Inflammatory polyp

Deputy Editor-in-Chief: Catherine E. Hagen, M.D.
Andrew L.J. Dunn, M.D.
Raul S. Gonzalez, M.D.

Last author update: 21 April 2021
Last staff update: 7 December 2023

Copyright: 2002-2024,, Inc.

PubMed Search: "Inflammatory polyp" colon

Andrew L.J. Dunn, M.D.
Raul S. Gonzalez, M.D.
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Cite this page: Dunn ALJ, Gonzalez RS. Inflammatory polyp. website. Accessed April 14th, 2024.
Definition / general
Essential features
  • Nonneoplastic colon polyp composed of inflamed mucosa
  • Typically shows surface erosion with surrounding granulation tissue and epithelial distortion
  • Inflammatory polyp as a diagnosis is generally used to describe small foci of nonspecifically inflamed colonic mucosa or inflammatory pseudopolyps
  • Inflammatory polyp as a category includes several subtypes, including:
ICD coding
  • ICD-10: K51.4 - inflammatory polyps of colon
  • Typically second and third decades for inflammatory bowel disease; incidence range of 10 - 20% in ulcerative colitis patients (World J Gastroenterol 2017;23:1541)
  • May occur in older patients with peripheral vascular disease
  • Can arise anywhere in the colon, especially at the ileocecal region in Crohn’s disease
  • May form at anastomotic sites
  • Believed to be secondary to repeated bouts of intense inflammation
  • Formation of inflammatory polyps may be related to increases in C reactive protein, C4 and procollagen III peptide (World J Gastroenterol 2003;9:619)
Clinical features
  • Sporadic inflammatory polyps are usually incidental at colonoscopy
  • May present with intussusception or obstructive symptoms
  • Presence of pseudopolyps in inflammatory bowel disease may represent recent flare, although lesions are found in active or dormant disease (World J Gastroenterol 2017;23:1541)
    • Also may be related to arthropathy or other extracolonic symptoms (Lancet 1969;2:555)
Case reports
  • Typically treated endoscopically via polypectomy
  • Examples related to inflammatory bowel disease may improve with infliximab (J Crohns Colitis 2010;4:707)
  • Argon plasma coagulation or ablation for bleeding control
  • Surgical resection if profuse bleeding, obstruction or intussusception
Gross description
  • Usually sessile and less than 3 cm
  • May be pedunculated or filiform
Gross images

Images hosted on other servers:

Inflammatory pseudopolyps in ulcerative colitis

Microscopic (histologic) description
  • Often consists of normal colonic mucosa in a polypoid configuration, with increased inflammation (expanded lamina propria and crypt abscesses or cryptitis)
  • Epithelium can show various degrees of surface erosion, crypt distortion / dilation or hyperplasia, along with reactive nuclear features within the mucosal epithelial cells
  • May consist entirely of granulation tissue (abundant thin walled and dilated vessels surrounded by mixed neutrophilic and lymphoplasmacytic inflammation)
  • Reactive stromal cells may be markedly pleomorphic and mimic sarcoma
  • Cases associated with inflammatory bowel disease may rarely show epithelial dysplasia
Microscopic (histologic) images

Contributed by Andrew L.J. Dunn, M.D.

Dense inflammation in lamina propria

Surface mucosal ulceration

Surface erosion with granulation tissue


Negative stains
Molecular / cytogenetics description
  • Usually no abnormalities

Inflammatory polyp on colonoscopy

Sample pathology report
  • Sigmoid colon, polypectomy:
    • Inflammatory polyp
Differential diagnosis
Board review style question #1
Which of the following is not a typical feature of colonic inflammatory polyps?

  1. Crypt distortion / branching
  2. Granulation tissue changes
  3. Microsatellite instability
  4. Surface mucosal erosion
Board review style answer #1
C. Microsatellite instability. Inflammatory polyps are a benign process with various degrees of mucosal erosion, increased vascular density similar to granulation tissue and architectural changes.

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