Lecture 12 - Large intestines and Inflammatory bowel disease

Question 1

Large intestines

Answer 1

Caecum to anal canal
Columnar epithelium

Absorbs water from gut contents in first half of colon- not as much as small intestines

Temporary storage for faeces

Question 2

Where does the colonic mucosa get most nutrients?

Answer 2

From fermentation of fibre by bacteria

Question 3

Sigmoid vulvulus

Answer 3

Sigmoid colon has its own mesentery

Can twist causing ischaemia and necrosis

Question 4

Rectum and peritoneum

Answer 4

upper 1/3rd - intra peritoneal
middle 1/3rd - retroperitoneal
lower 1/3rd - no peritoneum

Question 5

IMA branches

Answer 5

IMA - L3 slightly left

Left colic - descending colon
Sigmoid - descending colon and sigmoid
Superior rectal artery - upper 1/3rd rectum

Question 6

Venous drainage

Answer 6

Midgut - SMA - Portal vein

Hind gut - IMA - Splenic vein - Portal vein

Rectum:
Upper 1/3rd - superior rectal vein
Middle 1/3rd - systemic venous system that bypasses the liver
[site of portosystemic anastamoses]

Question 7

Large intestine structure

Answer 7

Shorter
Wider 
Peripheral 
Contain crypts not villi 
Haustra sacculations

External longitudinal muscles - 3 bands of teniae coli

Question 8

Water absorption in the colon

Answer 8

ENaC
Induced by aldosterone

Most absorption in proximal half of colon - tighter tight junctions for larger gradient to form as less back diffusion

Question 9

Inflammatory bowel disease

Answer 9

Group of conditions that involve idiopathic inflammation of the GI tract

Question 10

Crohn’s disease

Answer 10

• Affects anywhere in the GI tract from oesophagus to rectum
• Most commonly affects the terminal ileum
• Transmural - through bowel wall
• Perianal disease
• Cobblestone appearance
• Skip lesions
• Forms granulomas
• Fibrosis

Question 11

Ulcerative colitis

Answer 11

• Begins in rectum
• Continuous
• Lead pip appearance
• Can spread to whole colon = pan colitis
• May affect small intestine if back washed
• Crypt absesses
• Gross bleeding

Less malnutrition - doesn’t affect SI

Question 12

Extra intestinal problems with IBD

Answer 12

Arthritis

Skin conditions - psoriasis , erythema nodosum

Liver - primary sclerosing cholangitis

Eyes - uvietis

Question 13

Causes of IBD

Answer 13

Genetic
Microbiome
Immune response

Unknown triggers 
RF:
- Antibiotics
- Infections
- Smoking 
- Diet

Question 14

Smoking and ulcerative colitis

Answer 14

Stopping smoking can cause an exacerbation of UC

Smoking is a RF for Crohn’s

Question 15

Presentation of Crohn’s

Answer 15

Weight loss
RLQ pain - terminal ileum
Vomiting 
Ulceration
Low grade fever
Mild anaemia due to disease process not bleeding 
Mild perianal inflammation

Question 16

Colonoscopy of Crohn’s

Answer 16

Skip lesions
Fistulae
Cobblestone appearance
Strictures

Hyperaemia
Mucosal oedema
Superficial ulcers
Narrowing of lumen - thickened bowel wall

Question 17

Microscopic Crohn’s

Answer 17

Granuloma formation

- multinucleated giant cells

Question 18

Investigations of Crohn’s

Answer 18

Bloods - anaemia

CT/MRI - Bowel wall thickening, obstruction and extramural problems

Barium enema [not if fistula]

Question 19

Treatments of Crohn’s

Answer 19

Steroids
Antibiotics
Immunomodulators
Nutritional therapy 
Surgical intervention - resection

Question 20

Ulcerative colitis presentation

Answer 20

Bloody stools 
Mucus in stools 
Weight loss
Lower abdominal pain 
Painful red eye 

NO perianal inflammation
Normal temperature
Mildly tender abdomen

Question 21

Pathological changes in ulcerative colitis

Answer 21

Neutrophil and lymphocyte invasion into lamina propria

Villous atrophy

Crypt regeneration and distortion - irregular shaped glands with dysplasia and darker nuclei

Reduced number of goblet cells
Crypt abscesses
Superficial erosions

Question 22

Colonoscopy of UC

Answer 22

Pseudopolyps - due to healing after inflammation [ non- neoplastic]

Loss of haustra - lead pipe

Question 23

UC investigations

Answer 23

Bloods - anaemia and serum markers

Stool culture - blood and mucous

Colonoscopy

CT/MRI - used less as affects mucosal lining not transmural

Question 24

String sign of Kantour

Answer 24

On a barium follow through - long strictures

Question 25

Treatment of UC

Answer 25

1. Aminosalicylates - for flares and remissions
2. Corticosteroids - prednisolone (flare ups)
3. Immunomodulators - azathioprine (fistulas + maintanence)
4. Colectomy - curable

Question 26

When is a colectomy performed?

Answer 26

Toxic megacolon
Precancerous changes occur
Inflammation not settling