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Anorectal Manometry.enl
COMPARISON OF RECTOANAL AXIAL FORCES IN HEALTH AND FUNCTIONAL
DEFECATORY DISORDERS
Adil E. Bharucha1
Andrew J. Croak2
John B. Gebhart2
Lawrence J. Berglund3
Barbara M. Seide1
Alan R. Zinsmeister4
Kai-Nan An3
From the 1Clinical Enteric Neuroscience Translational and Epidemiological Research Program
(C.E.N.T.E.R.), Division of Gastroenterology and Hepatology, Department of Medicine, 2Division of
Gynecologic Surgery, 3Orthopedics Biomechanics Laboratory, and 4Division of Biostatistics, Mayo Clinic,
Rochester, MN
Address correspondence and reprints requests to:
Adil E. Bharucha, M.D.
Clinical Enteric Neuroscience Translational and Epidemiological Research Program (C.E.N.T.E.R.)
Mayo Clinic (CH 8-110)
200 First Street S.W.
Rochester, MN 55905
Tel: 507-538-5854
Fax: 507-538-5820
Email: [email protected]
Running Title: Rectoanal axial forces
Copyright © 2006 by the American Physiological Society.
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ABSTRACT
Anal manometry measures circumferential pressures, but not axial forces, which are responsible for
defecation and contribute to fecal continence. Our aims were to investigate these mechanisms by measuring
axial rectoanal forces with an intra-rectal sphere or a latex balloon, fixed at 8, 6, or 4 cm from the anal
verge, and connected to axial force and displacement transducers. Rectoanal forces and rectal pressures
within a latex balloon were measured at baseline (i.e., at rest) and during maneuvers (i.e., squeeze,
simulated evacuation, and a Valsalva maneuver) in 12 asymptomatic women and 12 women with symptoms
of difficult defecation. Anal resting and squeeze pressures were also assessed by manometry and were
similar in controls and patients. At rest, axial rectoanal forces were directed inward and increased as the
device approached the anal verge. Controls augmented this inward force when they squeezed and exerted
an outward force during simulated expulsion and a Valsalva maneuver. The force change during maneuvers
was also affected by device location and was highest at 4 cm from the verge. In patients, the force at rest
and the change in force during all maneuvers was lower than in controls. The rectal pressure during a
Valsalva maneuver was also lower in patients than in controls, suggestive of impaired propulsion. In
conclusion, a subset of women with defecatory symptoms had weaker axial forces not only during expulsion
but also during a Valsalva maneuver and when they squeezed (i.e., contracted) their pelvic floor muscles,
suggestive of generalized pelvic floor weakness.
Key Words: anal pressures, axial force, rectoanal, manometry, defecation, continence
Word count – 245
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INTRODUCTION
Current concepts suggest that defecation is accomplished by increased intra-rectal pressure
coordinated with relaxation of the pelvic floor muscles. In addition to the internal and external anal
sphincters, the pelvic floor muscles, especially the puborectalis, also relax during normal defecation (18).
However, several aspects of the anorectal functions responsible for fecal continence and defecation are
poorly understood, partly because our understanding is primarily based on manometry, which measures
anorectal radial pressures, but not axial forces that are responsible for defecation and contribute to fecal
continence. First, although a functional disorder of defecation has been traditionally attributed to impaired
relaxation of the anal sphincter and/or pelvic floor muscles (i.e., dyssynergia), recent studies suggest that
inadequate propulsive forces may also be important (15, 16). These studies need to be confirmed.
Moreover, the mechanisms responsible for generating the propulsive force during defecation, which is
assessed by recording pressure in the rectum, are unclear. Specifically, the contributions of increased intraabdominal pressure generated by voluntary effort (12) and rectal contraction (9) to this propulsive force
have been disputed. This is an important issue because straining may increase intrarectal pressure but not
improve evacuation (16), perhaps because the pelvic floor muscles also contract during straining (17).
Second, though clinical observations suggest that the location of stool affects the ease of evacuation, it is
unclear if axial rectoanal forces vary along the length of the rectum. Thus, patients with a defecatory
disorder often report it is harder to evacuate stool located in the upper rectum (i.e., the vault), than the lower
rectum (i.e., the ampulla). Third, though defecatory symptoms are attributed to impaired pelvic floor
relaxation during defecation, we recently demonstrated that pelvic floor motion assessed by dynamic MRI
was abnormal not only during evacuation, but also when patients contracted their pelvic floor muscles to
retain intra-rectal contents (3). These observations need to be confirmed by measuring anorectal forces
during contraction and expulsion.
