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Nutrition > Constipation And IBS > Flashcards

Constipation And IBS Flashcards

1
Q

what are 3 functions of the large bowel

A

1) modification storage and evacuation of waste
2) extraction of water and electorlytes from ileal contents
3) maintenance of bacterial flora and absorption of nutrients from bacterial degradation of luminal contents

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2
Q

what are the functions of the myenteric (Auerbach’s) plexus

A

sympathetic and parasympathetic nervous systems
motor to longitudinal and circular muscles
secretomotor to mucosa

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3
Q

what are the functions of the submucosal (Meissner’s) plexus

A

parasympathetic
motor to muscularis mucosae
mucosal receptors

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4
Q

which condition is aganglionic leading to absent peristalsis

A

Hirschprung’s disease

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5
Q

how does Hirschprung’s disease present

A

early presentation of faecal impaction

diagnosed by a full thickness rectal biopsy

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6
Q

how can the colon be divided functionally

A

proximal: ascending and transverse –> fluids/electrolytes and bacterial fermentation
Distal: distal and recto-sigmoid –> reservoir function

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7
Q

what regulates colonic motility

A

myogenic, neurogenic and hormonal factors

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8
Q

how long is normal colonic transit time

A

25-40hrs

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9
Q

how does colonic motility differ between the proximal and distal colon

A

PROX:

  • non-propulsive segmentation - slow wave activity circular contraction
  • mass peristalsis 1-3x day

DIST:
- non-propulsive segmentation - annular/segmental contraction

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10
Q

which neurotransmitters are involved in colonic motility

A

stimulatory - Ach and substance P (also used in pain sensation)

inhibitory - VIP and NO

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11
Q

how does acetylcholine enhance perstaltic contraction

A

by increasing the duration of slow waves in the inner borders of circular muscles

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12
Q

14 causes of constipation

A
  1. inadequate dietary fibre
  2. functional constipation (IBS/slow transit/megacolon)
  3. pregnancy
  4. colonic neoplasm
  5. diverticular disease
  6. immobility
  7. dehydration
  8. Crohn’s
  9. hypothyroidism
  10. hypercalcaemia
  11. pelvic mass
  12. Parkinson’s disease
  13. Hirschsprung’s
  14. drugs: opiates, Ca antag
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13
Q

which blood tests should be performed in constipated pts

A

UEs

TFTs

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14
Q

which metabolic states can cause constipation

A

hypothyroidism
hypercalcaemia
hypokalaemia
uraemia

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15
Q

what is the gastro-colic reflex

A

gastric distention leads to desire to defaecate 70-180 minutes after the meal –> probably mediated via gastrin

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16
Q

what is the autonomic actions on the internal anal sphincter

A

sympathetic excitatory

parasympathetic inhibitory

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17
Q

upon rectal distension what does the internal anal sphnicter do

A

relaxes
involuntary
aids defaecation

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18
Q

which nerve supplies the external anal sphincter

A

the pudendal nerve

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19
Q

upon rectal distension what does the external anal sphincter

A

increases tonic contraction

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20
Q

at what pressure does reflex defaecation occur

A

> 55mmHg

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21
Q

what is anismus

A

failure of normal relaxation of pelvic floor during defaecation

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22
Q

what is the result when sphincter tone > abdominal pressure

A

anorectal continence

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23
Q

causes of incontinence

A 
neonatal
cerebral
degenerative (autonomic neuropathy, wasting diseases)
trauma (obstetric, surgical)
idiopathic
disease (anorectal sepsis, IBD)
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24
Q

what techniques are used for examining anorectal physiology

A

manometry
balloon inflation (compliance)
pudendal nerve terminal motor latency
EMG

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25
Q

list four causes of obstructed defaecation syndrome

A

rectocoele
rectal intussusception
anismus
idiopathic megarectum

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26
Q

when is the peak incidence of rectocoele

A

forth or fifth decade

commonly follows childbirth

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27
Q

what is rectal intussusception

A

folding in of rectum - preliminary stage to rectal prolapse?

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28
Q

how would rectal intussusception present

A

incomplete evacuation
rectal fullness/pressure
tenesmus
perineal pain

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29
Q

which demographic most commonly has idiopathic slow transit constipation

A

young females who present opening their bowels once every 2-3 weeks

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30
Q

name some vascular pathologies of the large bowel

A 
acute ischamia (hernia strangulation, volvulus)
chronic ischaemia
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31
Q

how might chronic ischaemia of the bowel present

A

pain +/- diarrhoea

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32
Q

which area of the large bowel is often affected by chronic ischaemia

A

the splenic flexure

is a water shed area between SMA and IMA

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33
Q

what happens histologically in chronic large bowel ischaemia

A

loss of intestinal crypts

fibrosis of lamina propria of mucosa

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34
Q

name three bacterial infections which cause inflammation of the colonic mucosa

A

campylobacter
salmonella
shigella
c diff

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35
Q

what can happen following infection of c. diff in the colon

A

pseudomembranous colitis

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36
Q

what is the most common cause of bloody diarrhoea worldwide

A

infective colitis

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37
Q

what is the most common cause of bloody diarrhoea in the UK

A

UC

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38
Q

which viral infective pathology of the bowel causes an inflamed colon

A

CMV

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39
Q

which protozoal infection causes diarrhoea and blood pr common in tropics and subtropics

