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Section VII • Anorectal Physiology Testing 307
Fig. VII.51. Mechanism of anal occlu-
sion by the mechanical compression of
the triple-loop system of the external
anal sphincter (from Shafik [1]): external sphincter relaxed (a), direction of
ab c
contraction of external sphincter
loops (b), external sphincter contracted causing air-tight anal occlusion (c)
ly. The mechanical compression action is thus
momentary (40–60 s) and serves to occlude the
rectal neck by the time the detrusor relaxes as a
result of the voluntary inhibition reflex.
Stress Defecation
In internal sphincter damage, voluntary continence is induced only by the mechanical action of
the external sphincter [4]. Voluntary inhibition
reflex is lost. Being striped, the external sphincter
cannot contract long enough to withstand the
noninhibited, prolonged contraction of the loaded detrusor. Detrusor contraction continues
despite external sphincter contraction until the
latter fatigues and relaxes and the detrusor evacuates itself (Fig. VII.52). Hence, in cases of internal
sphincter damage, once the desire to defecate is
initiated, evacuation should occur.This condition,
which I gave the name “stress defecation” [4], is
observed in patients after internal sphincteroto-
Fig. VII.52. Mechanism of stress defecation: detrusor con-
traction with external sphincter contraction – internal
sphincter is damaged (a); detrusor continues contraction,
uninhibited by the damaged internal sphincter – external
sphincter fatigues, relaxes, and defecation occurs (b) (from
Shafik [4])
my for anal fissure. It could also explain the
impaired control of feces and flatus after internal
sphincterotomy.
Single-loop Continence
As a result of the separate arrangement of the
three external sphincter loops, and since each
loop has its own separate and bilateral innervation, any single loop can function as a sphincter
[4]. External sphincter continent action can be
achieved by a single-loop contraction and not
necessarily by the three loops.This constitutes the
basis of “single-loop continence” [4]. On contraction, a single loop induces continence by both the
voluntary inhibition reflex and mechanical occlusion. The latter action is significantly tight in loop
contraction, being effected not only by direct
compression but also by rectal-neck kinking [1].
Anogenital Muscle
A recent study has demonstrated that the base
loop of the EAS extends uninterrupted across the
perineum to the bulb of the penis where it
becomes continuous with the bulbocavernosus
muscle [6]. While lying over the bulb, the muscle
bundles were arranged into three groups: one
median and two lateral (Fig.VII.53). Median fibers
form the “retractor penis muscle,” which is inserted into the corpora cavernosa, while lateral fibers,
or the “compressor bulbae muscle,” are inserted
into the perineal membrane. Upon glans stimulation, both the EAS and the bulbocavernosus muscle contract synchronously with similar latency
and action potentials [6]. The bulbocavernosus
muscle is an integral part of the EAS, and the muscle in its entirety is appropriately named “anogenital muscle.” The muscle plays a dual and syn-
308 Benign Anorectal Diseases
External anal
Sphyncter
the rectal neck during straining at defecation, thus
preventing rectal prolapse [7]. Subluxation of the
longitudinal muscle shares in rectal prolapse genesis [8].
Bulb
Corpus Spongiosum
Corpus Cavernosum
Fig. VII.53. Diagram showing the lateral fibers of the base
loop of the external anal sphincter overlying the penile bulb
and forming the compressor bulbae muscle while the median
fibers proceed forward, forming the retractor penis muscle,
which bifurcates on either side of the corpora cavernosa
(from Shafik [6])
Compressor
bulbae
muscle
Retractor penis
muscle
chronous role in fecal control and sexual
response. It is suggested that external sphincter
disorders lead to sexual dysfunction and vice
versa.
Longitudinal Muscle
The longitudinal muscle consists of three layers:
medial, intermediate, and lateral [7]. (Fig. VII.48).
