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- •Preface
- •Contents
- •About the Editors
- •Contributors
- •3 Host Factors: Age, Gender, Lifestyle
- •4 IBD and Other Etiologically Relevant Comorbid Conditions
- •5 Anatomical Presentation and Rectovaginal Fistula
- •6 Anal Fistula Development: Microbiological Factors
- •7 Recurrence and Cancer Risk
- •8 Conclusion
- •References
- •1 Epidemiology of Anal Fistula and Abscess
- •1 Introduction
- •2 Incidence and Prevalence
- •2.1 Europe
- •2.2 USA and Canada
- •2 Anorectal Anatomy Related to Anal Fistula and Abscess
- •1 Introduction
- •2 Mucosal Layer and Submucosal Space
- •3 Internal Anal Sphincter
- •4 Intersphincteric Space and Conjoint Longitudinal Muscle
- •5 External Anal Sphincter
- •6 Pelvic Floor
- •7 Extra-anal Spaces/Ischioanal Fossae
- •8 Anal Glands
- •10 Conclusion
- •11 Cross-References
- •References
- •3 Anorectal Physiology Related to Anal Fistula and Abscess
- •1 Principal Aspects of Anorectal Physiology
- •1.1 Secretory Function of the Anorectum and the Cryptoglandular Hypothesis
- •1.2 Histology and Cellular Physiology of the Anorectum and Fistula
- •1.3 Microbiology and Fistula
- •1.4 Host Factors Relevant to Abscess and Fistula
- •1.5 Anal Continence
- •1.5.1 The Rectum
- •1.5.2 The Musculature of the Pelvic Floor and Sphincter Complex
- •1.6 Defecation
- •1.7 Anorectal Physiology Testing in the Context of Fistula
- •1.7.2 Perioperative Anorectal Physiology Testing
- •2 Conclusion
- •References
- •4 Unconventional Insights in the Pathogenesis and Etiology of Fistulas in the Perianal Region
- •1 Introduction
- •1.1 Etiology
- •1.2 Risk Factors for Development of Perianal Fistula
- •1.3 Risk Factors due to the Type of Perianal Fistula
- •1.4 Treatment-Related Risk Factors for Failure
- •1.5 Preliminary Conclusions
- •2.1 Anatomy of the Anal Canal
- •2.2 Histology of the Anal Canal
- •2.3 Histopathologic Concepts of Perianal Fistulas
- •3.1 Old Stories, New Histopathological Concepts?
- •3.2 Old Stories, New Clinical Concepts?
- •3.2.1 Basic Concepts
- •3.3 Based on Previous Medical History
- •3.4 Aspect and Localization of the Fistula Opening
- •3.5 Phenotype 1
- •3.6 Phenotype 2
- •3.7 Phenotype 3
- •3.8 Phenotype 4
- •3.9 Phenotype 5
- •4 Discussion and Conclusions
- •5 Cross-References
- •References
- •5 From Abscess to Fistula
- •1 Anorectal Abscess
- •References
- •6 Classification of Anal Fistula and Abscess
- •1 Introduction
- •2 Purpose and Attributes of a Classification
- •3 Overview of Anal Fistula Classifications
- •4 Anal Fistula Classifications
- •4.1 Parks Classification
- •4.1.1 Strong Points
- •4.1.2 Weak Points
- •5.1 Strong Points
- •5.2 Weak Points
- •6 Garg Classification
- •6.6 Strong Points
- •6.7 Weak Points
- •7 Status of Extrasphincteric Fistulas
- •8 Evaluation of Existing Classifications on Long-Term Data
- •9 Conclusions
- •References
- •7 Clinical Assessment of Anal Cryptoglandular Abscess and Fistula
- •1 Introduction
- •2 Types of Clinical Evaluation
- •3 Diagnosis
- •4 Topographic Evaluation
- •4.1 The Cryptic Endoanal Primary Opening
- •4.2 The Secondary Opening or Openings
- •4.3 The Main Tract of the Fistula
- •4.4 Possible Purulent Collections
