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YEAR 2: CSI > Crohn's disease > Flashcards

Crohn's disease Flashcards

1
Q

What is diarrhoea clinically defined as?

A

· Three or more loose or liquid stools per 24 hours, and/or
· Stools that are more frequent than what is normal for the individual lasting <14 days, and/or
· Stool weight greater than 200 g/day.

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2
Q

How can diarrhoea be classified?

A

By duration

  • Acute (≤14 days)
  • Persistent (>14 days)
  • Chronic (>4 weeks)
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3
Q

What are the 2 main categories of diarrhoea?

A
  • Inflammatory

- Non-inflammatory

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4
Q

What are the symptoms of inflammatory diarrhoea?

A

In inflammatory:

  • mucoid + blood in stool
  • fever
  • tenesmus (due to irritation in bowel)
  • severe crampy abdominal pain
  • abnormal histology
  • faeces small in volume
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5
Q

What is tenesmus?

A

The feeling that you need to pass stools, even though your bowels are already empty

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6
Q

What is the stool mucoid in inflammatory diarrhoea?

A
  • Increased mucus secretion due to increased goblet cells in LI
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7
Q

What causes inflammatory diarrhoea (infectious + non-infectious)?

A

Infectious

  • bacterial infection (Campylobacter, Salmonella, Shigella, Escherichia coli, or Clostridium difficile)
  • viral infection
  • parasitic infection

Non- infectious

  • bowel ischaemia
  • radiation injury
  • inflammatory bowel disease
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8
Q

What tests are done to confirm inflammatory diarrhoea?

A
  • FBC: anaemia, high ESR, high CRP
  • LFT: low albumin is marker of inflammation
  • Faecal calprotectin: non-specific marker of inflammation
  • stool examination (microbiology, ova and cyst checks)
  • Faecal occult blood test (which looks for blood in the faeces)
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9
Q

What is non-inflammatory diarrhoea?

A

Diarrhoea which is not driven by inflammation.

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10
Q

What are the 2 types of non-inflammatory diarrhoea?

A
  • Secretory

- Osmotic

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11
Q

What is secretory diarrhoea?

A

An altered transport of ions across the mucosa, which results in….

  • increased secretion as electrolytes enter via tight junctions
  • decreased absorption of fluids and electrolytes from the GI tract, especially in the small intestine.
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12
Q

What are the causes of secretory diarrhoea?

A

□ Enterotoxins, especially cholera toxin ( but also Staphylococcus aureus, enterotoxigenic E coli, and possibly HIV and rotavirus)
□ Hormonal agents (vaso-active intestinal peptide, small-cell cancer of the lung, and neuroblastoma)
□ Laxative use
□ Intestinal resection
□ Bile salts and fatty acids

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13
Q

What other conditions are associated with secretory diarrhoea?

A
  • coeliac disease
  • collagenous colitis
  • hyperthyroidism
  • carcinoid tumours
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14
Q

What are the symptoms of secretory diarrhoea?

A

○ watery, large-volume, frequent stool (>10 to 20 per day).

○ Histology of GI tract is preserved

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15
Q

Why is secretory diarrhoea so dangerous?

A

Huge volume depletion due to the high volume and frequency of bowel movements.

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16
Q

What is osmotic diarrhoea?

A

Presence of unabsorbed or poorly absorbed solute (magnesium, sorbitol, and mannitol) in the intestinal tract which causes an increased secretion of liquids into the gut lumen.

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17
Q

What are the 2 types of osmotic diarrhoea?

A
  1. Maldigestion

2. Malabsorption

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18
Q

What is maldigestion?

A

Impaired digestion of nutrients within the intestinal lumen/ at the brush border membrane.
- this is due to enzyme deficiency

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19
Q

What are some conditions that cause maldigestion?

A
  • pancreatic exocrine insufficiency

- lactase deficiency (lactose therefore remains in the bowels and can actually act as a sponge, drawing water in)

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20
Q

What is malabsorption?

A

Impaired absorption of nutrients -> bowel mechanisms impaired

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21
Q

What can cause malabsorption?

A
  • Foods containing sorbitol (which is found in laxatives)

- surgical resection

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22
Q

What are the symptoms of osmotic diarrhoea?

