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13
Fecal Incontinence
Jos!e Marı´a Remes-Troche
*, Karla Rocı´o Garcı´a Zermen˜o*,
Enrique Coss Adame
†
* DI G E S T IVE P H YSI O L O GY A N D GAS T R O I NTE S T I NAL M O TIL I T Y LAB O R A T ORY , I NST I T U T E O F
MED I C A L AND B I OLO G I C A L R E S E ARC H , U N IV E R S I TY O F VE RA C R U Z ANA , V ERA C R U Z, M E X ICO
†
DEP A R T M ENT O F GAS T R O E NT E R O L OGY A N D GI M O T ILI T Y LA BOR A T O RY , N A TI O N A L
INS T I T U TE O F MEDI C A L SCIE N C E S A N D N UT R I T I ON S A LVA D O R ZUBI R A´N,
MEX I C O CITY , M EXI C O
13.1 Introduction
Fecal incontinence (FI) is a devastating condition, given its accompanying social stigma. It
significantly deteriorates quality of life, negatively impa cting the physical and psychologic
health of the patient. It affects 2% of the population under 65 years of age, 10% of the population over 65years of age, and up to 50% of all geriatric patients residing in assistedliving facilities.
1
13.2 Definition
FI is the involuntary passage of stool or the inability to control the release of the intestinal
content through the anus.
2,3
Severity varies from the involuntary passage of gas to the
complete loss of bowel control.
13.3 Classification
FI can be classified into three subtypes: (a) passive incontinence: the unconscious and
involuntary release of stool or gas; (b) urge incontinence: the expulsion of stool despite
active attempts to retain the intestinal content, and (c) fecal seepage: the leakage of stool
after a normal bowel movement.
4
Comparing urge incontinence and passive incontinence
can provide clues to the pathophysiology of FI. Solid-stool incontinence suggests more
severe sphincter weakness than that of liquid stool alone.
5
Patients with urge incontinence
experience a sudden, strong desire to defecate, but do not have enough control to reach a
toilet in time. Conversely, in patients with passive incontinence, their awareness of the
desire to defecate before the incontinent episode is diminished or nonexistent. Patients
with urge incontinence often have reduced squeeze pressures and/or squeeze
duration,
6
reduced rectal capacity, and increased perception of rectal balloon distension,
whereas patients with passive incontinence often have lower resting pressures.
6,7
Anorectal Disorders. https://doi.org/10.1016/B978-0-12-815346-8.00013-8
© 2019 Elsevier Inc. All rights reserved.
161
13.4 Pathophysiology
The etiology of FI is multifacto rial and is the consequence of multiple anorectal alterations that can be primary or secondary.
8
Congenital causes (primary) are relatively
rare and include spinal cord defects and anorectal malformations. The most common
causes of secondary FI are obstetric injury and anorecta l surgery (hemorrhoidectomy,
fistulectomy, sphincterotomy, etc.)
2–5
(Table 13.1). Other causes include pathologies
that reduce the function of the reservoir or the adequate distension of the rectum, such
as surgical anastomosis after anterior low res ection, pro ctitis (e.g., inflammatory bowel
disease, ra diation, infectious colitis, etc.), or rectal prolap se. Nonstructural causes are
numero us and include infectious diarrhea, irritable bowel syndrome, postchol ecystectomy syndrome, and medication side effects. FI has more than one cause in over 80% of
patients.
9
13.4.1 Anal Sphincter and Pelvic Floor Muscle Injury
Injury to or weakness of the muscles that form the external anal sphincter (EAS) are the
main cause of urge FI.
10,11
In contrast, damage to the internal anal sphincter (IAS)
causes passive incontinence or fecal seepage that frequently presents under resting
conditions. Obstetric tra uma is the most common cause of anal sphincter injury. Sultan
et al.
12
demonstrated that 35% of primiparous women and 44% of multiparous women
presented with defects in the muscles of the IAS and/o r EAS after v aginal childbirth.
Furthermore, perineal tears, even if carefully repaired, should be c onsidered a risk factor, as well as forceps or vacuum-assisted deliveries, a prolonged second stage of labor,
elevated fetal weight at bir th, occiput posterior position of th e fetus, and mid-lateral
episiotomy.
2–5
Other causes of anatomic injury are anorectal surgery for hemorrhoids, fistula and fissures; accidental perineal trauma; or pelvic fracture. In a multicenter study, up to 9.5% of
the patients reported FI as a direct result of hemorrhoidectomy.
