S8.1 Large Intestine & IBD

Question 1

What are the functions of the large intestine

Answer 1

Water absorption (proximal)
Temporary storage until defaecation (distal)

Question 2

Describe the anatomy of the large intestine

Answer 2

Incomplete 3 bands of external longitudinal muscle (taenia coli), haustra are sacculations from taenia coli contraction.

Question 3

Describe the uptake of water and electrolytes in the intestines

Answer 3

Na+ leaves via Na+/K+ ATPase, creating a gradient for Na+ entry via Na+ channels (induced by aldosterone). Osmotic gradient leads to water uptake - isosmotic fluid uptake.

Question 4

Describe how the anal sphincter facilitate defecation

Answer 4

Internal anal sphincter relaxes (smooth muscle, parasympathetic), external anal sphincter relaxes (voluntary, striated muscle), intra-abdominal pressure rises as faeces are expelled.

Question 5

What is IBD and the two main types?

Answer 5

Group of conditions characterised by idiopathic inflammation of the GI tact.
Crohn’s disease and ulcerative colitis

Question 6

What is though to cause IBD?

Answer 6

Genetic, immune response triggered by antibiotic/smoking/infections/diet

Question 7

What are the potential extra-intestinal manifestations of IBD?

Answer 7

Arthritis
Psoriasis
Cholangitis

Question 8

Outline the key features of Crohn’s

Answer 8

Can affect anywhere from mouth to anus (commonly terminal ilium/ascending colon)
Transmural
Skip lesions
Granulomas

Question 9

What are the signs and symptoms of Crohn’s?

Answer 9

RLQ pain
Low grade fever
Weight loss

Question 10

What is seen on a colonoscopy of a patient with Crohn’s?

Answer 10

Ulcers
Cobblestone appearance with skip lesions
Fistula formation

Question 11

What investigations are done in Crohn’s?

Answer 11

Bloods
CT
Colonoscopy

Question 12

Outline the key features of Ulcerative colitis

Answer 12

Affects young adults, can be caused by diversion colitis when part of colon is removed
Begins in rectum and can extend to involve whole colon.
Continuous pattern of mucosal inflammation.

Question 13

What are the signs and symptoms of UC?

Answer 13

Mildly tender abdomen

LLQ pain usually

Question 14

Outline some of the pathological features of the bowel in UC

Answer 14

Crypt abscesses
Pseudopolyps
Loss of haustra

Question 15

What investigations are done in UC?

Answer 15

Bloods (may have anaemia due to bleeding)
Stool cultures
Radiograph

Question 16

What are the radiological features of Crohn’s?

Answer 16

String sign of contour

Question 17

What are the radiological features of UC?

Answer 17

Lead pipe colon due to continuous mucosal involvement

Question 18

Outline some medical treatments for IBD

Answer 18

Aminosalicylates then corticosteroids

Question 19

Outline some surgical treatments for IBD?

Answer 19

Crohn’s not curative

UC can have total colectomy