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Ischial spine
Site of
pudendal
nerve
stimulation
Pudendal nerve
{
Spinal cord
LI vertebral level
Site of spinal
{
stimulation
Sacral exit foramina
Sacral motor nerves
Section VII • Anorectal Physiology Testing 277
EAS
Fig.VII.21. Schematic representation of anal sphincter inner-
vation. EAS external anal sphincter, PR puborectalis muscle
until the patient feels a buzzing or tingling sensation
in the anus.At least three measurements need to be
taken, choosing the lower threshold value for the
report.A similar procedure is used for mucosal sensitivity analysis in the rectum. Rectal ampulla must
be reached by the electrode; under slowly increasing
Fig. VII.22. St. Mark’s pudendal electrode (13L40, Dantec
Electronics, Bristol, UK) used for recording pudendal motor
nerve latencies
PR
Fig. VII.23. Schematic representation of pudendal nerve
stimulation
current (parameters setting is different than that
used for the anal sensitivity test), three values
should be obtained, taking the lowest as the rectal
threshold sensation to be reported.
Finally, pudendal nerve terminal motor latency
(PNTML) is measured, allowing the evaluation of
pelvic floor neuromuscular integrity (Fig. VII.21).A
disposable St. Mark’s pudendal electrode is used,
mounted onto the volar side of the examiner’s
gloved index finger (Fig.VII.22). The index finger is
inserted into the rectum, the finger tip reaching the
course of each pudendal nerve and the proximal
phalanx sited within the anal canal (Fig. VII.23).
During this test, both electrostimulation and
recording function need to be activated. Four cables
run within the electrode, conveying stimuli (0.1 or
0.2 ms duration, 1 s. interval, not exceeding 15 mA)
from the machine to the finger tip (to the anode
and cathode) in order to stimulate the pudendal
nerve fibers and from the finger tip to the machine
to record the striated muscle response visualized on
the screen. The latency (expressed in milliseconds)
from the onset of the stimulus to the first deflection
of the response is calculated for each pudendal
nerve (n.v.: 2.0±0.2 ms) (Fig.VII.24).
278 Benign Anorectal Diseases
a b
Fig. VII.24. Normal pudendal nerve latencies on the right (a) and left (b). S stimulus, R response
Indications for Anorectal
Electrophysiology and Findings
In healthy subjects, the introduction of a needle
electrode is followed by a reactive discharge of
motor unit potentials. The pelvic floor muscles,
which include the levator ani, the puborectalis
muscle, and the EAS, have continuous tonic EMG
activity at rest. Squeeze determines an increase of
activity (fiber recruitment) while a decrease or
electrical silence is observed during attempted
defecation (push) (Fig.VII.25).
As mentioned above, indications for anorectal electrophysiology are usually decided on the
basis of patient history and physical assessment
if pelvic muscular and/or nervous disorders are
hypothesized; moreover, data from other diagnostic procedures (mainly manometry and
ultrasound) should confirm the need to submit
the patient to the anorectal electrophysiology
[1–3, 5].
In constipated patients, EMG is used to
demonstrate a paradoxical puborectalis contraction or lack of relaxation. In this condition, stri-
Fig. VII.25. Electromyographic find-
ings in a healthy subject.Resting activity (a). Squeeze determines an increase
of activity (fiber recruitment) (b). A
decrease or electrical silence is
observed during attempted defecation
(c)
Section VII • Anorectal Physiology Testing 279
a b
Fig. VII.26. Abnormal prolonged pudendal nerve latencies on the right (a) and left (b). S stimulus, R response
ated muscle activity recorded during straining is
either increased or not changed when compared
with at-rest activity. These findings could be
related to a paradoxical increase or unchanging
anal pressure during straining observed with
manometry. EMG features of pelvic floor incoordination is frequently observed even if a large
number of false positive results need to be considered; indeed, a significant number of patients
with this EMG result do not complain of relevant
constipation, so that it needs to be critically evaluated. In cases of constipation and EMG demon-
stration of anismus, cinedefecography could also
be useful.
In patients with sphincter lesions, no electrical
activity can be found in case of wide, complete
replacement of normal muscular tissue with scar
or, more frequently, polyphasic potentials as signs
of a reinnervation process may be registered.