The medial longitudinal muscle is a continuation
of the longitudinal rectal muscle coat. The intermediate muscle is the suspensory sling of the levator ani whereas the lateral muscle is the longitudinal extension of the top loop of the EAS [1].The
fleshy longitudinal muscle ends at the level of the
lower border of the internal sphincter by giving
rise to a fascial condensation called “central tendon” [7]. The latter splits into multiple fibrous
septa. The medial septum attaches to the rectalneck lining whereas the lateral passes into the
ischiorectal fossa. The intermediate septa penetrate the external sphincter base loop,decussate to
form the corrugator cutis, and insert in the perineal skin (Fig. VII.48). The longitudinal muscle
plays an important role in the mechanism of defecation [7]. On contraction at stool,it shortens and
widens the rectal neck. Furthermore,it helps to fix
Levator Hiatus and Tunnel
The levator ani consists essentially of the pubo-
coccygeus, the iliococcygeus being rudimentary
in humans. The puborectalis is not a part of the
levator; both differ in morphology, innervation,
and function [9, 10]. The pubococcygeus is funnel
shaped, with a transverse portion called “levator
plate” and a vertical portion called suspensory
sling [9, 10] (Fig. VII.48). The levator plate is an
oval cone, which stretches across the pelvis; the
levator hiatus occupies its anterior portion, and
the rectococcygeal raphe exists posteriorly
(Fig. VII.54). Two patterns of the rectococcygeal
raphe could be identified: single and triple decus-
sation (Fig. VII.55). The latter seems to give firmness to the levator plate and might be a factor in
resisting rectal prolapse [9]. The“hiatal ligament”
connects the medial border of the levator plate to
the anorectal junction [9, 10]. The levator plate
consists of two “crura”that bound the levator hiatus and of two “lateral masses” [10] (Fig. VII.54).
Three crural patterns were identified: classic,crural overlap,and crural scissor (Fig.VII.56).
The levator ani is the principal muscle of defecation. On contraction at defecation, it opens the
rectal neck for the stool to descend. Any interference with levator function results in disturbance
of the defecation act and leads to levator dysfunction syndrome [11], which presents as descending
perineum, intussusception, solitary ulcer syndrome, and rectal prolapse [8–10]. The different
patterns of the rectococcygeal raphe and levator
crura play an important role in rectal-neck support; their subluxation may eventually lead to rectal prolapse [8–10].
The “levator tunnel” is a muscular tube that
surrounds the intrahiatal organs (rectal neck,
prostate in males; vagina and urethra in females)
along their way down from the levator hiatus to
the perineum (Fig. VII.54). The posterior tunnel
wall (3–4 cm) is longer than the anterior one
(2.5–3 cm). The tunnel is double sheathed with an
inner coat of the suspensory sling and an outer of
the puborectalis. Both coats are of striped muscle
bundles. The inner coat is a tunnel “dilator,” which
opens the rectal neck at defecation, whereas the
Section VII • Anorectal Physiology Testing 309
Levator plate
Levator crus
Lateral mass
Rectum
Vagina
Urethra
a
Iliococcygeus
Rectococcygeal
raphe
Hiatal ligament
Pubococcygeus
(levator Plate)
Levator hiatus
Hiatal ligament
Puborectalis
Suspensory sling
Levator tunnel
b
Fig. VII.54. Diagram illustrating the
levator plate and tunnel (from Shafik
[10])
Fig. VII.55. Diagram illustrating
decussation patterns of the rectococcygeal raphe (from Shafik [10]): single
pattern (a), triple pattern (b)
outer coat is a tunnel“constrictor” [10]. The “tunnel septum,” a grayish white membrane, lines the
inner aspect of the levator tunnel and separates it
from the fascia propria of the intrahiatal organs
[10] (Fig. VII.48). It separates voluntary from
involuntary components of the levator tunnel. It
serves as an important landmark during mobilization of the intrahiatal organs from within the
levator tunnel as in the operation of anorectal
mobilization for rectal cancer [12, 13].
Rectococcygeal raphe
Rectum
Hiatal ligament
Vagina
Urethra
Crus
ab
Hiatal Ligament
The levator plate is connected to the intrahiatal
organs by a fascial condensation called the “hiatal
ligament” [9, 10] (Fig. VII.48). It arises from the
inner edge of the levator plate and splits fanwise
into multiple septa to insert into the upper rectal
neck, vesical neck, as well as into the upper vaginal end. Anteriorly, the ligament fills the gap
between the two levator crura at their origin,
b
c
Fig. VII.56. Different crural patterns
of the levator ani muscle (from Shafik
[10]): classic pattern (a),crural overlap
(b), crural scissor (c)
310 Benign Anorectal Diseases
forming the puboprostatic or pubovesical liga-
ment [9, 10]. The hiatal ligament plays a vital role
in harmonizing the action between levator plate
and intrahiatal organs during evacuation of their
contents (defecation and urination). Hiatal ligament subluxation interferes not only with the act
of evacuation but leads also to prolapse of the
intrahiatal organs [8, 9, 14].
