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304
S. W. Bell
tension from the retraction, and the tissue being
lifted broadens out from this point. Figure29.8
demonstrates this triangle appearance, and in this
example the underlying fascial plane has been
lifted because the dissection has been at the base
of the triangle. The dissection should be at the
apex of the triangle, allowing the tented tissues to
fall away, as opposed to dissection in the deeper
plane as seen in Fig.29.9.
Fig. 29.8 Retracting the rectum/mesorectum tents up the
attached underlying tissues producing a triangle appearance. Dissection should be guided to the apex of the triangle not the base
Too Deep Posteriorly: Presacral
Veins andtheSacrum
Immediately posterior to the deep layer of the fascia propria is a loose areolar plane with little adipose tissue that opens very easily. Posteriorly the
contents of this space are the presacral veins. This
is a venous plexus that results from anastomoses
between the lateral and median sacral veins.
These drain into the internal and common iliac
veins and also communicate to the deeper veins
within the sacrum via the sacral foramina. Injury
to these veins can lead to profuse and potentially
catastrophic bleeding as they are large veins. If
the injury involves the region of the sacral foramina, the vein can retract into the foramen making
hemostasis more difcult. As the posterior taTME
dissection extends proximally, it is imperative that
the surgeon anticipates the sacral curvature, executing an upward turn before colliding with the
sacrum as it becomes in-line with the plane of dissection. Alternatively, this portion of the dissection (the proximal TME dissection) can be
performed by the abdominal surgeon who likely
has a better vantage point, in most instances.
Too Deep Laterally: Major Vessels,
theUreter, andthe“Pelvic Tonsils”
Fig. 29.9 Dissection has been in a plane too deep, at the
base of the triangle (red line), thus lifting the endopelvic
fascia and exposing the puborectalis muscle. The correct
position for dissection is at the apex of the green
triangle
When dissecting laterally it is important to maintain the correct plane, and the tendency can be to
dissect too deeply, particularly in the mid and
upper pelvis. There is a fear of dissecting too
medially, into the mesorectum and to breach the
oncologic principles of a TME.This, along with
the often inviting loose areolar plane deep to the
extrafascial plane, can lead the surgeon to dissect
more widely. There are numerous important anatomical structures in this space, with some loose
supporting fatty tissue. The internal iliac artery
and its branches, along with the accompanying
veins, lie in this space, including the middle rectal artery. When the mesorectum and specimen
are retracted medially, this draws up the underlying tissues, again creating a triangle. In this lateral position, this is not just bro-fatty tissue
29 Critical Anatomical Landmarks inTransanal Total Mesorectal Excision (taTME)
underlying but may also include the terminal
branches of the internal iliac artery including the
superior vesical artery and the obturator artery.
These vessels normally run parallel to the plane
of dissection but appear to be crossing the plane
if they are retracted medially (see Fig.29.10a, b).
If dissection continues lateral to this fatty tissue,
it will “hang down” and become shifted slightly
medially to give the appearance of a tonsil (see
Fig.29.11). This has been coined the “pelvic tonsil” by Dr. Matthew Albert. The appearance of a
tonsil should alert the surgeon to the fact that the
dissection is too deep and the appropriate correction be made to the more medial plane. If this is
not recognized, and the dissection is continued in
a
Fig. 29.11 Operative photo of dissection on the right
pelvic side wall with the specimen on the right of the
photo. Dissection too far laterally exposes the fatty tissue,
coined the “pelvic tonsil” (shown in yellow). Dissection
deep to the tonsil (red line) will result in signicant bleeding, whereas the green line indicates the appropriate correction into a more medial plane
305
b
Fig. 29.10 (a) Lateral pelvic side wall without traction,
with a vessel lying at. (b) Lateral pelvic side wall with
traction on the rectum, tenting the side wall vessel into the
apparent plane of dissection (red line). The green line
indicates the correction that needs to be made to avoid
injury to the vessel
Fig. 29.12 Pelvic MRI scans demonstrating the incorrect
(red) and correct (green) planes of dissection on the lateral
pelvic side wall. If dissection is too lateral, the pelvic tonsil (yellow) may appear, and dissection further in this
plane could result in major vascular injury and signicant
bleeding
this deep plane, signicant vessels will be
encountered and possibly injured, leading to
major bleeding and a loss if the surgical view and
clear appreciation of the tissue planes. It is important to note that this tonsil does not appear when
performing an abdominal dissection of the pelvis
as the dissection passes directly over these tissues
and they are not lifted. As such, this appreciation
of the pelvic side wall anatomy is unique to the
taTME operation (see Fig.29.12).
306
S. W. Bell
Proximal to the pelvic tonsils in the anterolateral quadrant are the ureters. These are usually
dened more proximally when performing an
abdominal dissection and are then followed caudally into the pelvis. This maneuver is not possible when dissecting from below; however if
there are concerns during taTME dissection,
then identifying the ureters abdominally should
be completed. The ureters are often not seen during a taTME dissection but are only one plane
deeper than the dissection. It should be recognized that the direction of dissection in the upper
half of the pelvis is from a lateral position heading centrally and medially, as the specimen narrows toward the upper rectum. It is most common
to breach the peritoneum and join the peritoneal
cavity close to or in the midline anteriorly.
Having dened the correct position, the division
of the peritoneum can be taken further laterally.