13
Contrary to what is
believed, hemorrhoidectomy can cause incontinence through inadvertent damage to
the IAS, in addition to the fact that excision of the hemorrhoidal plexus reduces the resting
pressure of the sphincter by up to 15%.
Disorders of the skeletal muscle system (muscular dystrophy, myasthenia gravis, and
other myopathies), internal sphincter degeneration, reconstructive procedures (such as
ileoanal or coloanal reservoirs), or radiotherapy can also affect the function of the EAS
and puborectal muscle.
13.4.2 Neurologic Alterations
Intact pelvic floor innervation is indispensable for m aintaining continen ce. Sphincter
degeneration secondary to pudendal neuropathy and obstetric trauma are causes of FI
in women. In childbirth, the damage is often asymmetric and takes place during the delivery due to the stretching of the nerves during the elongation of the birth canal or through
direct trauma from the passage of the fetal head.
3
162 ANORECTAL DISORDERS
Approximately 10% of the patients with FI can present with neurologic proximal spinal
cord injury. The main abnormality is a lesion in the nerves that arises from the cauda
equina.
3
However, in a minority of patients there is a combination of peripheral and central lesions. Other factors associated with FI are multiple sclerosis, diabetes, demyelinating lesions (e.g., alcoholic neuropathy or traumatic neuropathy), dementia, and mobility
deterioration, especially in the geriatric population.
14,15
Table 13.1 Pathophysiologic Mechanisms of Fecal Incontinence
Category Cause Effect
Structural abnormalities
Muscular
IAS Trauma or defect (e.g., sphincterotomy), atrophy Loss of the sampling reflex
EAS Trauma or defect (e.g., obstetric injury), atrophy (aging) Sphincter weakness
Puborectalis muscle Trauma or defect (e.g., tears, excessive perineal
descent), atrophy
Sphincter weakness
Obtuse anorectal angle
Rectum Abnormalities of the mucosa, inflammation due to
radiation, UC, Crohn’s disease
Loss of accommodation
Loss of sensation
Hypersensitivity
Nerves
Pudendal nerve Neuropathy due to obstetric injury/surgical injury Sphincter weakness
Sensory loss
Abnormal reflexes
Autonomic nerves,
spinal cord, CNS
Trauma (pelvis, spinal cord, back, head)
Neurologic diseases (e.g., MS, stroke)
Systemic diseases (e.g., diabetes)
Damaged reflexes
Sensory loss
Loss of accommodation
Secondary myopathy
Functional abnormalities
Anorectal sensations Obstetric or surgical trauma
CNS and peripheral defects
Loss of stool awareness
Rectoanal agnosia
Fecal impaction Dyssynergic defecation Damaged sensation
Fecal retention with overflow
Stool characteristics
Volume and consistency Infection, UC, Crohn’s disease, IBS, medicines,
metabolic causes
Diarrhea and bowel urgency
Irritating agents Bile salt malabsorption, laxatives Rapid bowel transit time
damaged adaptation
Retention/hard stools Dyssynergic defecation/medicines Diarrhea
Fecal retention with overflow
Miscellaneous
Medicines Anticholinergics
Laxatives
Antidepressants
Constipation
Diarrhea
Altered sensation
Intolerance to foods Lactose/fructose/sorbitol
Caffeine
Malabsorption/diarrhea/gases
Sphincter tone relaxation
Cognitive function/
altered mobility
Aging, dementia, disability Multifactorial changes
CNS, central nervous system; EAS, external anal sphincter; IAS, internal anal sphincter; IBS, irritable bowel syndrome; MS, multiple sclerosis;
UC, ulcerative colitis.
Chapter 13 • Fecal Incontinence 163
13.4.3 Sensory Alterations
The perception of sensory stimuli in the rectal wall, pelvic floor, and anal canal are essential for defecation. The elderly, individuals with mental deficiency, and children with FI
frequently have reduced rectal sensation.
16,17
That hyposensitivity leads to an excessive
accumulation of stool, causing fecal impaction, megarectum, and fecal overflow incontinence. The factors associated with rectal hyposensitivity are central neurologic damage,
peripheral neuropathy, spinal cord injuries, and the use of certain medicines (particularly
opioids and antidepressants). On the other hand, inflammatory diseases at the level of the
rectal mucosa (Crohn’s disease, infectious proctitis) can condition FI that is associated
with rectal hypersensitivity.
13.4.4 Alterations in Stool Characteristics
Stool frequency and form, volume, and the presence or absence of irritating agents in stool
play an important role in the pathogenesis of FI.