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To address these questions, we measured anorectal axial forces exerted against a rigid sphere or a
latex balloon at specified locations in the anorectum during rectal expulsion and inward traction (REIT) in
healthy subjects and patients with symptoms of difficult defecation by a new device (i.e., the REIT device).
Previous studies have evaluated axial rectoanal forces to assess the mechanisms of fecal continence, but not
defecation (7, 8, 10). These studies have demonstrated that the axial force measured by an intra-rectal solid
sphere was correlated with anal pressures measured by manometry (7, 10). Moreover, the inward axial
force, reflecting contraction of the anal sphincters and the pelvic floor, was reduced in patients with fecal
incontinence (8, 10).
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MATERIAL & METHODS
Participants
Twelve healthy women, (age 31.3 ± 2.3 years, Mean ± SEM) and 12 women with symptoms of
difficult defecation (age 44.5 ± 4.3 years, Mean ± SEM) consented to participate in this study, which was
approved by the Institutional Review Board of the Mayo Clinic. A clinical interview and physical
examination were performed in all participants. Healthy controls were recruited by public advertisement.
Exclusion criteria for controls included significant cardiovascular, respiratory, neurological, psychiatric or
endocrine disease, irritable bowel syndrome as assessed by a validated bowel disease questionnaire (4),
medications (with the exception of oral contraceptives or thyroid supplementation), and abdominal surgery
(other than appendectomy or cholecystectomy). In addition, healthy subjects who had any previous
anorectal operations including hemorrhoid procedures, or had sustained anorectal trauma during delivery
(i.e. grade 3 or 4 laceration), as documented by obstetric records, were excluded. Patients were recruited
from a specialized clinic devoted to gastrointestinal motility disorders. All patients had two or more
symptom-based criteria for functional constipation (18). Colonic motor functions were evaluated by
assessing colonic transit with scintigraphy in 8 patients (6) or by assessing colonic motility (i.e., tonic and
phasic pressure activity in the descending colon under fasting conditions, after a meal, and after neostigmine
by a barostat-manometric assembly) in 1 patient.
Overall Study Design
On the morning of the study, subjects received 2 magnesium citrate enemas (Fleets ,C.B. Fleet,
Lynchburg, VA). Shortly thereafter, anorectal pressures and axial forces were measured by manometry and
an axial force transducer respectively. Prior to the anorectal assessments, an investigator, aided by a digital
rectal examination, coached subjects to contract the anal sphincter and pelvic floor muscles, simulate the
process of expulsion, and to do a Valsalva maneuver. During simulated expulsion, subjects were
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encouraged to mimic the process they usually employed to defecate. During a Valsalva maneuver, subjects
were instructed to expire forcefully against a closed glottis.
Anal Manometry, Rectal Balloon Expulsion, and Rectal Sensation
After 2 sodium phosphate enemas (Fleets ,C.B. Fleet, Lynchburg, VA), anorectal testing (i.e., manometry,
assessment of rectal compliance and sensation by a barostat, and assessment of rectal traction) was
conducted in the left lateral position by perfusion manometry. The manometric catheter assembly had 8
sensors, i.e., 4 circumferentially oriented sensors at each of 2 levels separated by 2 cm. Average anal
resting and squeeze pressures measured by the distal group of 4 sensors using the station pull-through
technique, and summarized as described previously (5). The recto-anal pressure gradient was measured
during expulsion; data were summarized by the difference between rectal and anal pressure, averaged over a
10 second interval during which anal pressure was at its lowest. The amount of external traction required to
facilitate expulsion of a rectal balloon filled with 50 ml of warm water was also assessed in patients (3, 14).
Rectal compliance and sensation were recorded using previously validated techniques by an “infinitely”
compliant 7-cm long balloon with a maximum volume of 500 ml (Hefty Baggies, Mobil Chemical Co.,
Pittsford, NY) linked to an electronic rigid piston barostat (Mayo Clinic, Rochester, MN) (2, 5). An initial
or conditioning distention followed by a rectal staircase distention (0-32 mm Hg in 4-mm Hg steps at 1
minute intervals) was performed. Rectal compliance and sensory thresholds for first sensation, desire to
defecate (DD), and urgency were recorded during the staircase distention; the threshold was the first
sensation of each symptom. Rectal pressure-volume relationships were analyzed by a power exponential
function and summarized by the pressure corresponding to half maximum volume (Prhalf) (2, 11).
