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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_1110_Библиотеки_им_академика_М_И_Перельмана
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Fig. VII.6. Anorectal catheter with balloon tied at the proxi-
mal end
A new kind of catheter, different from solidstate and water-perfused systems, is the Latitude
(Clinical Innovations) single-use, air-charged
catheter. Body diameter is 2.5 mm, and all four
sensors are circumferential (Fig. VII.7).
Section VII • Anorectal Physiology Testing 267
Finally, more sophisticated probes equipped
with microtransducers should avoid artefacts due to
the water infusion used in perfused catheters.They
are thinner but fragile, more expensive, and need a
special disinfection procedure. They can record the
finest pressure variations for better assessment of
sphincteric function and can be connected to a
portable data recorder, allowing prolonged anorectal pressure recordings of >24 h (Fig.VII.8). During
the recordings, all subjects are fully ambulant at
home and instructed to press a button on the data
recorder to mark the time of events such as eating,
walking, and sleeping. Data are then transferred
from the portable data recorder to a personal computer for further analysis.
Even if anorectal manometry is the oldest procedure in the functional diagnosis of anorectal
disorders, a number of controversies still exist
about the correct modality of examination [1–4].
There is no agreement between pressure units
(millimeters of mercury, mmHg or centimeters of
water, cmH
O) and due to the variability between
2
different instruments,normality values have to be
a
c
Fig. VII.7. Latitude single-use, air-charged catheter (Clinical Innovations) (a–c)
b
268 Benign Anorectal Diseases
Fig. VII.8. Ambulatory manometry device with monitoring
box for prolonged (24-h) recordings
derived from a number of normal subjects examined in each center so that a wide spread in reference values exists between investigators, with consequent problems in comparing and interpreting
similar clinical condition.
Examination Procedure
An enema is usually required before the procedure to clean the rectal ampulla. The most pre-
ferred patient position during anorectal manometry is the left lateral.All lines of manometry must
be perfused in order to eliminate air and then
avoid artefacts in pressure acquisition. Before
starting the pressure acquisition, a calibration of
the system is usually required. Insertion of the
catheter through the anus will follow, reaching the
lower rectum (Fig. VII.9). Each step of the examination procedure can be differentiated [1–4].
Measurement of resting pressure for 70–80%
expression of internal sphincter activity (normal
range: 40–80 mmHg) can be performed by rapid
or slow pull-through of the catheter; an automatic puller can be provided, maintaining a constant
speed of catheter extraction (Fig. VII.10). A pressure profile of the anal canal pressure is obtained,
and the high pressure zone (HPZ) can be identified
(Fig.VII.11). The HPZ, defined as the length of the
internal sphincter in which pressures are greater
Fig. VII.9. Diagram of the positioning of a multichannel
anorectal catheter with longitudinal side holes
Fig. VII.10. Automatic probe extractor
Section VII • Anorectal Physiology Testing 269
Fig.VII.11. Measurement of resting pres-
sure and high-pressure zone (HPZ). PB
pressure begin, PE pressure end
than half of the maximum pressure at rest,is generally about 2–3 cm in length in women and about
2.5–3.5 cm in men. The maximum and mean resting pressure is calculated, as well as the function-
al anal canal length. Several other parameters are
allowed by the computerized system of pressure
a
analysis concerning different segments of the anal
canal.A vector manometry profile of all pressures
acquired along the anal canal can be obtained
showing, in a three-dimensional view, the areas
and levels of the anal canal with increased or
decreased pressures (Fig.VII.12).
Fig. VII.12. Vector manometry profile
obtained during anorectal manometry. It
refelects all the pressures acquired along
the anal canal showing, in a three-dimensional view, the areas and levels of anal
canal with increased or decreased pressures. In (a) the vector profile is the
expression of all pressures registered. in
(b) it represents the “resistence” offered
by the anal canal to the water pressure
b
during manometric measurements
270 Benign Anorectal Diseases
a
b
With the catheter placed in the HPZ, the patient
is asked to squeeze as much and as long as possible
in order to calculate maximum squeeze pressure.
