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4
Physiologic Testing
Lee E. Smith and Garnet J. Blatchford
Physiologic testing has been used to assess pelvic floor and
anorectal disorders for the past 35 years, but only in the past
two decades has this testing become of value for clinical use.
These physiologic tests are performed in conjunction with a
history, diary of the disorder, physical examination,
endoscopy, and often imaging studies. Physiologic tests have
provided or confirmed a diagnosis in 75% of patients with
constipation, 66% of patients with incontinence, and 42% of
patients with chronic anorectal pain according to one study.
The original physiologic testing equipment was homemade, so that all of the studies were based on a specific unit,
which was not available anywhere else; thus, the ability to
compare studies was almost impossible. In the past two
decades equipment has been commercially produced such
that reproducible results are possible. Even now a major problem is lack of a good set of normal values for healthy patients
of both sexes and of all ages. Physiologic testing includes several tests that complement each other, because there is not a
single test that contributes the data necessary to analyze disorders of the pelvic floor. Unfortunately, many patients have
diseases or disorders that are of multifactorial pathophysiologies that will give several abnormal results, which then are
more difficult to interpret. These tests include manometry,
defecography, anal ultrasound, magnetic resonance imaging
(MRI), transit time, pudendal nerve terminal motor latency
(PNTML), and electromyography (EMG). This chapter
describes these tests and their usefulness in evaluating adult
diseases and disorders.
age is needed. These normal measurements may be obtained
from sites using the same system, or studies of your own normal patients.
Indications
First, manometry is used for evaluation of incontinence.
A sphincter defect can be located and quantified. Second,
1
constipation, mainly outlet obstruction type, is investigated to
determine whether abnormal pressures exist. The loss of the
rectoanal inhibitory reflex (RAIR) suggests Hirschsprung’s
disease. Third, some anorectal pain syndromes are associated
with abnormal pressures within the sphincter mechanism.
Fourth, the study is conducted to establish a baseline when an
anorectal or pelvic floor procedure is contemplated. For
example, if biofeedback or a surgical procedure is to be used
for incontinence or constipation, a pre- and postprocedure
study provides the means to quantify a change.
Equipment
The equipment consists of several essential components: the
probe, the transducers, the recorder, and the hydraulic pump
for water infusion methods. There are two frequently used
methods: the water-perfusion method and the solid-state
method. The choice is based on cost and user experience.
Probes
Manometry
Manometry is a technique for measuring pressures existing in
the rectum and anus, and pressures and reflexes elicited by
voluntary actions or by local stimuli. The equipment and techniques vary, but investigators are beginning to use more standardized equipment and methods so that our descriptions of
the equipment and techniques can be focused on just a few. To
be able to interpret the data, the range of normals by sex and
40
The probes may be water perfusion, solid state, small balloon,
or large balloon; they may be either open-tipped or sideopening. The open-tipped and balloon probes have fallen into
disfavor. The most popular type is the water-perfusion probe,
which is relatively inexpensive, durable, and easy to use.
The water-perfusion catheter probe has side holes through
which water is slowly perfused, and pressure resistance of
the sphincter is exerted against the holes. The simplest
catheters have four holes at the same level on the probe; this
circumferential array will show asymmetry within the anal
4. Physiologic Testing 41
canal. A balloon is attached to the tip, and a central channel
in the tube opens into the balloon so that it can be inflated to
elicit reflexes or elicit sensations in the rectum. Each of the
side holes has an individual channel that can be connected to
transducers. The mechanical water pressure is transmitted
to the transducer.
The solid-state catheter is expensive and fragile, but it gives
the most accurate, reproducible results. The sensors are
located at the same level on the catheter, and a balloon, which
is inflatable, is attached to the tip. One sensor is located at the
tip within the balloon to measure the pressures within the rectum. The sensors are wired to a computer which gives a digital readout and a graph to show the pressure measurements.
During this discussion, the terms probe and catheter will be
used interchangeably.
Hydraulic Water-Perfusion Machines
The water-perfusion machine is a key part of the waterperfusion method. The water is driven through each of the
individual channels in the tube at a chosen rate; the water perfuses through the holes near the tip and thus is exposed to
pressure changes.
Transducers
Transducers are an essential part of the water-perfusion system. The water-perfusion catheter has individual channels as
described above; each perfusion channel has a side channel
that connects to a transducer. The side holes through which
water is slowly perfused also transmits pressures back to individual transducers. The mechanical water pressure is changed
to electrical signals in the transducer.
