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
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
3
Q
what are the functions of the submucosal (Meissner’s) plexus
A
parasympathetic
motor to muscularis mucosae
mucosal receptors
4
Q
which condition is aganglionic leading to absent peristalsis
A
Hirschprung’s disease
5
Q
how does Hirschprung’s disease present
A
early presentation of faecal impaction
diagnosed by a full thickness rectal biopsy
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
7
Q
what regulates colonic motility
A
myogenic, neurogenic and hormonal factors
8
Q
how long is normal colonic transit time
A
25-40hrs
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
10
Q
which neurotransmitters are involved in colonic motility
A
stimulatory - Ach and substance P (also used in pain sensation)
inhibitory - VIP and NO
11
Q
how does acetylcholine enhance perstaltic contraction
A
by increasing the duration of slow waves in the inner borders of circular muscles
12
Q
14 causes of constipation
A
- inadequate dietary fibre
- functional constipation (IBS/slow transit/megacolon)
- pregnancy
- colonic neoplasm
- diverticular disease
- immobility
- dehydration
- Crohn’s
- hypothyroidism
- hypercalcaemia
- pelvic mass
- Parkinson’s disease
- Hirschsprung’s
- drugs: opiates, Ca antag
13
Q
which blood tests should be performed in constipated pts
A
UEs
TFTs
14
Q
which metabolic states can cause constipation
A
hypothyroidism
hypercalcaemia
hypokalaemia
uraemia
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
16
Q
what is the autonomic actions on the internal anal sphincter
A
sympathetic excitatory
parasympathetic inhibitory
17
Q
upon rectal distension what does the internal anal sphnicter do
A
relaxes
involuntary
aids defaecation
18
Q
which nerve supplies the external anal sphincter
A
the pudendal nerve
19
Q
upon rectal distension what does the external anal sphincter
A
increases tonic contraction
20
Q
at what pressure does reflex defaecation occur
A
> 55mmHg
21
Q
what is anismus
A
failure of normal relaxation of pelvic floor during defaecation
22
Q
what is the result when sphincter tone > abdominal pressure
A
anorectal continence
23
Q
causes of incontinence
A
neonatal cerebral degenerative (autonomic neuropathy, wasting diseases) trauma (obstetric, surgical) idiopathic disease (anorectal sepsis, IBD)
24
Q
what techniques are used for examining anorectal physiology
A
manometry
balloon inflation (compliance)
pudendal nerve terminal motor latency
EMG
25
list four causes of obstructed defaecation syndrome
rectocoele
rectal intussusception
anismus
idiopathic megarectum
26
when is the peak incidence of rectocoele
forth or fifth decade
| commonly follows childbirth
27
what is rectal intussusception
folding in of rectum - preliminary stage to rectal prolapse?
28
how would rectal intussusception present
incomplete evacuation
rectal fullness/pressure
tenesmus
perineal pain
29
which demographic most commonly has idiopathic slow transit constipation
young females who present opening their bowels once every 2-3 weeks
30
name some vascular pathologies of the large bowel
```
acute ischamia (hernia strangulation, volvulus)
chronic ischaemia
```
31
how might chronic ischaemia of the bowel present
pain +/- diarrhoea
32
which area of the large bowel is often affected by chronic ischaemia
the splenic flexure
| is a water shed area between SMA and IMA
33
what happens histologically in chronic large bowel ischaemia
loss of intestinal crypts
| fibrosis of lamina propria of mucosa
34
name three bacterial infections which cause inflammation of the colonic mucosa
campylobacter
salmonella
shigella
c diff
35
what can happen following infection of c. diff in the colon
pseudomembranous colitis
36
what is the most common cause of bloody diarrhoea worldwide
infective colitis
37
what is the most common cause of bloody diarrhoea in the UK
UC
38
which viral infective pathology of the bowel causes an inflamed colon
CMV
39
which protozoal infection causes diarrhoea and blood pr common in tropics and subtropics
amoebiasis
| histologically look like macrophages and phagocytose RBCs
40
name two types of autoimmune microscopic colitis
collagenous colitis
| lymphocytic colitis
41
how might collagenous and/or lymphocytic colitis present
watery diarrhoea
| most commonly in middle aged females (M:F=1:9)
42
what is seen histologically in collagenous colitis
thickened subepithelial collagenous band > 15um
43
what is seen histologically in lymphyocytic colitis
increased numbers of lymphocytes in the epithelium
44
a young adult presents with bloody diarrhoea with mucus, malaise, anorexia and weight loss
ulcerative colitis
| affects colon and rectum - tends to be distal
45
what can happen in fulminant UC whereby ulceration involves the muscle
perforation
46
a young male presents with remitting diarrhoea and pain
crohn's
| ill defined symptoms
47
what are skip lesions
lengths of diseased bowel separated by normal bowel in Crohn's
48
what is cobblestone appearance of the bowel
longitudinal ulcers and fissures seen in Crohn's disease
49
what might be seen on microscopy in Crohn's disease
- discontinuous patchy inflammation
- transmural inflam w/ lymphoid aggregates
- fissuring ulceration
- granulomas (in 60%)
50
what pathological phenomenon may follow chronic laxative abuse
melanosis coli - pigmentation of larger bowel due to deposition of lipofuscin pigment in macrophages in the lamina propria
51
name 2 congenital pathologies of the large bowel
Hirschsprungs
| Intestinal atresia
52
how might diverticular disease of the colon present
```
pain
altered bowel habit
bleeding
perforation
obstruction
```
53
what happens in diverticular disease
herniation of mucosa through the bowel wall
| can become inflamed and lead to stricture formation
54
what effects can thyroid disease have on the colon