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Rectal Traction
Procedure – Rectoanal axial forces were measured by a customized device (i.e., Rectal Expulsion
and Inward Traction (REIT) Device), adapted after a similar device described previously (7) (Figure 1).
This device comprised an intra-rectal device (i.e., either a latex balloon or a rigid sphere 2.5 cm diameter)
which was connected to tension-compression (Transducer Techniques, Temecula, Ca) and linear
displacement transducers (Novotechnik, Ostfildern, Germany) and interfaced to a computer. The intrarectal device was fixed at 8, 6, or 4 cm from the anal verge. We chose to use a sphere 2.5 cm in diameter,
because Bannister et al demonstrated that normal subjects could invariably expel a sphere of this size (1).
The latex balloon was inflated with 60 ml of water and the intra-balloon pressure was also measured during
maneuvers. Each maneuver began with a baseline period of 20 seconds during which the resting force was
assessed. Thereafter, subjects were asked to squeeze (i.e., contract) their pelvic floor and anal sphincter
muscles for 30 seconds, or to expel the device for 30 seconds, or, to do a Valsalva maneuver for 20 seconds
in that order. A rest period of 30 seconds separated consecutive maneuvers. Data were acquired, displayed
and analyzed by a customized Labview™ based program (National Instruments, Austin, Tx).
Data Analysis – In each subject, the baseline resting force was averaged over 10 seconds
immediately prior to each maneuver. The force change during maneuvers was calculated by subtracting the
baseline force from the force during maneuvers.
Statistical Analysis
Axial rectoanal forces at baseline and the force change during maneuvers (i.e., squeeze, expulsion,
and a Valsalva maneuver) were analyzed by a mixed-model analysis of covariance, fitting terms for
location, maneuver, and subject status (i.e., patient or control). To validate the measurements of force, the
relationship between force and pressure was assessed separately for each maneuver with a latex balloon in
each subject. The relationship between the recto-anal pressure gradient during expulsion measured by
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manometry and the force change during expulsion was also assessed. All results are expressed as Mean ±
SEM.
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RESULTS
Clinical Features
Consistent with the Rome II criteria, all patients reported two or more symptoms of functional
constipation for H 25% of time. Symptoms included excessive straining during defecation (92% patients),
hard stools (62 %), sense of incomplete evacuation after defecation (92%), sense of anorectal blockage or
obstruction (69%), infrequent stools (i.e., less than 3 times per week; 85%) and digital removal of stool from
the rectum (77%). The duration of symptoms ranged from < 1 year (n = 2), 1 to 5 years (n = 4), 5 to 10
years (n = 2), or more than 10 years (n = 4).
Anorectal Manometry, Standard Rectal Balloon Expulsion, and Colonic Motor Functions
Average anal resting pressures were comparable in controls (66 ± 6 mm Hg, Mean ± SEM)
and patients (65 ± 7 mm Hg). Average squeeze pressures were also comparable in controls (150 ± 17 mm
Hg, Mean ± SEM) and patients (137 ± 16 mm Hg). Ten patients had an abnormal rectal balloon expulsion
test and/or an abnormal recto-anal pressure gradient during simulated expulsion. The rectal balloon
expulsion test was normal (i.e.,
100 gm traction required) in 4 and abnormal in 8 patients. The recto-anal
pressure gradient during expulsion was also abnormal in 8 patients, including 2 patients in who had a
normal rectal balloon expulsion test. Seven patients had normal colonic motility assessed by scintigraphy (6
patients) or by an intraluminal colonic barostat-manometric assembly (1 patient). Two patients had delayed
colonic transit.
Rectal Compliance and Sensation
During rectal staircase balloon distention, 9 of 12 subjects tolerated distention up to the highest
pressure, i.e., 32 mmHg. Due to significant discomfort, this distention was terminated at 12 mmHg and 24
mmHg in 2 subjects, precluding an assessment of rectal compliance in these subjects. Among the remaining
subjects, the Prhalf for rectal compliance was within normal limits, i.e., 14.4 ± 0.5 mmHg. Three patients
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had a stiff rectum, as evidenced by a Prhalf which was above the 90th percentile value for healthy subjects in
our laboratory.