Puborectalis and the Double-Sphincter
Control
The puborectalis, as it proceeds backward from its
origin in the symphysis pubis, gives off muscle
bundles to each intrahiatal organ, forming “individual” voluntary sphincters for these organs [10,
15] (Fig.VII.57). It gives rise to the external urethral
sphincter and deep EAS in both genders, as well as
to the vaginal sphincter in the female and prostatic
sphincter in the male. However, the puborectalis
and deep EAS were found fused together, the conjoint muscle being named “top loop” [1]. Each
intrahiatal organ is thus provided with a double
voluntary sphincteric apparatus: (a) an “individual” organ sphincter, derived from the puborectalis
and specific for the organ,and (b) a “common”tunnel sphincter, the puborectalis itself, which acts on
the intrahiatal organs collectively. This separate
sphincteric activity for the individual organs under
the control of a common continent muscle secures
not only an immune sphincteric function to the
organ but a harmonized action among the structures enclosed within the levator tunnel [16, 17].
Further,the double sphincteric mechanism provided to each organ could be a guarantee of functional maintenance in case either of the two sphincters
is damaged. Injury of either sphincter alone does
not induce incontinence of the concerned organ.
Unless both sphincters – the “individual” and
“common” – are destroyed, continence could be
maintained by either [10,15, 17].
Mechanism of Defecation
Muscles of Defecation
The muscles that act on the rectal neck are the
external and internal anal sphincters, puborectalis, levator ani, and longitudinal muscle. The external and internal sphincters, as well as the puborectalis, are muscles of continence. Their role at
stool is to contract in order to interrupt or terminate the act of defecation [1, 16]. However, the
principal muscles of defecation are the levator ani
and the longitudinal muscles [7, 9, 10]. They act
jointly to open the rectal neck at defecation. The
two muscles are interrelated due to the fact that
the suspensory sling, a part of the levator, constitutes the middle layer of the longitudinal muscle
[7, 10] (Fig.VII.48).
Anatomical Mechanism of Defecation
With knowledge of the physioanatomical aspects
of the pelvic floor muscles and assisted by manometric EMG and barium enema studies, the precise mechanism of defecation could be explored
[18, 19].As stools enter the rectum, reflex detrusor
contraction and internal sphincter relaxation
occur. Continuation of defecation depends on two
factors: (a) external sphincter relaxation, and (b)
straining. If defecation is acceded to, the external
sphincter is voluntarily relaxed. Straining is nec-
Suspensory sling
Puborectalis
Top loop of external sphincter
Vaginal
sphincter
Suspensory sling
Urethral sphincter
Fig. VII.57. “Individual” sphincters
arising from the puborectalis, which
act as a “common” sphincter for the
intrahiatal structures (from Shafik [10,
15])
Section VII • Anorectal Physiology Testing 311
Hiatal ligament
Longitudinal
muscle
a
Levator
plate
Top loop
Anal
suspensory
sling
Intermediate loop
Central tendon
Base loop
essary to maintain defecation, as it raises the
intra-abdominal pressure. This serves a double
purpose: it compresses the detrusor, which helps
evacuation, and it stimulates levator contraction
through the straining-levator reflex [20].
Although the intra-abdominal pressure compresses the detrusor, the rectal neck is spared
owing to its protected location below the levator
plate. When the levator plate contracts, it moves
from the cone to the flat position and is elevated
and laterally retracted [9] (Fig. VII.58). This
results in pulling on the hiatal ligament, which in
turn pulls open the anorectal junction and partially opens the rectal angle. Simultaneously, the
suspensory sling contracts and not only pulls up
the base loop to unseal the anal orifice, but it also
partially opens the rectal neck (Fig. VII.58).
The longitudinal muscle joins the detrusor in
contraction, which results in shortening and
opening of the rectal neck as well as in complete
straightening of the rectal angle [7]. This brings
the rectal neck into alignment with the detrusor
so that efficient fecal pumping occurs. The final
result of the joint contraction of the detrusor,longitudinal muscle, and levator is the opening of the
rectal neck for the rectum to evacuate its contents.
Physiologic Mechanism of Defecation
The concerted functions of the anorectal musculature at defecation are initiated and harmonized
by voluntary impulses and reflex actions, as
demonstrated in recent communications [21–24].