Amplifier/Recorder
Many recording devices are available, but at present computerized systems with small amplifiers and recorders are preferable. Software has been designed to give chart, table, and
graph printouts. An attached monitor is a useful way to
observe the tracings as the procedure is in progress.
Technique of Manometry
Initial Considerations
Usually manometry is performed using either the waterperfusion method or the solid-state microtransducer method.
In this section, reference to both will be made. In our laboratory, we first used homemade systems, later the water-perfusion
method, and now the solid-state method. Most of the discussion
will be based on the solid-state system, but mention of differences between systems will be made when appropriate.
The informed consent form is not necessary in many
American and international institutions, but our institutional
policy requires that we obtain a signed consent form. The
study is performed with focus on the distal 5 cm, which is the
segment that contains the sphincter muscles. It is not possible
to separate the puborectalis muscle from the external
anal sphincter. However, the internal sphincter and the external sphincter may be analyzed based on the portions of pressure represented by the resting tone and the squeeze pressure.
Preparation
The preparation is a simple small, tap-water enema or commercially prepared enema to empty stool from the rectum and
anus before coming for the examination. The patient is placed
in the left lateral position with the hips and knees flexed to 90
degrees. A digital examination with a well-lubricated glove is
done first to verify that the rectum is empty, sense the direction of the rectal lumen, and recognize any abnormalities.
Instructions about what the patient is to expect regarding
relaxation, breathing normally, not talking, squeezing on
command, and sensing the balloon will make the conduct of
the examination quicker and easier for all.
Calibration
Calibration is critical to obtain accurate, reproducible results.
The calibration record should be saved with the actual procedure recording to validate the measurements. For the waterperfusion method, the reservoir is filled, and the hydraulic
pump is set for a pressure of about 10 psi at a rate of less than
3 mL per minute. A large volume of water introduced may
produce an error; so ideally the flow rate should be far less at
a rate of 0.2–0.4 mL per minute. The transducers and the perfusion holes in the catheter should be at the same level during
calibration and during the procedure, or the baseline must be
zeroed again at the beginning. The transducers need to be
inspected for the presence of air bubbles which produce error;
the bubbles need to be removed.
The solid-state system does not need to be kept at the same
level during the procedure. Following the vendors instructions, the zero atmospheric level is the baseline, and usually a
high point on the scale of 100 mm Hg is measured.
Resting Pressure
The probe is introduced higher than the 5-cm level and left in
place for 5 minutes to permit the temperature to equalize to
body temperature and the sphincter mechanism to relax to a
baseline. The probe is oriented so that the posterior sensor corresponds to the recording of the posterior aspect of the anus. The
recordings are made by either the station pull-through technique
or the continuous pull-through technique. Most laboratories use
the station pull-through method. The catheter is pulled through
at 1-cm intervals, stopping to record the pressure at each increment for 10 seconds. As the sensors enter the sphincter mechanism, the pressure will be seen to increase over the baseline
rectal pressure. There is usually a stepwise increase in pressure
as the sensors progress distally (Figure 4-1). As the sensor
leaves the sphincter mechanism, the pressure will drop to zero.
42 L.E. Smith and G.J. Blatchford
4
FIGURE 4-1. Normal tracing of resting tone in one quadrant on the manometry probe. The scale is 100 mm Hg. The pressure progressively
increases from the 4-cm level to 2-cm level with a small decrease in pressure at the 1-cm level, and then to zero as the probe exits.
In the continuous pull-through method, the probe is pulled
through with a small motor at a continuous rate. A curve
reflecting the pressure zone is generated. The pressures generated by continuous pull through tend to be higher than those
obtained from station pull through.
3
2
1
Squeeze-Duration Study
The probe is positioned in the site of the highest pressure in
the anal canal. The high pressure zone is the length of the anal
canal with resting pressures at least 30% higher than rectal
pressure.
2
The patient is instructed to squeeze and hold the
squeeze for 45 seconds as the recording is made (Figure 4-3).
Squeeze Pressure
The probe is reinserted to at least the 6-cm level and reoriented. The probe is again removed at 1-cm increments. The
patient is instructed to squeeze the sphincter muscles as if to
stop a bowel movement and hold the squeeze for 3 seconds
(Figure 4-2). The patient is also instructed to avoid using
accessory muscles, especially the gluteals.
