Colon (Large bowel, Large intestine)

General:

Normal Gross:

Normal Microscopic:
Mucosa: The luminal surface is flat except for occasional shallow cup-shaped depressions into which several crypts may open. The colonic crypts are closely packed in a parallel array (with suitable orientation this is called a "test tube" architecture), with roughly equivalent spacing. The crypts extend to the top of the muscularis mucosae (except in the rectum, where they stop several millimeters above). Occasional crypts are allowed to be bifid (like an inverted V) in normal mucosa, though in a suspicious setting with other changes or numerous such alterations may signify inactive or healed colitis. Crypt epithelium is composed primarily of tall, columnar, flask-shaped goblet cells with a basal nucleus and apical pale blue cytoplasm, though absorptive and endocrine cells are also present, if difficult to identify on H&E. Paneth cells are also normally present as far as the hepatic flexure. Plasma cells are normal inflammatory cells in the lamina propria, with rare lymphocytes, eosinophils, macrophages, and even neutrophils allowed.

Endoscopy artifact: Some acceptable changes due to either endoscope trauma or use of bowel prep cocktails includes lamina propria edema, mucosal vascular congestion, neutrophil margination, superficial fresh hemorrhage, and disruption or loss of surface epithelium (this remains distinct from ulceration). Glutaraldehyde has been used to disinfect endoscopes and may cause acute ischemic colitis. Hydrogen peroxide has also been used to disinfect endoscopes and may cause pseudolipomatosis (gas in the lamina propria).

Stains:

• Positive:
• Negative:

((())) Perspectives in Pediatric Pathology: Gastrointestinal Diseases. 1997, #20.

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