Small intestine
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
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.
- 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
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.[3]
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
- This is seen occasionally -- often in the context of IBD and more specifically Crohn's disease.
- Crohn's disease (and ulcerative colitis) is discussed in the colon article.
Nodular lymphoid hyperplasia
General
- An uncommon diagnosis
- Prominent lymphoid follicles
- May be assoc. with hypogammaglobulinemia.[4]
Specific conditions
Small bowel neoplasms
- Adenocarcinoma - like colonic.
- Adenosquamous carcinoma.
- Neuroendocine tumour.
- GIST.
- Schwannoma.
- Classically have a peripheral lymphoid cuff.[5]
Small diaphragm disease
General
- Strictures associated with chronic NSAID use.[6]
- Usu. mid to distal ileum.
Microscopic
Features:[6]
- Focal submucosal fibrosis.
- +/-Distortion of adjacent muscularis propria.
- +/-Adjacent mucosal erosions/granulation tissue.
See also
References
- ↑ URL: http://www.emedicine.com/EMERG/topic66.htm. Accessed on: 19 April 2011.
- ↑ TN 2007 GS21
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ 6.0 6.1 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/.