Dr  Sampurna Roy  MD

Large intestinal biopsies are taken at colonoscopy, sigmoidoscopy (rigid or flexible) or proctoscopy.

Proper orientation of the specimen is essential for accurate assessment of colonic biopsies.

The mucosal biopsies should be carefully handled during endoscopy.

Ideally the biopsies should be placed submucosa-down on the cellulose acetate strip, embedded on the edge and sections taken in ribbons from processed blocks.

The sections should be mounted on the slide in order according to the site of the biopsy. (Eg. Biopsy from proximal end of colon placed to the left of the slide when held horizontally).

Value of colonic biopsies in suspected cases of inflammatory bowel disease:

1. To establish the diagnosis of colitis, note the severity and extent of inflammation and follow the course of the disease.

2. To identify the specific type of colitis and differeniate from mimics of inflammatory bowel disease.

3. To rule out the possibility of any dyspepsia or malignancy.

Initial evaluation:

The pathologist must evaluate the requisition form to ascertain the relevent clinical features of the patients and to determine the site of the biopsy. 

The tissue submission form should include the following:

A simple diagram of the large intestine on which the endoscopist indicates the lesions seen and their locations ;

Clinical impression of the gastroenterologist ;

Clinical details include age, sex of the patient ;

Symptoms with duration (eg. abdominal pain, diarrhea, bleeding per rectum) ;

Endoscopic findings include mucosal features (friability and congestion)

Extent of the disease ;  pattern of ulceration and presence of any polyp or tumour ;

Radiological findings ;

Findings of other investigations (eg. stool culture);

 History of previous gastrointestinal  surgery or therapy and history of any systemic disease (eg. rheumatoid arthritis) ;

Presence of any relevent family history.

General assessment (low power):
1. Size (mm)       2. No of levels examined 

3.Orientation     4. Presence or absence of muscularis mucosae

5. Submucosa    6. Evidenceof biopsy trauma

Determine whether the biopsy is normal or abnormal: (Normal histology of the large intestine: click)

Determine whether the changes are focal or diffuse :

Points to remember:
Features of normal large bowel mucosa : click

Normal crypt density ;

No crypt architectural distortion ;

Flat mucosal surface ;

Cellular infiltrate in the lamina propria of normal density, distribution and population ;

No granulomas or giant cells are present Columnar surface epithelial cells are intact ;

Normal mucin content of goblet cells ;

Before reporting  a biopsy specimen as "Normal large bowel mucosa"- always search for discontinuous inflammation, intraepithelial lymphocytes, subepithelial collagen and mucosal prolapse changes.

Features of chronic idiopathic inflammatory bowel disease:

Decreased crypt density ;

Crypt architectural distortion ;

Irregular surface ;

Transmucosal or discontinuous increase in cellular infiltrate in the lamina propria ;

Surface epithelial flattening ;

Epithelioid granuloma ;

Neutrophil  infiltration.

Features of chronic inflammatory bowel disease in keeping with Ulcerative colitis:

Severe crypt architectural distortion ;

Widespread decrease in crypt density ;

Frankly villous surface;

Dense diffuse transmucosal increase in cellular infiltrate in the lamina propria ; 

Diffuse basal plasmacytosis;

Severe mucin depletion ;

Paneth cell metaplasia distal to the hepatic flexure.

Features of chronic inflammatory bowel disease in keeping with Crohn's disease:

Epithelioid granuloma ;

Discontinuous inflammation ;

Discontinuous crypt distortion ;

Focal cryptitis.

Features of acute infective type colitis:

Retention of normal architecture ;

'Withering' of crypts ;

 Increase in cellularity in the superficial part of the lamina propria ;

 Mucin depletion ;

Discontinuous inflammation ;

Focal cryptitis ;

Neutrophil infiltration in the early phase.