History and exam
Key diagnostic factors
common
obstetric trauma
Increased risk if forceps delivery, vacuum delivery, episiotomy, baby >4 kg, delayed second stage of labour, or occipitoposterior presentation.
This is the most common cause of incontinence in young women.[16] The underlying aetiology may be direct sphincter damage or indirect denervation injury due to pelvic floor stretching.
presence of other risk factors
Includes: female sex, older age, nursing home resident, history of inflammatory bowel disease, haemorrhoids, bowel resection, rectal surgery, rectal prolapse, or neurological disorder.
patulous anus
An open or spread-apart anus, which is a sign of low resting pressure.
weak squeeze pressure
Sign of external sphincter dysfunction. Maintenance of squeeze should also be assessed.
Other diagnostic factors
common
constipation
May result in overflow incontinence due to a constant seepage of faecal fluid from an impacted rectum. Typical patients are institutionalised, older, or those with cognitive impairment.
urinary incontinence
Faecal and urinary incontinence commonly coexist and may have similar underlying aetiologies.[6]
urgency
Broadly a sign of external sphincter dysfunction or reduced rectal capacity.
passive leakage
Indicative of internal sphincter dysfunction, as the internal sphincter provides the majority of resting tone, maintaining continence subconsciously. Note, however, that a proportion of resting tone is provided by the external sphincter and the anal cushions.[41] Passive leakage may therefore occur with external sphincter dysfunction and after haemorrhoidectomy. Passive leakage may also occur with lack of perception due to cognitive impairment.
faecal seepage
Commonly occurs after incomplete evacuation of stool and/or impaired rectal sensation.
perineal scarring
Indicative of previous surgery or injury.
uncommon
perianal fistulae
May indicate inflammatory bowel disease.
rectal mass
May indicate malignancy. This may reduce rectal capacity or affect sphincter function.
A faecal bolus may be palpated.
rectal prolapse
The cause of incontinence in these patients is unclear, but prolapse may result in incontinence by profound inhibition of the internal sphincter.[22] Repair of the prolapse can lead to recovery of continence. In order to demonstrate a rectal prolapse, it is best to sit the patient on a commode and ask them to attempt the Valsalva manoeuvre.
abnormal perianal sensation
Implies damage to the S2-4 nerve pathway. Saddle anaesthesia is typical of cauda equina syndrome.
Risk factors
strong
female sex
older age
The general deterioration of muscle and connective tissue with age increases the likelihood of symptoms occurring in this group.
nursing home resident
While the incidence of faecal incontinence in the community may be as high as 10%, up to 50% of nursing home residents are affected.[6] This may reflect the fact that many people are admitted to nursing homes as a result of incontinence.
forceps delivery
Obstetric sphincter damage is the commonest cause of incontinence in young women.[16] Sphincter damage has been estimated to occur in 11% of women who give birth vaginally.[12] Forceps delivery is associated with new symptoms of faecal incontinence in as many as 59% of women.[12] Based on meta-analysis of data from 22 studies (651,934 women, of whom 15,366 [2.4%] had severe perineal tears), forceps was one of the strongest risk factors for obstetric anal sphincter injury. Vacuum-assisted delivery was also associated with an increased, albeit lesser, risk of sphincter injury (OR 2.01; 95% CI 1.35 to 2.99).[18]
third- or fourth-degree perineal laceration
Obstetric sphincter damage is the commonest cause of incontinence in young women.[16] Sphincter damage has been estimated to occur in 11% of women who give birth vaginally.[12] In a study of women 5 to 10 years after first delivery, vaginal delivery with obstetric anal sphincter injury was associated with increased reporting of faecal incontinence symptoms compared with a caesarean control group without sphincter laceration (OR 2.32; 95% CI 1.27 to 4.26).[19] Women who sustain fourth-degree lacerations are at the highest risk of reporting bowel symptoms 6 months postpartum.[20] The American College of Obstetricians and Gynecologists (ACOG) has published guidelines on the repair and management of obstetric lacerations at vaginal delivery.[13]
episiotomy
Obstetric sphincter damage is the commonest cause of incontinence in young women.[16] Sphincter damage has been estimated to occur in 11% of women who give birth vaginally.[12] Based on meta-analysis of data from 22 studies (651,934 women, of whom 15,366 [2.4%] had severe perineal tears), midline episiotomy significantly increased the risk of anal sphincter injury (OR 3.82; 95% CI 1.96 to 7.42).[18] If there is need for episiotomy, mediolateral episiotomy may be preferred over midline episiotomy. However, mediolateral episiotomy may be associated with an increased risk of perineal pain and dyspareunia. The American College of Obstetricians and Gynecologists (ACOG) recommends restrictive episiotomy use over routine episiotomy but the absolute criteria for the procedure have not yet been established.[13]
baby >4 kg or delayed second stage of labour
Trauma may result from direct tearing of the anal sphincter. An episiotomy is more likely and this can result in iatrogenic sphincter damage. Indirect stretching of the pudendal nerve and the pelvic diaphragm can result in neuropathy to the sphincter complex.
Both episiotomy and third- or fourth-degree perineal laceration are significantly associated with anal incontinence.[21]
occipitoposterior presentation
Recognised to increase the risk of sphincter damage and subsequent faecal incontinence in women during labour.[12]
iatrogenic sphincter injury
Although a rare cause of faecal incontinence, many surgical procedures can directly compromise sphincter function. Some anal procedures such as lateral sphincterotomy and fistula surgery purposefully aim to cut the sphincter. Incontinence rates may be as high as 52%.[6] Bowel resection procedures, particularly involving rectal resection, indirectly affect continence by shortening bowel transit and reducing reservoir function.
multiple sclerosis/stroke/pudendal neuropathy/spinal injury
Continence requires an intact neuronal pathway to allow rectal sensation of stool, maintain subconscious tonic sphincter contraction, and allow higher centre control for defecation. Disruption of the pathway at any level (higher centre, spinal cord, cauda equina, peripheral nerves) may result in incontinence.
infectious diarrhoea or inflammatory bowel disease
The presence of liquid stool and rapid arrival into the rectum may overcome even an otherwise normally functioning sphincter complex. Conditions such as inflammatory bowel disease, radiation proctitis, and previous colorectal surgery may result in rapid transit coupled with a reduction in rectal compliance and reservoir function.
constipation/impaction
Patients with severe constipation often experience overflow incontinence due to a constant seepage of faecal fluid from an impacted rectum. Typical patients are institutionalised, are older, or have cognitive impairment. In addition, neurological injury may result in overflow due to the lack of sensory perception of a distended rectum.
rectal prolapse
The cause of incontinence in these patients is unclear, but prolapse may result in incontinence by profound inhibition of the internal sphincter.[22] Repair of the prolapse can lead to recovery of continence.
third-degree haemorrhoids
Prolapsed haemorrhoids can be severe enough to compromise sphincter function and this may contribute to faecal leakage.
congenital abnormalities of the anorectum
This mainly affects children; occasionally, despite surgical correction, incontinence symptoms may continue or recur in adult life.
dementia/learning difficulties
Cognitive dysfunction, general disability, and the tendency to ignore bowel habits, resulting in constipation and faecal impaction, contribute to the higher incidence in older, frailer age groups, particularly those in institutions.
pelvic radiotherapy
This may result in a pudendal neuropathy but also reduced rectal wall compliance and subsequent urgency.
central neurological disease
People with central neurological disease or injury have a much higher risk of both faecal incontinence and constipation than the general population.[23]
weak
diabetes mellitus
Autonomic neuropathy may result in internal sphincter dysfunction and passive incontinence.[11]
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