Polyphasic potentials present multiple spikes of
muscle activity, prolonged in duration, and an
increased fiber density. In evaluating sphincter
injury, EAUS has higher sensitivity and specificity
compared with EMG in mapping the lesion; however, only EMG can assess neuromuscular integrity.
In this respect, these two procedures are complementary.
Evaluation of anal mucosal electrosensitivity
could have clinical relevance in some clinical conditions. Apart from the alterations registered in
patients with prolapsing hemorrhoids (higher
threshold levels), in neurogenic incontinence, a
wide spectrum of findings can be observed, probably related to the degree of pudendal neuropathy.
Also, rectal sensation measurements by electrophysiology study are meaningful. In patients suffering constipation, threshold levels are frequent-
ly higher than normal even if this is not the rule.
In incontinent patients with only sphincter lesion,
mucosal electrosensitivity can be normal, whereas in those with neurogenic incontinence, a wide
variability of findings can be found. Concerning
manometric rectal sensation measurement, its
meaning must be carefully interpreted and correlated with results from other tests.
The utility of PNTML measurements remains
questionable; sensitivity and specificity are
uncertain, and reproducibility between different
examiners or on different days is unknown.
Alterations of PNTML are identified in relation to
patient age, being more frequent in older subjects. This is probably due to several reasons,
including chronic straining in constipated
patients, causing a perineal descent for continuous stretching of pudendal nerves. However, this
feature is inconstant, and the direct relationship
between pudendal neuropathy and constipation
is not demonstrated. In a large number of
patients with fecal incontinence (with or without
urinary incontinence) and rectal prolapse, the
PNTML is abnormally prolonged (Fig. VII.26).
PNTML levels are thought to have a predicting
value in patients undergoing treatment, but this
assumption remains controversial.
280 Benign Anorectal Diseases
References
1. Kamm MA (1994) Pelvic floor tests. In: Kamm MA,
Lennard-Jones JE (eds) Constipation. Wrightson
Biomedical, Hampshire, pp 145–153
2. Lubowski DZ, Kennedy ML (1997) Physiologic investigations.In: Nicholls RJ,Dozois RR (eds) Surgery of the
colon and rectum.Churchill Livingstone, New York, pp
167–194
3. Moreira H, Wexner SD (1998) Anorectal physiology
testing. In: Beck D, Wexner SD (eds) Fundamentals of
anorectal surgery.WB Saunders, London, pp 37–53
4. Read NW, Sun WM (1990) Anorectal manometry. In:
Henry MM, Swash M (eds) Coloproctology and the
pelvic floor, 2nd edn. Butterworth Heinemann, pp
119–145
5. Swash M (1990) Electromyography in pelvic floor disorders. In: Henry MM, Swash M (eds) Coloproctology
and the pelvic floor,2nd edn. Butterworth Heinemann,
pp 187–198
VII.3.
What Studies do we Really Need in the
Treatment of Benign Anorectal Diseases?
B. Cola, D. Cuicchi, R. Lombardi, P.F. Almerigi
Correct clinical management of benign anorectal
disorders depends on a detailed understanding of
the underlying physiopathological mechanisms.
Technological innovations provide the specialist
with functional investigation techniques and
increasingly sophisticated imaging methods
thanks to which the clinical examination, with its
subjective nature, is backed up by the acquisition
of information that makes it possible to quantify
the physiological parameters and to observe the
anatomical structures with a high degree of definition. The contribution of modern methods has
been further expanded by their integration
although there is as yet no agreement on the best
combination of diagnostic tools to be used for the
various individual conditions.
The aim of this chapter is to identify, based on
the features of the various benign anoperineal
disorders, a diagnostic standard justified by evidence that demonstrates their true clinical significance and the direct consequences on therapeutic management of patients.
Anal fissures and hemorrhoids are not dealt
with due to the substantial simplicity of the diag-
nostic approach unanimously considered to be
necessary. For both these disorders, diagnostic
integration has very little influence on the indication for surgery, which is mostly determined by
clinical assessment. It is,on the other hand, important in excluding associated diseases, such as
tumors and inflammatory bowel disease, in documenting preoperative functional or organic alterations, and also for forensic purposes. Attention
will therefore focus on three disorders of particular
interest as regards diagnostic integration and its
effects on therapy: perianal sepsis, fecal incontinence (FI), and obstructed defecation (OD).