- •1.1 Physical Examination of the Anus and Rectum: General Principles
- •4.5 Possible Secondary Extensions
- •5 Conclusion
- •References
- •8 Clinical Assessment of Crohn Perianal Abscesses and Fistulas
- •1 Introduction
- •1.2 Inspection
- •1.3 Palpation
- •1.4 Endoscopy
- •2 Clinical Presentation
- •2.1 Skin Lesions
- •2.2 Fistulas
- •2.3 Abscesses
- •2.4 Diagnostic Workup
- •2.4.1 General Principles
- •2.5 US
- •2.6 Effectiveness and Sensitivity
- •2.6.1 Endoscopy
- •2.7 MRI
- •2.7.1 CT Scan
- •2.7.2 Fistulography
- •2.8 Diagnostic Follow-up
- •References
- •9 Anorectal Physiology Assessment in Patients with Anal Fistula: When Necessary
- •1 Introduction
- •2 Anorectal Physiology Assessment
- •2.1 Anamnesis
- •2.2 Physical Examination
- •2.3 Anorectal Manometry
- •2.3.1 Equipment
- •2.3.2 Manometry Systems
- •2.4 Neurophysiologic Tests
- •2.4.1 Electromyography
- •2.4.2 Nerve Conduction Studies
- •2.5 Endoanal Ultrasound
- •2.6 Role of Anorectal Physiology Patterns in the Decision-Making
- •3 Discussion
- •References
- •1 Introduction
- •2 Anal Anatomy
- •3 Classification of Fistulas
- •4 EAUS Imaging
- •4.1 Probes EAUS
- •4.2 Performing EAUS
- •4.3 EUS in Perianal Fistulas
- •4.4 Adding Hydrogen Peroxide (H2O2)
- •4.5 Cryptoglandular Fistulas
- •5 Comparison with Other Diagnostic Modalities
- •5.1 Comparison with Surgery
- •5.2 Comparison with MRI
- •5.3 Perineal Ultrasound
- •6 Conclusion and Recommendation
- •References
- •1 Introduction
- •2 Imaging
- •2.1 Conventional Contrast Material-Enhanced Fistulography
- •2.2 CT
- •2.3 Magnetic Resonance Imaging
- •2.3.1 Anatomy MRI
- •2.3.2 MRI Technique (Coils, Volume, and Sequences) and Findings
- •2.3.3 MRI Reconstruction Techniques and Fistulography MRI
- •2.3.4 Internal and Cutaneous Opening
- •2.3.5 Classifications of Perianal Fistulas and Abscesses
- •2.3.6 Deep Posterior Anal Fistulas and Abscess
- •2.3.7 MRI Report
- •2.3.9 MR Role in the Evaluation of the Crypto-Glandular Fistulas
- •3 Conclusion
- •4 Cross-References
- •References
- •1 Introduction
- •2 Clinical Presentation
- •3 Utility and Limitations of Endoanal Ultrasound
- •4 Conclusion
- •5 Cross-References
- •References
- •1 Introduction
- •2 Imaging
- •3 Diagnosis
- •4 MRI Technique
- •5 Disease Monitoring
- •6 Future Directions
- •7 Conclusion
- •8 Cross-References
- •References
- •14 Future Perspectives in the Diagnosis of Anal Fistula and Abscess
- •1 Introduction
- •2 Assessment of Abscess and Anal Fistula
- •3 Abscess
- •3.1 Computed Tomography (CT)
- •3.2 Magnetic Resonance Imaging (MRI)
- •3.3 Endoanal Ultrasound
- •3.4 Transperineal Ultrasonography (TP-US)
- •4 Anal Fistula
- •4.1 Imaging
- •4.1.1 Endoanal Ultrasound
- •4.1.2 Magnetic Resonance Imaging
- •5 Conclusion
- •6 Cross-References
- •References
- •15 How to Drain an Abscess
- •1 Introduction
- •2 Epidemiology and Etiology
- •3 Classification
- •4 Clinical Manifestations and Diagnosis
- •5 Management
- •7 Wound Dressing
- •8 Microbiology and Antibiotics
- •9 General Postoperative Management
- •10 Conclusion
- •11 Cross-References
- •References
- •16 The Seton in Anal Fistula Management
- •1 Introduction
- •2 2500 Years of Setons
- •3 To Put or Not to Put
- •4 To Cut or Not to Cut
- •5 What Kind of Seton to Use?
