GI Path Online
Assessment of Abnormalities of Large Intestinal Biopsies -I
A. Assessment of the lumen, surface epithelium and the subepithelial zone:
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Debris covering the mucosa should be examined for microorganisms.
Luminal debris consisting of degenerate epithelial cells and inflammatory cells overlying a non-specific ulcer.
Debris usually consists of sloughed epithelial cells, neutrophils and sometime eosinophils.
Pus in the lumen is suggestive of pathology nearby.
Further levels are indicated.
Neutrophils arranged in a linear pattern in the lumen is suggestive of pseudomembranous colitis and deeper levels should be examined.
Amoebae are often present in the debris.
These should not be mistaken for foamy macrophages.
The organisms are PAS positive and contain red blood cells.
II. Surface epithelium:
Normal mucosal surface of the colon and rectum is almost flat. In chronic idiopathic inflammatory bowel disease surface irregularity is of variable severity.
In some cases the surface shows villous or pseudovillous pattern. This is a marker of inflammatory bowel disease.
[ Note: Erosion is loss of surface epithelium with underlying inflammation. Ulceration is characterized by damage to a greater thickness with underlying granulation tissue formation ].
Cuboidal change or flattening (loss of columnar shape of the epithelial cells) indicates mucosal damage and cell restitution.
Biopsy trauma may cause artifactual stripping of surface epithelium.
There are viable cells in the lumen, debris, red blood cells on the surface and absence of inflammatory infiltrate in the lamina propria.
Surface degeneration without inflammation could be due to poor tissue fixation.
Surface degeneration and superficial inflammation without other features could be due to irritative enema or due to some form of iatrogenic trauma.
Surface degeneration with acute inflammation is a non-specific feature of any of the causes of coloproctitis and is accompanied by other changes in the lamina propria.
(Example: Acute infective colitis).
Tufting of degenerated surface epithelium with acute inflammation, commonly noted in infective colitis and pseudomembranous colitis.
Further levels are indicated.
Microorganisms may be present. Spirochaetosis is characterized by fuzzy and thickened surface.
Organisms are better demonstrated by Warthin - Starry stain.
Cryptosporidia are identified as tiny haematoxyphilic dots.
This may be confused with stain deposits or nuclear debris.
Intraepithelial lymphocytes are increased in lymphocytic colitis (20 per100 epithelial cells).
IEL are also increased in coeliac disease.
(Normal IEL count - 5 IEL per 100 epithelial cells).
Increased number of apoptotic bodies in the surface epithelium is abnormal. (eg. Use of non-steroidal anti-inflammatory drugs ,, graft versus host disease, HIV infection).
III. Subepithelial zone:
Normal thickness of the subepithelilal collagen is usually not more than 3 micrometer.
According to some authors the normal range is 3 to 6.9 micrometer.
In collagenous colitis it is more than 10 micrometer.
The thickening may be patchy and confined to the proximal part of the colon.
Note: Diagnosis of collagenous colitis should not be made based only on thickened subepithelial collagen plate at any one point of the biopsy.
Differential diagnosis: Due to tangential cutting there is apparent thickening of basement membrane.
Nuclei in the surface epithelium may shift upwards resulting in eosinophilic subnuclear zone mimicking collagenous colitis.
Thickening of collagen plate has also been observed in some cases of diverticular disease, colonic carcinoma , Crohn's disease and pseudo membranous colitis
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