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resolution anorectal manometry in patients with chronic constipation and fecal incontinence. Am J
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defects? Arq Gastroenterol. 2016;53:240–245.
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(DRE) for anorectal dysfunction: does experience matter? A prospective study. Am J Gastroenterol.
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patients with dyssynergia. Clin Gastroenterol Hepatol. 2010;8:955–960.
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36 ANORECTAL DISORDERS
4
Diagnostic Tools in Anorectal
Disorders
Henriette Heinrich
AB D O M I N AL C E N T E R , B A U C H Z E N T R UM S T . C LA R A S P IT A L , B AS E L , S W I T Z E R L A N D D I V I S I O N O F
GA S T R O E N T E R O L O G Y A N D H E P A TO L O G Y , UN I V E R S I T€aTS S P I T A L Z€UR I C H , Z€UR I C H ,
SW I T Z E R L A N D
Abbreviations
3D ARM 3D high-resolution anorectal manometry
AD anorectal disorders
ARM anorectal manometry
BET balloon expulsion test
DD dyssynergic defecation
DRE digital rectal examination
EAS external anal sphincter
ED evacuatory dysfunction
EMG electomyography
EndoFLIP functional lumen imaging probe
FDD functional defecation disorders
FI fecal incontinence
HR-ARM high-resolution anorectal manometry
IAS internal anal sphincter
IBD inflammatory bowel disease
IBS irritable bowel syndrome
MRD magnetic resonance defecography
MRI magnetic resonance imaging
OASIS obstetric anal sphincter injury
PNTML pudendal nerve terminal motor latency
4.1 Introduction
Anorectal disorders (ADs) have a high prevalence and affect approximately 25% of the
general population.
1–3
Fecal incontinence (FI) and evacuatory disorders (EDs) not only
cause a significantly diminished quality of life in patients, but also represent a relevant
medical and economic challenge. Symptoms of AD are often not mentioned by affected
patients due to social stigma and/or being perceived as part of aging.
4
On the other hand,
doctors often neglect to screen for symptoms of AD.
1,2
Anorectal Disorders. https://doi.org/10.1016/B978-0-12-815346-8.00004-7
© 2019 Elsevier Inc. All rights reserved.
37
The physiology of fecal continence is a complex interaction of anal, rectal, colonic and
pelvic-floor structure, sensation, and function.
5
Symptoms of AD frequently overlap and
the underlying pathophysiology is often multifactorial.
6
Therefore diagnosis and therapy
of ADs based on symptoms alone is not sufficient.
5
The current tests for AD (Fig. 4.1) on their own do not provide an adequate assessment
of anorectal function and guidelines recommend a series of tests for better definition of
the underlying pathophysiology.
7
Diagnostic tools for the description of ADs based on physiology are presented in
Fig. 4.1.
4.2 Initial Approach to the Patient With Anorectal
Dysfunction
A detailed history,physical examination and standard investigations (blood tests, imaging,
endoscopy) to rule out serious underlying pathology, such as colorectal malignancy and
inflammatory bowel disease (IBD), are mandatory in patients with symptoms of anorectal
dysfunction.
8
After the relevant pathology has been ruled out by adequate testing, and first-line therapeutic measures, such as diet modification and medication, have failed to improve the
symptoms of AD, guidelines recommend a series of diagnostic tests of anorectal structure
and function to guide further m anagement and treatment.
History and symptoms alone cannot sufficiently diagnose the cause of anorectal dysfunction. Digital rectal examination (DRE) is a simple, cheap, office-based test to achieve
an initial assessment of anal sphincter and pelvic floor function. Despite its simplicity, it is
a vastly underused modality. A survey among 246 final-year medical students revealed
Parameter Diagnostic test
ARM, HR-ARM, 3D-ARM, anorectal
neurophysiology
Endoflip*
Endoanal and pelvic floor ultrasound, MRI
and barium defecography
Balloon distension, rectal barostat**
BET, barium, and MRI defecography
Anal motor function
Anal distensibility
Anal and pelvic floor structure
Rectal sensory and motor function
Rectal evacuation
* Not yet established clinical practice
** Onl
y
rectal barostat can assess rectal capacity and compliance
FIG. 4.1 Tests of anorectal physiology.
