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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_1056_Библиотеки_им_академика_М_И_Перельмана.pdf
220 S. Murad-Regadas and F. S. P. Regadas Filho
Fig. 5 (a–d) Male patient. Anterior and left lateral ischioanal cavity that crosse d the external
and int ernal anal sphincter and drained into the internal opening (IO) located at 2 o’clock at the
level of the mid-anal canal. (a) Axial plane: low anal canal – ischioanal cavity. (b)Mid-anal
canal – ischioanal that drained to the internal opening (IO). (c and d) Sa gittal plane: w hole
length of the cavity and IO. IAS, internal anal sphincter; EAS, external anal sphincter; PR,
puborectalis muscle
Cavanaugh et al. 2002). Garcia-Aguilar et al. demonstrated continence disorders in
38% of patients f ollowing fistula surgery when the external sphincter was kept
intact (Garcia-Aguilar et al. 1996). The increase of the external sphincter division
demonstrated a higher rate of incontinence. So, imaging modalities such as endoanal ultrasound (EAUS) or MRI are useful preoperative adjuncts to identify a
simple or complex anal fist ula as wel l as define the appropriate surgical procedure.
14 Future Perspectives in the Diagnosis of Anal Fistula and Abscess 221
Fig. 6 (a–d) Male patient. Right lateral and posterior supralevator abscess (with gas inside) located
at the perirrectal fat and intermuscular layers with an intersphincteric extension (right lateral and
posterior) at the level of the upper anal canal and drained into the internal opening (IO) located at
8o’clock. (a) Axial plane: low rectum (supralevator abscess). (b) Axial plane: Upper anal canal:
intersphincteric cavity. (c and d)sagittalandcoronal planes: whole length of the cavity and IO. IAS,
internal anal sphincter, EAS, external anal sphincter, PR, puborectalis muscle, MP, muscularis propria
Fig. 7 (a–c) Female patient without H202injection.Anterior intersphincteric anal fistula,curved tract
(between 10 and 2 o’clock) and internal opening (IO) located at 1 o’clock. (a and b)Axialplane:
anterior intersphincteric curved tract and IO. (c) Coronal plane: whole length of the curved tract
4.1 Imaging
It’s recommended imaging exams to evaluate all patients before surgery despite the
anal fistula be considered as simple by the physical examination. Sangwan et al. have
described that all so-called simple fistulas-in-ano cannot have readily detectable
222 S. Murad-Regadas and F. S. P. Regadas Filho
primary openings and can possess secondary tracks which preclude their behavior as simple fistula s ( Sangwan et al. 1994). Furthermore, Goodsall’s rule remains
in use by several surgeons for assessment of anal fistulae in pre- and transoperative phases. However, the overall accuracy is limited, and often without
evidence of concordance between rule and the surgical findings, it is unsafe to
confidently rely on Goodsall’s r ule in an attempt to predict the type of the tract, as
well as the internal opening position (Cirocco and Reilly 1992; Mur ad-Regad as
et al. 2015)(Fig.7).
The preoperative assessment plays a significant role in the choice of the operative
technique and, consequently, in the prevention of complications like disease recurrence and anal sphincter incontinence. Some studies recommend the 3D anorectal
ultrasound and others suggest MRI (West et al. 2004; Ratto et al. 2005; Sygut et al.
2010; Murad-Regadas et al. 2010; Joyce et al. 2008). Sygut et al. have shown that
endoanal ultrasound doubled the identification rate and thus decreased the risk of
recurrence. The relative risk of anal fistula recurrence was 20-fold higher in patients
in whom the internal opening was not identified than in those with identified internal
opening (Sygut et al. 2010).
4.1.1 Endoanal Ultrasound
The anorectal ultrasonic scanning can identify all the anal fistula components,
facilitating the surgical planning and preventing recurrence and fecal incontinence.
The three-dimensional scanning mode allows to accurately view the entire extension
of the fistulous tract and its relation to the sphincter muscles and the exact position of
the internal opening concerning the anal margin and any secondary tracts and/or
cavities as well as classify the anal fistula as well as the percentage of sphincter
muscle involved by the tract and to be sectioned during surgery (Fig. 8). To calculate
this percentage, the total length of the compromised sphincter is measured as well as
the distance from the distal part of each muscle to the point where the fistulous tract
crosses it (Figs. 9, 10, 11, 12, and 13). These measures are used in surgical planning
and help to prevent fecal incontinence (Murad-Regadas et al. 2010). Several studies
have shown significantly superior results with an injection of hydrogen peroxide in
the fistulous tract if compared with unenhanced studies and recommend it to improve
the accuracy of 3D ultrasound modality (Buchanan et al. 2005; Kim and Park 2009;
Nagendranath et al. 2014) (Figs. 9, 10, and 11).