Perianal Sepsis and Fistula-in-ano
The two most important failures of surgical treatment of anorectal sepsis are recurrences, due to
an incomplete drainage of collections, and postoperative FI that may be caused by extensive surgical intervention [1]. The art of fistula surgery is
therefore based on the right balance between
treatment of the sepsis (eradication of tracks and
drainage of any associated abscesses) and preservation of anal continence [2].The key to achieving
this aim is careful preoperative assessment direct-
ed at defining the topography of the fistula (the
internal opening, the external opening, the course
of the primary track, the presence of any secondary extensions) and its relationship with the
anal sphincter complex.
Clinical history and physical examination are
often sufficient for diagnosis. Anal exploration
can be also carefully carried out under general
anesthesia [examination under anesthesia (EUA)]
immediately before the surgical approach
(Fig. VII.27). In this way, fistula probing is less
painful and clinical evaluation is more accurate
than that performed in awake patients [3].
However, digital palpation may fail to depict complex fistulas or may lead to incorrect classification
and determination of the height of the track [4].It
may also be difficult, in the case of recurrence, to
distinguish the woody tissue caused by chronic
sepsis from scar tissue [4].
282 Benign Anorectal Diseases
Fig. VII.27. Multiple fistula probing in perianal Crohn’s dis-
ease
The main aim of preoperative imaging is to
identify unsuspected areas of sepsis so that they
can be targeted for subsequent treatment and to
define their relationship with the anal sphincter
complex more accurately.
Fistulography
Fistulography is the most traditional radiological
technique for defining fistula anatomy. It is not
expensive and is readily available, but its results are
difficult to interpret for two main reasons: (1) the
relationship between the fistula and the sphincter
muscle and, above all, the level of internal opening
can be only guessed because the sphincter complex
is not visualized (Fig. VII.28), and (2) secondary
extensions can be missed if they are plugged with
purulent secretions. Fistulography can be helpful
when an extrasphincteric fistula is suspected in the
presence of an external opening distant from the
anus and without abnormality of the anal canal.
In a retrospective study comparing fistulo-
graphic and operative findings in 25 patients,
Kuijpers and Schulpen [5] reported that fistulogra-
phy allowed a correct interpretation in only 16% of
cases, with an accuracy of 24% in recognizing an
internal opening into the anal canal.Fistulography
has been shown to be an inaccurate and unreliable
method of investigation in defining fistula anatomy and today has only a historical value.
Fig. VII.28. Horseshoe fistula with secondary extension
toward upper level
perianal sepsis. The main reason is the poor
intrinsic tissue contrast: the pelvic muscles are
not well identified, and their relationship with
tracks can only be inferred [6] (Fig. VII.29). CT is
also an expensive technique, and it is hampered
by risks related to the use of ionizing radiations
and contrast media.
Computed Tomography Scanning
Computed tomography (CT) scanning has not
acquired an important role in the assessment of
Fig. VII.29. Right lateral pelvirectal abscess (arrow)
Section VII • Anorectal Physiology Testing 283
Endoanal Ultrasonography
Endoanal ultrasonography (EAUS) is based on
ultrasound reflection at the interface between tissues with different densities of acoustic
impedance [7]. The use of EAUS in the study of
anoperineal suppurative disorders was revised
after the initial enthusiasm. In the early 1990s,
Choen et al. [8] reported a degree of accuracy
that was no higher than the clinical evaluation
carried out by expert operators although at that
time the criteria for interpreting ultrasonography
findings had still not been clearly defined. The
contribution of several studies published subse-
quently made it possible to increase the accuracy
of the method through identification of validated
criteria [9, 10].
The method does, however, have some significant limitations,such as the difficulty in differentiating scar areas from active lesions and the limited
visual field that makes it difficult to identify secondary extensions far away from the probe. The
use of hydrogen peroxide (H2O2) as a contrast
media inside the fistula tracks and abscesses,
described for the first time in 1993 by Cheong et al.,
[11] has reduced these limitations and made identification of the internal opening easier, making
EAUS one of the main techniques used to distinguish perianal sepsis (Fig. VII.30).