During rectal staircase distention, the sensory thresholds for first sensation, desire to defecate, and
constant urgency averaged 11.5 ± 1.4 mmHg, 15.7 ± 1.1 mmHg, and 23.5 ± 1.8 mmHg; these values were
within 10th – 90th percentile normal values for our laboratory. The corresponding volume thresholds were
110 ± 20 ml, 150 ± 17 ml, and 216 ± 19 ml respectively. While sensory thresholds expressed as pressure
were within the normal range for all subjects, volume thresholds for the desire to defecate were above the
90th percentile value in 2 patients.
Assessment of Axial Forces With a Sphere
Figure 2 provides representative tracings of axial forces recorded by a solid sphere during squeeze,
expulsion, and a Valsalva maneuver. Axial forces directed inward (i.e., orad) and outward (i.e., caudad)
were designated negative and positive respectively. At rest (i.e., before maneuvers), the sphere recorded an
inwardly oriented force at 4 and 6 cm and an outwardly oriented force at 8 cm from the verge (Figure 3).
Therefore, the resting force was influenced (p < 0.0001) by the location of the sphere in controls and
patients. Moreover, the inward resting force was weaker (p = 0.01) in patients compared to controls (Figure
3).
Both controls and patients exerted an outwardly directed force against a sphere during expulsion and
a Valsalva maneuver (Figures 3 and 5). Conversely, both controls and patients generated an inwardly
directed force when they squeezed (i.e., contracted) their pelvic floor muscles. Compared to controls,
patients generated a significantly (p < 0.0001) lower outward force during expulsion and a Valsalva
maneuver; these differences were most pronounced at 4 cm from the verge (Figure 5). However, the inward
force during squeeze was comparable in controls and patients.
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Similar to the resting force, the force change during maneuvers was also affected by location of the
sphere in controls (p = 0.0002), but not in patients. Thus, in controls, the outward force during expulsion
and a Valsalva maneuver was highest at 4cm, intermediate at 6 cm, and lowest at 8 cm from the verge.
During squeeze, the force change was higher at 4 cm compared to 6 cm, and in turn, compared to 8 cm from
the verge; however differences among locations were not significant.
Assessment of Axial Forces by a Latex Balloon
At rest, forces measured by a latex balloon were comparable to a sphere, affected (p < 0.0001) by
device location (i.e., inward at 4 and 6 cm, and outward at 8 cm from the verge), and of smaller magnitude
in patients than controls (Figure 4).
During voluntary maneuvers, controls and patients generated an inward force when they squeezed
their pelvic floor muscles, and an outward force during expulsion and a Valsalva maneuver. Both controls
and patients exerted a stronger outward force during expulsion against a latex balloon compared to a sphere
(Figures 3-5). Similar to a sphere, outward forces during expulsion and a Valsalva maneuver were weaker
in patients, compared to controls. However, in contrast to a sphere, (i) the inward force during squeeze was
also weaker in patients compared to controls; and (ii) the force change during maneuvers with a balloon was
not significantly different across locations (i.e., at 4, 6, and 8 cm from the verge), in controls nor patients.
The recto-anal pressure gradient during expulsion measured by anal manometry was correlated (r =
0.44, p = 0.04) with the axial force during expulsion of a latex balloon at 4 cm from the verge. However,
the recto-anal pressure gradient was not correlated with axial forces during expulsion of a latex balloon
located at 6 or at 8 cm from the anal verge.
Relationship Between Force and Pressure Assessed by a Latex Balloon
Table 1 provides the pressures recorded by a latex balloon at rest and the change in pressure during
maneuvers. Compared to rest, rectal pressures generally increased during all maneuvers. In controls, the
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rectal pressure change during expulsion and a Valsalva maneuver was comparable (i.e., 95% confidence
intervals overlapped). Among patients, the axial force during a Valsalva maneuver was significantly lower
than during expulsion.
To validate force measurements, we examined the correlation between axial forces and pressures
measured by the latex balloon. Figure 6 and Table 2 demonstrate that force and pressure during maneuvers
with a latex balloon were correlated. These correlations were modest to excellent at all locations during
expulsion and a Valsalva maneuver, and at 4 and 6 cm during squeeze. During squeeze, these correlations
were negative because forces were negative (i.e., directed inward).