38 ANORECTAL DISORDERS
that approximately 20% had never performed DRE and that 50% could not confidently
interpret obtained findings.
9
Inspection of anorectal skin can reveal inflammation and excoriation from fecal soiling
as well as indications for fistula or skin tags. DRE can detect strictures, tumors in the anal
canal or distal rectum, tenderness, or the presence of stool or blood in the rectum. Furthermore, the presence of rectal prolapse and rectocele can be assessed. While sphincter
defects can be palpated during DRE, specificity for the distinction of small from severe
anal sphincter defects is low.
10
Resting and squeeze tone of the anal sphincter, pelvic floor movement, and anal relaxation during push maneuvers can be assessed during DRE. Dyssynergic defecation (DD),
i.e., paradox contraction of the anal sphincter during simulated defecation, can be diagnosed with high sensitivity (75%) and specificity (87%) by a skilled investigator with DRE,
even when compared to manometry.
11,12
A full DRE should be performed as a first-line assessment, before further tests of anorectal function and structure are undertaken.
4.3 Tests of Anal Motor Function
4.3.1 Anorectal Manometry
Anorectal manometry (ARM) is the most commonly performed, widely accepted and bestestablished investigation of anorectal motor function and recto-anal coordination in FI
and ED. Pressures in the anal canal at rest and during squeeze and simulated defecation
are recorded utilizing pressure-sensing catheters. Pressure changes in the anal canal and
rectum are visualized either by line traces (conventional manometry) or color-contour
plots (high-resolution manometry). Water perfused and solid-state catheters with varying
numbers of sensors and different designs are used in clinical practice.
4.3.1.1 Anorectal Manometry for the Investigation of FI
Several studies have demonstrated low anal resting pressure on ARM to be associated with
passive FI; however, sensitivity for this finding is low.
13
Urge FI is correlated with low pres-
sure during squeeze maneuvers.
14
However, conventional manometry measures of rest
and squeeze show a significant overlap between health and disease possibly limiting its
diagnostic accuracy in FI.
15
High-resolution anorectal manometry (HR-ARM), utilizing a higher number of closely
spaced pressure sensors with data presented as color-contour pressure topography plots,
not only allows for a more intuitive analysis of obtained data but also offers improved sensitivity in the distinction between health and FI when newer metrics of contractility are
applied.
16
3D-ARM, which is performed using a rigid catheter with 256 circumferential sensors,
can depict the physiological asymmetry of the anal canal with higher pressures in the
Chapter 4 • Diagnostic Tools in Anorectal Disorders 39
posterior proximal and anterior distal parts of the sphincter complex and pressure defects
seen on 3D-ARM correlate with findings of endoanal ultrasound.
17
4.3.1.2 Anorectal Manometry in the Diagnostic Workup of ED
“Defecatory forces” and recto-anal coordination are usually defined and quantified by
manometry to diagnose DD according to the RAO classification (
Fig. 4.2) as a cause for
ED. While HR-ARM can detect more functional and structural abnormalities during
simulated defecation in comparison to conventional manometry and shows high concordance wi th magnetic resonance imaging (MRI) defecogra phy, patterns of DD are frequently seen in health.
18
Pelvic-floor akinesia, i.e., lack of pelvic-floor movement on
simulated defecation and squeeze is a new HR-ARM metric with high sensitivity and specificity for poor evacuatory function.
19
Both HR-ARM and 3D-ARM c an be used to detect pressure phenomena suggestive of
structural disease such as rectocele, prolapse, and intraanal intussusception when compared to other imaging modalities. 3D-ARM can also depict pelvic-floor decent to a degree
comparable to defecography in experienced hands.
20,21
Regardless of these innovations, interpretation of manometric findings is still challenging, as marked variability regarding protocol, equipment, and metrics exists.