Poen et al. [12] compared intraoperative findings in 21 patients with results of the clinical
examination, the standard scan,and the hydrogen
peroxide enhanced ultrasound (HPUS). With the
use of the contrast medium, the fistula track was
identified in 95% of patients compared with 62%
at the standard EAUS scan and 38% at the clinical
examination while localization of the internal
opening was possible in only 48% of cases.
In a more recent study,Navarro-Luna et al.[13]
compared surgical findings with results of HPUS
in 80 patients with complex or recurrent fistulas.
The percentage of agreement as regards identification of fistula level and internal opening and
detection of chronic fistula tracks was 91%, 85%,
and 75%, respectively. The authors concluded
HPUS performed by colorectal surgeons with
appropriate experience makes it possible to
achieve excellent results in the preoperative
assessment of anal fistulas.
Buchanan et al. [14] reviewed the diagnostic
value of H2O2 in distinguishing recurrent and
complex fistulas and found no statistically significant differences between three-dimensional (3-D)
EAUS with and without H2O2 as regards identification of the internal opening (p=1),level of the fistula track (p=0.072), and secondary extensions (p=1).
In a study on 102 patients with cryptogenic
anal fistulas undergoing EAUS-guided surgery,
Ratto et al. [15] reported a recurrence rate of 2%
and no case of postoperative incontinence. Basing
their surgical decisions on US findings, they
report that it is possible to perform curative
surgery in a significantly high number of patients
without impairing sphincteral continence.
Endoanal ultrasound is a simple method,
quick to perform, inexpensive, safe, and widely
available. For all these reasons, it must be considered the first study to be carried out in distinguishing perianal sepsis, and in expert hands, it
also plays an important part in the assessment of
complex and recurrent fistulas.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) has acquired
growing importance in distinguishing perianal
sepsis thanks to the excellent intrinsic tissue contrast and the multiple scanning planes (Fig.VII.31).
This method accurately defines the topography of
the septic process and, by identifying the septic
areas missed with EUA,it is also able to modify the
surgical approach in a significant number of
patients [4].
In an attempt to quantify the added clinical
value of MRI with respect to anal EUA alone,
Beets-Tan et al. [16] reported changes to the surgical approach in 21% of cases. This percentage rose
to 24% in the group of patients with recurrent fistulas and to 40% in the group with perianal
Crohn’s disease while only 8% of subjects with
simple fistulas benefited from the additional
information provided by MRI.
In a study performed in 71 patients with
recurrent fistulas in which the results of MRI
were revealed at the end of the surgical operation, Buchanan et al. [17] reported agreement
between MRI and EUA findings in 25 patients
(35%). In the remaining cases, the decision to
perform an MR-guided surgical revision was left
to the discretion of the surgeon: in 15 patients
(21%), an in-depth clinical examination was
decided on, leading to further agreement
between the two assessments, showing a true
therapeutic impact of the method in these cases,
while in the remaining 31 patients (44%), the sur-
284 Benign Anorectal Diseases
a b
c d
Fig. VII.30. Intersphincteric fistula at mid canal level. Primary track at 5 o’clock (a) with secondary intersphincteric extension
(b) (arrows). After hydrogen peroxide enhancement both primary and secondary tracks are more clearly visible (c, d)
gical approach was not changed and the disagreement between MRI and EUA remained.At a
mean follow-up of 1 year, only 13% of patients
(5/40) in whom the two assessments agreed
developed a recurrence compared with 52%
(16/31) of cases in which the disagreement
remained (p=0.0005). In addition, in this last
group, all recurrences developed at sites indicated by preoperative MRI. This study demonstrated that, with regard to recurrent fistulas, MRguided surgery can reduce the rate of recurrence
by approximately 75%.
