209 - Constipation / IBS

Question 1

What is constipation?

Answer 1

Infrequent, hard, difficult to pass stooles
+/- abdo pain

Dry, hard, small, large - perceptions vary

Question 2

What are primary/functional causes for constipation?

Answer 2

Never learnt?
Dysmotility = insuficience luminal residue, abnormal neuromuscular activity
Mechanical = Obstructed defaecation syndrome, weak pelvic floor

Question 3

What are some secondary/organic causes for constipation?

Answer 3

Obstruction
Metabolic ( hypothyroid, hypercalcemia, hypokalaemia, hypopituitarism, diabetes)
Drugs (narcotics, iron, psychotropic, non-mg antacids, calcium channel blockers, ganglion blockers)

Question 4

What are some neuromuscular causes of constipation?

Answer 4

CNS disease (parkinsons, stroke, MS, spinal injury)
Hirshsprungs - lack of enteric ganglion cells

Question 5

What are the first/primary investigations you’d do in constipation?

Answer 5

Barium enema
Colonoscopy
AXR

Question 6

What further tests may you do in constipation?

Answer 6

Sigmoidoscopy
colonic transit studies
defaecating proctogram
Endoanal U/S

Question 7

What physiological testing might you do in constipation?

Answer 7

Manometry
Balloon inflation
Pudendal nerve terminal motor latency
EMG recording

Question 8

Advice is the first step in management of constipation, what advice would you give?

Answer 8

Fluid intake - 2l/day
Reduce caffine
Dietry advice - high fibre
Low alcohol
exercise
FODMAP diet?
probiotics?

Question 9

What is the order you’d try laxatives in constipation?

Answer 9

Faecal softener
Bulk-forming
Osmotic
Stimulant (with a softener!)

Question 10

How do faecal softeners work? 2 examples

Answer 10

Docusate, poloxamer combo

Reduce surface tension of stool so allow water to enter and soften it

Good for hard/painful stools

Question 11

How do bulk forming laxatives work? 1 example

Answer 11

Fybogel

Retains fluid and increases mass of stool - stimulates peristalsis

Takes 2-3 days to work

Good if stools small and hard or weak anal sphincter

Question 12

How do osmotic laxatives work? 3 examples

Answer 12

Lactulose, movicol, magnesium hydroxide

Makes hyperosmolar conditions - draws water into bowel, distension, peristalsis, softens.

Good for impaction and chronic constipation

Causes distension + lots of flatulence!

Question 13

How do stimulant laxatives work? 3 examples

Answer 13

Senna, dandtron, sodium picosulfate

Stimulates colonic/rectal nerves - peristalsis

Needs a softener with it

For short term relief, pre-op.

Question 14

What surgery could be offered as a last resort to chronic constipation due to dymotility issues?

Answer 14

Colectomy + IRA (ileorectal anastemosis) - a surgical laxative

Sacral nerve stimulation

ACE - Antegrade colonic enema - flush through stoma

Question 15

What surgery could be offered for obstructed defaecation / pelvic floor issues?

Answer 15

Try repair prolapse/rectal intussusception.
Rectoplexy (sling around rectal prolapse)
Perineal approach (prolapse)
Transperineal surgery + rectocoel repair
Ventral rectoplexy

Question 16

What is IBS?

Answer 16

Irritable bowel syndrome

Recurrent periods of abdo pain/discomfort assoc with:
- improvement with defecation
Change in freq. of stooles
Change in form of stooles

Question 17

Do you get constipation in IBS?

Answer 17

Can be diarrhoea dominant or constipation dominant or a mix of both

Question 18

What are the management options for IBS?

Answer 18

Antispasmodics
Psychological therapy
Antidiarrhoeal drugs
Peppermint oil eg. colpermin

Question 19

What antispasmodics can be used in IBS?

Answer 19

Smooth muscle relaxants (anticholinergics)

Antimuscarinic agents eg. Meberverine

Question 20

Why can antidepressants help with IBS?

