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Small bowel (small intestine)

Infectious disorders


Reviewer: Hanni Gulwani, M.D. (see Reviewers page)
Revised: 17 December 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.


● Common cause of bacterial enteritis in US, Canada, Australia, Western Europe, Northern Europe (eMedicine)
● Infection due to Y. enterocolitica, Y. pseudotuberculosis, gram negative invasive rods
● Bacteria present in infected milk, pork, water supplies, domestic pets and farm animals
● Causes enterocolitis, acute appendicitis, mesenteric lymphadenitis in children and adolescents
● Pathogenic strains invade small intestinal mucosa via M cells overlying Peyer’s patches, multiply there and within regional nodes, then spreads hematogenously and via lymphatics
● Patients homozygous for Thalassemia major are at risk of Y. enterocolitica, because they have iron overload and the bacteria require iron for growth


● Ileum, right colon, appendix


● Culture

Case reports

● 4 year old boy with intussusception due to Y. enterocolitica infection (Arch Pathol Lab Med 2001;125:1486)

Micro description

● Elongated ulcerations overlying lymphoid hyperplasia
● Also small aphthoid ulcers overlying colonies of gram negative rods and with neutrophils at ulcer base
● Also necrotizing granulomas (particularly with Y. pseudotuberculosis)
● Mesenteric nodes show follicular hyperplasia with variable scattered microabscesses and epithelioid granlomas

Micro images

Various images

Differential diagnosis

Crohn’s disease
Typhoid fever

End of Small bowel (small intestine) > Infectious disorders > Yersinia

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