- •7 Seton 2.0: New Perspectives
- •8 Uncomfortable Questions (How to Do It)
- •9 What Patients Should Know
- •10 Conclusions: Seton in Guidelines
- •References
- •17 Fistulotomy
- •1 Introduction
- •2 Indications
- •3 Fistulotomy: Standard Technique
- •4 Other Fistulotomy Techniques
- •4.1 Addition of Loose Seton
- •4.2 Slow Dissection of the Sphincter: Cutting Seton
- •4.3 Addition of Marsupialization
- •5 Fistulotomy with Immediate Primary Sphincteroplasty (FIPS)
- •7 Postoperative Care
- •8 Complications and Recurrence Rate
- •9 Discussion
- •10 Conclusion
- •References
- •18 Fistulectomy
- •1 Introduction
- •2 Preoperative Evaluation
- •2.1 Patient Selection
- •2.2 Imaging
- •2.3 Physiologic Testing
- •2.4 Endoscopic Examination
- •3 Technique
- •3.1 Patient Preparation
- •3.2 Patient Positioning
- •3.2.1 Technical Steps
- •4 Postoperative Care
- •5 Results
- •5.1 Fistulectomy
- •6 Fistulectomy with Sphincter Reconstruction
- •7 Conclusions
- •References
- •19 Utility of Adding Sphincter Reconstruction to Fistulotomy/Fistulectomy
- •1 Introduction
- •2 General Classification
- •3 Preoperative Preparation
- •4 Surgical Technique Step by Step
- •5 Results
- •6 Conclusion
- •7 Cross-References
- •References
- •20 Utility of Marsupialization Following Anal Fistula Surgery
- •1 Introduction
- •2 Marsupialization
- •3 Clinical Evidence
- •4 Conclusion
- •References
- •21 Transanal Advancement Flap Repair
- •1 Introduction
- •2 Nomenclature
- •3 Effectiveness of the Technique
- •4 Effectiveness of Repeat Procedures
- •5 Impact on Fecal Continence
- •6 Severity of Incontinence
- •7 Perioperative Care
- •7.1 Bowel Preparation
- •7.2 Antibiotic Prophylaxis
- •7.3 Prolonged Antibiotic Therapy
- •7.4 Type of Anesthesia
- •7.5 Immobilization
- •7.6 Bowel Confinement
- •7.7 Stool Softeners
- •7.8 Position
- •8 Aspects of Surgical Technique
- •8.1 Preoperative Care
- •8.2 Step 1
- •8.3 Step 2
- •8.4 Step 3
- •8.5 Step 4
- •8.6 Step 5
- •8.7 Postoperative Care
- •8.8 Types of Flap
- •8.9 Shape of Flap
- •8.10 Thickness of Flap
- •8.11 Addition of Accessory Techniques
- •9 Necessity of Preoperative Imaging
- •10 Factors Contributing to Successful Healing
- •10.1 Fistula-Related Factors
- •10.2 Patient-Related Factors
- •10.3 Influence of Covering Ostomy
- •10.4 Impact of the Use of Draining Setons
- •11 Conclusion
- •References
- •22 Dermal Flap Anoplasty for Trans-sphincteric Anal Fistula
- •1 Rationale
- •2 Technique
- •3 Other Dermal Flaps
- •4 Discussion
- •5 Cross-References
- •References
- •23 (LIFT) Ligation of Intersphincteric Fistula Tract
- •References
- •24 Anal Fistula: Glue and Paste Injection
- •1 Introduction
- •2 Fibrin Glue
- •3 Collagen Paste
- •4 Conclusion
- •5 Cross-References
- •References
- •25 VAAFT
- •1 Introduction
- •1.1 VAAFT Story
- •2 Surgical Equipment and Accessories
- •3 VAAFT Indications
- •3.1 Preoperative Assessment
- •4 VAAFT Procedure
- •4.1 Diagnostic Phase (Fistuloscopy)
- •4.2 Operative Phase
- •5 Closure of the Internal Opening
- •5.1 Use of a Linear or Semicircular Stapler
- •5.2 Advancement Flap
- •5.3 Use of a Bioabsorbable Mesh (Xenograft)
- •5.4 Autologous Dermis Graft
- •5.4.1 VAAFT Associated to the LIFT Procedure
- •5.5 Postoperative Management
- •6 Discussion
- •7 Conclusions
- •References
- •26 The Laser Treatment of Anal Fistulas
- •1 Introduction
- •1.1 Literature Review
- •1.3 Diagnosis and Treatment of Complex Anal Fistulas