Answer 20

Due to their side effect profile/anticholinergic effect
If diarrhoea a problem - tricyclic
If constipation a prob - SSRI

Question 21

What are some new agents that are being used in constipation management?

Answer 21

Selective Serotonin 5HT4 receptor agonists - stimulates serotonin - facilitates peristalsis eg. prucalopride

Selective type 2 chloride channel activator therapy - increases water secretion into lumen

Question 22

What are the 2 nerve plexi that are in the bowel wall?

Answer 22

Myenteric (outer one)
Submucosal (closest to lumen)

Between circular and longitudinal muscle

Question 23

How is gut motility controlled?

Answer 23

By myogenic, neurogenic and hormonal factors

Question 24

Describe the gut’s motility in the proximal colon

Answer 24

Most contractions here

• Non propulsive segmentation - slow, wave, mixes contents, haustra formed as circular muscles contract
• Mass peristalsis - 1-3 times a day, simultaneous SM contractions over large areas, distally propels contents

Question 25

Describe the gut’s motility in the distal colon

Answer 25

Mainly non propulsive segmentation

Question 26

What controls gut motility?

Answer 26

Intramural plexi have direct control, extramural plexi modulate it

• stimulatory - acetylycholine + substance P
• Inhibitory - VIP + nitric oxide

Question 27

Which neurotransmitters are involved in stimulatory control of the gut?

Answer 27

Acetylcholine

Substance P

Question 28

Which neurotransmitters are involved in inhibitory control of the gut?

Answer 28

VIP (vasoactive intestinal polypeptide)

Nitric Oxide

Question 29

The circular muscle layer of the Colon has 2 ways of functioning. What type of activity do the interstitial cells on the outer border make?

Answer 29

Produce myenteric oscillations of low amplitude and high freq - for viscous distension and flatus passage

Question 30

The circular muscle layer of the Colon has 2 ways of functioning. What type of activity do the interstitial cells on the INNER border make?

Answer 30

Produce regular flow waves - 3cycles/min
High amplitude, low freq
for defaecation

Question 31

What is the gastro-ileal reflex?

Answer 31

When food leaves the stomach it causes the caecum and ileocoecal valve to relax

Question 32

What is the delayed gastro-colic reflex?

Answer 32

Gastric distension -> desire to defacate 70-180 minutes later.

Question 33

What in the duodenum increases gut stimulation?

Answer 33

Fat

Question 34

Describe the steps of defaecation

Answer 34

1) cortical perception of filling
2) Voluntary decision taken
3) Straining
4) reduced tone of pelvic floor and sphincter muscles
5) reduced anorectal angle
6) Increased tone of abdo muscles
7) Passage of stool

Question 35

What is the normal colonic transit time?

Answer 35

24-48 hrs

Question 36

The anus has 2 sphincters, what are they? What type of muscle makes up each?

Answer 36

Internal involuntary sphincter - circular muscle

External voluntary sphincter - striated muscle

Question 37

What part of the NS controls the internal anal sphincter?

Answer 37

Autonomic - symp = excitatory/sphincter closed

Question 38

What is sampling? (done by the internal anal sphincter)

Answer 38

Senses whether the contents is gas or solid - if gas, allows slight relaxation for gas to pass

Question 39

What nerve innovates the external anal sphincter?

Answer 39

Pudendal nerve

Question 40

When there is rectal distension, what occurs to both the internal and external anal sphincter?

Answer 40

Internal - involuntary relaxation

External - tonic contraction is increased

Question 41

How is anorectal continence achieved?

Answer 41

Sphincter tone > abdo pressure

• requires:
• Central control
• Functioning reservoir
• Strong pelvic floor
• Intact sphincters
• Absence of peripheral neuropathy

Question 42

What imaging modalities could be used in imaging the colon?

Answer 42

U/S + endoanal U/S
Barium enema
CT
MRI
CT colonography
Colonscopy

Question 43

What is the apple core sign in radiology?

Answer 43

Classic appearance of colon cancer - leaves apple core shape of colon, with shouldering