In a more recent prospective study, the same
authors [18] applied the same study design to a
sample of 30 patients with simple fistulas. MRI
guided the surgical revision in only three
patients (10%), showing the presence of two
internal openings missed during the initial
surgery, while surgical revision was not performed in 12 cases (40%) despite the disagreement between MRI and EUA. At a mean followup of 12 months, no recurrences were observed,
suggesting a lesser clinical impact of MRI in the
assessment of simple fistulas.
Fig. VII.31. Scar tissue in left ischioanal fossa (arrows)
Evidence [16, 17] shows that MRI is a powerful
and validated diagnostic tool that, especially in
complex and recurrent fistulas, is able to increase
the percentage of success of surgical treatment.
Magnetic Resonance Imaging with an
Endoanal Coil
The use of an endoluminal coil makes it possible
to obtain images in which fistula tracks inside the
sphincter complex and the site of the internal
opening are displayed with greater resolution
than with an external coil. However, since image
definition decreases as the distance from the coil
increases, this method is less accurate in distinguishing tracks that are far away from the anal
sphincter [4]. This method has two other significant limitations: it is not widely available,and it is
quite expensive [2].
Diagnostic Integration
In the preoperative assessment of perianal sepsis,
EAUS and MRI should be considered as complementary rather than antagonistic techniques
(Fig. VII.32) [4]. A number of studies have compared the results of MRI and EAUS in distinguishing perianal septic lesions; however, only two studies used a more accurate gold standard than the
mere surgical specimen, thus being more precise.
In 19 patients with complex Crohn’s disease fistulas, Schwartz et al. [19] compared the accuracy of
Section VII • Anorectal Physiology Testing 285
biplanar ultrasound,MRI, and EUA,considering as
the gold standard the unanimous agreement
reached by operators in cases of initial disagreement between the three assessments. The study
showed almost identical accuracy: ultrasound and
surgical assessment correctly identified 91% of
lesions and MRI 87%. Since a combination of any
two studies achieved almost 100% accuracy, and
considering that 53% of patients required surgery,
the authors suggest that EUA should be combined
with one of the two imaging techniques.
Buchanan et al.[1] recently evaluated the accuracy of the clinical examination, EAUS, and MRI,
considering the outcome of MR-guided surgery as
the reference gold standard in the event of agreement between radiological method and EUA and
the clinical follow-up in the event of disagreement,following the principle whereby healing of a
fistula represents the only guarantee of complete
eradication of the septic sites. In a series of 108
patients (27% simple fistulas and 73% complex
fistulas, 9% of which were Crohn’s fistulas) it
emerged that clinical examination, EAUS, and
MRI correctly classified the primary tracks in
61%, 81%,and 90% of cases and the internal openings in 78%, 91%, and 97% of cases, respectively.
The accuracy of the three methods decreased in
identifying abscesses and horse-shoe secondary
extensions (36%, 70%, and 88% respectively). The
authors concluded that EAUS is closer in accuracy
to MRI than are clinical examination and that
EAUS is particularly useful in defining primary
tracks and internal openings. On the contrary,it is
less precise in identifying secondary lesions.
In conclusion, evidence suggests that EAUS
should be considered a first-level investigation
method in distinguishing perianal sepsis.
Although clinical examination is often sufficient
for low and simple fistulas, the low cost, simplici-
ty and ability to identify preexisting sphincter
defects justify the use of EAUS even in these
patients. The high degree of accuracy of MRI in
identifying secondary tracks and in differentiating fibrosis from sepsis makes this method particularly useful in distinguishing complex lesions
and recurrent fistulas (Fig.VII.33 and 34).
Fecal Incontinence
Fecal incontinence (FI) is a symptom common to
various disorders that can alter one or more of the
mechanisms involved in maintaining continence
286 Benign Anorectal Diseases
a b
c d
e f
Fig. VII.32. Multiple recurrent fistulas in a 54-year-old man. Left lateral suprasphincteric fistula at mid (a) and high (b) anal canal
level after administration of hydrogen peroxide on endoanal ultrasound (arrows). The same primary fistula on magnetic resonance
imaging (MRI) (arrow) (c). Supralevator anterior horseshoe extension (arrow) with internal opening in the left anterior quadrant
(arrowhead) on endoanal ultrasound (d) and MRI (e).Area of fibrosis located far from the sphincter on MRI (arrow) (f)
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