A

amoebiasis

histologically look like macrophages and phagocytose RBCs

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40
Q

name two types of autoimmune microscopic colitis

A

collagenous colitis

lymphocytic colitis

41
Q

how might collagenous and/or lymphocytic colitis present

A

watery diarrhoea

most commonly in middle aged females (M:F=1:9)

42
Q

what is seen histologically in collagenous colitis

A

thickened subepithelial collagenous band > 15um

43
Q

what is seen histologically in lymphyocytic colitis

A

increased numbers of lymphocytes in the epithelium

44
Q

a young adult presents with bloody diarrhoea with mucus, malaise, anorexia and weight loss

A

ulcerative colitis

affects colon and rectum - tends to be distal

45
Q

what can happen in fulminant UC whereby ulceration involves the muscle

A

perforation

46
Q

a young male presents with remitting diarrhoea and pain

A

crohn’s

ill defined symptoms

47
Q

what are skip lesions

A

lengths of diseased bowel separated by normal bowel in Crohn’s

48
Q

what is cobblestone appearance of the bowel

A

longitudinal ulcers and fissures seen in Crohn’s disease

49
Q

what might be seen on microscopy in Crohn’s disease

A
  • discontinuous patchy inflammation
  • transmural inflam w/ lymphoid aggregates
  • fissuring ulceration
  • granulomas (in 60%)
50
Q

what pathological phenomenon may follow chronic laxative abuse

A

melanosis coli - pigmentation of larger bowel due to deposition of lipofuscin pigment in macrophages in the lamina propria

51
Q

name 2 congenital pathologies of the large bowel

A

Hirschsprungs

Intestinal atresia

52
Q

how might diverticular disease of the colon present

A 
pain
altered bowel habit
bleeding
perforation
obstruction
53
Q

what happens in diverticular disease

A

herniation of mucosa through the bowel wall

can become inflamed and lead to stricture formation

54
Q

what effects can thyroid disease have on the colon

A

thyrotoxicosis - diarrhoea as increased gut motility

hypothyroidism constipation

55
Q

how is IBS diagnosed

A

via exclusion

56
Q

how might IBS present

A

intermittent long standing symptoms
alternating constipation and diarrhoea
abdominal pain/cramps

57
Q

In which demographic is IBS most common

A

M:F = 1:4

20-40yrs

58
Q

what might cause IBS

A

abnormal gut motility

increased sensitivity to intestinal distension

59
Q

what is the inheritance pattern of FAP

A

autosomal dominant

most commonly due to a mutation in the APC gene

60
Q

what is the treatment of FAP

A

colectomy before the age of 25

61
Q

where is adenocarcinoma most common in the colon

A

rectum>sigmoid>caecum>rest of colon

62
Q

which conditions increase the risk of adenocarcinoma of the colon

A

adenomas (FAP)

UC

63
Q

which type of malignancy is most common in the anus

A

squamous cell carcinoma

shows keratinisation on histology

64
Q

constipation can be divided into two groups, what are they

A

primary/functional/idiopathic:

  • never learnt
  • dysmotility
  • mechanical

Secondary/organic:

  • obstruction
  • drugs
  • metabolic
65
Q

how might ods (mechanical) constipation present

A 
straining
laxative/enema dependancy
incomplete evacuation
fragmented defaecation
rectal pain
perineal support/digitation
66
Q

list some medications which may contribute to constipation

A 
narcotics
iron supplements
non-magnesium antacids
calcium channel blockers
inadequate thyroid hormone supplementation
psychotropic drugs
anticholinergics
67
Q

what are the Rome II criteria for IBS

A

> 12 wks in the past 12 months of abdo pain/discomfort with 2 of 3:

  • relieved with defaecation
  • and/or change in stool frequency
  • and/or change in stool form
68
Q

which investigation might be used to evaluate constipation

A

colonic transit study
if after 5 days normal
scattered rings –> hypomobility
rings gathered in rectosigmoid –> outlet obstruction

