Mar1 M3-Defecatory disorders Flashcards
number 1 cause of institutionalization of elderly
fecal loss and fecal incontinence (often bc of dementia)
inferior rectal artery vs hemorrhoidal supply
- inferior rectal artery comes from inferior pudendal artery (off iliac)
- hemorrhoidal supply from IMA
rectum function and when disturbed
- rectum capacitance through series of reflex arcs
- Crohn’s or UC: rectal wall inflamed, edematous and no longer distends
internal vs external anal sphincter
internal = tissue there insensate, SM, involuntary, has a resting tone external = anoderm there is sensate, skeletal muscle, voluntary
surgical anal canal and dentate line
above dentate line = hemorrhoid, insensate hindgut
below dentate line = ectoderm derived anoderm, sensate
*crypts and glands in anal canal
anal transition zone (ATZ) def + fct
- transitional coacogenic epithelium
- IMPORTANT fct: sample, sense consistency of poop or if it’s a fart
- below ATZ, anoderm: sensate, non-keratinzed epithelium
role of PSS innervation in the gut
-GIT motility
-continence and rectal capacitance
-pelvic fct
(cranio-vagal, caudal-sacral)
SS role in the gut
- SLOWS colonic motility
- thoraco-lumbar
contractions and peristalsis in the colon
- high amplitude contractions (HAC): 5-6x a day, occur with waking and after meal
- low amplitude contractions (LAC): related to meals and sleep-wake cycle
- segmental contractions (DON’T propagate)
problems related to HAC and LAC imbalance
HAC > LAC = faster transit
LAC >HAC = slower transit (constipation, etc.)
anatomic factors to maintain continence
- internal anal sphincter resting tone (45%)
- external (ONLY VOLUNTARY CONTINENCE) anal sphincter (30%)
- hemorrhoidal plexus (10-15%)
functional factors to maintain continence
anorectal angle, puborectalis, flap-valve
4 important reflex arcs in the bowel
- gastro-colic (food in mouth triggeres colonic motility and segmental contractions)
- recto-anal inhibitory reflex (rectal distension) (RAIR)
- recto-anal excitatory reflex (rectal distension) (RAER)
- bulbocavernosus reflex (S2,3,4)
RAIR and RAER fct
- RAIR triggers relaxation of INTERNAL anal sphincter when poop is there
- RAER triggers EXTERNAL sphincter contraction when poop in rectum
how normally inhibit defecation
- pressure receptors in rectal wall and pelvic side wall (not in rectum itself) trigger RAIR and RAER
- reflex arcs for rectum to distend and urge to defecate will pass
normal things involved in defecation
- valsalva maneuver (incr. abd pressure)
- puborectalis muscle RELAXATION (opens anorectal angle, pelvic floor descent)
- external sphincter relaxation
(EXAM) pro-defecatory stimuli
- exercise (stimulates HAC)
- distension (bulky stools)
- waking up
- eating
- drugs (laxatives)
risk factors for constipation
- increasing age
- low-fiber, Western diet
- less physical activity
- low SES
- limited education
- depression
(IMPORTANT) number 1 cause of constipation
lifestyle neglect
investigations in constipation patient
- hypothyroidism
- IBS
- meds
- neurogenic cause
- psychological (depression, anorexia, ..)
problem in laxatives in constipation
can get tolerant and they don’t work anymore
treatment principles in constipation
- consider colonoscopy
- rule out mechanical obstruction
- talk about lifestyle neglect
- need laxatives?
(IMPORTANT) only time you consider indication for surgery in constipation
neurologic disorder of colonic failure (true slow-transit constipation), diagnosed by a Sitzmark study
types of laxatives for constipation
- bulk laxatives (water, fiber, supplement)
- osmotic laxatives (non digested sugar, MgOH2)
- docusate sodium or Senekot (detergent, emollient: softens stool)
