIN NORMAL LIMITS.
TERMINAL ILEUM, BIOPSY:
- SMALL BOWEL MUCOSA WITH MORPHOLOGICAL BENIGN LYMPHOID AGGREGATES, NO SIGNIFICANT PATHOLOGY.

The segments

Duodenum

The duodenum is often biopsied by gastroenterologists.

Common reasons for biopsy:

  • Suspected giardia.
  • Suspected celiac sprue.
  • Is this cancer?
  • Looks normal... want to dot the i's and cross the t's.

Jejunum

  • Uncommonly seen by pathologists.
  • May be seen in the context of a resection done for a bowel obstruction.

Ileum

Specific conditions

Small bowel obstruction

  • Abbreviated SBO.

General

The usual causes of bowel obstruction (large & small) are (mnemonic) SHAVING:

  • Strictures (think IBD).
  • Hernias.
  • Adhesions.
  • Volvulus.
  • Intussusception.
  • Neoplasia.
  • Gallstone ileus.

The top three are:[2][3]

  • Adhesions > hernias > neoplasms.

In the context of bowel obstructions and IBD, pathologists often see resected stomas (that were put in place emergently). These specimens are usually fairly straight forward.

Radiology

  • Air-fluid levels.

Gross

  • +/-Adhesions.
  • +/-Bowel contorted.
  • +/-Luminal narrowing +/-proximal dilation.
  • +/-Serosal exudate.
    • Suggestive of perforation.

Microscopic

Features:

  • +/-Adhesions (serosal).
    • Dense fibrous tissue replaces the adipose tissue.
    • +/-Increased vascularity.
  • +/-Submucosal fibrosis.
  • +/-Serositis - seen in small bowel perforation.
  • +/-Foreign body-type granuloma - due to previous surgical intervention.

DDx:

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SMALL BOWEL, RESECTION:
- SMALL BOWEL WITH FIBROUS ADHESIONS (EXTENSIVE) ASSOCIATED WITH FOCAL LUMINAL
  NARROWING.
- NEGATIVE FOR DYSPLASIA AND NEGATIVE FOR MALIGNANCY.
SMALL BOWEL, RESECTION:
- SMALL BOWEL WITH FIBROUS ADHESIONS (EXTENSIVE), FOCAL LUMINAL NARROWING AND A
  FOREIGN BODY-TYPE GRANULOMA.
- NEGATIVE FOR DYSPLASIA AND NEGATIVE FOR MALIGNANCY.

Small bowel neoplasms

Ileal nodular lymphoid hyperplasia

  • AKA nodular lymphoid hyperplasia of the terminal ileum.

General

  • An uncommon diagnosis.
  • May be associated with hypogammaglobulinemia.[5]

Gross

  • Mucosal nodularity.

Microscopic

Features:

  • Lymphoid nodules +/- germinal centre formation.

DDx:

IHC

  • CD20 and CD3 - mixed population of lymphocytes.
  • CD23 - follicular dendritic cells.
  • Cyclin D1 -ve.

Note:

  • IHC should be used if there is:
    • Clinical suspicion.
    • Histologic suspicion - either:
      • Sheets of lymphocytes without apparent germinal centre formation in a larger area (~ 2 mm).
      • Lymphoepithelial lesions.

Sign out

TERMINAL ILEUM, BIOPSY:
- SMALL BOWEL MUCOSA WITH LYMPHOID NODULES WITH GERMINAL CENTRE
  FORMATION -- NO SIGNIFICANT PATHOLOGY.
- NEGATIVE FOR ILEITIS.
TERMINAL ILEUM, BIOPSY:
- SMALL BOWEL MUCOSA WITH LYMPHOID HYPERPLASIA -- NO SIGNIFICANT PATHOLOGY.

Micro

The sections show small bowel mucosa with lymphoid hyperplasia.

Immunostains for CD3, CD20 show a mixed population of lymphocytes. CD23 show follicular dendritic cells. Cyclin D1 is negative.

Multiple lymphomatous polyposis

  • Abbreviated MLP.
  • AKA lymphomatous polyposis.

General

Microscopic

Features:

  • Lymphoid nodules consisting of (small) atypical lymphocytes with an abnormal architecture.

IHC

See small cell lymphomas.

Small bowel diaphragm disease

  • AKA diaphragm disease.

General

  • Strictures associated with chronic NSAID use.[8]
  • Usu. mid to distal ileum.

Microscopic

Features:[8]

  • Focal submucosal fibrosis.
    • +/-Distortion of adjacent muscularis propria.
    • +/-Adjacent mucosal erosions/granulation tissue.