69
Q

give three examples of bulk-forming laxatives and how do they work

A 
ispaghula husk
methylcellulose
sterculia
retain fluid in stool and increase faecal mass --> stimulate peristalsis
also soften stools
70
Q

give two examples of osmotic laxatives and how do they work

A 
lactulose
macrogols
increase fluid in large bowel
distension leading to sitmulation of peristalsis
stool softening properties
71
Q

give 3 examples of stimulant laxatives and explain how they work

A

senna - hydrolysed into active substrate in large bowel
bisacodyl
sodium picosulfate
stimulate colonics nerves (senna)
or
colonic and rectal nerves (bisacodyl, sodium picosulfate)

72
Q

give 2 examples of surface wetting agents used as laxatives

A

docusate
poloxamer
reduce the surface tension of the stool allowing water to penetrate and soften it

73
Q

which laxative is first line

A

bulk forming then osmotic

74
Q

which three types of antispasmodics are used in the pain management of IBS

A

anticholinergic agents (dicyclomine, hyoscine) - smooth muscle relaxant; can aggravate constipation

antimuscarinic agents (mebeverine, alverine citrate)

peppermint oil (colpermin)

75
Q

how much fluid is recommended to be taken per day to avoid constipation

A

1.5 litres (6cups)

76
Q

what is prucalopride

A

selective 5HT4 R agonist

77
Q

how to cl channel activators work

A

lubiprostone is a selective Cl-2 channel activator (on luminal side)
promotes water secretion into the lumen

78
Q

constipation is a risk factor for which cancer

A

rectal cancer

79
Q

which types of constipation may benefit from surgery

A

dysmotility

mechanical

80
Q

which surgeries are options for dysmotility

A

colectomy with ileorectal anastamosis
SNS
ACE

81
Q

what must be excluded before colectomy

A

disorders of defaecation
normal small bowel motility
weak sphincters
inappropriate expectations from patient and family

82
Q

which proceedure is performed before a colectomy

A

ileostomy
checks small bowl works
confirms can live with stoma if all else fails

83
Q

what causes most polyps

A

most are sporadic
FAP and HNPCC (Lynch’s sydrome causes 3-10% of all CRC) also associated
incidence increases with age

84
Q

how do polyps present

A

rectum/sigmoid -> rectal bleeding
large villous –> profuse diarrhoea with mucus and hypokalaemia
proximal tend to be asymptomatic

85
Q

what is the average age at diagnosis for colorectal carcinoma

A

60-65 yrs

86
Q

how is CRC staged

A

using Duke’s classification

87
Q

which risk factors increase the likelihood of developing CRC

A 
age
animal fat and red meat consumption
sugar consumption
colorectal polyps
FHx
obesity
smoking
acromegaly
abdo radiotherapy
uterosigmoidoscopy
88
Q

which factors are protective for CRC

A

vegetable, garlic and milk intake
exercise
aspirin and other NSAIDs

89
Q

what is the most common histology of CRC

A

adenocarcinomas

signet ring cells (mucin displaces the nucleus) have a poor prognosis

90
Q

how does CRC present

A

left sided -> looser more frequent stools
rectal/sigmoid –> bleeding
caecum and right –> asymptomatic until iron def anaemia develops

91
Q

what are the most common tumours of the small intestine

A

50% adenocarcinomas
lymphomas - in developed countries B cell type from MALT and are distal, proximal Tcell and are ulcerated plaques or strictures
tumour similar to Burkitt’s lymphoma commonly affects terminal ileum of children in north africa and middle east

92
Q

what is Turcot’s syndrome

A

FAP/HNPCC colon cancer with brain tumours

93
Q

what is Gardner’s syndrome

A

FAP desmoid tumours with osteomas ofthe skull

94
Q

describe hamartomatous polyps

A

large and stalked polyps
juvenile –> autosomal dominant cause bleeding and interssusception in first decade of life
peutz-jeghers syndrome

95
Q

which conditions can predispose for adenocarcinoma and lymphoma of the small intestine

A

coeliac -> T cell lymphoma and adenocarcinoma (gluten free diet decreases risk)

Crohn’s -> small inc in adenocarcinoma in small bowel

Immunoproliferative small intestinal disease –> B cell disorder, most commonly found in countries surrounding Mediterranean. Presents as malabsorptive syndrome with diffuse lymphoid infiltration

96
Q

which type of laxative can potentially induce uterine contractions in the third trimester of pregnancy

A

stimulants (senna)

97
Q

which laxative can cause red urine

A

Dantron - a stimulant laxative

licensed only for the terminally ill

98
Q

which type of laxatives are most suitable for patients who are impacted and chronically constipated

A

osmotic such as lactulose, movicol or magnesium hydroxide

99
Q

which laxative might be used for bowel evacuation prior to examinations/proceedures

A

picolax - sodium picosulfate with magnesium citrate

Nutrition (11 decks)

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