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Gastrointestinal > The Large Intestine and Irritable Bowel Disease > Flashcards

The Large Intestine and Irritable Bowel Disease Flashcards

1
Q

What makes up the Large Intestine?

A

Caecum to the anal canal.

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2
Q

What epithelium is found in the large intestine?

A

Columnar epithelium.

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3
Q

What are the functions of the large intestine?

A
  1. Removes water from all the indigestible gut contents (proximal).
  2. Truns chyme into a semi-solid.
  3. Production of certain vitamins like vitamin K.
  4. Acts as a temporary storage unit unit defaecation (distal).
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4
Q

Where does the Colonic Mucosa get the majority of its nutrients?

A

Not from the blood but the fermentation of fibre, indigestible carbohydrates and short fatty acids.

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5
Q

What are the byproducts of fermentation?

A

CO2, methane and hydrogen gas.

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6
Q

Which structures of the large intestine are retroperitoneal (behind the peritoneum)?

A
  1. Ascending colon.
  2. Descending colon.
  3. Middle 1/3 of the rectum.
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7
Q

Which structures of the large intestine have their own mesentery?

A
  1. Transverse colon (transverse mesocolon).

2. Sigmoid Colon.

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8
Q

Which structures of the large intestine are intra-peritoneal?

A
  1. Upper 1/3 of the rectum.
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9
Q

Which structures of the large intestine have no peritoneum?

A
  1. Lower 1/3 of the rectum.
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10
Q

What does the Superior Mesenteric Artery supply in the large intestine?

A

The midgut structures.

  1. Caecum.
  2. Ascending Colon .
  3. 2/3 proximal Transverse Colon.
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11
Q

What is the artery that supplies the caecum?

A

Ileo-colic Artery.

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12
Q

What is the artery that supplies the ascending colon?

A

Right Colic Artery.

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13
Q

What is the artery that supplies the proximal 2/3 of the Transverse Colon?

A

Middle Colic Artery.

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14
Q

What does the Inferior Mesenteric Artery supply in the large intestine?

A

The hindgut structures.

  1. 1/3 distal transverse colon.
  2. Descending colon.
  3. Sigmoid colon.
  4. Upper 1/3 of rectum.
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15
Q

What artery supplies the distal 1/3 of the transverse colon?

A

The ascending branch of left colic artery (branch of IMA).

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16
Q

What artery supplies the descending colon?

A

Left Colic Artery.

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17
Q

What artery supplies the sigmoid colon?

A

Two-to-four sigmoid arteries (branch of inferior mesenteric artery).

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18
Q

What artery supplies the upper 1/3 of the rectum?

A

Superior rectal artery.

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19
Q

What is the venous drainage of the midgut?

A

Superior mesenteric vein.

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20
Q

What is the venous drainage of the hindgut?

A

Inferior mesenteric vein.

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21
Q

Describe the venous drainage of the rectum.

A

Upper 1/3 drains into the superior rectal vein.

Middle 1/3 and lower 1/3 drains into the systemic venous system which is a site of the portosystemic anastomosis.

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22
Q

What is the marginal artery?

A

Anastamoses of the descending and ascending branches of the middle and right colic artery and the ileocolic artery.

23
Q

What is the superior rectal artery?

A

The superior rectal artery is the continuation of the inferior mesenteric artery. It descends into the pelvis between the layers of the mesentery of the sigmoid colon, crossing the left common iliac artery and vein.

24
Q

Compare the structure of the small and large intestine.

A
  1. The large intestine is much shorter (6ft compared to 20ft).
  2. Large intestine is much wider (6cm vs 3cm).
  3. LI has crypts not villi.
25
Q

Describe the structure of the large intestine.

A

Its external longitudinal muscle is incomplete, creating three distinct bands (teniae coli).
There are haustra which are sacculations caused by contraction of teniae.

26
Q

What are teniae coli?

A

The taeniae coli (also teniae coli or tenia coli) are three separate longitudinal ribbons (taeniae meaning ribbon in latin) of smooth muscle on the outside of the ascending, transverse, descending and sigmoid colons. They are visible and can be seen just below the serosa or fibrosa.

27
Q

What are haustra?

A

Sacculations caused by contraction of teniae.

28
Q

How is water absorbed in the large intestine?

A

Facilitates by ENaC on the apical membrane. ENaC is induced by aldosterone.
Approximately 1500ml of water enters the colon every day and no more than 100ml is removed.
Most absorption occurs in the proximal colon, where there are much tighter tight junctions to allow for a bigger gradient to form to allow less back diffusion.
Water follows sodium.

29
Q

Where does most of the water absorption in the large intestine occur?

A

The proximal colon.

30
Q

What is Inflammatory Bowel Disease?

A

A group of conditions characterised by idiopathic inflammation of the GI tract. They affect the function of the gut.

31
Q

What are the 2 important types of Inflammatory Bowel Disease?

A
  1. Crohn’s disease.

2. Ulcerative Colitis (young adults).

32
Q

What are the main characteristics of Crohn’s disease?

