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
Effect of puborectal muscle relaxation
Opens up anorectal angle and causes pelvic floor descent
5 pro-defecatory stimuli
- Exercise
- Distension (bulky stools, fiber)
- Waking up
- Eating
- Drugs (laxatives)
Why is exercise a pro-defecatory stimulus?
Stimulates HAC
Rome II criteria for adult constipation
Two or more of the following for at least 12 weeks (no necessarily consecutively) in the preceding 12 months:
- Straining during >25% of bowel movements
- Lumpy or hard stools for >25% of bowel movements
- Sensation of incomplete evacuation for >25% of bowel movements
- Sensation of anorectal blockage for >25% of bowel movements
- Manual maneuvers to facilitate >25% of bowel movements (i.e. digital evacuation or support of the pelvic floor)
- <3 bowel movements per week
- Loos stool not present and insufficient criteria for IBS
Rome II criteria for constipation in infants and children
- Pebble-like, hard stools for a majority of bowel movements for at least 2 weeks
- Firm stool less than or equal to 2 times per week for at least 2 weeks
- No evidence of structural, endocrine, or metabolic disease
Describe the prevalence of constipation in North America and the groups of people affected by it
NA prevalence ~15%
- Women >> men (3:1)
- Nonwhites > whites
Reasons why women experience constipation more often than men
- Longer coloncs, slower transit (36h vs. 29h)
- Pregnancy can exacerbate
7 risk factors for constipation
- Increasing age
- Low-fiber, Western-style diet
- Decreased physical activity
- Low income, socio-economic status
- Limited education
- History of sexual abuse
- Depression
What must constipation be dinstinguished from?
Obstructed defecation syndrome (i.e. rectal prolapse, non-relaxing puborectalis, etc…)
Number one cause for constipation
Lifestyle neglect
Example of an endocrine cause for constipation
Hypothyroidism
Examples of medications that can cause constipation
- Narcotics
- Anti-cholinergics
- Anti-psychotics
Examples of neurogenic causes of constipation
Central vs. peripheral; i.e. slow-transit constipation, Chagas’ disease)
Examples of psychological causes of constipation
Depression and anorexia
4 treatment principles of constipation
- Seek to identify the underlying cause
- Rule out mechanical obstruction – combination of clinical history and/or imaging
- Strongly consider a full colonoscopy to rule out neoplasm
- In younger patients, lifestyle neglect is #1 cause – can proceed with dietary changes +/- adjuncts
What is the number one reason for admittance to a nursing home?
Recal incontinence
Describe the groups of people affected by fecal incontinence and the prevalence
- 2 - 18% of population affected
- 50% of nursing home residents
3 things that are important to define in the setting of fecal incontinence
- The cause of the incontinence (establish the diagnosis)
- Degree of incontinence
- Degree to which the patient is affected (impact)
6 examples of “pseudo”-incontinence that must be ruled out if fecal incontinence is suspected
- Urgency and stool loss from poor rectal compliance (IBD)
- Overflow incontinences from stool impaction/ severe constipation
- Poor hygiene
- Anorectal STDs (gonorrhoea, chlamydia)
- Prolapse (rectum and hemorrhoids)
- Anorectal neoplasms
5 Determinants of continence
- Intact neurologic function
- Anal sphincters
- Proper function of pelvic floor musculature
- Stool consistency and volume
- Rectal compliance
4 neurological causes of fecal incontinence
- Spinal cord injury
- Severe diabetes
- Dementia
- Defective RAIR
2 ways the anal sphincters can be affected to lead to fecal incontinence
Trauma and rectal prolapse
An example of how imporper function of pelvic floor musculature can lead to fecal incontinence
Prudendal nerve injury
2 examples of fecal incontinence related to stool consistency and volume
Fecalomas and diarrhea