The estimated characteristics of squeeze pressure
are essentially the absolute pressure level (normal
range: 90–180 mmHg), the difference from basal
pressure (normal range: two to three times the
baseline resting value),and the duration of contraction (Fig. VII.13). These parameters are expressions
of striated muscle activity. The EAS should normally stay contracted for at least 3–5 s. Less than 3 s is
considered abnormal. Squeeze pressure is unequally distributed. The pressures are radially equal in
the middle of the anal canal while in the proximal
anal canal, the pressure is highest posteriorly and
Fig. VII.13. Measurement of squeezing
pressure (a, b)
lowest anteriorly because of the force provided by
the puborectalis. Also during the voluntary squeezing, a vector manometry can be obtained.
Moreover,pressures can be recorded during straining to investigate the normal decrease (expression
of relaxation of both IAS and EAS) or, otherwise, a
paradoxical increase or lack of decrease of resting
pressure in pathological conditions (anismus and
pelvic floor muscles incoordination).
A confirmation of anismus is obtained with
the balloon expulsion test. This test is performed
by asking patients to expel on a commode a waterfilled balloon placed in the rectum in order to
explore defecation pattern.Water is instilled into a
10-cm-long latex balloon. The total volume intro-
Section VII • Anorectal Physiology Testing 271
a
b
duced is the minimum required to induce sustained desire to defecate. The test is considered
normal if the balloon can be expelled in <60 s. It
is important to individualize the volume of water
used to fill the balloon because a sustained feeling
of defecation is necessary to start the defecatory
maneuver. The use of a volume insufficient to
achieve a constant desire to defecate would overdiagnose anismus.
The study of rectoanal inhibitory reflex (RAIR)
is usually performed with the catheter within the
HPZ (measuring anal canal pressures during
reflex) and the balloon located in the rectum. The
operator rapidly inflates the balloon with air (or
water), eliciting the following events (Fig. VII.14):
– Rectal contraction consequent to the percep-
tion of the balloon, which mimics stools; this
contraction induces the balloon to proceed to
the anal canal reaching the sensitive mucosa
– Relaxation of the IAS, with a prompt decrease
Fig. VII.14. Rectoanal inhibitory reflex
(RAIR): rectal balloon inflation elicits
inhibition of the internal anal sphincter
(IAS) with decreasing of resting tone
and contractile response of the external
anal sphincter (EAS).R rectum, A ampli-
tude, D duration (a). The graph shows a
normal RAIR (b)
of resting pressure proportional in amplitude
and duration to the intensity of the stimulus.
Usually, this relaxation does not proceed to a
complete weakness of the anus in order to
avoid lack of feces, the physiologic meaning
being only to ascertain the presence of stools
to be evacuated (sampling reflex)
– Contraction of the EAS, sending back the bal-
loon into the rectum and recovering the previous anal resting pressure; physiologically, this
phase allows the patient to delay defecation in
an appropriate time and condition.
The minimal volume required to elicit the IAS
relaxation (decrease in pressure 10–15 mmHg) is
defined (n.v.: present with volumes of 10–20 ml).
Increasing the inflation of air or water, the RAIR
threshold and the best relaxation/contraction
profile can be determined.
Rectal compliance is studied with the balloon
placed in the rectum and the catheter within the
272 Benign Anorectal Diseases
Fig. VII.15. The sigmoid-shaped curve of
rectal compliance
anal HPZ. The balloon is inflated with air at increments of 30–60 ml. The slope of the pressure-volume curve allows calculation of compliance
(DV/DP), maximum compliance being the ratio of
the maximal tolerable volume and the corresponding measured pressure (Fig. VII.15).
Rectal sensations are consciously perceived
during inflation of a balloon placed in the rectal
ampulla. This phase of the examination is inappropriately named as a part of anorectal manometry because no pressure is measured, but the
same catheter can be used. Actually, only the line
connected to the balloon is needed: the balloon is
slowly and progressively inflated with air (or
water), and the patient is asked to indicate the following three levels of rectal sensation:
– Threshold sensation: the first constant sensation
– Urgency sensation: the first defecatory desire
– Maximum tolerated volume: the higher volume
tolerated by the patient before lack of feces.