Using the continuous pull-through method, the patient is
asked to squeeze and hold the squeeze as a motor pulls the
catheter through the sphincter mechanism. The pull through
can be performed several times and the results can be averaged.
Some investigators perform this maneuver once and others do
two or three runs and average the results. This study is also
termed sphincter endurance.
Reflexes
The probe is again positioned in the high pressure zone in the
anal canal to observe for the RAIR. Then 10 cc of air is injected
into the balloon and the pressures are observed for 10 seconds.
Then air is inflated into the balloon at 20-, 30-, 40-, 50-, and
60-cc increments (Figure 4-4). The recording normally shows
a relaxation from the baseline, which verifies the intact reflex
from the stimulated rectal wall to the internal sphincter.
The probe is positioned in the high pressure zone again,
and the patient is asked to cough to elicit the “cough reflex.”
The squeeze pressure increases involuntarily to counteract the
increased abdominal pressure. Unfortunately, the artificial
situation in the laboratory while lying on the left side on a
table interferes with the patient’s willingness to make as good
efforts as they would in the privacy of their own toilet.
FIGURE 4-2. Normal tracing of voluntary squeeze in one quadrant on
the manometry probe. The scale is 100 mm Hg. The squeeze essentially doubles the resting pressure.
Strain Maneuver
The probe is positioned in the high pressure zone. The patient
is instructed to bear down as if to defecate for at least 5 seconds.
The pressure is normally reduced for a few seconds similar to
the RAIR (Figure 4-5). This maneuver is repeated after a 30second rest. The result is obtained by averaging the total runs.
To appreciate what is happening to the sphincter, the rectal
4. Physiologic Testing 43
IGURE 4-3. Normal squeeze duration study in one quadrant on the manometry probe positioned in the highest pressure zone.
F
100
mmHg
Stim 50cc
U
100
mmHg
U
Pos
Stim 40cc
Pos
Stim 30cc
Pos
Pos
Stim 20cc
Stim 15cc
FIGURE 4-4. Normal RAIR in one quadrant on the manometry probe. The scale is 100 mm Hg.
pressure is measured at the same time with the rectal balloon,
which corresponds to the increased abdominal pressure.
Rectal Sensation
The balloon is inflated in 10-cc increments until the patient
senses the balloon. The first sensation is normally at or before
20-cc inflation. The compliance test can be recorded by
continuing the balloon inflation as detailed below.
Compliance
Having recorded the first rectal sensation, the balloon is
inflated slowly in 50-cc increments. The patient will feel a
point at which there is a strong urge to defecate. This is
recorded. At a further point, the patient will experience a
discomfort, which is recorded as the maximal tolerated
volume. In the normal-sized rectum, this will be 200–250 cc
(Figure 4-6).
Pos
1st Sens 15cc
44 L.E. Smith and G.J. Blatchford
FIGURE 4-5. Normal strain maneuver. A relaxation occurs.
100cc
Stim 50cc
FIGURE 4-6. Normal compliance in one quadrant on the manometry probe. The patient reports the insufflation causing the first sensation, the
first urge, and the last tolerable volume.
Stim
Other
Ambulatory Anorectal Manometry
To record pressures over a long period of time, a sleeve
catheter, which simply records the highest pressure in the anal
canal, is fixed in place. The patient then carries a recorder during the decided upon time, perhaps 24 hours. This is generally
a research tool at this time.
150cc
Stim
Stim 200cc
circumferentially; and in the distal anus the pressure is
slightly less posteriorly. Overall, men and young patients have
higher pressures. However, there is overlap of normal measurements by sex and age.
4
The resting pressure has contributions from both the internal and external sphincters, with the
internal sphincter providing 75%–80% of the total. The
squeeze pressure is derived dominantly from the voluntary
external sphincter.
250cc
Stim
Normal values are difficult to verify, because the literature
Vector Manometry
This is best achieved with a probe that contains eight sensors in
radial orientation. The probe is drawn through the anal canal,
and the pressure profile shows the direction of abnormally
sources are based on small numbers of patients. Some of the
values vary, but by combining the totals from several authors,
average numbers for practical purposes can be obtained.
5,6
These will be listed in the following sections.
decreased pressure. Vector manometry has been generally
replaced by anal ultrasound.
Interpretation of Resting Pressure
Interpretation
Normals
In the anal canal there are subtle differences in the upper, middle, and distal segments.
riorly is lower; in the mid anus the pressures are about equal
3
In the upper anus the pressure ante-
The resting pressure is the pressure in the high pressure zone
at rest after a period of stabilization.
