Small intestine

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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.

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.[3]

Small bowel neoplasms

  • Adenocarcinoma - like colonic.
  • Adenosquamous carcinoma.
  • Neuroendocine tumour.
  • GIST.
  • Schwannoma.
    • Classically have a peripheral lymphoid cuff.[4]

See also

References

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