209 - constipation/ibs

Question 1

what is the rome criteria for constipation?

Answer 1

bowel movements less than three times a week

Question 2

what is 1ry constipation?

Answer 2

functional constipation which is chronic. Due to dysmotility or mechanic problems eg obstructed defaecation syndrome (rectocoele, rectal intussusception, anismus)

Question 3

what is 2ry constipation?

Answer 3

caused by a drug or medical condition such as:
diabetes (dysmotility), hypothyroidism (↓motilty & slow transit), panhypopituitarism(↓secretion of all hormones)/pheochromocytoma(adrenal gland tumour)/endocrine Ca) which cause hypocalcaemia/hypokalaemia, CNS diesease (parkinson,MS,CVA, spinal injury), drugs (opioids, iron, Ca channel blockers, anticholinergic agents like TCAs

Question 4

what is the criteria for irritable bowel syndrome

Answer 4

at least 12 week history in past year of abdo pain/discomfort plus 2 of following 3:
*relieved with defaecation
*change in stool frequency
*change in stool form
Also mucous & bloating with distension - constipation dominant, diarrhoea dominant or both

Question 5

what investigations are available for constipation?

Answer 5

• colonic transit study - capsules with radio opaque plastic rings taken for 3 days. On 5th day XR taken. If 5 or less rings = normal colonic transit, most rings scattered in colon = hypomotility/colonic inertia, if most rings gathered in recto sigmoid = functional outlet obstruction
• colonoscopy, sigmoidoscopy, endocanal US, rectal biopsy

Question 6

what management options are available for constipation?

Answer 6

1st adjust constipating medicine & ↑ fluid intake (1.5L no diuretics) & avoid fat (gastrocolic reflex - cramping) then laxatives:

• 1st - bulk forming (isphagula husk, methylcellulose) - retain fluid in stool, soften, ↑mass which stimulates peristalsis
• 2nd - osmotic (lasctulose) - ↑fluid in colon, cause distension which stimulates peristalis. also soften
• if soft - stimulant (senna, bisacodyl) - stimulate colonic +/- rectal nerves
• surface wetting agents (docusate) - ↓ surface tension of stool allowing water to penetrate & soften

Question 7

apart from constipation therapies what management techniques are available for IBS?

Answer 7

• pain management - anticholinergics (relax smooth muscle), antimuscarinics (mebeverine), peppermint oil
• psychological therapies eg CBT
• dietary management - avoid carbs & sugar alcohol
• motility drugs - serotonin 5-HT4 receptor agonist (stim peristalsis), selective ty2 Cl channel activator (stim cl/h20 secretion into lumen)

Question 8

what are the two parts of the enteric nervous system?

Answer 8

• myenteric plexus - between circular & longitudinal muscles, continuous network of ganglia from oesophagus to anus with symp, para & somatic communication, controls muscularis externa
• submucosal plexus - in submucosa, absent in oesophagus & limited in stomach, only para & somatic communication, controls muscularis mucosae

Question 9

how is the enteric nervous system innervated & affected by the parasympathetic, sympathetic and somatic sensory systems?

Answer 9

• para (vagus, pelvic splanchnic (s2-4)) - speeds motility, relaxes sphincters, ↑ acid & glandular secretions
• symp (sup & inf mesenteric ganglia) - slows motility, contracts sphincters, stim enzymatic secretion & inhibits glandular
• somatic sensory (afferents to spinal ganglia & some vagus) - registers pain

Question 10

what are the functions of the 2 parts of the colon?

Answer 10

• ascending & transverse (propulsive) - fluid & electrolyte absorption (liquid stool to solid), bacterial fermentation, absorption of fatty acids from fermentation
• descending, sigmoid, rectum (non-propulsive) - reservoir (storage of stool), defaecation

Question 11

what causes diarrhoea in the small bowel and colon?

Answer 11

• ↓ absorption in small bowel - osmotic (coeliac or mgso4), ↑ permeability of mucosa (crohn’s, infection), secretion of fluid into lumen (cholera)
• abnormal constituents of lumen (cystic fibrosis, pancratic insufficiency
• abnormal colon function - ↓absorption in ulcerative colitis

Question 12

what type of muscles are the external/internal anal sphincters made from and how does each function?

Answer 12

• external - striated muscle. controlled involuntarily by spinal reflexes which cause contraction to maintain continence in sampling and inhibition reflex inhibits contraction during straining for defaecation. Also Controlled voluntarily
• internal - smooth circular muscle of rectum. Innervated by autonomic system (symp excitatory, para inhibit) & functions involuntarily to relax on rectal distension to allow sampling

Question 13

what is the anorectal sampling reflex?