1,3
In the presence of liquid and voluminous stools that often transit rapidly, continence can only be maintained through intact
sensation and an intact sphincteric barrier. In patients with bile salt malabsorption, lactose intolerance, or fructose intolerance, bowel transit is too fast in relation to both gaseous content and stool content and can overwhelm the continence mechanisms.
Stimulants such as products with caffeine, fiber supplements, or laxatives also cause diarrhea, thus conditioning FI.
13.5 Diagnosis
13.5.1 Clinical Evaluation
The first step in the evaluation of FI is to establish a good doctor–patient relationship.
A detailed clinical history should be obtained. In general, patients are reluctant to
acknowledge incontinence-related symptoms, and so direct questioning about FI by
the physician is suggested wh en interviewing all patients with diarrhea, constipation,
or other anorectal problems.
1,3,18
It is important for the evaluation to include the amount,
pattern, and duration of FI, as well as its conditions (i.e., incontinence of gases or of liquid
or solid stools) and impact on quality of life. The use of sanitary pads or other accessories
and the capacity to distinguish between formed and nonformed stools and gas should be
documented. A prospective stool diary can also be useful.
A detailed medical interview encompassing obstetric history and associated diseases
such as diabetes mellitus, as well as pelvic radiation, neurologic problems, spinal cord
injury, hygienic-dietary habits, and the coexistence of urinary incontinence is fundamental.
4
The following FI instruments are currently used in clinical trials: the Wexner (Cleveland Clinic), Vaizey (St Marks), Rockwood, and Fecal Incontinence and Constipation
Assessment scoring systems, and the International Consultation on Incontinence Questionnaire Bowel module.
5
164 ANORECTAL DISORDERS
Physical examination is crucial in FI evaluation to define the anatomy and baseline
function. Perineal inspection includes the presence of scars, skin ruptures, thinning of
the perineal body, a lack of cleanliness, fistulas, hemorrhoids, and/or prolapse of the
mucosa. Digital rectal examination is necessary and should be performed routinely, assessing the length of the anal canal, the tone of the sphincter at rest and in contraction, and
the degree of coordination or lack thereof. Perianal sensation should also be evaluated.
The integrity of the connection between the sensory nerves and the skin, the intermediate
neurons in the S2, S3, and S4 segments of the spinal cord, and the motor innervation of the
EAS are examined through the anocutaneous reflex. The absence of this reflex suggests
either afferent or efferent neuronal damage.
1,3,18
13.5.2 Diagnostic Tests
Various tests can be employed (
Table 13.2) in the evaluation of the patient with FI.
18–20
Depending on the age of the patient, colonoscopy or flexible sigmoidoscopy are recommended for assessing luminal disease that could contribute to FI. In the absence of luminal patho logy, endoanal ultrasound and physiologic tests (e.g., manometry, anorectal
sensation, pudendal nerve terminal motor latency, etc.) are carried out to objectively
obtain morphologic and functional parameters. Test selection depends on etiologic factors, symptom severity, impact on quality of life, and patient age.
13.5.2.1 Anorectal Manometry
Anorectal manometry (ARM) is considered the gold standard in the evaluation of patients
with FI (
Fig. 13.1).
18,19
ARM provides information on the function of the resting anal
sphincter, as well as the changes that occur during the voluntary contraction, descent,
and reflex activation of the pelvic floor. The information is obtained through the introduction of catheters with solid-state microtransducers or with water or air perfusion that
records the resulting pressure of the muscle structures of the anorectal region. The test
can be carried out with conventional (catheters with 4–6 sensors), high-resolution
(12–16 sensors), or high-definition (256 sensors) systems.
19,21
Normal anal sphincter pressures vary according to sex, age, and measuring methodology. In general, pressures are higher in adult men and young persons, but there is considerable variation in the values.
22
ARM can also facilitate biofeedback training.
Reduced resting pressure is correlated with IAS alteration and reduced contraction
pressures are correlated with EAS defects (
Fig. 13.1). In addition, the capacity of the
EAS to contract as a reflex during abrupt increases in intraabdominal pressure, such as
coughing or sneezing, is altered, which can be demonstrated by having the patients blow
up a balloon by mouth.
19
To preserve continence, the anal sphincter pressure becomes
higher than the rectal pressure, through that reflex response. This response is triggered
by receptors in the pelvic floor and mediated by a spinal arc reflex. In patients with spinal
cord injury above the medullary cone, that reflex response is present but the response to
Chapter 13 • Fecal Incontinence 165
the voluntary effort can be absent, whereas in patients with lesions that affect the cauda
equina or the sacral plexus, both the reflex response and response to a voluntary effort are
absent.