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DISCUSSION
Anal manometry measures circumferential pressures, but not axial forces which are responsible for
expulsion when directed outwardly or contribute to continence when directed inwardly. In previous studies,
the axial force measured by an intra-rectal solid sphere was correlated with anal pressures measured by
manometry (7, 10). Moreover, the inward axial force, reflecting contraction of the anal sphincters and the
pelvic floor, was reduced in patients with fecal incontinence (8, 10). Similar to previous studies, we
observed that when subjects squeezed, they exerted an inward axial force even when an intra-rectal device
was located above the anal canal, reflecting pelvic floor contraction (8). Using a new device (REIT), we
measured axial forces not only during squeeze, but also during expulsion and a Valsalva maneuver at
specified locations within the anorectum. Consistent with the length of the anal sphincter (i.e., between 2-5
cm from the anal verge), the resting force was strongest at 4 cm from the anal verge, (i.e., within the anal
canal). Moreover, the inward force was augmented during squeeze to a greater extent as the intra-rectal
device approached the anal verge. Simultaneous measurements of axial force and pressure by a latex
balloon during maneuvers were significantly correlated at most locations, validating force measurements by
the REIT device against the existing standard (i.e., pressure).
Four observations from this study provide insights into the mechanisms of normal and disordered
continence and expulsion. First, healthy subjects augmented the resting inward force when they squeezed
(i.e., contracted) their pelvic muscles, and exerted an outward force during expulsion and a Valsalva
maneuver. Second, compared to controls, patients with defecatory symptoms exerted a weaker inward force
when they squeezed the pelvic floor and a weaker outward force not only during expulsion, but also during
a Valsalva maneuver, supporting the concept of generalized pelvic floor weakness. Third, rectoanal forces
were higher for a latex balloon, which provides a closer approximation to a normally formed stool than does
a sphere. Lastly, forces were influenced by the location of the device relative to the anal verge. Thus, the
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outward force during expulsion and a Valsalva maneuver was strongest at 4 cm from the verge, perhaps
explaining why patients find it easier to evacuate stool located in the lower, compared to the upper rectum.
During a Valsalva maneuver in controls, the axial force, which reflects the net outward force, was
comparable to the outward force during expulsion. The intrarectal pressure, which is a surrogate marker of
the propulsive effort, increased by an average of 31 mm Hg during a Valsalva maneuver. This increase in
intrarectal pressure is similar to that reported in a previous study, in which intra-abdominal pressure
increased by 36 mm Hg during a Valsalva maneuver (13). Among patients, the axial force and intrarectal
pressure change during a Valsalva maneuver were lower than in controls. Taken together, these
observations suggest that the lower outward axial force during a Valsalva maneuver in patients may be
explained by a weaker propulsive effort. The outward axial force during expulsion was correlated with the
recto-anal pressure gradient during expulsion measured by manometry. However, in contrast to a Valsalva
maneuver, the intrarectal pressure during expulsion was comparable in patients and controls, suggesting that
increased outlet resistance accounted for the weaker outward force during expulsion in patients. These
observations expand on the concept introduced by Rao et al that symptoms of obstructive defecation are
associated with inadequate propulsive forces and/or with increased resistance to expulsion (16). They also
reinforce the concept that impaired expulsion in obstructive defecation is not a fixed process but is strongly
influenced by voluntary actions. Similar to anal manometry, forces were assessed in the decubitus position.
Further studies are necessary to compare forces in the seated and decubitus positions.
In addition to a weaker outward force, the inward force during squeeze against a latex balloon was
also weaker in patients than in controls. However, the inward force exerted against a sphere was not
significantly different in patients and controls. These results confirm previous observations that the
rectoanal axial force is influenced by the size of the intra-rectal device (7). They also corroborate recent
observations that pelvic floor motion during squeeze, assessed by dynamic MRI, was reduced in women
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with defecatory symptoms (3). Taken together, these findings (i.e., reduced axial forces during expulsion,
Valsalva maneuver, and squeeze), are consistent with the hypothesis that a subset of patients with
defecatory symptoms have generalized pelvic floor weakness, rather than an isolated impairment of pelvic
floor relaxation during expulsion. This hypothesis needs to be substantiated by simultaneous assessments of
abdominal wall activity, (e.g., by EMG) and axial forces during voluntary maneuvers.
