Incontinence

Involuntary leakage of faecal material in anyone over four years old.

Terminology

• Anal incontinence incorporates loss of flatus, faecal incontinence does not
• Urge incontinence (aware, running to bathroom but don't make it - suggests external sphincter problem) vs passive incontinence (unaware of occurrence - suggests more a problem with internal sphincter)

Factors contributing to normal continence

Mechanical/anatomical factors

• • Anal sphincter
    • Internal - 70% of resting sphincter pressure, but only 40% after distension of the rectum
    • External - contributes via voluntary control
  • Anal vascular cushions - 10-20% of resting tone
  • Puborectalis muscle/anorectal angle which acts like a flap valve

Rectal/anal sensation

• • Pudendal nerve (S2, 3, 4) innervates EAS
  • Pelvic branches (S3 and 4) innervate puborectalis
  • Rectal distension is transmitted along S2, 3, 4 PNS nerves
  • Recto-anal inhibitory reflex - when distended with stool, the internal sphincter relaxes, followed by reflexive contraction of EAS, creating a sensation of urgency. This is followed by pelvic floor relaxing, decreasing acuity of ano-rectal angle, and defecation (if appropriate). Voluntary contraction of the pelvic floor and EAS causes the sensation of urgency to subside as the rectum accommodates.
  • Anal sampling - as the IAS relaxes, a small amount of stool can be 'sampled' and moved down to anus, allowing for differentiation of gas and solid stool.

Rectal compliance

• • Storage of stool to defer defecation

Stool consistency

• • Especially important in patients with other functional problems

Aetiology

Structural problems

• • Anal sphincter disruption
    • Obstetric (most common) - trial non-operative options, then surgically repair or SNS
      • Prolonged second stage (pudendal nerve injury)
      • Actual passage of baby
      • Instruments
      • Often doesn't become symptomatic until post-menopause
    • Iatrogenic - fix underlying cause, then optimise medical management, consider SNS
      • LIS
      • Fistulotomy
      • Haemorrhoidectomy
      • Radiation
    • Anorectal disease - fix underlying cause - surgically
      • Rectal prolapse
        • Lead-point of prolapse acts like an intussusception, causing stretch of anal canal, and subsequent damage
      • Prolapsing internal haemorrhoids
  • Disruption of pelvic floor - surgically repair or SNS
    • Associated with ageing - diminished muscle bulk and strength
    • Excessive perineal descent - associated with denervation of the pelvic floor
    • Traumatic
      • Perineal impalement
      • Voluntary anoreceptive intercourse
      • Foreign bodies
      • Sexual abuse

Functional problems - bowel regime to prevent constipation

• • Neurologic - loss of stool awareness and sensation, often leading to mega-rectum with overflow incontinence (requires faecal impaction)
    • Obstetric (pudendal nerve injury)
    • MS
    • CNS disease - spinal cord injury or tumour
    • Diabetes
    • CVA
  • Reduced rectal compliance - treat underlying cause
    • IBD
    • Radiation proctitis
    • Distal rectal cancer
    • Rectal surgery including pouches

Changes in stool characteristics - treat underlying cause

• • Severe diarrhoea

Others - manage symptoms and in some cases stoma

• • Physical mobility
  • Dementia
  • Intellectual disability

History

• Differentiate true incontinence from urgency/frequency
• Solids/liquids/gas
• Onset
• Duration
• Frequency
• Amount
• Type
• Nocturnal episodes
• Precipitating events
• Awareness of incontinence
• Consider neurologic cause (lower back/perianal pain, motor or sensory symptoms in extremities, urinary incontinence)
• Prior anorectal surgery, pelvic irradiation, diabetes, neurologic disease
• Obstetric history (number of vaginal deliveries, prolonged labour, use of forceps, lacerations)
• Ask if tissue ever protrudes
• St Mark's incontinence score

Exam

• Inspection (chemical dermatitis, fistula, prolapsing haemorrhoids, rectal prolapse)
• Perianal sensation (absence of anal wink reflex suggests nerve damage)
• DRE (mass, assess resting anal tone and strength of squeeze, rectocoele, rectal prolapse, rectal mass, stricture, fistula)
• Anoscopy or proctoscopy - look for proctitis/cancer

