Pathology -- Defecatory Disorders Flashcards
2 defecatory disorders
Constipation
Fecal incontinence
9 causal conditions of constipation
- Diet, lifestyle
- Irritable bowel syndrome
- Drugs
- Neurogenic (central or peripheral)
- Myopathic
- Metbaolic
- Pregnancy
- Obstructive lesions
- Anorectal disease
Define fecal incontinence
- Varies from inadvertent soiling with liquid stool to the involuntary excretion of feces
- Insufficient voluntary control of gas or stool
- NOT a diagnosis, but a symptom
4 causal conditions of fecal incontinence
- Pelvic floor intact
- Neurological conditions
- Overflow (i.e. impaction)
- Pelvic floor affected
- Acquired (i.e. traumatic birth)
- Congenital
4 consequences of being unable to poop normally
- Social isolation and stigmatization
- Physical disability
- Psychological distress
- Societal costs – direct care, institutionalization, loss of productivity
Right colon and transverse colon functions
Churning and mixing
Left colon function
Water absorption and stool delivery
Rectum function
Stool storage until socially appropriate moment, termed capacitance
Norma capacitance of stool in rectum
200 - 250 mL
Anus function
- Muscular cork to prevent involuntary stool loss
- Allows us to distinguish between solid and liquid stool ,flatus
Dscribe the internal anal sphincter’s characteristics
Continuous with inner circular muscle
- Smooth muscle
- Involuntary control
- Resting tone
Describe the external anal sphincter’s characteristics
Continuous with pelvic floor
- Skeletal muscle
- Voluntary control
4 layers of the anus
- Internal anal sphincter
- External anal sphincter
- Longitudinal muscle
- Anoderm
Define the dentate line
Endodern (hindgut) and ectoderm junction
Define the anal transition zone
Location of transition from endoderm to ectoderm, so has transitional epithelium (cloacogenic)
2 characteristics of the anoderm
- Sensate (vs. insensate rectum)
- Non-keratinized squamous epithelium
Parasympathetic pathway functions in GIT
- Generally promotes GIT motility
- Role in continence/rectal capacitance
- Pelvic function
Efferent position of parasympathetic nerves for colon
Cranio-caudal
Sympathetic pathway functions in colon
- Slows colonic motility
- Fight or flight system
Effect position of sympathetic pathways to colon
Thoraco-lumbar
3 types of contractions in colon
- High amplitude propagated contractions (HAC)
- Low amplitude propagated contractions (LAC)
- Segmental contractions
Characteristics of HAC
- Transport stool over long distances (5 - 6 x/day)
- Occur with waking and after meals
Characteristics of LAC
- Related to meals/sleep-wake cycle (not clearly understood)
- Propagate stool short distances, but more frequently (not clearly understood)
When is transit in the colon decreased?
LAC > HAC
When is transit in the colon normal
LAC = HAC
When is transit in the colon increased?
HAC > LAC
4 anatomic factors to maintain continence in order of importance
- Internal anal sphincter resting tone (45%)
- External sphincter (30%)
- Hemorrhoidal plexus (10 - 15%)
- Aorectal angle/puborectalis/flap-valve
4 important reflex arcs relating to the colon and rectum
- Gastro-colic
- Recto-anal inhibitory reflex (RAIR)
- Recto-anal excitatory reflex (RAER)
- Bulbocavernosus reflex
Trigger and effect of gastro-colic reflex
Food in mouth –> colonic motility, segmental contractions
Trigger and effect of recto-anal inhibitory reflex (RAIR)
Rectal distension –> RELAXATION of INTERnAL anal sphincter
Trigger and effect of recto-anal excitatory reflex (RAER)
Rectal distension –> CONTRACTION of EXTERNAL anal sphincter
Lowest spinal reflex and the efferent position
Bulbocavernosus reflex from S2,3,4
Location of CNS awareness of stool moving into rectum
Anterior cingulate and frontal gyri
What receptors does rectal distension stimulate?
Pressure receptors in rectum and pelvic side wall
Purpose of RAIR in normal defecation
“Sampling” of contents (air? solid?)
Purpose of RAER in normal defecation
Prevent involuntary loss
If defecation is not appropriate at the time that stool enters the rectum, what is the body’s response?
- Voluntary contraction of EAS
- Rectal accomodation (capacitance and compliance)
4 events if the decision to defecate is made
- Valsalva maneauver (increase abdominal pressure, glottic closure)
- Puborectal muscle RELAXATION
- EAS relaxation
- Emptying of rectal contents