2
Seventy-five to 80% of
the resting pressure is a measure of the internal sphincter
7
tone.
For women, the resting pressure is approximately 52
mm Hg (range, 39–65). For men, the resting pressure is
approximately 59 mm Hg (range, 47–71). Sometimes a normal patient may have low pressures, but does not have a
4. Physiologic Testing 45
1m
mmHg
U
FIGURE 4-7. Low resting and voluntary squeeze pressures in an incontinent patient.
4
complaint if the stool is well formed. However, a patient may
have “normal” pressures, but yet complains of incontinence.
These measurements cannot be interpreted alone, but must be
analyzed in the context of the history and other measurements. At times, slow waves of 8–12 cycles/minute can be
seen on the tracings, but these are not associated with any specific pathology.
Low resting pressures are usually seen in patients who have
the chief complaint of incontinence (Figure 4-7).
who have low pressures may not be good candidates for a surgery that will leave them with a poorly formed or liquid stool,
such as total colectomy with ileorectal anastomosis or proctocolectomy with ileal pouch to anal anastomosis; these patients
might be better served with a permanent ileostomy.
3
2
3
1
pressure is examined as a total squeeze pressure, which
includes the resting pressure plus the squeeze, and as a maximum squeeze pressure, which is the squeeze pressure minus
the resting pressure.
A low squeeze pressure may be associated with sphincter
injury or nerve damage from surgery, especially anal fistula
surgery, obstetric trauma, or other anorectal trauma (Figure
4-7). Sometimes a patient will not cooperate during the test,
6,8,9
Patients
often because of local pain. At this point, use of an anal ultrasound is appropriate to identify possible sphincter injury.
High squeeze pressure is found in those patients who have
pelvic floor spasm (anismus), often associated with anorectal
pain. These same patients are unable to relax the sphincter
when asked to bear down as if to defecate.
High basal pressures may be associated with anorectal
pain. Some patients have spastic sphincters, which may be
associated with outlet obstruction. Also, patients with anal
fissure have a spastic internal sphincter with high pressure
measurements as part of the pathophysiology. These patients
may be candidates for lateral internal sphincterotomy.
Pharmacologic relaxation may be achieved in lieu of surgery.
Relaxation of internal sphincter spasm can be achieved by 10
mg of sublingual nitroglycerine. Topical 0.2% nifedipine or
0.2% nitroglycerine applied to the anoderm relaxes the underlying muscle.
10
Observation with a longer baseline tracing may show periods in which there is relaxation of the sphincter, even down to
the zero level; incontinence might be expected to be a complaint from patients with this finding. However, the opposite
can happen with episodes of spasms of high pressure. Some
of these patients can be seen to have ultraslow wave activity
of 1–2 cycles/minute.
Interpretation of Squeeze Duration
The sphincter duration is the length of time the patient can
maintain a squeeze pressure above the resting pressure. The
duration of squeeze should be >30 seconds at >50% of maximum squeeze pressure. When patients are unable to maintain
a squeeze, they may be incontinent. In this case, there may be
too few Type I motor nerves. There is a conversion from a
dominantly Type I nerve to Type II nerves as patients grow
older. The actual importance for this part of the manometry
study is not clear.
Interpretation of Reflex Studies
The RAIR is the transient decrease in resting anal pressure by
>25% of basal pressure in response to rapid inflation of a
rectal balloon, with subsequent return to baseline.
decrease in pressure during the RAIR test is a measure of
the internal sphincter relaxation.
Interpretation of Squeeze Pressure
The maximum voluntary pressure is the highest pressure
recorded above the zero baseline at any level of the anal canal
during maximum squeeze effort by the patient.
pressure is the pressure increment above resting pressure after
voluntary squeeze contraction and is a calculated value that is
the difference between the maximum voluntary pressure and
the resting pressure at the same level of the anal canal. The
squeeze pressure is mainly a measure of the external sphinc-
11
ter.
For women, the squeeze pressure is approximately
128 mm Hg (range, 83–173). For men, the squeeze pressure
is approximately 228 mm Hg (range, 190–266). The squeeze
2
The squeeze
volume inflated into the balloon, the rate of inflation, and
the rectal compliance. This reflex may be present even with
central nervous system disorders; however, disease that interferes with the peripheral nerves or ganglion cells of the myenteric plexus or fibrosis of the internal anal sphincter may
interfere with a measurable reflex relaxation. Likewise, a
megarectum might be associated with a poor reflex, because the
balloon does not touch the rectal wall to stimulate the reflex.
