Pathology of Colon

Question 1

What is the presentation of colon cancer?

Answer 1

1) Abdominal pain (right)
2) Unintentional weight loss (right)
3) Altered bowel habit (left)
4) Faecal occult blood (left)
5) Anemia (left)
6) Fatigue
7) Obstruction (either side)

Question 2

What is the aetiology of colon cancer?

Answer 2

Often unknown

Multifactorial

Question 3

What are the risk factors for colon cancer?

Answer 3

1) Smoking
2) Being elderly
3) Family history of colorectal cancer
4) Having IBD
5) Streptococcus bovis bacteraemia

Question 4

What are the different types of large bowel neoplasia?

Answer 4

1) Dysplasia (high or low grade)
2) Malignancy (colorectal carcinoma)

Question 5

How does dysplasia present in CRC and what are the characteristics of low grade and high grade dysplasias?

Answer 5

Dysplasia presents as solitary adenomas/polyps

Low grade dysplasia:

1) Increased number and size of cells
2) Reduced mucin

High grade dysplasia:

1) Carcinoma in situ
2) Crowded
3) Very irregular
4) Not yet invasive

Question 6

How is the enteric nervous system organised?

Answer 6

Myenteric Plexus is arranged as follows:

Meissener’s plexus - base of submucosa (innervation of epithelium and smooth muscle)

Auerbach plexus - between inner circular and outer longitudinal muscle layers and provides motor innervation

The myenteric plexus works to innervate the peristaltic action of the small and large intestines, along with the autonomic innervation

Question 7

What are the main histological features of the small bowel?

Answer 7

• Lots of vili
• Simple columnar epithelium
• Goblet cells
• Crypts of Lieberkuhn

Question 8

What are the main histological features of the large bowel?

Answer 8

• Flat - no vili
• Tubular crypts
• Simple columnar epithelium
• Crypts of Lieberkuhn
• Goblet cells

Question 9

What are the features of the intestinal immune system?

Answer 9

• GI tract has a large surface area for exposure to environmental antigens
• The immune system must be able to balance between harmless substances and active defense reactions to microbial invaders
• Dysfunction of the GI immune system leads to:
  1) Chronic disease
  2) Life threatening acute conditions

Question 10

What are the pathological features of Ischaemic colitis?

Answer 10

1) Ischaemic lesions
2) Acute occlusion of 1 of the 3 major supplying vessels leads to infarction (coeliac, inferior, superior mesenteric)
3) Lumen gets congested with mucin
4) Vascular dilatation
5) Oedema

Question 11

What are the pathological features of radiation colitis?

Answer 11

• Radiation colitis is caused by abdominal irradiation impairing the normal proliferative activity of small and large bowel epithelium
• Damage depends on dose
• Specifically targets blood vessels and crypt epithelium

Histology:

• Ulceration
• Necrosis

Question 12

What are the pathological features of appendicitis?

Answer 12

• Acute inflammation
• Causes obstruction
• Obstruction leads to increased intraluminal pressure and eventually ischaemia
• Fibrinopurulent exudate
• Perforation
• Abscess
• Puss in lumen
• Necrosis