Normal range for threshold rectal sensation is
40–70 ml, for urgency sensation 60–130 ml, and for
maximum tolerated volume 150–230 ml.
Ambulatory manometry has shown that the
rectum undergoes periodic episodes of prolonged
high-pressure activity.This pattern of activity has
been termed rectal motor complexes (RMC). A
typical RMC consists of a burst of regular pressure fluctuations from 20 to 60 mmHg with a fre-
quency of three or six cycles per minute and duration from 3–to 30 min (Fig. VII.16). The nature
and the function of this activity is poorly under-
Fig. VII.16. Typical rectal motor com-
plex
Section VII • Anorectal Physiology Testing 273
stood. Sleep results in a reduction of rectal motor
activity whereas a meal provides a stimulus for
increased rectal motor activity.
Indications for Anorectal Manometry and
Findings
Patient history and physical examination (particularly digital) can indicate the need of performing
anorectal manometry.Several symptoms could be
suggestive of anorectal functional disorders: constipation (particularly obstructed defecation and
rectal prolapse), incomplete evacuation, straining
during defecation, necessity of digitation to evacuate,anal pain, tenesmus,minor or major incontinence, pruritus ani, previous anorectal trauma,
surgery, malformation, central or peripheral nervous diseases, or metabolic diseases with suspected secondary anorectal disorders.
At the digital examination (at rest and during
squeezing and straining), a few characteristics
could indicate anorectal manometry: a tight or patulous anus with apparent hypertonic or hypotonic
sphincters, respectively; lack of normal perianal
plication; scars (including those located in the
perivulvar/vaginal area); anal fissure; descent perineum; paradoxical sphincter contraction during
straining; decreased squeezing; rectal prolapse.
Other procedures can be indicated in conjunc-
tion with anorectal manometry: anoscopy,
endoscopy, myography, endoanal ultrasound
(EAUS) and radiologic tests [defecography, computed tomography (CT) scan,magnetic resonance
imaging (MRI)]. In most patients, only a multidisciplinary diagnostic evaluation allows the highest
accuracy in clinical assessment, this being the
appropriate way of planning effective treatment
[1–4].
The only functional disease in which anorectal
manometry has a primary role in diagnosis is
Hirschsprung’s disease. In this clinical condition,
frequent in children presenting with constipation
due to aganglionosis of the bowel, manometry
demonstrates the absence of RAIR irrespective of
volumes of air inflated. Similar manometric (and
functional) features can be observed in patients
with a significantly reduced number of bowel
ganglia.
Increased resting pressure is the most frequently associated manometric finding in
patients with an anal fissure; it can be observed
also in patients with constipation, either idiopath-
ic or associated with other pelvic floor disorders
(obstructed defecation, rectocele, enterocele,
internal intussusception, anismus, internal
sphincter hypertrophia). The resting pressure
profile should be accurately evaluated (distinguishing total or distal hypertonic anal canal) to
explain pathophysiology of the disorder and
choose the appropriate therapy. On the other
hand, a decreased resting pressure can be found in
patients with minor (soiling or seepage, incontinence to flatus) or major incontinence (to liquid
or solid stools), idiopathic, secondary to anal traumatic or surgical (not only for anal diseases but,
unfortunately,also due to obstetric causes) events,
or neurogenic and metabolic diseases; moreover,
IAS atrophy shows reduced resting pressure.
Detailed analysis of pressures recorded from
each channel as well as data from vector manometry can be of help in identifying the site of a possible sphincter lesion. However, even if study of
the pressure profile is of primary importance in
the diagnostic assessment, manometric data
should be related to other diagnostic findings,
particularly from EAUS or MRI, which seems
more accurate in locating site(s) and extent of
sphincter defect(s).