22
Catheter
configuration, diameter (water perfused vs solid-state design), sensor configuration of
FIG. 4.2 All four types of DD classified according to rectal pressure during simulated defecation and anal pressure are
shown. Note that type IV (pelvic-floor akinesia) in conjunction with poor voluntary function during squeeze is
associated with poor evacuatory function.
40 ANORECTAL DISORDERS
HR-ARM solid-state catheters (unidirectional vs multidimensional), and sensor density
(3D-ARM vs HR-ARM) impact on measurements and only limited sets of normal values
obtained from sufficient numbers of healthy volunteers stratified according to age, sex,
parity, and gender exist.
23
4.3.2 Functional Lumen Imaging Probe
The functional lumen imag ing probe (EndoFLIP) is a new diagnostic tool used to
assess distensibility in the gastrointestinal tract via impedance planimetry. The use
of EndoFLIP in the anal canal has not yet entered routine clinical practice, but in
the esophagus it is used to guide treatment in achalasia and before and after
fundoplication.
24
The distensibility of the anal canal plays a role in the continen ce mechanism, as
recent studies comparing anal distensibility in FI patients with healthy controls have
shown. Pat ients had higher distensibility of the an al c anal regardless of the underlying
pathomechanism of FI (atrophy vs. sphincter injury) when compared to healthy
controls.
25
EndoFLIP showed increased anal distensibility in a subset of FI patients with normal
sphincter pressures at rest and during voluntary effort on HR-ARM.
26
Anal distensibility
may therefore be more sensitive to clinically relevant pathology than anorectal
manometry alone.
4.3.3 Anorectal Neurophysiology
Electromyography (EMG) and evaluation of pudendal nerve terminal motor latencies
(PNTML) are mainly used in the investigation of FI symptoms. EMG can assist to identify
sphincter defects of the external anal sphincter (EAS), can be used to assess striated muscle function, and can be used for the investigation of neural injury.
The neuromuscular integrity between the pudendal nerve and the anal sphincter is
investigated by PNTML.
5
Both tests are usually performed in postpartum FI to detect denervation of the EAS due
to stretch injury during pregnancy and after (forceps assisted) delivery.
Today, EMG is most commonly applied in biofeedback therapy and pelvic-floor
retraining for FI and ED to provide visual feedb ack during squeeze and push maneuvers.
27
Abnormal EMG activity (i.e., pathologic motor unit action potential activity, fiber density,
and jitter) correlate with sphincter pressures measured on ARM and can distinguish
between health and disease.
28
Prolonged latencies on PTNML indicate pudendal neuropathy but the technology is
highly operator-dependent, the sensitivity and specificity of results are low, and results
are marred by a significant variability in health. Therefore its utility in clinical practice
is disputed.
5
Both tests are mainly used in tertiary care centers and need to be performed in conjunction with other tests of anorectal function.
Chapter 4 • Diagnostic Tools in Anorectal Disorders 41
4.3.4 Trans-Lumbar and Trans-Sacral Rectal and Anal Motor Evoked
Potentials
Another promising tool for the investigation of spino-anorectal pathways is magnetic
stimulation of the lumbar and sacral regions overlying the nerve plexus to record motor
evoked potentials (MEPs). Translumbar and transsacral MEPs of the rectum and anus are
better indicators of neuromuscular injury in FI but this technique is not widely available
and still confined to research.
29
4.4 Tests of Anorec tal Structure
4.4.1 Endoanal and Pelvic Floor Ultrasound
Endoanal ultrasound is an easy, widely available and well-tolerated diagnostic test that
allows depiction of the internal anal sphincter (IAS) and EAS. It is performed for a wide
range of indications: assessment of sphincter defects in FI (especially when surgery is considered), obstetric anal sphincter injuries (OASIS), anal fistula assessment prior to surgery
or anal trauma, congenital anorectal malformations, and staging of anal neoplasms.
30
Findings associated with passive FI on endoanal ultrasound are defects and atrophy of
the IAS.
31
Hypertrophy of the IAS can be seen in structural disease such as the presence of
prolapse or rectal intususception.
