An introduction to gastrointestinal pathology

Gastrointestinal pathology is a large part of pathology as radiologists can often describe the extent of disease... but don't get the diagnosis right all the time.

Normal

Layers

Layers of the alimentary canal:

• Mucosa (epithelium, lamina propria, muscularis mucosa).
• Submuscosa and submucosal plexus (or Meissner's plexus).
• Muscularis externa (inner longitudinal, myenteric plexus (or Auerbach's plexus) outer circumferential).
• Adventitia (if retroperitoneal), serosa (if intraperitoneal).

Cell types

• Goblet cells.
  • Secrete mucin.
• Enterochromaffin cells, AKA Kulchitsky cells.
  • Subnuclear eosinophilic granules.
    • Serotonin.
• Paneth cells.
  • Supranuclear eosinophilic granules.

Memory device:

• Supranuclear granules = paneth cell.

Bowel

Small bowel

• Villi - should see three good ones in a normal biopsy.
• Crypts.
• Paneth cells.
• Goblet cells.
  • Few in proximal small bowel (duodenum).
  • Abundant in distal small bowel (ileum).

Duodenum

• Small bowel (as above).
• Submucosal glands (Brunner's glands).

Large bowel vs. small bowel

• Small intestine.
  • Villi (key feature).
  • Brunner's glands - duodenum only (key feature).
  • Paneth cells more common.
    • Paneth cells are in the base of the crypts and have eosinophilic granules. They are found (normally) in the small bowel and right colon. They may appear on the left side (i.e. descending colon) in pathologic states, e.g. IBD.
• Large intestine
  • More goblet cells.
  • More lymphocytes usually.

Luminal gastroenterology

Intestinal polyps

Main article: Intestinal polyps

The bread and butter of gastrointestinal pathology.

Esophagus

Main article: Esophagus

Largely forgotten organ at SB... but no shortage of these at SMH.

Stomach

Main article: Stomach

H. pylori, cancer and more...

Small bowel

Main article: Small bowel

The part of the GI tract that pathology has mostly forgot. Crohn's disease is dealt with in a separate article.

Duodenum

Main article: Duodenum

Commonly biopsied. Celiac... cancer... giardia?

Colon

Main article: Colon

Includes discussion of the rectum. Colorectal tumours are dealt with in colorectal tumours. Crohn's disease and ulcerative colitis are dealt with in the inflammatory bowel disease article.

Appendix

Main article: Appendix

Acute appendicitis and more...

Accessory GI

Gallbladder

Main article: Gallbladder

A growth industry... with the expanding waist lines in the (Western) world.

Liver

Main article: Liver

An organ that pathologists now sometimes forget. There are separate articles for the medical liver diseases and liver neoplasms.

Pancreas

Main article: Pancreas

An organ that is occasionally afflicted by cancer. It is primarily seen in large centers where they do ERCPs and Whipples.

See also

• Introduction.