- •2 Materials and Methods
- •3 Conclusion
- •References
- •27 Treatment by Over-the-Scope-Clip
- •1 Introduction
- •2 Technical Background
- •3 Surgical Application
- •4 Principle of Action
- •5 Clinical Data
- •References
- •28 Stem Cells in Cryptoglandular Anal Fistulas
- •1 Introduction
- •2 History of a Novel Approach
- •2.1 Mesenchymal Stem Cells
- •2.2 Adipose Tissue: The Ideal MSCs Source
- •2.3 Adipose Tissue Graft
- •2.3.1 Lipogems
- •3 Results
- •3.1 Literature Review
- •3.2 Personal Experience
- •4 Discussion and Conclusion
- •References
- •1 Introduction
- •2 Perianal and Rectovaginal Fistulas
- •2.1 Epidemiology and Diagnosis
- •2.2 Classification
- •2.3 Treatment Modalities
- •3 Flap Reconstruction
- •3.1 Overview and Considerations for Flap Reconstruction
- •4 Gracilis Interposition Flap
- •4.1 Background and Indications
- •4.2 Operative Technique
- •4.3 Results/Complications
- •5 Martius Interposition Flap
- •5.1 History and Indications
- •5.2 Surgical Technique
- •5.3 Results/Complications
- •6 Gluteal Muscle Interposition Flap
- •6.1 History and Indications
- •6.2 Surgical Technique
- •6.3 Results/Complications
- •7 Conclusion
- •References
- •30 Quality of Life Following Anal Fistula Treatment
- •1 Introduction
- •2 Quality of Life with an Anal Fistula
- •2.1 Cryptoglandular Fistulas
- •2.3 Conclusion
- •3 Quality of Life with a Seton and a Fistula

11 Magnetic Resonance and Traditional Radiology in the Diagnosis of... 189
These conclusions were supported in a follow-up study of 35 patients that demonstrated a correct MRI assessment in 33 of the patients (94%), including two cases in
which examination under anesthesia failed to identify distant sepsis.
More studies soon confirmed Lunnis’ excellent results.
In 2001 Beets-Tan et al. (2001) evaluated the importance of the additional
information that MRI examination can provide. The study included 56 patients
with anal fistulas who underwent high-spatial resolution MRI. The information
gained by the MRI made the surgeon decide to continue the surgery in only 21%
(12/56) of the patients. They concluded that MRI results provide significant additional information about secondary extensions and recurrent fistulas, particularly in
patients with Crohn’s disease; therefore, the authors recommended the execution of a
preoperative MRI to guide the surgeon to a more precise surgical planning.
In 2004 Buchanan et al. (2004) performed a larger study including 71 patients
with recurrent anal fistula in which MRI findings were revealed after initial fistula
surgery. The recurrence rate in the postoperative period was analyzed: in particular
the authors compared the recurrence rate when the surgeons acted basing their
decisions always on MRI results, the recurrence rate when surgeons acted only
sometimes basing on MRI findings, and the recurrence rate when MRI results
were completely ignored. The first group, when surgeons’ decisions were guided
by MRI findings, had a significant lower recurrence rate (16%), compared to the
other two groups (30% and 57%, respectively). Additionally, in the 16 patients who
required further unplanned surgery, MR images had initially accurately located the
site of disease in all cases, attesting that surgery guided by MRI reduces further
recurrence of anal fistula by 75% and should be performed in all patients, especially
the ones with recurrent fistula.