A

○ Stool volume is relatively small
○ Improves/stops with fasting
○ Stool electrolytes shows increased osmotic gap

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23
Q

In a healthy person, what happens when the gut is empty?

A
  • Na+ enters lumen from blood
  • Cl- enters lumen from blood
  • Water osmoses into the intestines to keep in moist
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24
Q

What is the mechanism behind inflammatory diarrhoea?

A

Low absorption due to inflammation (incl. cytokines) caused by destruction of enterocytes.

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25
Q

How can inflammatory diarrhoea be treated?

A

Anti-inflammatories

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26
Q

What is the main limitation of using oral anti-inflammatories?

A

The drug can be absorbed into the blood while in the GI tract which may cause side effects elsewhere.

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27
Q

How does cholera toxin cause secretory diarrhoea?

A

It activates Cl- and Na+ channels so they enter the intestinal lumen and sets off water cascade.

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28
Q

What are some specific drugs that can be used to treat secretory diarrhoea?

A

Inhibitors of

  • Cl- channel
  • cyclic AMP channel
  • Ca2+ channel
  • SGLT-1 (Na+/Glucose transporters) ==> ORS
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29
Q

What is ORS?

A

Oral rehydration salts -> used to treat acute diarrhoea by giving bolus Na+ and glucose -> it causes water to flood the GI tract.

30
Q

What are the disadvantages of using these channel inhibitors?

A

These channels are also found in other parts of the body (incl heart) so side effects are probable.

31
Q

How can maldigestion be treated?

A

Enzyme addition

Probiotics

32
Q

What is the main limitation of adding enzymes?

A

Enzymes are likely to be metabolised before reaching SI.

33
Q

What is serum osmolar gap?

A

Total osmolarity of blood - conc of Na+/K+/Glucose

34
Q

What is the gap in healthy individuals?

A

<10
Gap is small because Na+/K+/ Glucose mainly contribute to osmolarity.
If the gap is too big, it suggests metabolic derangement.

35
Q

Compare the osmolarity of blood and faeces.

A

It is the same (~290)

36
Q

How is the faecal osmolar gap calculated?

A

Total osmolarity of faeces - conc of Na+/K+/Glucose

37
Q

What is the faecal osmolar gap in healthy individuals?

A

50-100

38
Q

Why is it bigger than the serum osmolar gap?

A

Faeces contain more than just Na+/K+/Glucose -> there are other ions that contribute to the osmolarity.

39
Q

What does a faecal osmolar gap <50 suggest?

A

Secretory diarrhoea -> Na+ are pumped into intestines by damaged enterocytes.

40
Q

What does a faecal osmolar gap >100 suggest?

A

Osmotic diarrhoea -> due to malabsorption, more solutes remain in the GI tract/ enter the faeces -> they make bigger contributions to the faecal osmolarity.

41
Q

What is the difference between IBS and IBD?

A

Irritable Bowel syndrome (IBS) -> functional condition (not a disease/ no inflammation) which is only diagnosed through exclusion of differentials.

Inflammatory Bowel Disease -> organic disease which can cause destructive, chronic inflammation + permanent harm. It is associated with an increased risk of bowel cancer.

42
Q

Describe the main symptoms of IBD.

A
  • weight loss
  • fever
  • blood in stool
43
Q

Describe the main symptoms of IBS.

A
  • alternating constipation/ diarrhoea
  • mucus in stool
  • bloating
44
Q

What symptoms do both conditions share?

A
  • abdominal pain
  • faecal urgency
  • fatigue
  • diarrhoea
45
Q

What 2 conditions make up IBD?

A
  • Crohn’s disease (more pathogen based)

- Ulcerative collitis (more autoimmune based)

46
Q

Describe the relationship between genes and IBD.

A

You need to be genetically predisposed to get IBD.

47
Q

What is Crohn’s disease?

A

Chronic inflammatory disease that can affect any part of the GI tract.

48
Q

What is Ulcerative Collitis?

A

Chronic inflammation and sores (ulcers) along the superficial lining of your large intestine (colon) and rectum.

49
Q

What are some risk factors for Crohn’s?