The 3D modality shows to be very useful to better understand the anal canal and
pelvic floor anatomy due to the multiplay images, as demonstrated in a previous
study that assessed the anatomical conformation of the anal canal. It is easily
identified in the anal fistula tract and the internal opening (IO) according to gender
and hemicircumference (anterior vs. posterior) position. The anal canal muscles are
longer in males, and the dentate line is asymmetrical. In fema les, the percentage of
compromised EAS was greater in the anterior hemicircumference, while in males,
the percentage of compromised IAS was greater in the posterior hemicircumference
(Murad-Regadas et al. 2011).
14 Future Perspectives in the Diagnosis of Anal Fistula and Abscess 223
Fig. 8 (a–c) Male patient without H202injection. Right lateral (between 6 and 9 o’clock).
Intersphincteric anal fistula with secondary intersphincteric tract (between 6 and 11 o’clock) and
internal opening (IO) located at 8–9o’clock. (a) Axial plane: primary tract, curved, located between
6 and 9 o’clock at the level of the low and mid-anal canal. (b) Axial plane: low rectum, secondary
tract, curved, located between 6 and 11 o’clock. (c) Coronal plane: whole length of the primary
intersphincteric tract and the secondary intersphincteric tract from internal opening to low rectum
(intermuscular rectal layers). IAS, internal anal sphincter, EAS, external anal sphincter, PR,
puborectalis muscle, MP, muscularis propria
4.1.2 Magnetic Resonance Imaging
MRI image can be a useful modality for distinguishing complex from simple
perianal fistulae as well to define the anatomic relationships of the fistula in order
to predict the risk of postoperative fecal incontinence, and it is also able to demonstrate hidden areas of sepsis and secondary extensions, both of which contribute to
the high rate of recurrence after surgery (de Souza et al. 1998; Halligan and Bartram
1998; Buchanan et al. 2004).
It has been suggested that MRI yields improved images when an endoanal coil is
used (de Souza et al. 1998). However, reports in the literature of its usefulness vary,
224 S. Murad-Regadas and F. S. P. Regadas Filho
Fig. 9 (a–d) Male patient with H202injection.High transsphincteric anal fistula, curved tract, located
between 9 and 4 o’clock and internal opening (IO) located at 5 o’clock. (a) (without) (b)withH
mid-analcanal – tract outside the EAS. (c)(without)(d)withH
EAS-PR, EAI, and IO at 5 o’clock. (e)(without)(f)withH
upper anal canal. Tract crossing the
202
whole length of the transsphincteric
202
202
tract. Line 1: total length of the posterior EAS plus PR. Line 2: total length of the EAS compromised
by the tract. IAS, internal anal sphincter, EAS, external anal sphincter, PR, puborectalis muscle
–
14 Future Perspectives in the Diagnosis of Anal Fistula and Abscess 225
Fig. 10 (a–c) Female patient with H202injection. High transsphincteric anal fistula, linear tract,
located between 11 and 12 o’clock and internal opening (IO) located at 12 o’clock. (a) Mid-anal
canal – Tract outside the EAS. (b) Mid-anal canal. Tract crossing the EAS, IAS, and OI at
12 o’clock. (c) Whole length of the transsphincteric tract. Line 1: total length of the anterior
EAS. Line 2: total length of the anterior EAS compromised by the tract. IAS, internal anal sphincter,
EAS, external anal sphincter, PR, puborectalis muscle
and additionally, MRI scanning with an endoanal coil is uncomfortable in symptomatic patients (Halligan and Bartram 1998). Diffusion-weighted MRI can be the
next improvement in scanning techniques to yield better images, but this is only
available in a few centers (Hori et al. 2009).
The development of the 1.5 Tesla and 3.0 Tmagnets in the acquisition of images
has enabled them to perform the MRI without endoanal coil in the evaluation of anal
and rectal disease (Garg 2018).
Studies comparing endoanal ultrasound with MRI for the assessment of idiopathic and Crohn’s perianal fistulas have demonstrated comparable sensitivities at
226 S. Murad-Regadas and F. S. P. Regadas Filho
Fig. 11 (a–d) Male patient with H202injection. One transsphincteric tract outside the EAS at
5o’clock and the other one transsphincteric tract outside the EAS at 7 o’clock, joined at 6 o’clock,
as horseshoe tract and extending through the EAS, IAS, and internal opening (IO) located at 6–7
o’clock. (a) Low anal canal – two tracts outside the EAS at 5 o’clock and at 7 o’clock. (b) Mid-anal
canal. Horseshoe tract. (c) Mid-tract crossing the EAS, EAI, and IO at 6–7o’clock. (d) Whole
length of the tract. Line 1: total length of the posterior EAS plus PR. Line 2: total length of the
posterior muscles compromised by the tract. IAS, internal anal sphincter, EAS, external anal
sphincter, PR, puborectalis muscle
detecting perianal fistulas, although the specificity of MRI was higher than endoanal
ultrasound. However, both specificity values are considered to be diagnostically
poor. Due to data heterogeneity and the shortage of applicable studies, it is not yet
possible to get a final conclusion about the results of both modalities for clinical
practice (Siddiqui et al. 2012).