In 2017 Garg (2017) evaluated MRI contribution to surgical management in a
large study, which included 229 patients. They reported that MRI added important
information in patients with additional tracts, horseshoe tracts, supra-levator extension, unsuspected abscess, and multiple internal openings. They concluded that MRI
was capable of adding significant information to 46.7% of the surgeries when
assessing these parameters.
In 2018 Konan et al. (2018) evaluated the contribution of MRI in the surgical
management of anal fistulas. MRI signi ficantly helped the clinical assessment in
33.8% of the patients. MRI more often provided important information for c omplex
fistulas than for simple fistulas. Also when the external opening was more than 2 cm
away from the anal canal or when a horseshoe fistula was present, MRI demonstrated
to have a more relevant role.
Following these studies, it could be argued that all patients should be imaged
preoperatively, especially if MRI can be easily performed (Halligan 2020).
Supporting this, even though the therapeutic impact of MRI is more pronounced
in patients with a complex disease (Beets-Tan et al. 2001; Halligan 2020), it has been
estimated that MRI can prove around 10% of first time apparently simple presenting
fistulas, to be more complex than expected (Buchanan et al. 2004). Where MRI
access is more restricted and cannot be performed to study every patient, the
referring clinician needs to be more selective. MRI should be routinely performed

190 L. M. Minordi et al.
in patients with recurrent disease, because there is a high evidence of the benefits of
MRI, which can modify surgical therapy and improve clinical outcomes (Halligan
2020). As well patients presen ting for the first time with a fistula seemingly complex
on clinical examination and patients with known Crohn’s disease (since the prevalence of complex fistulas in this type of patients is so high) should undergo MRI
examination (Halligan 2020).
There are other surgical situations where imaging is likely to be extremely
helpful, even when the fistula itself is simple. For example, the anterior external
sphincter is very short in women, and dividing this during fistulotomy is a risk for
postoperative incontinence, even when the fistula is simple (Halligan 2020). In this
case, rather than incising the fistula, the surgeon may decide to pass a seton thread
through the track to stimulate drainage (Halligan 2020).
3 Conclusion
The anatomy of the anal and perianal region is complicated, and many different
abnormalities may be seen in this limited anatomical area. Almost any imaging
technique may be helpful for studying the perianal area; however, MRI, with its
brilliant and superior to any other modality soft tissue resolution, emerges as the
modality of choice. Furthermore, MRI examination is exceptionally useful in preoperative planning by outlining the extent and secondary ramifications of the fistula
tract as well as detecting the anal and cutaneous openings and associated abscesses.
4 Cross-References
▶ Endoanal Ultrasound in the Diagnosis of Cryptoglandular Anal Fistulas and
Abscesses
▶ Magnetic Resonance Imaging in the Diagnosis, Characterization, and Manage-
ment of Crohn’s Fistula
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Utility and Limitations of Endoanal
Ultrasound in the Diagnosis of Crohn’s Anal
12
Fistula and Abscess
Lucia Camara Castro Oliveira
Contents
1 Introduction . ............... .................................................................. 193
2 Clinical Presentation ......................................................................... 194
3 Utility and Limitations of Endoanal Ultrasound ............................................ 195
4 Conclusion ................................................................................... 199
5 Cross-References .......................... ............................................. ..... 200
References ............................ ............................................... ............ 200
Abstract
Distinction between cryptoglandular and Crohn’s fistulas may be difficult, but is
important to guide treatment. Ultrasonography is an imaging method that has
great utility for the evaluation of the anorectal region. The development of high-
resolution transducers, with higher frequencies and three-dimensional configura-
tion, provides an evaluation of complex fistula tracts including those associated
with perianal Crohn’s disease.