When the rectal detrusor is distended with fecal
mass and the stretch receptors are stimulated, the
rectoanal inhibitory reflex [21] is initiated by
which the rectal detrusor contracts and the inter-
Fig. VII.58. Mechanism of defecation:
at rest (a); at defecation – flattening of
b
levator cone as well as suspensory
sling contraction result in opening of
anal canal (b) (from Shafik [4, 18])
nal sphincter relaxes. Detrusor contraction triggers two reflexes: the rectopuborectalis reflex [22]
and the rectolevator reflex [23]. These two reflexes act simultaneously yet have opposite functions;
on detrusor contraction, the rectolevator reflex
effects a reflex levator contraction, which opens
the rectal neck. At the same time, the reflex puborectalis contraction, actuated by the rectopuborectalis reflex, functions to close or keep closed
the rectal neck as impulses reach the conscious
level to probe the circumstances for defecation. If
inopportune, the puborectalis continues volun-
tary contraction.
Voluntary puborectalis contraction evokes two
reflex actions: (a) reflex levator relaxation through
the levator-puborectalis reflex [24], and (b) reflex
detrusor relaxation by means of the voluntary inhibition reflex [4]. Meanwhile, it aborts the rectoanal
inhibitory reflex,which relaxes the internal sphincter. Hence, voluntary puborectalis contraction,
through the voluntary inhibition reflex, prevents
internal sphincter relaxation,which results in reflex
detrusor relaxation and waning of the urge to defecate [4]. However, as soon as circumstances would
allow defecation and the sensation of desire is felt,
the puborectalis muscle relaxes voluntarily,and the
detrusor evacuates its contents. This demonstrates
that the act of defecation is under voluntary control
despite the presence of reflex actions sharing in the
mechanism of defecation. Thus, although the rectoanal inhibitory and rectolevator reflexes function
to open the rectal neck, the rectopuborectalis and
the levator-puborectalis reflexes keep the rectal
neck closed until the decision for defecation has
been made.
Straining at the start of defecation is a normal
physiological process and as such is part of the
mechanism of defecation. By elevating the intra-
312 Benign Anorectal Diseases
abdominal pressure,it triggers the straining-leva-
tor reflex [20], which effects levator contraction
and the opening of the rectal neck for spontaneous evacuation of stools.
Anorectal Physiology Testing
As regards the studies needed in the treatment of
benign anorectal disease, valuable information
can be obtained from a physical workup, including neurologic and proctologic examination.
Investigations comprise barium enema,
colonoscopy and biopsy studies, defecography
[25, 26], intestinal transit, anorectal manometry,
balloon expulsion test [27], and defecometry [28],
as well as electromyogram (EMG) of anal sphincters and levator ani muscle. This is in addition to
endoanal ultrasonography (EAU) and magnetic
resonance imaging (MRI). However, conventional
examinations of the anorectum commonly reveal
little correlation between subjective symptoms
and investigative results.Although they offer valuable information regarding anorectal function,
they are not representative of the act of defeca-
tion, and the range of normality is quite broad.
Herein, we present new methods that can add to
the diagnostic tools investigating the anorectum.
L 49, DISA, Copenhagen, Denmark) of 65 mm in
length and 0.65 mm in diameter is inserted through
the perianal skin 2–2.5 cm lateral to the anal orifice
[23, 29]. The needle is directed upward to an approximate depth of 2–2.5 cm.A standard EMG apparatus
(type MES, Medelec,Woking, UK) is used to amplify and display the potentials recorded. Correct needle position is checked by the burst of activity heard
on the EMG loudspeaker and visualized on the
oscilloscope screen on muscle contraction.
Fecoflowmetry
Since the introduction of the fecoflowmeter,
which we developed to obtain an authentic and
detailed recording of the act of defecation [30–32]
fecal flow rate can be studied from curves that
represent the changes occurring in rate versus
time. Fecal flow rate is the product of rectal detru-
sor action against outlet resistance.A 1-l enema is
given, and the subject sits on the commode of the
fecoflowmeter when he/she feels the desire to
defecate. Fecoflowmetry provides quantitative
and qualitative data regarding the act of defeca-
tion (Figs.VII.59 and 60). It is simple, easy, nonin-
vasive, and nonradiological.