The presence of a normal RAIR rules out Hirschsprung’s
disease (Figure 4-8).
contraction may be seen in patients who have a hypertonicity of
the sphincter mechanism. Patients with fissures may also
manifest this rebound phenomenon.
5
4
13
When the balloon is deflated, a rebound
3
2
12
The reflex varies with the
1
2
The
46 L.E. Smith and G.J. Blatchford
15:02.2
FIGURE 4-8. Absent rectoanal reflex (RAIR), consistent with Hirschsprung’s disease. Each spike is an insufflation, but no RAIR follows.
The cough reflex is the pressure increment above resting
pressure after a cough, and is a calculated value that is the difference between the maximum pressure recorded during
cough and the resting pressure at the same level in the anal
2
canal.
The cough reflex, also equated with a Valsalva reflex,
is a rectal reflex to counter a sudden abdominal pressure
increase. This sacral reflex prevents soiling during abdominal
pressure increases. This reflex may be abolished if there is a
disruption of nerves in the cauda equina, sacral nerves, pudendal nerves, or peripheral nerves, but is maintained if nerves
higher than the sacrum are injured.
Interpretation of Strain Maneuver
The ability to defecate requires both anal relaxation and
abdominal compression. As mentioned previously, the patient
has difficulty straining and bearing down as if to defecate in
this artificial environment. Embarrassment and fear of accidental passage of gas, liquid, or solid stool prevents complete
cooperation.
Low abdominal pressures may be seen when there is central nervous system disruption or skeletal muscle disorders
that prevent abdominal compression. Very high abdominal
compression occurs when the anal sphincter does not relax,
permitting high, recurrent pressures to be exerted on the
pelvic floor.
The failure for the sphincter to relax appropriately is
termed anismus or paradoxical pelvic floor contraction
14
(Figure 4-9).
Such outlet obstruction may also interfere with
interpretation of a transit time study. The failure to relax has
been found in sexually abused patients and in neurologic disorders where inhibitory pathways are ablated.
FIGURE 4-9. Paradoxical increase in sphincter pressure during the strain maneuver, rather than a relaxation, is consistent with anismus.
4. Physiologic Testing 47
Interpretation of Rectal Sensation
The sensory threshold is the minimum rectal volume perceived
by a patient.
tion is approximately 15-mL (range, 9–25) inflation. Poor or
absent sensation portends a poor response to biofeedback. The
inability to sense suggests neural impairment, which may be
related to a primary or secondary disorder, such as diabetes or
amyloidosis. Constipated patients who have severe straining
may progressively lose their ability to sense rectal fullness.
Hypersensitivity may be evident in patients who have inflammatory bowel diseases, or have irritable bowel syndrome.
2
A normal value for perception of rectal disten-
Interpretation of Compliance
The urge sensation is the volume associated with the initial
urge to defecate.
size and shape, and the distance up within the rectum may alter
the result. Therefore, the laboratory must standardize their
method. The maximum tolerated volume is the volume at
which the patient experiences discomfort and an intense desire
to defecate.
are reduced in patients who have a fixed, noncompliant rectal
wall. For example, patients who have had proctectomy, fibrosis
caused by ischemia, or fibrosis caused by inflammatory bowel
disease will have lower maximal tolerable volumes and lower
pain thresholds. A low tolerable volume may indicate rectal
hypersensitivity and irritability. Increased compliance may be
found in the megarectum. Decreased compliance caused by
rectal reservoir reduction will result in fecal frequency and
urgency with possible incontinence.
2
The rate of inflation, fast or slow, the balloon
2
The maximal tolerable volume and pain threshold
Equipment
The equipment is standard or inexpensive pieces that can
be obtained from commercial surgical supply houses or
hardware stores.
Table
A standard fluoroscopic table capable of cineradiography,
which can be used in the supine or erect positions, is used.
Ideally, large radiograms are used, but fluorographic spot
films might be substituted.
Videocassette Recorder
Video recordings and spot films are helpful in analyzing the
stages of defecation.