A
  • smoking
  • NSAIDs (naproxen, indomethacin)
  • family history
50
Q

What are the differences between Crohn’s and UC? Gut layer

A

Crohn’s: transmural (goes through all layers)

UC: mucosa

51
Q

What are the differences between Crohn’s and UC? regions

A

Crohn’s: affects entire GI tract

UC: limited to colon

52
Q

What are the differences between Crohn’s and UC? pattern

A

Crohn’s: cobblestone, fistulas, creeping fat

UC: pseudopolyps (benign)

53
Q

What are the differences between Crohn’s and UC? macroscopic findings

A

Crohn’s: non- continuous areas of ulcers

UC: continuous ulcers

54
Q

What are the differences between Crohn’s and UC? microscopic findings

A

Crohn’s: non-caseating granulomas (clumps of immune cells) ,increased goblet cells
UC: crypt abscesses

55
Q

What are the 5 layers of GI tract?

A
  1. Mucosa
  2. Submucosa
  3. Muscularis propia
  4. Serosa/ Adventitia
56
Q

How does Crohn’s disease increase risk of fistulas?

A

Fistulas -> abnormal passageway that connects 2 organs.

Because inflammation is transmural, it is more likely to create a passageway.

57
Q

What is the main immune cell involved in UC?

A

Neutrophils

58
Q

What is the main immune cell involved in Crohn’s?

A

Macrophages

59
Q

What are major acute red flag symptoms for diarrhoea?

A
  • unexplained weight loss
  • unexplained rectal bleeding
  • dehydration, low CO2, low BP, shock
60
Q

What are major acute red flag symptoms for chronic diarrhoea?

A
  • PR bleeding
  • Unexplained weight loss
  • Anaemia
  • Abdominal/ rectal mass
  • FHx of Bowel cancer -> should be referred via 2 week wait pathway
61
Q

What are some bed side tests that can be conducted when investigating diarrhoea?

A
  • NEWS2

- Urine tests

62
Q

What are some blood tests that can be conducted when investigating diarrhoea?

A
  • FBC
  • LFT
  • TFT (hyperthyroidism can increase gut motility)
  • ferritin/ B12/ folate
  • Coeliac serology (IgA antibody testing)
63
Q

What are some stool tests that can be conducted when investigating diarrhoea?

A
  • Microbiology
  • Ova and cyst parasitic test
  • Faecal calprotectin (sign of neutrophil migration into intestinal lumen)
64
Q

What is some imaging that can be carried out when investigating diarrhoea?

A
  • colonoscopy with biopsy
  • CT/MRI
  • Ultrasound
65
Q

How can Crohn’s be treated medically?

A
  • chronic steroids like Budesonide + Prednisolone
  • immuno-suppressants (e.g. Azathioprine, Mercaptopurine, Methotrexate)
  • pain relief
  • NSAIDs (fewer side effects than steroids but less effacious)
  • Monoclonal antibodies (TNF alpha inhibitors like Adalimumab, Infliximab, Vedolizumab
    Ustekinumab)
66
Q

What are the side effects of using chronic steroids?

A

Weight gain + Cushing’s disease

67
Q

How do immunosuppressants work?

A

Interfere with DNA synthesis in WBCs -> should use intermittently to allow WBCs to recover

68
Q

How can Crohn’s be treated surgically?

A

Resection/ Keyhole surgery

  1. Making small cuts in your tummy (keyhole surgery).
  2. Removing a small inflamed section of bowel.
  3. Stitching the healthy parts of bowel together.

Surgery is a last resort intervention if perforation of bowel is seen. Usually, this doesn’t cure the disease because Crohn’s can occur anywhere in the GI tract. Resection would work for UC.

69
Q

Why is an ileostomy usually needed after resection surgery?

A

SI is diverted through an opening in the abdomen (stoma) so your stools pass into a disposable bag -> this is to let the bowels recover after surgery.

70
Q

What are some non-medical interventions that can help reduce inflammation?

A
  • stopping smoking
  • fibre diet
  • liquid diet
  • trying to avoid triggers
71
Q

What are the less common symptoms of Crohns?

A
  • a high temperature
  • feeling and being sick
  • joint pains
  • sore, red eyes
  • patches of painful, red and swollen skin– usually on the legs
  • mouth (aphtha) ulcers

YEAR 2: CSI (8 decks)

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