,
EMG: levator ani muscle
With the patient in the left lateral position, a concentric needle electromyographic electrode (type 13
Determination of Residual Stools
Twenty healthy volunteers, mean age 35.7 years,
and 25 patients with chronic idiopathic constipa-
tion (CIC), mean age 31.2 years, were evaluated for
Fig. VII.59. Normal fecoflowmetry
(upper tracing) and intra-abdominal
pressure (lower tracing). Intra-abdominal pressure increased before the start
of flow curve. When flow started, pressure dropped (from Shafik [31])
Section VII • Anorectal Physiology Testing 313
Fig. VII.60. Fecoflowmetry (upper
tracing) and intra-abdominal pressure
(lower tracing) in chronic constipation. Mean and maximum flow rate
was small, and flow curve showed a
plateau compared with normal flow
curve. Flow was maintained as long as
high pressure was maintained ( from
Shafik [31])
residual stools in the rectum after defecation [33].
The act of defecation was studied by fecoflowmetry. A 1-l water enema was administered, and
fecoflowmetric studies were done while the subject was evacuating the enema.After evacuation, a
rectal tube was introduced to evacuate the residual fluid for quantitative assessment. Six of the 20
healthy volunteers had a mean volume of residual
fluid of 32.3 ml; the remaining subjects had no
residual fluid.All constipated patients had a mean
residual fluid of 370.6 ml.
Rectometry
Rectal volume, pressure, and compliance at first
rectal and urge sensation are assessed in one test
by a simple and noninvasive new parameter: rec-
tometry [34]. The shape of the rectometrogram is
also informative. Rectometry was performed on
36 subjects: 20 healthy volunteers and 16 patients
with constipation. Carbon dioxide was infused
into a balloon introduced into the rectum and
connected to a pressure transducer. The rectal
neck and intra-abdominal pressures were mea-
sured simultaneously. A rectometrogram was
obtained (Fig. VII.61). It reads the volume of car-
bon dioxide infused and the intrarectal and
detrusor pressure at both the first rectal and urge
sensation. In addition to quantitative values, the
curve configuration could differentiate between
not only normal and constipated subjects but also
obstructive and inertia-type constipation. Apart
from its diagnostic value, rectometry can be used
to monitor the effectiveness of pharmacotherapy
on detrusor function.
Fig. VII.61. Rectometrogram. Normal
rectometrogram (a): first dash below
curve denotes first rectal sensation,
second dash denotes sensation of urge.
Rectometrogram of constipation (b):
Patient failed to expel the balloon
(from Shafik [34])
314 Benign Anorectal Diseases
Rectal-neck Pressure Profilometry
Rectal-neck pressure profile was measured by
means of a catheter with a ring of side holes at its
distal end [35].After the catheter was inserted into
the rectum, carbon dioxide was infused. Pressure
in the rectal neck was recorded while the catheter
was being withdrawn automatically by a device.
Important parameters that could be studied from
the rectal-neck pressure profile include: maximum
rectal-neck pressure, maximal closing rectal-neck
pressure, as well as functional and anatomical rectal-neck lengths. Mean rectal-neck pressure and
the pressure index could also be calculated.
Normal profilogram was bell shaped (Fig. VII.62).
The ascending limb showed a two-step rise, the
first rise of which was gradual and affected by
internal anal sphincter tone while the second was
steep and evoked by external and internal anal
sphincter tone.A formula was introduced to calcu-
late separately the pressure induced by each of the
140
external and internal sphincters. In constipated
subjects, two patterns of rectal-neck pressure pro-
file could be recognized: inertia and obstructed.
Each pattern had its characteristic parameters and
curve configuration. In addition, the rectal-neck
pressure profile was able to define whether
obstructive constipation was caused by external or
internal sphincter spasm and whether fecal incon-
tinence was partial or complete. The rectal-neck
pressure profile is useful in evaluating sphincter
activity at various levels along the rectal-neck
length. It also measures the individual sphincter
activity.Furthermore,it can help to identify some
types of constipation and fecal incontinence.
Water Enema Test
Anorectal investigations can also be performed by
a recently introduced, simple office test – the water
enema test [36]. Water (1.5 l) contained in a gradu-
120
100
O)
2
Pressure (Cm H
a
80
60
40
20
0
Maximum
RN
closing
pressure
Rectal
pressure
Maximum
RN
pressure
Functional RN length
Anatomical RN length
1
2
345
6
Fig. VII.62. Anal pressure profilometry.
Normal rectal-neck pressure profile (a).
Rectal-neck pressure profile in constipat-
b
ed subject (b) (from Shafik [35])
Section VII • Anorectal Physiology Testing 315
ated vessel and incubated at 37°C is instilled under
gravity into the rectum through a 16F Nelaton
catheter at a rate of 150 ml/min. The subject is asked
to report on the first rectal sensation as well as on
the desire and urge to evacuate. The volume of
water infused at the time of these occurrences is
determined and compared with standard levels in
controls. Defecation disorders may be identified
with this easy and noninvasive test.
