Flashcards in Week 209 - Constipation/IBS Deck (34)
Week 209 - Constipation/IBS: How much water on average does the colon absorb?
Converts 2l into 200ml
Week 209 - Constipation/IBS: The colon can be divided into two main parts, the proximal and distal, what is the function of each?
• Proximal - absorbs fluids/electrolytes, bacterial fermentation.
• Distal - reservoir.
Week 209 - Constipation/IBS: What is the normal colonic transit time?
Week 209 - Constipation/IBS: What are the two types of motility that occur in the proximal colon?
• Non-propulsive segmentation - generated by slow-wave activity which produces circular muscle contraction - mixing/absorption of contents.
• Mass peristalsis - (1-3x/day) simultaneous smooth muscle contraction propels contents.
Week 209 - Constipation/IBS: What are the three controlling factors of colonic motility?
• Intramural plexi - directly controls contractile behaviour.
• Extramural - modulate function.
• Transmitters - Stimulatory - Acetycholine and substance P. Inhibitory - VIP and Nitric Oxide.
Week 209 - Constipation/IBS: What is the definition of constipation?
• Infrequent passage of small amount of faecaes, leading to symptoms.
• Is not the same as obstructed defaecation.
Week 209 - Constipation/IBS: What are the main two mechanisms for constipation?
• Luminal residue insufficiency.
• Abnormalities of neuromuscular activity.
Week 209 - Constipation/IBS: What are the causes of chronic constipation?
• Purgative abuse
• Idiopathic bowel disease (IBS, slow transit, mega-colon)
• Metabolic (Hypothyroidism, hypercalcaemia, hypokalaemia, uraemia)
• Drugs (opiates, iron, ganglion-blockers, anticholinergics)
• Neuromuscular disease
Week 209 - Constipation/IBS: Which nerve supplies the external anal sphincter?
Week 209 - Constipation/IBS: What occurs to allow defaecation?
• Cortical perception of rectal filling.
• Voluntary decision
• Decreased tone in pelvic floor and sphincters.
• Anorectal angle is reduced.
• Increase in abdominal tone.
• Passage of stool.
Week 209 - Constipation/IBS: What are the five factors that help to ensure continence?
• Central control.
• Functioning reservoir.
• Strong pelvic floor.
• Intact sphincter mechanism.
• Absence of peripheral neuropathy.
Week 209 - Constipation/IBS: What are the causes of incontinence?
• Cerebral - Old age, psychiatrically disturbed.
• Degenerative - Autonomic neuropathy, Wasting diseases.
• Trauma - Obstetric, surgical, accidents.
Week 209 - Constipation/IBS: What are the four causes of obstructed defaecation?
• Rectal intussusception
• Idiopathic megarectum
Week 209 - Constipation/IBS: What is a rectocoele?
Protrusion of anterior wall of rectum, commonly follows childbirth.
Herniation may lead to obstructed defaecation.
Week 209 - Constipation/IBS: What is rectal intussusception?
• Preliminary stage to rectal prolapse.
• Rectal fullness or pressure.
• Perineal pain.
Week 209 - Constipation/IBS: What are the symptoms of obstructed defaecation syndrome?
• Laxative/enema dependancy
• Incomplete evacuation
• Fragmented defaecation
• Rectal Pain
• Perineal support
Week 209 - Constipation/IBS: What is the initial investigation for a patient presenting with chronic constipation? What are the possible findings?
• Excludes carcinoma.
• Normal calibre colon/rectum.
Week 209 - Constipation/IBS: Following a barium enema for the investigation of chronic constipation, you find that the colon/rectum is of normal calibre. What are the follow-up investigations?
• Defaecating proctogram.
• Colonic transit study.
• Anorectal physiology.
• Endoanal ultrasound.
Week 209 - Constipation/IBS: What are the techniques used for anorectal physiology analysis?
• Balloon inflation.
• Pudendal nerve terminal motor latency.
• EMG recording.
Week 209 - Constipation/IBS: What is functional constipation?
This is chronic constipation without a known cause, also known as primary and idiopathic constipation.
Week 209 - Constipation/IBS: What is secondary constipation?
Constipation caused by a drug or medical condition, also known as organic constipation.
Week 209 - Constipation/IBS: What is the difference between chronic constipation and IBS-constipation dominant?
IBS-C, has more pain associated with it. Patients with less pain are classified as chronic constipation.
Week 209 - Constipation/IBS: What is the diagnostic criteria for IBS?
At least 12 weeks of the last 12 months with abdo. pain/discomfort and two of the following symptoms;
- Relieved with defaecation.
- And/or change in stool frequency.
- And/or change in stool form.
Week 209 - Constipation/IBS: What are the four types of laxatives?
• Bulk-forming laxatives.
• Osmotic laxatives.
• Stimulant laxatives.
• Surface-wetting laxatives.
Week 209 - Constipation/IBS: How do bulk-forming laxatives work? Give examples.
• Retain fluid within the stool, increasing faecal mass, stimulate peristalsis.
• Ispaghula husk, Methylcellulose.
Week 209 - Constipation/IBS: How do osmotic laxatives work? Give examples.
• Increase fluid in large bowel, causing secretion and stimulation of peristalsis.
• Macrogols, lactulose.
Week 209 - Constipation/IBS: How do stimulant laxatives work? Give examples.
• Peristalsis by stimulating colonic nerves (Senna)
• Or by stimulating colonic and rectal nerves (bisacodyl, sodiumpicosulfate).
Week 209 - Constipation/IBS: How do surface-wetting laxatives work? Give examples.
• Reduce the surface tension of the stools allowing water to enter.
• Docusate, poloxamer.
Week 209 - Constipation/IBS: How should short duration constipation be managed in adults?
• Adjust any constipation-inducing medication.
• Dietary advice (Fluids, fibre)
• And oral laxatives if these are ineffective, beginning with a bulk-forming laxative.