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
Main article: Gastrointestinal pathology
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
Main article: 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.
- Neuroendocrine tumour.
- GIST.
- Schwannoma.
- Classically have a peripheral lymphoid cuff.[5]
Small diaphragm disease
General
Microscopic
Features:[6]
- Focal submucosal fibrosis.
- +/-Distortion of adjacent muscularis propria.
- +/-Adjacent mucosal erosions/granulation tissue.
Meckel diverticulum
General
- Most common congenital anomaly of the gastrointestinal tract.[7]
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.
Gross
- Antimesenteric attachement.
Image:
Microscopic
Features:[7]
- Gastric mucosa:
- Foveolar epithelium: champagne flute-like columnar epithelium.
- Oxyntic mucosa: parietal cells (pink) and chief cells (purple).
- Pancreatic epithelium:
- Pancreatic acini.
Images:
- Gastric foveolar epithelium in a MD (radiographics.rsna.org).
- Gastric glands in a MD (radiographics.rsna.org).
- Pancreatic glands in a MD (radiographics.rsna.org).
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.[8]
Diagnosis is clinico-pathologic:[8]
- Intact immune system.
- Autoantibodies.
- Anti-enterocyte antibody.
- Anti-goblet antibody.
- Lack of response to gluten-free diet.
Microscopic
Features:[8]
- +/-Loss of goblet cells.
- +/-Loss of paneth cells.
- Villous blunting.
DDx:
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/.
- ↑ 7.0 7.1 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.
- ↑ 8.0 8.1 8.2 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/.