Keywords
Ultrasound · Anorectal · Crohn’s disease · Anal fistula
1 Introduction
Anorectal abscess usually originates from the infection and obstruction of the anal
glands. However, aside from this cryptoglandular origin, there are a number of other
causes of anorectal suppuration including Crohn’s disease. It is well known that
L. C. C. Oliveira (*)
Department of Anorectal Physiology of Rio de Janeiro, CEPEMED, Rio de Janeiro, Brazil
© Springer Nature Switzerland AG 2022
C. Ratto et al. (eds.), Anal Fistula and Abscess, Coloproctology,
https://doi.org/10.1007/978-3-030-76670-2_14
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194 L. C. C. Oliveira
anorectal abscess can drain spontaneously and may completely heal, or it can recur at
the same site and develop a fistula tract. In fact, in the majority of cases, anorectal
fistulas arise from a previous abscess. According to the Park’s classification, a fistula
tract can be intersphincter ic, trans sphincteric, suprasphincteric or extra sphincteric
(Parks et al. 1976). Therefore, adequate evaluation of fistulas and fistula tracts is
crucial to determine the appropriate intervent ion, minimizing the risks of anal
incontinence.
In patients with Crohn’s disease, perianal fistula can be a challenging situation
and in 20–30% of the cases it is the first presentation of the disease. The pathog enesis
of Crohn’s fistulas remains not well understood but certainly is distinct from the
cryptoglandular origin.
One of the theories associates the deep ulcers with invasion of fecal material and
bacteria. Those fistulas are more complex and can have mul tiple tracts. The clinical
presentation can be difficult to distinguish between other etiologies of perianal
disease, such as hidradenitis and sexually transmitted diseases. Because endoanal
ultrasound probe is introduced into the anal canal, the proximity of the anatomic
structures allows a better evaluation of the sphincter muscles and the tracts itself.
When accuracy of physical examination and endoanal ultrasound (EAUS) is compared, advantages of EAUS are clearly observed, especially in more complex cases,
such as in patients with Crohn’s disease. Accuracy of EAUS is around 85% for the
detection of horseshoe tracts and 85% for the location of the internal fistula orifice
compared to 56% and 69%, respectively, for the physical examination (Toyonaga
et al. 2008).
2 Clinical Presentation
Distinction between cryptoglandular and Crohn’s fistulas may be difficult, but is
important to guide treatment. Although the pathogenic mechanisms are very
different, some patients may remain undiagnosed when the clinical presentation
is not very clear for Crohn’s disease. Usually the complex tracts associated to
Crohn’s disease are located in atypical locations and have a poor healing rate,
regardless of the utilized treatment. Patients usually have constant anal pain that
can be maximized during evacuation, fever can be present, but interestingly, the
external fistula openings and the perianal skin are seldom painful. (Fleshman and
Tay 2014) In the evaluation process, active disease in the colon and small bowel
should be ruled out as the persistence of the inflammatoryprocessisassociated
with the maintenance of the perianal fistula disease. Another specificcharacteristic
of the Crohn’s fistula patients is the development of atypical skin tags which can
help to establish the diagnosis, as the pathognomonic non-caseating granulomas
can be demonstrated. In addition t o the skin tags, swelling, induration, and redness
of the perianal skin can be seen, as well as purulent discharge and multiple external
openings (Fig. 1).

12 Utility and Limitations of Endoanal Ultrasound in the Diagnosis of Crohn’s... 195
Fig. 1 Male patient with
multiple fistula tracks
associated with perianal
Crohn’s disease
3 Utility and Limitations of Endoanal Ultrasound
Ultrasonography is an imaging method that has great utility for the evaluation of the
anorectal region (Santoro and Murad-Regadas 2017). This imaging modality provides a clear evaluation of the anorectal muscles and pararectal spaces. Patients are
examined in the left lateral decubitus and gentle lubrication of the anus is advised.
The development of high-resolution transducers, with higher frequencies and
three-dimensional configuration, provides an evaluation of complex fistula tracts
including those associated with perianal Crohn’s disease (Santoro and Fortling 2007)
(Fig. 2).
In the case of suppurative processes and complex fistulas, including those related
to Crohn’s disease, ultrasound evaluation allows the identification of inflammatory
cavities, primary and secondary fistulous tracts, and the complexity of the tracts in
relation to the anorectal muscles (Fig. 3). In these cases, evaluation of the sphincter
muscles also brings important information to the surgeon, since the tracts may be
intersphincteric or transsphincteric. The information provided is valuable for proper
planning of the surgical approach as well as to classify and determine the extent of
the disease, avoiding the risk of incomplete healing, recurrent fistula, and inadvertent
sphincter injury.