18–21
ARM is relevant because not only does it confirm the diagnosis of FI, but it also pro-
vides information that influences and guides the medical treatment.
Table 13.2 Diagnostic Test Usefulness in the Evaluation of Fecal Incontinence
Test Advantage Disadvantage Benefit (s)
Anorectal
manometry
• Conventional
• High-
resolution
• High-
definition
(3D)
Lower cost, simple
Topographic analysis
3D reconstruction
Scant availability,
requires training
Costly, requires
training
Extremely costly
Motor and sensory evaluation of
the anorectal unit, gold standard,
enables diagnosis and guides
treatment (biofeedback)
Balloon expulsion
test
Available at all levels of care, easy
to perform
Not widely used More useful in constipation,
predicts pelvic floor dyssynergy
Endoanal
ultrasound
Availability, minimally invasive Requires training,
operatordependent, lack of
clinical correlation
The gold standard for structural
defects of the EAS
Magnetic
resonance
imaging
Noninvasive, detects small lesions High-cost, scant
availability, requires
specific training
Better than ultrasound for IAS
defects and atrophy
Pudendal nerve
terminal latency
Identifies pudendal neuropathy Low sensitivity and
specificity, operatordependent
A positive result highly suggests
neuropathy, but a negative result
does not rule it out
Defecography Objectively evaluates the anorectal
angle, pelvic floor descent, length
of the anal canal, presence of
rectocele, rectal prolapse or
intussusception of the mucosa
Radiation exposure,
scant availability,
uncomfortable for
the patient
Useful in cases of rectocele, more
useful in constipation than in
incontinence
Electromyography Better evaluates EAS motor
activity, complementary to
anorectal manometry
Limited availability
and uncomfortable
for the patient
Very good option for incontinence
biofeedback
Barostat The gold standard for evaluating
sensitivity and rectal distension
Limited availability,
uncomfortable for
the patient, costly
Objectively diagnoses
hyposensitivity or hypersensitivity.
Retraining can be carried out
Translumbar or
transsacral
magnetic
stimulation
Noninvasive evaluation of lumbar
and sacral nerve roots
Limited availability,
costly, limited
usefulness in clinical
practice
A more complete and better
evaluation than pudendal latency
for diagnosing neuropathy
EAS, external anal sphincter; IAS, internal anal sphincter; 3D, three-dimensional.
166 ANORECTAL DISORDERS
FIG. 13.1 High-definition (3D) manometry utilizing a catheter with 256 sensors. (A) The 3D reconstruction of the anal sphincter, which is intact in all planes.
The 2D image has a “delta” shape, in which greater pressure (red and purple) in the posterolateral regions is observed. (B) The 3D reconstruction of the anal
sphincter in a patient with fecal incontinence, in which a loss of continuity in the right anterolateral region (white arrow) can be seen. The 2D image shows the
sphincter with low pressures (blue) conditioned by the previously described sphincteric defect.
Chapter 13 • Fecal Incontinence 167
13.5.3 Rectal Sensory Testing
Rectal sensation is traditi onally measured by determining the sensory thresholds (first
sensation, desire to defecate, and urgency to defecate) in response to the distension of a
balloon previously placed in the rectum (e.g., barostat or latex balloon insufflation).
17,19
Subjects with FI can have rectal hypersensitivity, as well as rectal hyposensitivity. Due to
the fact that sensory alterations can be the consequence of changes in the confor mation
of the rectal wall, it is also important to evaluate rectal distensibility. The ideal study is
the rectal barostat , because changes in rectal p ressure and conformation can be evaluated during distension, thus reflecting the distensibility and accommodation capacity.
13.5.3.1 Pudendal Nerve Motor Terminal Latency
Pudendal nerve motor terminal latency (PNMTL) measures the functional integrity of the
terminal portion of the pudendal nerve.
18,20
It is based on the recording of the muscle
action potential of the anal sphincter in response to electric stimulation of the pudendal
nerve. The most widely used technique is the St. Mark’s method. That measurement aids
in distinguishing whether the weakness of the sphincter is due to muscle or nerve injury.
Prolonged latency of the nerve suggests pudendal neuropathy, which can occur after
obstetric or surgical trauma, excessive perineal descen t, diabetes mellitus, or idiopathic
FI. However, normal PNMTL does not exclude pudendal neuropathy because the presence of a few intact nerve fibers can give a normal result, but an abnormal latency tim e
is more significant.
Another way to evaluate PNMTL is by utilizing magnetic stimulation to activate the
neuromuscular tissue of the EAS.
