Microscopic colitis

Histological criteria[6]Miehlke S, Guagnozzi D, Zabana Y, et al. European guidelines on microscopic colitis: United European Gastroenterology and European Microscopic Colitis Group statements and recommendations. United European Gastroenterol J. 2021 Feb 22;9(1):13-37. https://onlinelibrary.wiley.com/doi/10.1177/2050640620951905 http://www.ncbi.nlm.nih.gov/pubmed/33619914?tool=bestpractice.com

Diagnosis is confirmed by the presence of the following characteristic pathohistological findings, which identify three histological subtypes of microscopic colitis:[6]Miehlke S, Guagnozzi D, Zabana Y, et al. European guidelines on microscopic colitis: United European Gastroenterology and European Microscopic Colitis Group statements and recommendations. United European Gastroenterol J. 2021 Feb 22;9(1):13-37. https://onlinelibrary.wiley.com/doi/10.1177/2050640620951905 http://www.ncbi.nlm.nih.gov/pubmed/33619914?tool=bestpractice.com

• Collagenous colitis: characterised by a thickened subepithelial collagenous band of ≥10 micrometres (normal <5 micrometres) combined with an increased inflammatory infiltrate in the lamina propria.

  [Figure caption and citation for the preceding image starts]: Biopsy demonstrating collagenous colitis with a thickened subepithelial collagen bandTome J et al. Microscopic Colitis: A Concise Review for Clinicians. Mayo Clin Proc. 2021 May;96(5):1302-8; used with permission [Citation ends].

• Lymphocytic colitis: characterised by an increased number of intraepithelial lymphocytes of ≥20 per 100 surface epithelial cells (normal <5 micrometres) combined with an increased inflammatory infiltrate in the lamina propria. The collagenous band is not significantly thickened (<10 micrometres).

  [Figure caption and citation for the preceding image starts]: Biopsy demonstrating lymphocytic colitis with intraepithelial lymphocytosisTome J et al. Microscopic Colitis: A Concise Review for Clinicians. Mayo Clin Proc. 2021 May;96(5):1302-8; used with permission [Citation ends].

• Microscopic colitis incomplete (also known as microscopic colitis not otherwise specified): comprises incomplete collagenous colitis (defined by a thickened subepithelial collagenous band of >5 micrometres but <10 micrometres) and incomplete lymphocytic colitis (defined by >10 but <20 intraepithelial lymphocytes per 100 epithelial cells and a normal collagenous band). Both types show a mild inflammatory infiltrate in the lamina propria.