Chair and Cushion
A defecography chair, which has a standard-shaped toilet
seat, fits onto the footboard of the table. The seated position
on a toilet is better accepted by the patient, because the act of
defecation is easier, and the staff performing the study find it
to be cleaner than defecation while the patient is lying on the
radiologic table. For the person analyzing the study, the
seated position is more physiologic. A cushion is placed on
the toilet seat to raise the patient off the opaque seat, which
interferes with imaging the anal area. Films can be made
through the cushion filled with water, permitting the best
images to the lowest point of perineal descent. If air is used in
the cushion, it gives adequate images, and there is a slightly
lower radiation dose.
Defecography
Defecography is a dynamic fluoroscopic examination performed with rectal contrast to study the anatomy and function
of the anorectum and pelvic floor during defecation.
procedure may be performed using standard radiology equipment and with relatively low radiation exposure. The specific
points to be analyzed may be captured on still radiographs,
but cineradiography provides a better look at the potential
pathophysiologies that may influence and perhaps interfere
with successful and normal evacuations.
Indication
The use of defecography is indicated as part of the evaluation
of a patient who has an outlet obstruction type of constipation.
There are several mechanical obstructions that may be evident; however, these obstructions must fit symptoms associated, because normal patients have been found to have what
appears to be an abnormal finding, which does not result in
outlet constipation. This study may be used after a repair for
outlet obstruction to compare the efficiency of the defecation
process before and after the procedure.
2
This
Contrast System
High density, barium paste (Anatrast E-Z-EM, Westbury, NY;
or Evacupaste) is introduced into the rectum. These come
prepackaged in a caulking tube. This tube fits into a standard
caulking gun. Some radiologists place a thinner barium mixture into the rectum first and thus up into the sigmoid colon to
better appreciate sigmoidocele. A thin, 240-cc barium contrast similar to that for a small bowel study may be given
orally to better elucidate an enterocele. A tampon soaked in
barium may be used to outline the vagina. Contrast in the
bladder may be used to identify a suspected cystocele. Barium
paste may be placed on the perineal skin to better see the
lower limits of the perineal descent. More recently, the use of
a water-soluble contrast in the peritoneal cavity outlines the
depth of the cul-de-sac and structures within it.
15
Technique
Preparation
The bowel may be studied with or without preparation. Our
preference is to use a small enema an hour before the examination to minimize interference with sharp outlines of the
48 L.E. Smith and G.J. Blatchford
rectal wall. Friendly, clear explanations of what the patient
is to expect and to do aids in conducting a rapid, complete
examination.
Introduction of Contrast
The clinician will have decided which sites require contrast
based on the clinical history. The rectum, vagina, bladder,
colon, small bowel, perineal skin, and/or peritoneum may be
marked with contrast material.
If an enterocele is suspected, the patient should take 240 cc
of diluted liquid barium orally 1 hour before the procedure.
This use of barium must be used cautiously in the severely
constipated, slow transit patient, because barium mixed with
stool will harden to rock-like consistency during transit.
The patient is placed on a table with their left lateral side
down. Tubing for injection of the contrast material is well
lubricated and inserted through the anus into the rectum. The
initial rectal contrast introduced is 50 cc of liquid barium to
coat the rectal mucosa. To evaluate the sigmoid colon, additional barium may be injected, which will flow upwards. Air
may be insufflated to better outline the mucosa. Then 250 cc
of the thick barium paste in the caulking tube is inserted into
the rectum using a caulking gun. If the bladder is to be evaluated, a urinary catheter is introduced into the bladder, and
water-soluble contrast is injected.
If the vagina needs to be seen, a tampon soaked in barium is
inserted. If the cul-de-sac of the peritoneal cavity is to be seen,
under sterile technique, a needle is inserted into the cavity, and
100 cc of water-soluble contrast is injected. When the patient
16
assumes an upright position, the contrast fluid will descend by
gravity into the cul-de-sac. To see the perineal skin level, barium paste may be spread across the skin down the midline,
anterior and posterior to the anus.
Imaging
The patient is asked to be seated on the defecography chair
(toilet), which is adjacent to the radiography table which has
been erected to an upright 90-degree angle. The chair must
have a water-filled cushion placed on the toilet seat to elevate
the patient above the opaque seat. The patient is oriented so
that lateral films can be taken. Video recording and fluoroscopy are begun. A baseline resting spot film is first (Figure
4-10). Second, the patient is asked to squeeze as if to hold a
bowel movement tightly while the film is taken (Figure 4-11).