Answer 13

rectum fills, internal sphincter relaxes to allow portion of rectal content to enter upper anal canal where sampled epithelium (gas, liquid or solid), external sphincter instantly contracts to maintain continance

Question 14

what is the process of defacation?

Answer 14

rectal filling detected by stretch receptors, voluntary decision made to defaecate & voluntary contraction of abdo muscles to strain, simulataneous reflexes reduce tone in sphincters & pelvic floor to reduce anorectal angle, then stool propelled out of anus

Question 15

what maintains continence and what causes incontinence?

Answer 15

• continence - sphincter tone, intact central control, intact pathways & peripheral nerves, functioning reservoir (rectal capacity), enorectal angle
• incontinence - neonatal (not learnt), cerebral (old age & psych), trauma (obs, surg, accidents), diseases (anorectal sepsis, IBD esp crohns)

Question 16

what techniques can be used to investigate anorectal physiology?

Answer 16

• manometry - measures resting pressure (internal sphincter) & maximum squeeze (ext sphincter)
• balloon inflation - water filled balloon in anal canal/rectum & sensation tested as P incr.
• Pudendal nerve terminal motor latency (PNTML) - pudendal nerve stimulated with electrode & time for muscular contraction/relax measured

Question 17

what is a rectocoele and what causes it?

Answer 17

protrusion of anterior rectal wall into vagina caused by childbirth or sometimes asymptomatic px. Results in obstructed defaecation

Question 18

what is rectal intussusception, what effects does it bring, what investigations should be done and what is the management?

Answer 18

bunching of rectal wall commonly found with rectocoele resulting in incomplete evacuation, rectal fullness/pressure, tenesmus, perineal pain. Investigate with defaecating proctogram (barium enema, x-ray when defecaeting). Management is surgery in large symptomatic px

Question 19

what three surgical options are available for dysmotility and what should be ruled out first?

Answer 19

• colectomy & ileo-anal resection (IAR) - ileostomy done first. re-op, abdo pain , bloating
• Sacral nerve stimulation (SNS) - effects on rectal sensation & colonic motor pathways incr contractions
• Antegrade Colonic Enema (ACE) - catheter in caecum for irrigation
• defaecation disorders, weak sphincters must be ruled out first

Question 20

what is obstructed defaecation syndrome?

Answer 20

affects multiparous women where chronic straining causes stretching & redundancy of the distal rectum. Causes intussusception, retrocoele, perineal decent (elongation of rectum). Symptoms - straining, incomplete evacuation, rectal pain. Surgery - retrocoele repair, internal intussusception repair (ventral rectopexy or STARR procedure - resection of rectum to stretch)

Question 21

what are the layers of the appendix?

Answer 21

• mucosa - crypts with columnar cells (absorb), goblet cells (secrete mucous), endocrine cells (contain somatostatin & vasoactive intestinal peptide & substance P), stem cells
• submucosa - fat, nerves, blood cells and agglomerations of lymphoid tissue covered by dome epithelium (M cells) - MALT
• muscularis propria - inner circular layer, outer longitudinal layer
• serosa

Question 22

what pathological changes can happen to the crypts and endocrine cells of the appendix?

Answer 22

• crypts divide over time & split in two (bifid crypts). In IBD distortion and loss occurs
• endocrine cells - tumours (carcinoid tumors) . release serotonin into blood causing carcinoid syndrome (bronchial wheezing, skin flush, diarrhoea)

Question 23

what causes appendicitis and how does it progress?

Answer 23

common in low fibre diets - obstruction of lumen by impacted faecal matter which becomes infected. Inner wall becomes inflammed (peri-umbilical pain), outer wall & parietal pleura inflammed (RIF pain & rebound tenderness) then may perforate (peritonitis)

Question 24

what are the layers of the colon & rectum?

Answer 24

• mucosa - crypts in plicae semilunaris with columnar cells (absorb), goblet cells (secrete mucous), endocrine cells (contain somatostatin & vasoactive intestinal peptide & substance P), paneth cells (in R colon produce lysozyme), stem cells
• submucosa - fat, nerves, blood cells and agglomerations of lymphoid tissue covered by dome epithelium (M cells) - MALT
• muscularis propria - inner circular layer, outer longitudinal layer in three bands (taeniae coli)
• serosa