In the literature, there are few data of imaging exam advantages to evaluate the
supralevator and extrasphincteric fistulas. Perhaps due to the reduced use of
14 Future Perspectives in the Diagnosis of Anal Fistula and Abscess 227
Fig. 12 (a–e) Male patient with H202injection. Left and posterior transsphincteric tract outside the
EAS at 5 o’clock and extending through the EAS, IAS, and internal opening (IO) 5 o’clock. The
tract courses as a secondary horseshoe tract, from left to right at the level of mid-upper anal canal.
(a) Low anal canal. Tract outside the EAS at 5 o’clock. (b) Mid-anal canal. Tract and IO. (c) Upper.
228 S. Murad-Regadas and F. S. P. Regadas Filho
Fig. 13 (a–e) Male patient with H202 injection. Suprasphincteric anal fistula. Right lateral curved
tract (between 11 and 7 o’clock) through the ischiorectal fossa (outside the EAS, PR) and following
above the PR at 7 o’clock, passing to the left side. The tract courses below the PR, as
intersphincteric tract (between 6 and 2 o’clock) and internal opening (IO) located at 5 and 6 o’clock.
(a) Mid-anal canal. Right lateral curved tract (between 11 and 7 o’clock) through the ischiorectal
fossa. (b) Upper anal canal. The right lateral curved tract (between 11 and 7 o’clock), the left
intersphincteric tract (between 6 and 2 o’clock), and IO at the 5 and 6 o’clock. (c–e) 3D reconstruction following the tortuous tracts below and above the PR. IAS, internal anal sphincter, EAS,
external anal sphincter, PR, puborectalis muscle
endoanal ultrasound and MRI in the evaluation of these types of fistulas, the
diagnosis and delineation of supralevator fistulas were not only challenging but
ä
Fig. 12 (continued) Secondary horseshoe tract. (d) Whole length of the primary and secondary
tract. (e) Whole length of the primary tract. Line 1: total length of the posterior EAS plus PR. Line 2:
total length of the posterior muscles compromised by the tract. IAS, internal anal sphincter, EAS,
external anal sphincter, PR, puborectalis muscle
14 Future Perspectives in the Diagnosis of Anal Fistula and Abscess 229
also imprecise. The main reasons for this are the relative rarity of supralevator fistula
and the difficulty in managing them. Similarly the extrasphincteric fistula is complicated to treat. Then surgeons were not inclined to intervene in supralevator fistulas
because extrasphincteric fistulas were assumed to be a significant proportion of these
fistulas (Garcia-Granero et al. 2014).
The optimally balancing benefits, the 3D ultrasound is a safe and relatively
inexpensive technique, performing in the office which can also be used in patients
who cannot undergo MRI because of claustrophobia, obesity, and the presence of a
pacemaker or metal implant. In the light of the presented information, MRI is a very
efficient method with an external coil. It is min imally invasive, painless, and with
92% sensitivity. It seems that sensitivity is better in the diagnosis of high and
complex fistul as rather than low and simple fistulas (Williams et al. 2001). The
disadvantage of endorectal MRI is the high cost; consequently, some centers favor
using ultrasound. However, using in combination, diagnostic yield may MRI and US
3D increase, but the cost needs to be considered. Besides , some institutions do not
have the facility for MRI while others do not have for 3D ultrasound. From the
patient perspective, MRI is not indicated for those patients with claustrophobia as
well as the limited availability of MRI in surgical centers.
5 Conclusion
We suggest that all patients with abscess and anal fistula should be assessed by image
and all colorectal unit could have colorectal surgeon trained in 3D endoanal ultrasound and/or radiologist that perform MRI trained in colorectal disorders and may
provide careful evaluation and identification of all anal fistula components, facilitating the surgical planning, avoiding the recurrence, and preventing fecal
incontinence.
6 Cross-References
▶ Endoanal Ultrasound in the Diagnosis of Cryptoglandular Anal Fistulas and
Abscesses
▶ Magnetic Resonance and Traditional Radiology in the Diagnosis of
Cryptoglandular Anal Fistula and Abscess
References
Bollard RC, Gardiner A, Lindow S et al (2002) Normal female anal sphincter: difficulties in
interpretation explained. Dis Colon Rectum 45:171–175
Buchanan GN, Halligan S, Bartram CI et al (2004) Clinical examination, endosonography, and MR
imaging in preoperative assessment of fistula in ano: comparison with outcome-based reference
standard. Radiology 233:674–681