Difference between revisions of "Small intestine"

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Revision as of 12:55, 21 March 2011

The small bowel is a relatively well-behaved piece of machinery from the perspective of pathology. It is uncommonly affected by malignancies.


Anatomy

Consists of three segments:

  • Duodenum (which 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.

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:[1][2]

  • 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.

Immunohistochemistry

  • Normal small intestine is CK20 +ve... while adenocarcinoma of the small bowel may be CK20 -ve.[3]

Histology

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

Nodular lymphoid hyperplasia

General

  • An uncommon diagnosis
  • Prominent lymphoid follicles
  • May be assoc. with hypogammaglobulinemia.[4]

Small bowel neoplasms

  • Adenocarcinoma - like colonic.
  • Adenosquamous carcinoma.
  • Neuroendocine tumour.
  • GIST.
  • Schwannoma.
    • Classically have a peripheral lymphoid cuff.[5]

See also

References

  1. http://www.emedicine.com/EMERG/topic66.htm
  2. TN 2007 GS21
  3. 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.
  4. 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.
  5. 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.