Gastrointestinal Pathology: Introduction to GI tract

Question 1

What kinds of differences does the GIT show?

Answer 1

Regional differences morphologically, functionally, and with blood supply.

The same range of pathological problems are seen in all regions but with different frequency

Question 2

What are the layers of the GI tract?

Answer 2

Mucosa (subdivided into mucosal epithelium and lamina propria)

Submucosa

Muscularis externa

Serosa (visceral peritoneum)

Question 3

Where is the muscularis mucosa located?

Answer 3

Between lamina propria of the mucosa and the submucosa

Question 4

How does the anal canal and the rectum show local specialization?

Answer 4

The anal canal needs to be protected so it is covered by stratified squamous epithelium whereas the rectum doesn’t need protection in the same way so it is lined by simple columnar epithelium.

Question 5

What are the tissue and cell types of the GI tract?

Answer 5

Epithelium (sepcialized in different areas depending on function)

Smooth muscle (Muscularis mucosae and muscularis propria)

Nerves and ganglia (Submucosal and myenteric plexus)

Neuroendocrine / enterochromaffin cells

Blood vessels (VAL)

Immune tissues (MALT, lymph nodes, lymphatics)

Connective tissue (fat, fibrous tissue, skeletal muscle)

Question 6

What is the function of the GI tract?

Answer 6

Intake

Digestion

Absorption

Elimination of waste

Question 7

What can go wrong with GIT fucntion?

Answer 7

Intake: Excess intake, imbalance and deficiency

Digestion: Maldigestion

Absorption: Malabsorption, defective transport

Elimination of waste: Functional or mechanical obstruction

Question 8

How can site of pathology be narrowed down?

Answer 8

Time course, location, severity, and duration of symptoms can assist in understanding GIT pathology.

Question 9

What are the symptoms of GIT problems?

Answer 9

Often non-specific and non-localising

Blockage of hollow tube = rapid, severe pain

Inflammation of mucosa = variable

Inflammation of serosa = often severe

Nausea and vomiting

Malabsorption and nutrient deficiency

Loss of appetite / loss of weight

Diarrhoea

Constipation / Obstruction

Question 10

What are the ways that blood can present in stool?

Answer 10

Melaena (black, malodourous) stools indicating bleeding proximally

Haematochezia (bright red) indicates bleeding distally or massive bleed..

Occult blood: Not visible, detectable biochemically and may have anaemia

Question 11

What are the signs of GIT problems?

Answer 11

Blood in stool

Tenderness (“rebound”)

Abdominal distention

Palpable mass (late)

Peritonitis due to perforation

Systemic infection (sepsis)

Question 12

How can GIT problems be investigated?

Answer 12

History and exam of patient

Imaging: Xray, U/S, CT, MRI, etc

Lab tests: Stool sample, FOBT, microbiology, biochemistry

Endoscopy from top or bottom +/- biopsy

Question 13

How should diagnostics be approached in GIT?

Answer 13

A structured approach should be taken with systematic thinking.

Question 14

How can disease aetiology be divided in GIT?

Answer 14

“VITAMIN C”

Question 15

What are the possible vascular pathologies that can arise in GIT?

Answer 15

Arterial occlusion resulting in ischaemia and infarction. (Due to embolism, thrombosis, and vasculitis) Rupture results in haemorrhage.

Venous obstruction results in congestion, ischaemia +/- infarction and is often due to mechanical obstruction.

Question 16

What are the possible inflammatory pathologies that can arise in GIT?

Answer 16

Regardless of trigger causes pain and dysfunction. This can be due to:

Infection: All organism types can do this

Non-infective: Autoimmune, chemical/drug, idiopathic

Named according to site (gastritis, oesophagitis, etc)

Question 17

What are the consequences of GIT inflammation?

Answer 17

Consequences are damage to surface resulting in ulceration and haemorrhage with or without perforation.

Usually resolves but chronic inflammation can lead to architectural changes in epithelium as well as fibrosis and scarring and thickening of muscle wall, peritoneal adhesions, and narrowing of lumen.

Question 18

What are the possible consequences of trauma to GIT?

Answer 18

Organ damage/rupture (necrosis, dysfunction, peritonitis)

Vascular damage (Haemorrhage, haematoma, ischaemia, infarction)

Question 19

What causes Boerhaave syndrome?

Answer 19

Boerhaave syndrome is caused by excessive vomtiing tearing the oesophagus.

Question 20

What do autoimmune conditions do to GIT system?

Answer 20

Inflammation

Damage to a specific type of cell or tissue by the immune system

Question 21

What are the metabolic causes of GIT problems?

Answer 21

Enzyme deficiencies (leads to malabsorption)

Question 22

What common GIT conditions are caused by drugs?

Answer 22

Pseudomembranous colitis (overgrowth of C. difficile) due to antibiotic treatment

Radiation colitis (caused by drug for rectal carcinoma)