A
  1. Crohn’s disease can affect anywhere in the GI tract.
  2. The ileum is involved in most cases.
  3. It is transmural, going deep.
  4. There are skip lesions.
33
Q

What are the main characteristics of Ulcerative Colitis?

A
  1. Begins in the rectum.
  2. Can extend to involve the entire colon.
  3. Is mucosal inflammation so is only superficial.
  4. It is continuous in pattern (no skip lesions).
34
Q

What other, non-GI problems are associated with IBD?

A
  1. MSK pain such as arthritis.
  2. Skin problems like psoriasis.
  3. Liver/biliary tree problems like primary scelerosing cholangitis.
  4. Eye problems, like Uveitis (middle eye inflammation).
35
Q

What are the causes of IBD?

A
  1. Genetic.
  2. Gut organisms, an altered interaction.
  3. An immune response, with a trigger like antibiotics, infections, smoking (makes Crohn’s worst and improves UC) or diet.
36
Q

What is the common presentation of Crohn’s?

A 
Symptoms:
1. Loose stools (non-bloody).
2. Weight loss.
3. RLQ pain.
4. Joint pain.
Signs:
1. tender mass RLQ.
2. Mild perianal inflammation/ulceration due to the transmural nature of Crohn's.
3. Low grade fever.
4. Mild anaemia.
37
Q

What is the gross pathology of Crohn’s disease?

A
  1. Skip lesions.
  2. Hyperaemia (excess blood in vessels).
  3. Mucosal oedema.
  4. Discrete superficial ulcers.
  5. Deeper ulcers.
  6. Transmural inflammation causing thickening of the bowel wall and narrowing of the lumen.
  7. Cobllestone appearance from the ulcers.
  8. Fistulae- bowel into the bowel/bladder/vagina/skin.
38
Q

What is the microscopical appearance in Crohn’s disease?

A

Granuloma formation, organised collection of epithelioid macrophages.

39
Q

How would you investigate Crohn’s disease?

A
  1. Bloods- would show anaemia and increased CRP.
  2. CT/MRI scan, showing bowel wall thickening, obstruction and. extramural problems.
  3. Barium enema/follow through which is used less would show strictures/fistulae.
  4. Colonoscopy: gross-patholigcal changes can be seen in an endoscopy (skip lesions, cobblestone appearance, fistulae, strictures).
40
Q

What is the classic presentation of someone with Ulcerative colitis?

A 
Symptoms:
1. Frequent bloods stools, with mucusin.
2. Mild lower abdominal pain/cramping.
3. Painful red eye.
Signs:
1. Mildly tender abdomen.
2. No perianal disease.
3. Normal temperature.
41
Q

What is the microscopical appearance of UC?

A
  1. Chronic inflammatory infiltrate of the lamina propria.
  2. Crypt abscesses (neutrophilic exudate in crypts).
  3. Crypt distortion: irregular shaped glands with dysplasia and darker crowded nuclei.
  4. Reduced number of goblet cells.
42
Q

What is the gross appearance of UC?

A
  1. Pseudopolyps can develop from repeated episodes, where there is inflammation then healing which are non-neoplastic and more common in UC.
  2. Loss of haustra as inflammation reduces the appearance of haustra on imaging.
43
Q

How do you investigate UC?

A
  1. Bloods: anaemia and serum markers present.
  2. Stool cultures.
  3. Colonoscopy.
  4. Plain abdominal radiographs.
  5. Barium enema can show UC in mild cases.
  6. CT/MRI is less useful in diagnosing uncomplicated UC.
44
Q

It is hard to distinguish between UC and Crohn’s disease. What is a consequence of this?

A

10% of cases have indeterminate colitis which can seriously effect the wellbeing of a patient with this diagnosis.

45
Q

When is fibrosis more common?

A

In Crohn’s disease.

46
Q

UC or Crohn’s disease, which is associated with crypt abscesses?

A

UC.

47
Q

Which IBD has friable mucosa (contact bleeding)?

A

UC.

48
Q

Describe radiological investigations of Crohn’s disease.

A

Barium follow through- sometimes see long strictures called string sign of kantour.

49
Q

Describethe radiological features of UC.

A

In a double contrast enema there is a featureless descending and sigmoid colon which lack haustral markings, described as a lead pipe colon.
It is continuous lesions without skipping, effecting the whole colon.
Mucosal inflammation in present, causing a granular appearance.

50
Q

What are the treatment options of IBD?

A
  1. Aminosalicylates: for flares and remission.
  2. Corticosteroids: prednisolone, for flares only.
  3. Immunomodulators: for fistulas and maintenace of remission.
51
Q

What is the surgical option for Crohn’s disease?

A

Not curative with strictures/fistulas the patient may choose to have some bowel removed, as little as possible as adhesions are common.

52
Q

What is the surgical option for UC?

A

Surgery is a curable method (colectomy) if the inflammations not settling and their is precancerous changes or toxic megacolon. Can leave a little bit of distal rectum to maintain continence.

53
Q

What is megacolon?

A

Megacolon is an abnormal dilation of the colon. The dilation is often accompanied by a paralysis of the peristaltic movements of the bowel.

Gastrointestinal (10 decks)

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