thyrotoxicosis - diarrhoea as increased gut motility
hypothyroidism constipation
55
how is IBS diagnosed
via exclusion
56
how might IBS present
intermittent long standing symptoms
alternating constipation and diarrhoea
abdominal pain/cramps
57
In which demographic is IBS most common
M:F = 1:4
| 20-40yrs
58
what might cause IBS
abnormal gut motility
| increased sensitivity to intestinal distension
59
what is the inheritance pattern of FAP
autosomal dominant
| most commonly due to a mutation in the APC gene
60
what is the treatment of FAP
colectomy before the age of 25
61
where is adenocarcinoma most common in the colon
rectum>sigmoid>caecum>rest of colon
62
which conditions increase the risk of adenocarcinoma of the colon
adenomas (FAP)
| UC
63
which type of malignancy is most common in the anus
squamous cell carcinoma
| shows keratinisation on histology
64
constipation can be divided into two groups, what are they
primary/functional/idiopathic:
- never learnt
- dysmotility
- mechanical
Secondary/organic:
- obstruction
- drugs
- metabolic
65
how might ods (mechanical) constipation present
```
straining
laxative/enema dependancy
incomplete evacuation
fragmented defaecation
rectal pain
perineal support/digitation
```
66
list some medications which may contribute to constipation
```
narcotics
iron supplements
non-magnesium antacids
calcium channel blockers
inadequate thyroid hormone supplementation
psychotropic drugs
anticholinergics
```
67
what are the Rome II criteria for IBS
>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
which investigation might be used to evaluate constipation
colonic transit study
if after 5 days normal
scattered rings --> hypomobility
rings gathered in rectosigmoid --> outlet obstruction
69
give three examples of bulk-forming laxatives and how do they work
```
ispaghula husk
methylcellulose
sterculia
retain fluid in stool and increase faecal mass --> stimulate peristalsis
also soften stools
```
70
give two examples of osmotic laxatives and how do they work
```
lactulose
macrogols
increase fluid in large bowel
distension leading to sitmulation of peristalsis
stool softening properties
```
71
give 3 examples of stimulant laxatives and explain how they work
senna - hydrolysed into active substrate in large bowel
bisacodyl
sodium picosulfate
stimulate colonics nerves (senna)
or
colonic and rectal nerves (bisacodyl, sodium picosulfate)
72
give 2 examples of surface wetting agents used as laxatives
docusate
poloxamer
reduce the surface tension of the stool allowing water to penetrate and soften it
73
which laxative is first line
bulk forming then osmotic
74
which three types of antispasmodics are used in the pain management of IBS
anticholinergic agents (dicyclomine, hyoscine) - smooth muscle relaxant; can aggravate constipation
antimuscarinic agents (mebeverine, alverine citrate)
peppermint oil (colpermin)
75
how much fluid is recommended to be taken per day to avoid constipation
1.5 litres (6cups)
76
what is prucalopride
selective 5HT4 R agonist
77
how to cl channel activators work
lubiprostone is a selective Cl-2 channel activator (on luminal side)
promotes water secretion into the lumen
78
constipation is a risk factor for which cancer
rectal cancer
79
which types of constipation may benefit from surgery
dysmotility
| mechanical
80
which surgeries are options for dysmotility
colectomy with ileorectal anastamosis
SNS
ACE
81
what must be excluded before colectomy
disorders of defaecation
normal small bowel motility
weak sphincters
inappropriate expectations from patient and family
82
which proceedure is performed before a colectomy
ileostomy
checks small bowl works
confirms can live with stoma if all else fails
83
what causes most polyps
most are sporadic
FAP and HNPCC (Lynch's sydrome causes 3-10% of all CRC) also associated
incidence increases with age
84
how do polyps present
rectum/sigmoid -> rectal bleeding
large villous --> profuse diarrhoea with mucus and hypokalaemia
proximal tend to be asymptomatic
85
what is the average age at diagnosis for colorectal carcinoma
60-65 yrs
86
how is CRC staged
using Duke's classification
87
which risk factors increase the likelihood of developing CRC
```
age
animal fat and red meat consumption
sugar consumption
colorectal polyps
FHx
obesity
smoking
acromegaly
abdo radiotherapy
uterosigmoidoscopy
```
88
which factors are protective for CRC
vegetable, garlic and milk intake
exercise
aspirin and other NSAIDs
89
what is the most common histology of CRC
adenocarcinomas
| signet ring cells (mucin displaces the nucleus) have a poor prognosis
90
how does CRC present
left sided -> looser more frequent stools
rectal/sigmoid --> bleeding
caecum and right --> asymptomatic until iron def anaemia develops
91
what are the most common tumours of the small intestine
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
what is Turcot's syndrome
FAP/HNPCC colon cancer with brain tumours
93
what is Gardner's syndrome
FAP desmoid tumours with osteomas ofthe skull
94
describe hamartomatous polyps
large and stalked polyps
juvenile --> autosomal dominant cause bleeding and interssusception in first decade of life
peutz-jeghers syndrome
95
which conditions can predispose for adenocarcinoma and lymphoma of the small intestine
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
which type of laxative can potentially induce uterine contractions in the third trimester of pregnancy
stimulants (senna)
97
which laxative can cause red urine
Dantron - a stimulant laxative
| licensed only for the terminally ill
98
which type of laxatives are most suitable for patients who are impacted and chronically constipated
osmotic such as lactulose, movicol or magnesium hydroxide
99
which laxative might be used for bowel evacuation prior to examinations/proceedures
picolax - sodium picosulfate with magnesium citrate