A decreased squeeze pressure is a manometric
sign of reduced activity of striated muscle
(including EAS,puborectalis muscle, and,at large,
levator ani muscle). It could be due to an EAS
lesion (secondary to trauma or obstetric or anal
surgery) or to idiopathic or neurogenic muscle
insufficiency. Also, in case of reduced squeeze
pressure, analysis of pressure profile characteristics and vector manometry is useful, as well as the
myographic evaluation, but EAUS or MRI are
more accurate in determining the precise morphology of sphincter lesions.
As mentioned above, the balloon expulsion
test is a simple and meaningful phase of manometric study, identifying patients with impairment of normal defecation during straining.
Inability to push out the balloon may reflect lack
of sphincter relaxation (functional outlet constipation) or mechanical obstruction. This test has
not been proved to be of clinical value,but it helps
to identify patients with pelvic dyssynergia,
defined as paradoxical contraction or failure to
relax the pelvic floor muscles during attempts to
defecate.
Abnormalities of functional anal canal length
can be frequently observed: higher values in
hypertonic anal canal; lower values in patients
274 Benign Anorectal Diseases
with sequelae of anal surgery or fecal inconti-
nence. These features need to be correlated to
other manometric and nonmanometric findings.
Except for Hirschsprung’s disease, just what
diagnostic role should be attributed to the modifications of RAIR characteristics (threshold, rate
and duration of relaxation,and contraction) is not
well defined. Especially, loss of proportionality
between intensity of the stimulus and amplitude
and duration of RAIR, eventually associated with
abnormalities of rectal sensation, or the absence
or significant reduction of anal contraction during voluntary squeeze may indicate central neurologic disease. Rectal compliance presents
increased values in patients with rectal hypotonia
while it can be decreased when a prevalence of
fibrosis of the rectal wall is present (inflammatory
bowel disease or chronic sequelae of high-dose
pelvic radiation therapy).
Abnormalities of rectal sensations play a major
role in several functional disorders of defecation.
Increased levels of rectal sensation parameters can
be frequently found in patients with chronic constipation; in these cases, a larger amount of feces is
necessary to elicit awareness of defecation need,
and, consequently, the patient delays evacuation too
long. Similar manometric alterations are also frequently found in patients with megarectum or
obstructed defecation in presence of rectocele,
internal intussusception, or rectal prolapse.
Pathophysiology of these abnormalities involves
the afferent/efferent nerve supply to the rectal wall
and perirectal space, particularly nerve endings
(thought as desensitized) and nerve fibers (toward
the pudendal nerves, which could be altered by
muscle and nerve stretching that occur frequently
during straining). Moreover, chronically constipated patients (in particular, older and institutionalized subjects) could present increased rectal sensation with pseudoincontinence due to the passive
passage of liquid stools (not perceived because of
too high a threshold of rectal sensation) between
rectal wall and large and hard, solid stools in the
rectal lumen. Also, decreased rectal sensations are
frequently observed, in particular in subjects with
hypersensitized nerve receptors. This condition is
typical of patients with inflammatory bowel disease
or treated with high-dose pelvic radiation therapy
and who complain of frequent tenesmus as well as
soiling or transient episodes of major incontinence.
No univocal alterations of rectal sensation
(increased or decreased levels) can be recorded in
patients presenting with similar clinical condi-
tion, either constipation or incontinence. This is
possibly due to a secondary deregulation of the
physiologic balance between the different nervous
systems (sympathetic, parasympathetic, somatic,
motor, sensory, etc.) involved in the complex defecation (and voiding) functions. Damage of one
system could impact the others with prevalence of
their functions. Pelvic nerve damage secondary to
pelvic surgery (frequently for gynecologic reasons
or rectal tumors) is more frequently associated
with higher levels of rectal sensations and subsequent constipation (and urinary retention). Also,
patients with partial or complete spinal cord
injury could present increased rectal sensation
parameters associated with constipation (and urinary retention).A number of patients with neurogenic fecal incontinence not due to sphincteric
lesions present different patterns of rectal sensations, including increased, decreased,or even normal levels. These clinical and manometric conditions are under investigation in order to elucidate
more detailed aspects of the influence of sensory
functions on normal and altered defecation and
the impact of specific therapies (i.e., sacral neuromodulation) on their improvement.