Third, forceful straining without evacuating is urged for a spot
film (Figure 4-12). Fourth, the patient evacuates as completely as possible with maximal straining. Ideally, this activity is captured on high-resolution videotape, plus a spot film
near the end of evacuation. Last, a postevacuation film is
taken. Anteroposterior filming may be done if there is a question of a lateral abnormality. The same procedures are
performed with the patient facing the fluoroscope sitting in a
semi-erect position in order to view the pelvic structures with
the legs out of the image. It is important to remember that
patients sometimes are quite embarrassed and intimidated by
the mechanisms of this study; abnormal defecation dynamics
may be nothing more than inability to defecate caused by
embarrassment.
FIGURE 4-10. Defecography. The rectum at rest. R is rectum; A is the
margin of the distal anus.
FIGURE 4-11. Defecography. The rectum with a voluntary squeeze.
R is the rectum; A is the margin of the distal anus. The arrow shows
the angle created by the puborectalis muscle pull.
4. Physiologic Testing 49
evacuation, the angle becomes obtuse in the range of 110 to
180 degrees.
Perineal Descent
FIGURE 4-12. Defecography. Rectum during bearing down. R is rectum; A is margin of the distal anus. The anorectal angle opens as the
puborectalis muscle relaxes.
Interpretation
Nonetheless, measurements and observations must be
recorded on a data sheet which is designed to note all of the
potential abnormalities. Having the study as cinedefecography allows repeated viewing of points where abnormality is
suspected. The patient certainly does not want to do repeated
studies. The findings include the anorectal angle, perineal
descent, efficiency of emptying, and possibly rectocele, enterocele/sigmoidocele, anismus, and intussusception. There is
an overlap of symptomatic and asymptomatic patients, so that
the findings must be correlated with the clinical symptoms
and signs. The patient at rest serves as the control, and the
actions can then be observed. Future defecographies may be
compared with this baseline study. This is important when a
surgery is performed, and a change can be noted.
Anorectal Angle
The anorectal angle is the proctographic angle between the
mid-axial longitudinal axis of the rectum and the anal canal.
The videodefecography can be reviewed to see that the puborectalis muscle relaxes appropriately. The anorectal angle
decreases during squeezing and increases during defecation
and straining. This change shows that the puborectalis muscle
is tightening and relaxing.
ranges from 90 to 110 degrees.
becomes more acute in the range of 75 to 90 degrees. On
17
The resting anorectal angle
2
During squeeze, the angle
Perineal descent is the caudad movement of the pelvic floor
with straining.
2
A baseline is a line drawn from the tip of the
coccyx to the underside of the pubis, the pubococcygeal line.
The descent and ascent can be measured from this line.
Normally the pelvic floor will rise during squeezing and
lower during straining and evacuation.
17–19
The pelvic floor
should not rise or fall more than 4 cm from the pubococcygeal
line. If there is greater descent, it suggests a decreased muscle
tone, which is most often the result of pudendal nerve injury.
This finding is usually associated with other mechanical
abnormalities.
Anal Canal Length
During maximal evacuation, the length of the anal canal can
be measured. The width of the anal canal can be noted to open
and close adequately. During maximal strain to evacuate, the
width of the anal canal should not exceed 2.5 cm. Wider
openings suggest an incompetent muscle and possible incontinence.
Efficiency of Emptying
Normally the rectum should empty completely, but 90% is the
lower limit of normal. If an ileal pouch is being examined,
60% evacuation is the lower limit of normal.
Rectocele
The rectocele is the most common finding in defecography.
A rectocele is a bulging of the rectum into the posterior wall
of the vagina (Figure 4-13).
2
A rectocele is much better
defined by defecography than by clinical examination, giving
better measurements of the size and adequacy of empty-
17–19
ing.
Generally one that is <3 cm is not of consequence.
Yet, even large rectoceles must be associated with outlet
obstruction symptoms to be considered pathologic. Most of
these patients have found that pressing upon the bulge of the
rectocele aids them in evacuation. The best time to recognize
a rectocele is during maximal straining to evacuate. The
postevacuation film may show barium to be trapped in the
rectocele. These bulges may be seen to be most often anterior,
but occasionally posterior.
2
Enterocele/Sigmoidocele
Enterocele is a protrusion of the peritoneum between the rectum and vagina containing small intestine (Figure 4-14).
A sigmoidocele (pouch of Douglas descent) is a protrusion of
the peritoneum between the rectum and vagina that contains
sigmoid colon.
loop of contrast-filled small bowel or sigmoid colon.
2
During straining is the best time to look for a
2
17–19
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