DDx:

Meckel diverticulum

General

  • Most common congenital anomaly of the gastrointestinal tract.[9]
    • Remnant of the omphalomesenteric duct - a connection of the yolk sac and midgut.

The rule of 2s:

  • 2 feet from the terminal ileum
  • 2% of the population
  • 2% symptomatic.
  • 2 inches long.
  • 2 year old.
  • 2 types of epithelium - gastric and pancreatic.

Main clinical DDx of a symptomatic Meckel diverticulum:

Gross

  • Antimesenteric attachement, i.e. a Meckel's diverticulum hangs off the side opposite of the mesentery.

Image:

Microscopic

Features:[9]

  • Small bowel mucosa.
  • +/-Gastric mucosa:
    • Foveolar epithelium: champagne flute-like columnar epithelium.
    • Oxyntic mucosa: parietal cells (pink) and chief cells (purple).
  • +/-Pancreatic epithelium:
    • Pancreatic acini.

Images:

Ischemic enteritis

General

  • Typically elderly and due to atherosclerosis.
  • Rare.
  • High mortality.[10]
  • May occur together with ischemia of the colon, i.e. ischemic colitis, in which case it is known as ischemic enterocolitis.

Etiologies:

Microscopic

Features:

DDx:

Weird stuff

Autoimmune enteropathy

  • Abbreviated as AIE.

General

  • Considered a pediatric disease.
  • Super rare in adults - there are only ~11 reported cases in the literature.[11]

Diagnosis is clinico-pathologic:[11]

  1. Intact immune system.
  2. Autoantibodies.
    • Anti-enterocyte antibody.
    • Anti-goblet antibody.
  3. Lack of response to gluten-free diet.

Microscopic

Features:[11]

  • +/-Loss of goblet cells.
  • +/-Loss of paneth cells.
  • Villous blunting.

DDx:

See also

References

  1. Chen ZM, Wang HL (October 2004). "Alteration of cytokeratin 7 and cytokeratin 20 expression profile is uniquely associated with tumorigenesis of primary adenocarcinoma of the small intestine". Am. J. Surg. Pathol. 28 (10): 1352–9. PMID 15371952.
  2. URL: http://www.emedicine.com/EMERG/topic66.htm. Accessed on: 19 April 2011.
  3. TN 2007 GS21
  4. Levy AD, Quiles AM, Miettinen M, Sobin LH (March 2005). "Gastrointestinal schwannomas: CT features with clinicopathologic correlation". AJR Am J Roentgenol 184 (3): 797–802. PMID 15728600. http://www.ajronline.org/cgi/content/full/184/3/797.
  5. Yamaue H, Tanimura H, Ishimoto K, Morikawa Y, Kakudo K (1996). "Nodular lymphoid hyperplasia of the terminal ileum: report of a case and the findings of an immunological analysis". Surg. Today 26 (6): 431-4. PMID 8782302.
  6. Ruskoné-Fourmestraux, A.; Audouin, J. (Feb 2010). "Primary gastrointestinal tract mantle cell lymphoma as multiple lymphomatous polyposis.". Best Pract Res Clin Gastroenterol 24 (1): 35-42. doi:10.1016/j.bpg.2009.12.001. PMID 20206107.
  7. URL: http://www.pathmax.com/gilymph.html. Accessed on: 1 April 2012.
  8. Jump up to: 8.0 8.1 McCune KH, Allen D, Cranley B (October 1992). "Small bowel diaphragm disease--strictures associated with non-steroidal anti-inflammatory drugs". Ulster Med J 61 (2): 182–4. PMC 2448949. PMID 1481311. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2448949/.
  9. Jump up to: 9.0 9.1 Levy, AD.; Hobbs, CM.. "From the archives of the AFIP. Meckel diverticulum: radiologic features with pathologic Correlation.". Radiographics 24 (2): 565-87. doi:10.1148/rg.242035187. PMID 15026601.
  10. Nakase, H. (Jul 2008). "[Ischemic enteritis].". Nihon Rinsho 66 (7): 1330-4. PMID 18616124.
  11. Jump up to: 11.0 11.1 11.2 Akram, S.; Murray, JA.; Pardi, DS.; Alexander, GL.; Schaffner, JA.; Russo, PA.; Abraham, SC. (Nov 2007). "Adult autoimmune enteropathy: Mayo Clinic Rochester experience.". Clin Gastroenterol Hepatol 5 (11): 1282-90; quiz 1245. doi:10.1016/j.cgh.2007.05.013. PMC 2128725. PMID 17683994. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2128725/.