23
In one study,magnetic PNMTL was comparable in precision to measurement through the conventional method, but it was better tolerated . In
addition, magnetic stimulation enabled the combined measurement of PNMTL and sacral
root latency, thus facilitating the evaluation of the proximal and distal portions of
the nerve.
13.5.3.2 Endoanal Ultrasound
Anal endosonography is currently the ideal study for examining anal sphincter morphology. It reveals the thickness and structural integrity of the muscles of the IAS and EAS
and can detect the presence of cicatrization, thinning of the sphincter, loss of muscle tissue, and other local pathologies (
Fig. 13.2), whi ch are present in approximately >35% of
primiparous women after vaginal delivery.
24–26
Even though it can be difficult to view the
EAS because its echogenicity is similar to that of the ischioanal fat, its usefulness is undeniable, given that it has 100% sensitivity and specificity for identifying defects of the
sphincter.
27
The use of USG 3D equipment has recently been described. It allows all the planes of
the anal canal to be seen (coronal, sagittal, and transversal), making it much easier for the
operator to correctly identify the structures that conform the sphincter, including the puborectalis muscle.
168 ANORECTAL DISORDERS
13.5.3.3 Other Imaging Studies
Defecography is utilized to objectively evaluate parameters such as the anorectal angle,
pelvic floor descent, the length of the anal canal, the presence of rectocele, and rectal prolapse or intussusception of the mucosa. In that radiographic test, approximately 150mL of
contrast material is placed inside the rectum and the patient is asked to perform defecatory maneuvers such as contracting the sphincter or attempting to expel the contrast
material. Nevertheless, interobserver concordance for measuring the anorectal angle
and the diagnosis of pelvic floor descent is very low and provides little additional information to that obtained through manometry. Another disadvantage of the test is radiation
exposure time, and therefore the continuation of its performance has been questioned.
Magnetic resonance imaging (MRI) is the only imaging modality that can visualize the
anal sphincters and overall movement of the pelvic floor in real time, with no radiation
exposure. Endoanal MRI has been shown to provide a superior image of the EAS with better spatial resolution.
26
The addition of dynamic pelvic MRI utilizing rapid imaging
sequences, or MRI colpocystography, which involves filling the rectum with ultrasound
gel as a contact agent and asking the patient to evacuate it while lying down inside the
scanner, can define the anorectal structures with greater accuracy.
28
With the availability
of open upright scanner units, dynamic MRI can now be performed with the patient in the
more physiologic seated position.
13.6 Treatment
The goal of treatment in patients with incontinence is to restore continence and improve
quality of life. A diagnostic-therapeutic algorithm for FI is illustrated in
Fig. 13.3.
2,4
13.6.1 Noninvasive Treatments
13.6.1.1 General Measures
Before considering pharmacologic therapy or surgical treatments, all patients should be
offered support measures that include the dietary modifications of reduced intake of
FIG. 13.2 Endoanal ultrasound images. (A) The image of a healthy subject, showing the internal anal sphincter (IAS) as
a complete hypoechogenic ring (short white arrow). The external anal sphincter (EAS) is shown as a thicker, round,
hyperechogenic structure (long white arrow). (B) The image of a patient with a defect that encompasses
approximately 90 degrees of the IAS and EAS (orange and green dotted lines).
Chapter 13 • Fecal Incontinence 169
Fecal incontinence
(FI)
Diarrhea with FI
YES
YES
YES
YES
Weak sphincter
no defects
Normal PNTML
Sensory abnormalities
hypo / hypersensitivity
Weak sphincter
Sphincter defects
Normal PNTML
Weak sphincter
Sphincter defects
Abnormal PNTML
Dyssynergic defecation
NO
NO
NO
NO
Assess etiology of
diarrhea
Consider fecalseepage due to
constipation-related overflow
or fecal impaction
No further evaluation is required
Recurrence
Persistent FI Constipation with FI
Clinical evaluation
Physical exam
Risk factors
Anorectal manometry
endoanal ultrasound
PNTML
Anorectal manometry
balloon expulsion test
defecography
General recommendations, diet, anal hygiene, symptomatic treatment
BFT
BFT
BFT
BFT
+
Surgery
BFT
+
SNS
Improve
Improve
Improve
Improve
TPNS, anal Plugs,
bulking agents, SECCA
Stem cell therapy
Transanal irrigation,
malone procedue,
colostomy
SNS
FIG. 13.3 Algorithm to approach patients with fecal incontinence. BFT, biofeedback therapy; SNS, sacral nerve stimulation; PNTML, pudendal nerve terminal
motor latency; PTNS, posterior tibial nerve stimulation.
170 ANORECTAL DISORDERS
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