The use of three-dimensional transducers has allowed the location of the fistulous
tracts in all planes (Fig. 4). In addition, when an external opening is present, it is
possible to introduce 1–2 ml of hydrogen peroxide to improve the visualization of
the tracts and the internal opening (Fig. 5).
Zawadzki et al. (2012) described the characteristic Crohn’s fistula imaging by
EAUS as a hypoechogenic fistula track surrounded by a hyperechogenic area
extending into the perianal tissue with a thin, regular hypoechogenic edge. This
finding can help the distinction between the various perianal fistulas.
One of the main advantages of EAUS is the possibility of performing
the evaluation at the office, when the patients are comfortable wi th the presence of

196 L. C. C. Oliveira
Fig. 2 High-resolution B-K
360 3D transducer for better
evaluation of anorectal region
Fig. 3 Anorectal abscess area
on coronal and axial plane
the probe. The high-resolution 3D transducers can demonstrate different plans of the
anorectal region and the more complex tracts can be easily demonstrated. Because
those transducers record the exam in automatic scanning the procedure can be
revised after the examination, which can, as with magnetic resonance imaging

12 Utility and Limitations of Endoanal Ultrasound in the Diagnosis of Crohn’s... 197
Fig. 4 High intersphincteric tract on sagittal and axial planes
Fig. 5 Endoanal ultrasound enhancement with hydrogen peroxide to improve the visualization of
the tracts and the internal opening
(MRI), overcome the barriers of having a non-experienced professional performing
the acquisition.
Portable systems with 2D probes can also be easily brought to the theater and
patients can be evaluated under sedation (Fig. 6).
In a study comparing 51 patients that underwent 3D-EAUS and MRI for Crohn’s
disease the authors were able to demonstrate that both studies can be used to assess
transsphincteric fistulas. However, they reported that using 3D-EUAS alone, up to
14% of suprasphincteric fistulas can be overlooked or not correctly diagnosed
(Alabiso et al. 2016). The advantages of MRI, according to this study, are the
evaluation of suprasphincteric and extrasphincteric fistulas with a broader

198 L. C. C. Oliveira
Fig. 6 Portable systems with
2D probes can also be easily
brought to the theater and
patients can be evaluated
under sedation
(360 Morpheus – Prometheus)
visualization of the hole pelvic floor thus showing the fistula track in the context of
the surrounding structures.
Although MRI has been widely utilized in the assessment of perianal CD, it
seems less accurate than EAUS in the detection of anorectal abscesses (Orsoni et al.
1999).
Another study, in fact, a meta-analysis performed in 2012, compared EAUS and
MRI in the identification and classification of perianal fistulas in patients with Crohn’s
disease, confirming a high sensitivity (87%) of both techniques (Siddiqui et al. 2012).
When a combination of a clinical activity index (Fistula Drainage Assessment (FDA)
and Perianal Disease Activity Index (PDAI)) with an imaging modality such as EAUS
was performeda demonstration of an improvementin diagnosticaccuracy was obtained
and both being complementary to each other (Losco et al. 2009; Botti et al. 2013).
These findings were also observed by de la Portilla et al who even presented a
ultrasonographic classification for patients with perianal Crohn’s disease (de la
Portilla et al. 2015) (Table 1).
The incidence of intersphincteric abscesses diagno sed by EAUS in a prospective
cohort of patients with CD was published in 2010 (Viganò et al. 2011). The authors
diagnosed perianal fistulas or abscesses in the presence of a hypoechoic track
originating from the subepithelial or submucosal layer of the anal canal, extending
toward the anal sphincters, and containing hyperechoic spots consistent with the
presence of gas bubbles within the fistulizing track. They included 55 patients and
demonstrated that EAUS is a valuable modality for the assessment of patients with
intersphincteric abscesses and pain.
In our series, EAUS helped to identify abscesses and complex fistula tract, as in
this example: a 43-year-old male patient with Crohn’s disea se and a large
ischiorectal abscess (Fig. 7).
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