32
When the EAS is assessed by endoanal ultrasound the presence of defects, scarring
or atrophy can be observed.
33
EAS disruption is a characteristic feature of OASIS,34is
associated with anal hypocontractility, and may be found in up to two-thirds of patients
with FI.
35–37
Pelvic-floor ultrasound (i.e., transvaginal and transperineal ultrasound) is an emerging
office-based test, complimentary to ARM and defecography, which can detect organ prolapse during pelvic-floor movement, as well as structural and functional causes of ED.
38,39
However, it is mostly used in specialist centers.
MRI of the anal sphincter and especially the pelvic floor is mostly available in tertiary
care centers. Endoanal MRI allows comprehensive real-time assessment of EAS anatomy
and pelvic floor organ movement with reported impact on surgical management.
4.5 Tests of Anorectal Sensory and Motor Function
4.5.1 Balloon Distension and Rectal Barostat
The assessment of rectal sensory function is a cornerstone in the diag nostic work up of AD.
It can identify rectal hyper- or hyposensitivity in patients with FI and ED and give more
insight into the underlying pathomechanism and the competence of the rectal reservoir.
In a busy clinical practice rectal sensory testing via simple, fast balloon distension is
most commonly performed. An elastic balloon mounted on a Foley or a manometr y catheter is placed in the rectum and inflated with air either via syringe or pump to interrogate
42 ANORECTAL DISORDERS
sensory thresholds for first sensation, urge, and maximum tolerable volume. Balloon distension can detect hypo- and hypersensitivity in patients with FI and ED, but test performance remains poorly standardized.
5
Rectal barostat is the gold standard for assessment of rectal sensitivity, capacity, and
compliance. However, this technology is not widely available and time consuming to perform. Rectal barostat testing can give more information in patients with altered sensory
thresholds on balloon distension or where reduced/enlarged rectal capacity or hypo- and
hypercompliance are suspected.
5
An “oversized,” nonelastic bag with indefinite compliance is placed in the rectum and
inflated by a computerized pump at a predefined rate producing pressure/volume curves
allowing calculation of rectal capacity and compliance. The minimal distending
(i.e., intraabdominal) pressure is documented during a “conditioning” distention. In analogy to simple balloon distension sensory thresholds are interrogated during ramp or
phasic distensions.
The recent development of a short protocol barostat that cuts down investigation times
to about 10 min and can be performed either using a hand-held or a pump-driven device
could allow the use of barostat testing in wider clinical practice (Fig. 4.3).
40
When hyposensitivity is present in FI patients report involuntary loss of sto ol and sensory retraining has been shown to improve continence.
41
Hypersensitivity is frequently
FIG. 4.3 Schematic depiction of the differences between balloon distension and rectal barostat. While balloon
distension is usually manually driven and performed with an elastic balloon, rectal barostat is performed with an
oversized barostat bag that adapts to rectal anatomy. Assessment of rectal capacity and function is possible due to
recording of rectal filling volume and pressure.
Chapter 4 • Diagnostic Tools in Anorectal Disorders 43
encountered in patients with urge FI and is associated with reduced rectal compliance
and/or capacity.
13
In diarrhea predominant IBS, ulcerative colitis, radiation proctitis,
and after low anterior resection rectal hypersensitivity is common and is associated with
symptom severity.
42
Rectal hyposensitivity can be a frequent feature in constipation either with or without a
large rectal volume and increased compliance (megarectum).
5
Both balloon distension and rectal barostat measurements are affected by age, the rate
and pattern of distention, patient position, and biomechanical and structural properties
of the rectum and the balloons used. Therefore interpretation of results needs to be based
on appropriate normal values.
5
4.6 Tests of Evacuation
4.6.1 Balloon Expulsion Test
The balloon expulsion test (BET) is a simple and low-cost tool to assess the ability to evacuate stool and diagnose ED. Patients are positioned in the left lateral position with the hips
and knees flexed. A lubricated, preferably nonlatex balloon attached to a plastic catheter
with a stop lock is inserted into the rectum and inflated with 50 mL of warm water. The
patient is seated on a commode or toilet and asked to expel the balloon in private. The
time until balloon expulsion is recorded. The test should be stopped after 2min if the balloon has not been expelled. Failure to expel the balloon in the given time frame is indicative of ED with sensitivity and specificity ranging between 68%–94% and 71%–81%,
respectively.
