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)
best laxatives and downside
bulk laxatives (psyllium, fibers) downside = fermented in bowel: get pain and gas
fecal incontinence def
insufficient voluntary control of gas or stool (number 1 cause admission in nursing home). NOT A DX. is a symptom
fecal incontinence: things to rule out
- inflam disorders like CD, UC causing poor rectal compliance
- overflow incontinence from severe constipation
- poor hygiene
- anorectal STDs (gonorrhoea, chlamydia)
- prolapse (rectum, hemorrhoids)
- anorectal neoplasms
determinants of fecal continence (what can be the cause of incontinence)
- neurologic function (RAIR is absent in Hirschprung’s)
- anal sphincter fct (trauma, prolapse)
- pelvic floor musculature fct (pudendal nerve injury)
- stool consistency
- rectal compliance (neoplasms, inflam conditions)
(EXAM) number 1 cause of fecal incontinence
-obstetrical trauma (damage later in life when muscle atrophy)
(other causes are pudendal nerve damage, iatrogenic, congenital malformations, rectal prolapse)
(EXAM) best test for fecal incontinence
endoanal ultrasound
what endoanal US does
measures structures of sphincter and rules out sphincter injury
management of fecal incontinence
establish dx, treat underlying cause (normalize stool consistency), constipating agents
fecal incontinence caused by damaged sphincter treatment
surgery: overlapping sphincteroplasty (repair of damaged sphincter)
miscellaneous fecal incontinence treatments
- sacral nerve stimulator (put near the spine)
- artificial bowel sphincter (pump placed in scrotum or labium) if anal muscles are destroyed