Investigations

• Stool studies in patients with diarrhoea
• Endoscopy
  • Flex sig in patients <40yo with no increased risk of CRC
  • Colonoscopy otherwise
• Endorectal US (if fail to respond to initial management)
  • Looking for sphincter defects
• Defecography (defecating proctogram, or defecating MRI proctogram)
  • Looking for rectocoele or other pelvic floor defects
  • Partial evacuation of contents
  • Order if there are features of obstructed defecation
• Anorectal manometry (if fail to respond to initial management)
  • Looking for sphincter defects
  • Both with and without anal squeeze
• Balloon expulsion test
• Electromyography
• Pudendal nerve terminal motor latency
  • Controversial

Initial management

Supportive care

• • Wait 9-12 months after childbirth to investigate
  • Avoid food or activities known to worsen symptoms
    • Avoid incompletely digested sugars (fructose, lactose) and caffeine
  • Keep a food or symptom diary
  • Improve perianal skin hygiene
    • Keep clean and dry, without excessive wiping
    • Can use wet wipes
    • Barrier cream eg zinc oxide to perianal skin
    • Incontinence pads

Medical therapy - aimed at reducing stool frequency or improving stool consistency

• • Bulking agents, esp in patients with low-volume, loose stools
    • Fibre - psillium husk
  • Anti-diarrhoeal agents - can trial loperamide
    • Be aware this can exacerbate things in patients with decreased rectal compliance (radiation proctitis, rectal stricture)
    • If no response to loperamide, bismuth subsalicylate or cholestyramine may provide benefit, especially in patients post-cholecystectomy or post-ileal resection
  • If faecal impaction, should be disimpacted
  • Evacuation of rectum with suppositories or enemas
    • Esp useful for patients with neurogenic bowel dysfunction - reduces rectal load

Subsequent management

• Additional evaluation with some combination of anorectal manometry and USS and defecography
• Biofeedback therapy - refer to pelvic floor physiotherapist
  • Particularly useful in patients with intact anal sphincters and urge incontinence or decreased rectal sensation; not useful with isolated internal anal sphincter injury; not useful with neuro-psychiatric conditions; not useful with impaired distension
  • Rectal sensory retraining, sphincter exercises, learning to co-ordinate voluntary external sphincter contraction with the onset of rectal distension
  • Non-invasive
  • Time-consuming, but 64-89% see an improvement, especially if there is some degree of preserved voluntary sphincter contraction
  • Low-risk - worth a try

Surgical options:

• Reserved for patients in whom conservative management has failed
  • Not for those with overflow incontinence
• Injectable bulking agents (PTQ)
  • Enhanced mechanical barrier to faecal loss
  • Injected into submucosa, just above dentate line, four areas evenly spaced around anal canal
  • Evidence supports slight benefit but limited role now
• Sacral nerve stimulation
  • Stimulate S3 nerve root by delivering mild electrical pulses
  • Tined lead is placed next to root under fluoro
  • Mechanism of action not entirely clear, but seems to reduce reported episodes of incontinence and decreased urgency. Possibly enhances the ability of rectum to sense distension.
  • Most patients see an improvement, and about half of patients achieve full continence
• Overlapping anterior sphincteroplasty
  • Best use is probably for young patients who don't want to have an SNS for life
  • Appropriate for patients with a localised 90 to 180 degree full-thickness defect
  • Should not be done for at least 3-6 months after obstetric injury
  • Function is often initially good but deteriorates with time
  • Direct repair of anal sphincter - usually repair both sphincters as one muscle
  • Technique
    • Perform under GA with bowel prep. Consider diversion for difficult cases.
    • Hemicircumferential incision around anus
    • Dissect out into ischiorectal fat to expose the anus
      • Mobilise the anus from the vagina if needed
    • Split the muscle scar down its length and develop the plane between the anal mucosa and the muscle on either side
    • Reapproximate sphincter edges with 2-0 PDS horizontal mattress suture - like repairing a tendon. Aim for overlap of about 2cm.
• Repair of pelvic floor injury
  • Indications
    • Rectal prolapse
    • Other pelvic floor injury
• Stoma creation
  • Indications: failure of medical therapy and other invasive therapies, patient preference
  • Mostly sigmoid colostomy, although in slow transit constipation, an ileostomy can be necessary