Anorectal Electrophysiology
This diagnostic approach includes a few tests
directed to patients already investigated with history and physical assessment and other procedures (mainly manometry and ultrasound) in
whom pelvic muscular and/or nervous functions
seem to be altered.Electrophysiological tests used
to study the anorectum are derived from myographic and nerve conduction examinations performed in other parts of the body, and over the
last 20 years an evolution of instruments, techniques of examination, and indications has been
registered [5].These tests add important addition-
al information on the physiology of defecation
and continence [1–3, 5].
Technique of Anorectal Electrophysiology
Electrophysiological studies are usually carried
out using a neuromyography system equipped
with software dedicated to anorectal physiological
evaluation (Fig.VII.17). The examination includes
tests evaluating electrical muscle activity and
nerve functionality [5]. In performing such tests,
Fig. VII.17. Keypoint electromyographic system (Medtronic)
either a recording function or an electrostimulating function or both can be requested. The neuromyographic instrument needs to be connected
to dedicated cables and electrodes. As with
anorectal manometry, before anorectal electrophysiology, an enema is usually required to clean
the rectal ampulla; thus, when available, both
examinations could be performed in the same session (electrophysiology must follow manometry
in order to avoid sphincters manipulation before
measurements of resting pressures). The most
preferred patient position during this procedure
is the left lateral,and a ground electrode soaked in
normal saline is placed around the thigh.
The purpose of electromyography (EMG) is to
investigate electrical activity of the EAS and the
Section VII • Anorectal Physiology Testing 275
other striated pelvic floor muscles at rest and during squeezing and straining. Over time,four different types of electrodes have been developed: concentric needle, monopolar wire, single-fiber electrode, and surface electrode (Fig.VII.18). The concentric needle electrode consists of a thin needle
(0.1 mm in diameter) covered by an insulating
resin, which is able to uptake electrical activity of
the small area into which it has been inserted; this
needle is unable to record single muscle fiber
action potentials. Under the guidance of digital
anal exploration, the needle must be inserted into
the EAS or puborectalis muscle; recordings from
the four anal canal quadrants should be obtained
(Fig. VII.19). This procedure is quite uncomfortable for the patient; the electrode could slide in a
different position during trace acquisition and,
even if multiple recording samples are taken, the
mapping obtained is far from being considered
sufficient to delineate accurately the area of normal and abnormal muscle. The monopolar wire
should reduce the patient’s discomfort and avoid
the electrode sliding because it is kept in site by a
small hook placed at the electrode tip. The singlefiber electrode is thinner than the monopolar wire
and is able to record individual motor unit potentials. An appropriate amplification of the signals
recorded is necessary. Also, fiber density can be
calculated based on 20 different recordings from
each anal hemisphere. Evaluation with the singlefiber electrode is more accurate than the two elec-
trodes previously described but remains uncomfortable. Surface electrodes, mounted on an
endoanal plug or a small external adhesive plaque,
are able to record gross muscle activity but unable
a
b
c
Fig.VII.18. St. Mark’s pudendal electrode
(a), surface electrodes (b), and needle
electrode (c)
276 Benign Anorectal Diseases
a
c
Fig. VII.20. Surface electrodes positioning
b
Fig. VII.19. Needle electrode positioning (a). The needle is
introduced at the level of puborectalis muscle (b) and then is
withdrawn until it reaches the external sphincter (c)
to delimit areas of functional deficit (Fig. VII.20).
They are more useful to study paradoxical contraction of striated muscles than to evaluate
sphincter damage in incontinent patients.
Mucosal sensitivity can be evaluated with electrostimulation not only in the rectum (as does
manometry) but also in the anal canal using a bipolar ring electrode (containing two platinum wires
1 cm apart) mounted on a Foley catheter.An appropriate setting of stimulus duration and rate must be
done before starting the examination. During this
test, the electrode is inserted into the anus first.
From zero,the current amplitude is slowly increased
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