Physiology: motility disorders

Question 1

Constipation: what is it?

Answer 1

Infrequent passage of stools (less than 3 a week)
Passage of hard stools
Straining (more than 25% of the time)
Incomplete evacuation/sense of incomplete emptying

Question 2

Causes of constipation:
- Lifestyle: can inadequate fibre intake, dehydration cause it and immobility/sedentary lifestyle cause it?
- Drugs: can opiates, central calcium channel blockers, and anti muscarinic cause it?
- Psychological: can depression and anorexia nervosa cause it?
- Diseases: can diabetes, hypocalcemia and hypothyroidism cause it?
- Neurological: can spinal cord lesions and Parksinsons cause it?
- GI disease: can IBS, construction, cancer, aganglionosis (Hirschprung’s) cause it?
- Defectatory disorders: can rectal prolapse, pelvic floor dyssynergia (failure to relax) cause it?
- Can it occur post surgery?

Answer 2

Yes to all

Question 3

Causes of constipation
- How can pregancy lead to constipation?

Answer 3

Many pregnancy hormoens can cause GIT relaxation
Baby can press against GIT, causing constipation

Question 4

What are 3 complications of constipatoin?

Answer 4

Fecal impaction
Risk of anal fissure
Straining can cause hemorrhoids, which can bleed out

Question 5

How to treat constipation?

Answer 5

Laxatives
Manual evacuation (eg. enemas)

Question 6

Hirschsprung’s disease:
- What is its cause?
- How does it lead to constipation?

Answer 6

Neural crest cells fail to migrate to the distal colon - leading to an aganglionic segment of the distal colon.

Means that parasympathetic innervation is lost in the distal colon. Fails to relax –> contracts. Fecal matter accumulates proximally –> contractions

Question 7

Hirschsprung’s disease:
- Diagnosis?
- Treatment

Answer 7

Biopsy, stained for ganglionic cells and acetylcholinesterase (elevated in Hirschsprung’s)
Surgical removal of the aganglionic section

Question 8

Diarrhoea: 3 causes? What can cause it?

Answer 8

Drugs
Radiation therapy
Laxatives
Enteritis (viral or bacterial (food))
Nervous tension (excessive stimulation of the PNS)
Ulcerative colitis

Question 9

Diarrhoea: 4 mechanisms?

Answer 9

Osmotic
Secretory
Inflammatory
Abnormal motility

Question 10

Diarrhoea: treatments?

Answer 10

Treat underlying cause
- Anti infective agents
Fluid and electrolyte replacement - to treat dehydration
Anti diarrhoeal agents

Question 11

How can glucose drinks help treat diarrhoea

Answer 11

In the ileum, sodium and glucose are cotransported.
So, glucose drinks can enhance sodium (and thus water) absorption

Question 12

What is dysphagia

Answer 12

Difficulty swallowing
Sensation of obstruction during the passage of liquid or solid through the pharynx or oesophagus

Question 13

Causes of dysphagia:
- Can tonsillitis cause?
- Can goitre cause?
- Can intrinsic lesions (eg. outpoutching of pharynx and oesophagus) cause?
- Can neuromuscular disorders (eg. involving impaired innervation of the oesophagus) cause?
- Can oesophageal motility disorders cause?

Answer 13

Yes

Question 14

Dysphagia:
- Treatments

Answer 14

Treat the underlying cause
If due to structural abnormality, do surgery.

Question 15

Achalasia:
- Is it a type of dysphagia?
- What causes it?

Answer 15

Yes
Degeneration of neural network of the myenteric plexus –> lower sphincter doesn’t relax during swallowing

Question 16

Achalasia: what do we see in oesophageal manometry?

Answer 16

No drop in lower oesophageal pressure after swallowing - it doesn’t relax

Question 17

Achalasia:
- Treatments?

Answer 17

Endoscopic dilation of the sphincter with balloon (weaknes the sphincter)
Endoscopic injection of botox (short term results)
Surgery (removing the circular muscle of the sphincter)

Question 18

Gastroparesis:
- What GI organ does it affect?
- What is it

Answer 18

The stomach
Poor/loss of propulsive motility, leading to delayed gastric emptying

Question 19

Gastroparesis:
- What often causes it?

Answer 19

commonly due to diabetic autonomic neuropathy (BV damage leads to nerve damage)

Question 20

Gastroparesis:
- Treatments?

Answer 20

Liquefied/pureed diet, smaller and more frequent meals
Medications to stimulate motility
Botox on pyloric sphincter (relaxes)

Question 21

Vomiting
- Is it a motility disorder?
- Why does it occur?
- What is the first trigger?

Answer 21

No - a protective reflex
Remove toxic materials from the GI tract before they are absorbed
Excessive distension/irritation of the duodenum

Question 22

Vomiting:
- What factors can trigger it?

Answer 22

• Chemicals in blood
• Pain
• Touching back of pharynx (gagging)
• Disturbed equilibrium (eg. car and sea sickness)
• Higher centres of the brain (cortex - sight or smell of something gross)

Question 23

Vomiting:
- Where are inputs sent to in the brain

Answer 23

Vomiting centre in the medulla

Question 24

Vomiting: what are the outputs

Answer 24

Wave of reverse peristalsis beginning in teh small intestine
Relaxation of lower oesophageal sphincter
Strong downwards contraction of the diaphragm, contraction of abdominal muscles (increases intra abdominal pressure)
PNS: excessive salivation
Initial deep breath, then respiration is inhibited - epiglottis and soft palate close off trachea to prevent aspiration

Question 25

Vomiting:
- Why are patients required to fast for ~6 hours before surgery?

Answer 25

Vomiting and swallowing reflexes are paralysed during deep anaesthesia - aspiration