43
However, about 16% of healthy volunteers cannot evacuate the balloon,
suggesting that BET performed on its own is not sufficient to diagnose ED.
44
A recent prospective study in 100 patients with functional constipation has shown only moderate
agreement between BET and ARM and poor agreement with other test of evacuatory
function.
45
In spite of excellent reproducibility in disease, study equipment, inflation medium,
inflation volume, and patient position are not standardized, and due to the variability
in methodology there are differing cut offs (>1 min, >2 min) for pathologic BET.
43,44
Demographic factors have an impa ct with healthy male subjects showing a shorter BET
than women and balloon expulsion time increasing with age.
46
The BET should therefore
be performed in conjunction with other tests of evacuation as BET cannot distinguish
between functional and structural causes of ED and is therefore used as a screening test
to inform on the necessity of further investigations.
4.6.2 Colonic Transit
Although colonic transit testing is not a test of evacuation per se, it can be used in patients
with constipation to distinguish slow and normal transit constipation from structural or
functional ED. Patients are asked to stop laxatives at least 5 days prior to testing and swallow a capsule containing radiopaque markers; transit of the markers is monitored by
44 ANORECTAL DISORDERS
abdominal radiographs taken at different time points depending on the center’s specific
protocols. When at least 80% of the markers have been passed on the final X-ray the study
is considered normal. Pooling of markers in the rectum suggests ED and scattered markers
throughout the colon are suggestive of slow-transit constipation.
47
4.6.3 Defecography
Evacuation proctography with barium and MRI defecography (MRD) are established diagnostic tools used to identify the structural or functional causes of ED. They depict the
pelvic-floor anatomy before and after treatment and can rule out organ prolapse.
9
Both
technologies evaluate the morphology of the rectal wall as well as pelvic-floor movement
and rectal evacuation.
48
MRD has the additional advantage of not exposing the patient to
radiation and enables the imaging of all pelvic compartments.
49
Barium defecography and MRD image the anorectum during contraction of the pelvicfloor muscles and evacuation (simulated defecation) after barium paste, or ultrasound gel
mixed with gadolinium in the case of MRD, has been instilled into the rectum.
50
Although
seated configuration MRIs exist and have been shown to be superior in the diagnosis of
intussusception, MRD is mostly perfor med in the supine position.
During barium proctography patients are seated upright, in the physiological position
for defecation.
Both methods are used to assess evacuation and can diagnose anatomical and
“functional” problems in ED, such as rectocele, rectal prolapse and megarectum, DD,
and levator-ani and descending perineum syndrome.
48
Although multiple systems for defining and gradin g pelvic floor structure exist
for MRD and barium proctography, standardization and normal values are still
lacking.
51,52
Furthermore, recent comparative studies of tests of evacuation have shown limited
diagnostic agreement and significant overlap in results between patients and healthy controls. According to these studies the presence of rectoceles of up to 4cm is frequently
found in asymptomatic females.
45,50
When compared to MRD, barium defecography,
due to its performance in the upright or sitt ing position, is more accurate in diagnosing
intussusceptions and retentive rectoceles.
53,54
However, only defecography can simultaneously assess rectal emptying and pelvic
floor anatomy, making it one of the first-line imaging tests in the diagnosis of ED.
8
4.7 Summary
There are multiple Tools to assess the symptoms of anorectal dysfunction which might not
all be available in clinical practice. However, to provide a comple te and comprehensive
assessment of the complexity of anorectal function, guidelines recommend a combination of anorectal tests to assess anal motor function, rectal sensory function, and evacuation. A minimum set of tests could be anorectal manometry, balloon distension, and
Chapter 4 • Diagnostic Tools in Anorectal Disorders 45
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