The intrarectal sphere or balloon was connected to the transducers by a solid, inelastic segment, thus
avoiding the drawback of an elastic connection that stretches and affects the force measured during
maneuvers (10). In contrast to a previous study, the intra-rectal latex balloon or sphere was fixed relative to
the anal verge during assessments to avoid reflex sphincter contraction induced by movement of the device
(7). However, we cannot exclude the possibility that the resting axial force was influenced by
proprioceptive input resulting from an object within the anorectum. The force change during maneuvers
was substantially higher with a balloon compared to a sphere, perhaps because the balloon was in contact
with, and therefore measured forces exerted by a larger surface area (~ 100 cm2) compared to a sphere (16
cm2 ). It is also conceivable that a hydraulic effect, (i.e., displacement of fluid within a balloon during a
maneuver), also increased the axial force exerted against a balloon. From a practical perspective, a latex
balloon may be preferable to a sphere because it approximates more closely to stool, and also because it is
easier to introduce a deflated balloon compared to a sphere into the rectum in subjects with high resting anal
pressure. On the other hand, a sphere was more useful for characterizing the effects of location on rectoanal
forces, probably because it had a smaller surface area than the balloon. Diamant et al showed previously
that the axial force was not influenced by friction, because similar forces were recorded by a regular sphere
and another sphere with a smooth Teflon surface (7).
In summary, our studies demonstrate that the rectoanal forces responsible for defecation and
contributing to fecal continence can be measured at specific locations within the anorectum by a new
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device. Rectoanal axial forces during voluntary actions (i.e., squeeze, expulsion, and a Valsalva maneuver)
were influenced by device location within the anorectum. Both devices recorded weaker axial forces during
expulsion and a Valsalva maneuver in patients compared to controls. The force during squeeze against a
latex balloon was also weaker in patients, consistent with the concept that some patients with defecatory
symptoms have generalized abdomino-pelvic weakness, rather than an isolated impairment of pelvic floor
relaxation.
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ACKNOWLEDGEMENTS
This study was supported in part by USPHS NIH Grants R01 HD38666 and R01 HD41129, and by
the General Clinical Research Center grant #RR00585 from the National Institutes of Health in support of
the Physiology Laboratory and Patient Care Cores.
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and Zinsmeister AR. Relationship between symptoms and disordered continence mechanisms in women
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Fernandez-Fraga X, Azpiroz F, and Malagelada JR. Significance of pelvic floor muscles in anal
incontinence. Gastroenteroogy 123: 1441-1450, 2002.
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Sapsford RR, Hodges PW, Richardson CA, Cooper DH, Markwell SJ, and Jull GA. Coactivation of the abdominal and pelvic floor muscles during voluntary exercises. Neurourology &
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Table 1.
Rectoanal Pressures Measured by a Balloon at Rest and During Maneuvers in Healthy
Subjects
Epoch
Resting pressure
(i.e. before
maneuver)
Latex balloon pressure (95% CI)
4 cm
6 cm
8 cm
Controls
Patients
Controls
Patients
Controls
Patients
25 (13, 36) 28 (17, 39)
22 (12, 34) 24 (14, 35) 38 (27, 50) 31 (20, 42)
Squeeze
(During – Before)
26 (16, 37)
11 (1, 20)
14 (3, 25)
8 (-2, 17)
-5 (-16, 6)
6 (-3, 16)
Expulsion
(During – Before)
17 (2, 32)
29 (16, 43)
29 (14, 43)
37 (24, 51)
35 (20, 50)
39 (25, 52)
Valsalva
(During – Before)
24 (12, 35)
13 (2, 24)
27 (16, 38)
13 (2, 24)
32 (20, 43)
11 (0.0, 22)
All values are mean (95% C.I.) for pressure measured in mm Hg
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Table 2.
Relationship Between Axial Force and Pressure Measured by a Latex Balloon During
Maneuvers
Maneuver
Squeeze
4 cm
-0.71 (-0.97, -0.51)
Location
6 cm
-0.65 (-0.96, -0.44)
Expulsion
0.62 (0.27, 0.9)
0.80 (0.72, 0.96)
0.69 (0.52, 0.97)
Valsalva
0.54 (0.15, 0.93)
0.87 (0.83, 0.96)
0.87 (0.85, 0.98)
8 cm
-0.01 (-0.61, 0.49)
All values are mean (95% C.I.) for the correlation coefficient (r)
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G-00487-2005.R2 21
Figure Legends
Figure 1.