Fecal-Leak Test
To assess results of repair and the degree of fecal
incontinence, another simple office test was performed in 24 patients with complete incontinence who had undergone direct suture operation [37]. Rectal pressure and infusion volume
were recorded during rectal filling with saline at
a rate of 50 cc/min. Two rectal-leak pressures
were determined: resting and coughing. Before
incontinence repair, coughing rectal-leak pressure was significantly higher than the resting one
whereas the infused saline volume at the two
pressure levels showed an insignificant differ-
ence. After operative repair, 16 patients who
became totally continent had no leakage. Six
patients who improved following partial incontinence exhibited a significant increase in resting
and coughing rectal-leak pressures compared
with preoperative values. Infused saline volume
at the two leak pressures also increased significantly. The two patients who remained incontinent after repair showed an insignificant difference in resting and coughing rectal-leak pressure
or infused saline volume against prerepair levels.
The degree of continence increased with the
increase in resting and coughing rectal pressure.
Resting rectal-leak pressure determines outlet
resistance under normal conditions while
coughing rectal-leak pressure determines outlet
resistance under stress conditions. The rectalleak pressure test is a simple, reproducible, and
cost-effective test to assess incontinence and the
results of treatment.
applied laterally to each of the two sacroiliac
joints,and a third one was placed midway between
the left greater trochanter and ischial tuberosity.
The reference electrode was applied to the right
lower limb.At least two 20-min recording sessions
were performed for each of the 24 subjects. In
addition, an intrarectal electrorectographic
recording was done in ten of the 24 subjects using
silver-silver chloride electrodes attached to the
rectal mucosa by suction. Pacesetter potentials
(PPs) were recorded transcutaneously. The wave
was triphasic, with a small positive, a large negative, and another small positive deflection
(Fig. VII.63). PPs had a regular rhythm and were
reproducible. The mean frequency was
3.1 cycles/min. Transcutaneously recorded PPs
could be confirmed by the intrarectal route. Both
routes had similar electrorectographic recordings
Transcutaneous Electrorectography
A transcutaneous recording of rectal electric
activity, or an electrorectography, was obtained
from 24 healthy volunteers with a mean age of 39.6
years [38]. A silver-silver chloride electrode was
Fig. VII.63. Transcutaneous electrorectogram. Electrodes
applied to skin (a); electrorectogram in normal subject (b);
electrorectogram in constipation due to rectal inertia, pace-
setter potentials show low frequency, amplitude, and velocity
of conduction, a condition we call “bradyrectia” (c); elec-
trorectogram of obstructive constipation showing abnormal-
ly high frequency, a condition we call “tachyrectia” (d) (from
Shafik [38])
316 Benign Anorectal Diseases
except for the action potentials, which did not
show in the transcutaneous electrorectogram.
Reflexometry
Additional investigative tools to obtain reliable,
objective, and substantial information on the
physiologic state of pelvic floor muscles and the
nerves supplying them are the reflexes described
above [4, 19–24, 29, 39, 40]. Evaluation of reflex
actions of the pertinent musculature contributes
to establishing the diagnosis in anorectal disorders with even greater accuracy, in a more comprehensive manner, and in less time because the
approach is direct. The technique follows an easy
principle: a balloon-tipped catheter is introduced into the rectum and a needle electrode,
inserted into the muscle to be tested, records the
response of the muscle to distension of the rectal
balloon. Detectable changes in latency or amplitude of motor unit action potentials or the
evoked response may indicate a defect in the
reflex pathway that could be due to muscle or
nerve damage.
Andrological Investigations
Recent studies have shown that anorectal patho-
logical conditions, in particular, acute and chron-
ic anal fissures, and external anal sphincter
injuries, were found to be associated in some
cases with erectile dysfunction [41, 42]. These
findings seem to be related to the close relation-
ship of the external anal sphincter to the bulbo-
cavernosus muscle which is a muscle of erecttion.
The bulbocavernosus muscle, was found to be an
extension of the external anal sphincter and
pathologic conditions in volving the external
sphincter may affect the erectile process [42]. For
these reasons, while investigating patients with
anorectal condition, it seem indicated to inquire
about, and investigate form erectile dysfunction.
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