2 examples of defective rectal compliance that can lead to fecal incontinence
Neoplasms and inflammatory conditions
Number one cause of fecal incontinence
Obstetric
3 risk factors for obstetric-related fecal incontinence
- Forceps
- Episiotomies
- 1st baby
3 obstetric events that can lead to pudendal nerve injury
- Prolonged straining (2nd stage of labor)
- Forceps
- Big babies
Frequency of anal tears in the obstetric setting
0.6 - 9% and may breakdown/weaken with time even post-repair
4 categories of causes for fecal incontinence
- Obstetric
- Iatrogenic
- Congenital malformations
- Rectal prolapse
3 iatrogenic causes of fecal incontinence
- Fistulotomy
- Sphincterotomy
- Radiation proctitis
3 congenital causes of fecal incontinence
- Spina bifida
- Myelomeningocele
- Imperforate anus
3 steps in evaluation of a patient with fecal incontinence
- Detailed history and physical exam
- Look for scarring, trauma from birthing, excoriation/skin changes from chronic soiling, patulous anus, associated conditions
- Digital rectal exam for fecalomas, anal sphincter condition, anal squeeze
3 specific aspects of the detailed history and physical exam for patients with fecal incontinence
- Stool diary
- Incontinence scale
- Rule out diarrheal states and pseudo-incontinence
4 diagnostic tools for a patient with fecal incontinence
- Full colonoscopy
- Endoanal ultrasound
- Pudendal nerve terminal motor latency (PNTML)
- Anal manometry
Purpose of full colonoscopy for fecal incontinence patients
Rule out other lesions
Best test to assess fecal incontinence
Endoanal ultrasound
Aspects evaluated by endoanal ultrasound
- Internal and external sphincters
- Distance between the vaginal orifice, size of perineal body, anal musculature
What is defined as an abnormal finding by endoanal ultrasound?
Perineal body thickness of less than 10 mm
Purpose of PNTML for fecal incontinence patient
Checks the pudendal nerve for injury
Normal range of pressure measured by anal manometry
40 - 70 mm Hg
What does anal manometry check?
RAIR and rectal compliance
2 steps of treatment for fecal incontinence
- Estbliash the diagnosis and treat the underlying condition
- Medical management
4 types of medical treatments for fecal incontinence
- Meds to normalize stool consistency
- Conspitating agents
- Biofeedback
- Injectable sphincter-bulking agents (silicone-based)
2 ways to normalize stool consistency
- Bulking (by psyllium, for example)
- Treatment of diarrhea and constipation (scheduled disimpactions if necessary)
3 constipating agents
- Loperamide (imodium)
- Lomotil
- Codeine
Describe biofeedback
Visual and auditory feedback for pelvic physical therapy
Benefits of biofeedback for fecal incontinence patients
- 44% achieve complete continence
- 76% achieve improved continence
by 3 months
5 surgical options for fecal incontinence
- Overlapping sphincteroplasty
- Artificial bowel sphincter
- Sacral nerve stimulatory (SNS)
- Antegrade enema
- Permanent colostomy
How does an antegrade enema access the rectum?
By cecostomy button or appendix
Benefit of antegrade enema
Large volume (3 - 4 saline enema) can clean colon for up to 48 hours
When is permanent colostomy used?
When many modalities have failed
Define overlapping sphincteroplasty
Surgical repair of damaged sphincters to reconstitue the anatomy
Benefit of overlapping sphincteroplasty
- Good initial results
- ~50% remain continent to both solid and liquid stool at 5 years
- Can repeat the surgery to “re-tighten” muscles
Initial purpose of sacral nerve stimulation
Treatment for urinary incontinence
Explain how sacral nerve stimulation works
Mechanism is unclear, but overal effect is increased resting tone by placing the stimulator by the 3rd sacral n. root
Describe the artificial bowel sphincter
If the anal muscles are destroyed, an aritificial sphincter can be recreated with an inflatable cuff, with the pump place in scrotum/labium
Problem with artificial bowel sphincter
High infection rates