Rectal expulsion and inward traction (REIT) device. A sphere (thin arrow) or a latex balloon
(not shown) were connected to a pressure transducer (thick arrow) and to axial force and linear displacement
transducers (arrowhead).
Figure 2.
Representative example of rectoanal axial forces during squeeze (left panel), expulsion
(center panel), and a Valsalva maneuver (right panel). During squeeze, forces were more negative (i.e.,
directed inward) when the sphere was located at 4, compared to 6 and 8 cm from the verge. During
expulsion, the positive (i.e., outward) force during expulsion was considerably higher at 4 compared to 6
and 8 cm from the verge. During a Valsalva maneuver, outward forces were generated at all locations.
Figure 3.
Rectoanal axial forces measured by a sphere during voluntary maneuvers in controls (left
panel) and patients (right panel). Positive and negative values represent outward and inward forces
respectively. Values are for absolute force at rest and the force change (during – before) during maneuvers.
Particularly at 4 cm, outward forces during expulsion and a Valsalva maneuver were weaker in patients
compared to controls. Inward forces were augmented by squeeze to a similar extent in patients and controls.
Values are mean ± 95% CI.
Figure 4.
Rectoanal axial forces measured by a latex balloon during voluntary maneuvers in controls
(left panel) and patients (right panel). Positive and negative values represent outward and inward forces
respectively. Values are for absolute force at rest and the force change (during – before) during maneuvers.
Values are mean ± 95% CI.
Figure 5.
Rectoanal axial forces measured by a sphere (left panel) and a latex balloon (right panel) at 4
cm from the anal verge. Values are for absolute force at rest and the force change (during – before) during
maneuvers.
Figure 6.
G-00487-2005.R2 22
Tracings of axial force and pressure measured during simulated expulsion of a latex balloon
fixed at 6 cm from the anal verge. Observe the correlation between force and pressure.
Figure 1
G-00487-2005.R2 23
G-00487-2005.R2 24
Figure 2
6 cm
4 cm
800
800
600
600
600
400
400
400
200
0
-200
-400
-600
-800
Squeeze
(30 s.)
Force (gm)
800
Force (gm)
Force (gm)
8 cm
200
0
-200
-400
-600
-800
Expulsion
(30 s.)
Out
200
0
-200
-400
-600
-800
Valsalva
Maneuver
(20 s.)
In
G-00487-2005.R2 25
Figure 3
Controls
Patients
500
400
300
200
100
0
-100
-200
-300
-400
6 cm
8 cm
4 cm
Mean + 95% C.I.
*
0
5
Rest
Squeeze
10
15
Expulsion Valsalva
20
Force (gm)
Force (gm)
4 cm
500
400
300
200
100
0
-100
-200
-300
-400
6 cm
8 cm
Mean + 95% C.I.
0
5
Rest
10
15
Squeeze Expulsion Valsalva
20
G-00487-2005.R2 26
Figure 4
Controls
Patients
500
400
300
200
100
0
-100
-200
-300
-400
6 cm
4 cm
8 cm
Mean + 95% C.I.
0
5
Rest
Squeeze
10
15
Evacuation Valsalva
20
Force (gm)
Force (gm)
4 cm
500
400
300
200
100
0
-100
-200
-300
-400
-500
6 cm
8 cm
Mean + 95% C.I.
0
5
Rest
Squeeze
10
15
Evacuation Valsalva
20
G-00487-2005.R2 27
Figure 5
Controls
Patients
1000
800
600
600
400
400
Force (gm)
Force (gm)
Controls
Patients
800
200
200
0
-200
-400
0
-200
-600
-400
-800
-1000
Rest
Squeeze Expulsion Valsalva
-600
Rest
Squeeze Expulsion
Valsalva
G-00487-2005.R2 28
Figure 6
Pressure
(mmHg)
Force
(gms)
500
Force (g-force)
Pressure (gm)
400
110
100
90
80
70
300
60
50
40
30
200
100
20
0
10
0
0
20
40
60
Time (s)
80
100