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Assessment of Abnormalities of Large Intestinal Biopsies- 2  

B. Assessment of crypt density, architecture and epithelium :



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1. Crypt density:

The biopsy should be well-oriented with muscularis mucosae included and should be assessed along the entire length. Lymphoid follicles should be avoided.

Normally there are 7 to 8 closely packed crypts per millimeter length of muscularis mucosae.

(Normal histology) 

In chronic inflammatory bowel disease there are about 4 to 5 crypts per mm so that the intercryptal space is equivalent to or greater than the crypt diameter.

Note: There is increase in the intercryptal space in normal caecal and distal rectal mucosa and should not be confused with chronic idiopathic inflammatory bowel disease.

2. Crypt architecture:  

Distortion, branching, atrophy, degeneration, serration, dilatation and misplaced crypts:

Crypt distortion - characterized by non-parallel crypts of variable diameter. After severe damage the crypts may run parallel to the surface.

Crypt branching or bifurcation indicates growth or regeneration after injury.

Criteria for assessment of abnormality -

(i) Biopsy should be well oriented  

(ii) Include at least 2 mm length of muscularis mucosae 

(iii) Should contain more than two branched crypts.

Crypt irregularity is present in -

(i) Ulcerative colitis. 

(ii) Following re-epithelialization and healing of ischaemic ulceration. 

(iii) In normal biopsy due cross cutting of crypts.

Crypt alignment is usually maintained in:

(i) Crohn's disease  (ii) Infective colitis.

Crypt atrophy or shortening is characterized by reduction of number of crypt and increased distance between crypt bases and muscularis mucosae.

Paneth cells may be present in shortened crypts in chronic cases.

Crypt atrophy is present in -

(i) chronic ulcerative colitis

(ii) healed ischaemic colitis

(iii) radiation colitis  

(iv) graft versus host disease.

Biopsy mimicking features of crypt atrophy -

(i) Uniform shortening due to tangential cutting

(ii) Biopsy from normal caecum, distal rectum and from mucosa close to anal margin

(iii) Thickening of the lamina propria due to oedema.

Crypt degeneration of the superficial half of the crypts occur in ischaemia and pseudomembranous colitis.

Degenerative changes throughout the full length of the crypts occur in ischaemic colitis or infective proctocolitis.

['Withered' crypts are present in infective colitis and are characterized by thin crypts, uneven lumen and pointed crypt base. The crypt cells appear small and pyknotic and there is mucin depletion].

Multifocal crypt necrosis is present in graft versus host disease.

Crypts have a 'moth-eaten appearance'.

Necrotic crypt epithelial cells are surrounded by plasma cells and lymphocytes.

Crypt serration is present in metaplastic/ hyperplastic polyp.

Crypt dilatation with some polymorphs within the crypt may be due to obstruction of mouth of a crypt.

Further deeper sections should be examined.

Groups of dilated crypts with inflammatory debris may be present in a case of pseudomembranous colitis.

Cystic dilatation may be present in polypoid lesions

(Example: Juvenile polyp, Cronkhite-Canada syndrome).

Misplaced crypts are characterized by crypt epithelium below the muscularis mucosae.

This may be present in the following conditions -

(i) Solitary ulcer of the rectum 

(ii) Mucosal damage due to ischaemic infarction or torsion.

(iii) Colitis cystica profunda 

(iv) Lymphoid glandular complexes.

3. Crypt epithelium :  Mucin depletion, regenerative hyperplasia, dysplastic epithelium, neutrophil polymorph infiltration (cryptitis & crypt abscess).

Mucin depletion - Diffuse loss of goblet cells (graded as mild, moderate or severe) occurs in ulcerative colitis , ischaemic, infective and radiation colitis.

In Crohn's disease it is less prominent and focal in nature.

Regenerative hyperplasia is characterized by increase in undifferentiated crypt base cells.