Session 8 - Large Intestine And IBD

Question 1

What are the functions of the large intestine?

Answer 1

Removal of water from indigestible gut contents - turns chyme into a semi solid.
Acts as a temporary storage until defaecation.
Production of certain vitamins (e.g. vitamin K is produced by bacteria in the large intestine).

Question 2

Describe the appearance of the lining of the large intestine to the naked eye.

Answer 2

Flat surface, no plicae circulares or villi.
Has teniae coli (three distinct bands of longitudinal muscle)
Haustra

Question 3

Describe the structural differences between the large intestine and small intestine.

Answer 3

The large intestine:

• is much shorter
• is much wider
• has crypts not villi
• has incomplete longitudinal muscle forming teniae coli
• has haustra
• has no plicae circulares

Question 4

What is the gastrocolic reflex?

Answer 4

Mass movement of the contents of the colon into the rectum, triggered by food entering the stomach after eating.

Question 5

How does water absorption occur in the colon?

Answer 5

Facilitated by ENaC.
Sodium moves into epithelial cell via epithelia sodium channel (ENaC).
Water follows the sodium into cell through aquaporins.

Question 6

What is inflammatory bowel disease?

Answer 6

A group of conditions characterised by idiopathic inflammation of the GI tract.

Question 7

What are the two most common types of inflammatory bowel disease?

Answer 7

Crohn’s disease

Ulcerative colitis

Question 8

Who is most commonly affected by Crohn’s disease?

Answer 8

15-30 yr olds and 60+ yr olds

Question 9

Who is most commonly affected by ulcerative colitis?

Answer 9

Young adults

Question 10

Give examples of types of inflammatory bowel disease other than Crohn’s disease or ulcerative colitis.

Answer 10

Diversion colitis
Pouchitis
Microscopic colitis

Question 11

What are the differences between Crohn’s disease and ulcerative colitis?

Answer 11

Crohn’s disease:

• affects anywhere in the GI tract
• ileum involved in most cases
• transmural (deep inflammation, through the wall)
• skip lesions (unaffected areas of mucosa in between affected areas)

Ulcerative colitis:

• begins in the rectum, move proximally
• can extend to involve entire colon
• continuous
• superficial mucosal inflammation

Question 12

What problems can inflammatory bowel disease cause outside of the intestines?

Answer 12

MSK pain - arthritis
Skin - erythema nodosum, pyoderma gangrenosum, psoriasis
Liver/biliary tree - primary sclerosis cholangitis (PSC)
Eye problems

Question 13

What are the possible causes of inflammatory bowel disease?

Answer 13

Not entirely clear. Multifactoral with a genetic element.

• genetics
• altered interaction with gut organisms
• immune response (possibly to antibiotics, infections, smoking, diet)

Question 14

How would Crohn’s disease present?

Answer 14

Loose non-bloody stools
Weight loss
Right lower quadrant pain

Question 15

What gross pathological processes are visible in a bowel with Crohn’s disease?

Answer 15

Cobblestone appearance
Hyperaemia (increase blood flow to tissues)
Mucosal oedema
Discrete superficial ulcers,
Deep ulcers
Transmural inflammation (can lead to thickening of the bowel wall due to scar tissue and narrowing due to strictures)
Fistulae (e.g. between bowel and bladder)

Question 16

What microscopic finding is pathognomonic of Crohn’s disease?

Answer 16

Granuloma formation

Question 17

What investigations would you use to help diagnose Crohn’s?

Answer 17

Colonoscopy - look for ‘cobblestone’ appearance and ulcers
Bloods - anaemia
CT/MRI scans - bowel wall thickening, obstruction, extramural problems
Barium enema/follow through - strictures/fistulae

Question 18

How would ulcerative colitis present?

Answer 18

Bloody stools
Weight loss
Mild lower abdominal pain/cramping
Normal temp
No perianal disease

Question 19

What pathological changes occur in ulcerative colitis?

Answer 19

Chronic inflammation of the lamina propria
Crypt abscesses
Pseudopolyps (islands of regenerating mucosa)
Loss of haustra

Question 20

What investigations would you use to help diagnose ulcerative colitis?

Answer 20

Colonoscopy
Bloods - anaemia, serum markers
Stool cultures
Plain abdominal radiographs
Barium enema 
CT/MRI

Question 21

What is meant by intermediate colitis?

Answer 21

IBD that cannot be classified into UC or Crohn’s even after diagnostic evaluation. Has characteristics of both.

Question 22

What medical treatments are used for Crohn’s disease and ulcerative colitis?

Answer 22

1. Aminosalicylates (e.g. sulfasalazine) - for flares and remission
2. Corticosteroids (e.g. prednisolone) - for flares only
3. Immunomodulators (e.g. azathioprine) - for fistulas and maintenance of remission

Question 23

Can surgery cure Crohn’s disease?

Answer 23

No, as you can’t remove every skip lesion without removing too much of the small intestine.

Question 24

Can surgery cure ulcerative colitis?

Answer 24

Yes, through a colectomy.

Question 25

In what cases would a colectomy be considered to treat ulcerative colitis?

Answer 25

If the inflammation is not settling, there are precancerous changes or a toxic megacolon.

Question 26

What is toxic megacolon?

Answer 26

Toxic megacolon is the clinical term for an acute toxic colitis with dilatation of the colon. The dilatation can be either total or segmental. It is a complication of ulcerative colitis, and more rarely Crohn’s disease.