This will keep the dissection medial to the ureter
Fig. 29.13 The position of the right ureter (yellow) at the
point of breaching into the peritoneal cavity as seen from
below. The red line indicates dissection too laterally putting the ureter at risk, whereas the more medial dissection
along the green line is the correct plane
and should avoid the dissection drifting too far
laterally (Fig.29.13).
29 Critical Anatomical Landmarks inTransanal Total Mesorectal Excision (taTME)
Too Deep Anteriorly: Vagina,
Prostate, andUrethra
The anterior dissection is distinctly different in
a male and female patient. In the female the rectovaginal septum is often very clear, and the
more anterior structures including the urethra
are not in danger. This plane can be affected by
tumor, radiotherapy, and previous surgery such
as gynecological prolapse procedures. In the
normal state, however, this plane is clear and
often the easiest to dene. The direction of dissection is quite “horizontal,” with the operating
instruments passing horizontally and the surgeon’s hands at the same level as the access
channel.
Anterior dissection in a male must be undertaken with some caution. One of the more publicized and feared complications of taTME is
male urethral injury, and this can be prevented
with a clear understanding of the anatomy and
careful dissection and recognition of the anatomical landmarks. When the urethra has been
exposed and at risk, the problem has usually
occurred earlier in the dissection. Having placed
a purse- string suture and performed a rectotomy, the rectum becomes mobile. Retraction
posteriorly on this mobile rectum transmits posterior traction on the prostate while it is still
attached. It is usually necessary to mobilize the
prostate laterally to expose the urethra, and this
occurs when dissection has been in a plane too
deep around the distal rectum posteriorly and
laterally and continued anteriorly and cranially.
Figure 29.14 demonstrates the correct and
incorrect planes that lead to lateral mobilization
of the prostate. With posterior retraction and the
weight of the rectum and prostate assisting, the
urethra comes into view (Fig.29.15). The dumb-
bell appearance of the rectum and attached prostate may be able to be seen. The urethra may
also be visible as a longitudinal cord centrally.
There is no plane to dissect here, and efforts to
try to dissect this tissue will lead to urethral
injury.
The clues that the prostate has been mobilized
include:
Fig. 29.14 MRI scans of the pelvis demonstrating the
correct (green) plane of dissection around the mesorectum and the incorrect (red) deeper plane of dissection
that leads to mobilization of the prostate along with the
rectum. This deeper dissection drops the prostate posteriorly, exposing the urethra and placing it at risk of
injury
1. The dumbbell appearance of the rectum and
prostate fused together, both being posterior
to the plane of dissection.
2. Visible muscle bers on the anterolateral pelvic wall (there should be no muscle bers
anteriorly in a man).
307
308
Fig. 29.15 Operative images during taTME demonstrating inadvertent mobilization of the prostate, exposing the
urethra as a midline cord
3. The longitudinal midline cord without a tissue
plane.
4. The operating surgeon’s hand being placed
low with the instruments angling upward,
indicating the dissection is too anterior.
5. Bleeding at the 10 and 2 o’clock position from
the neurovascular bundle of Walsh, when this
is distracted downward into the plane of
dissection.
Denonvilliers’ fascia can be clearly identied
from below, and the dissection can pass anterior
or posterior to this at the surgeon’s discretion.
The caudal end of Denonvilliers’ fascia is not a
distinct structure and so can be difcult to dene
at its distal most extent where it inserts onto the
urogenital diaphragm. Once dissection has
passed a short distance, the fascial tissue becomes
clearer. At this point a decision can be made to
dissect anteriorly with the capsule of the prostate
gland on view, or posteriorly, lifting Denonvilliers’
fascia and leaving it attached to the prostate (see
Fig.29.16).
Entering thePeritoneal Cavity
Identifying the peritoneal reection is most clear
when operating synchronously with both a transanal and an abdominal surgeon. With both views
S. W. Bell
Fig. 29.16 taTME view of Denonvilliers’ fascia being
reected posteriorly, with dissection passing between this
and the prostatic capsule. The lower most extent of
Denonvilliers’ fascia is not a clear structure. As such,
when it is identied, it may be necessary to actively incise
to pass into the plane anteriorly
the dissection can be guided safely, and vital
structures, including intraperitoneal organs such
as the small bowel, can be easily avoided. When
operating with a single team, there are a number
of cues that the peritoneal reection is being
approached. When dissecting anteriorly, in both
females and males, there is slightly more extraperitoneal fat in the region of the peritoneal
reection compared to more distally. The tissues
here are also more loosely attached. The pressure
differential between the pneumopelvis and the
pneumoperitoneum can lead to a “uttering” of
the tissues, both just before and just after incising
the peritoneum. As the defect in the peritoneum
enlarges, this uttering diminishes and disappears as the two cavities merge and the pressures
equalize. There may also be the impression of
small bowel or other intraperitoneal organs moving subtly, seen through the thin peritoneum
before division. This is an important sign to recognize so as to avoid inadvertent injury when
incising the peritoneum. Laterally it is important
to be aware of the position of the ureters and
avoid dissecting too laterally, as described previously and shown in Fig.29.13. It is often safer to
breach the peritoneal reection anteriorly and
then continue division of the peritoneum toward
the lateral structures to be certain that these are
protected.
29 Critical Anatomical Landmarks inTransanal Total Mesorectal Excision (taTME)
section, achieving a high-quality total mesorectal
excision and avoiding complications.
Suggested Reading
Atallah S, Albert M, Monson JR.Critical concepts and
important anatomic landmarks encountered during
transanal total mesorectal excision (taTME): toward
the mastery of a new operation for rectal cancer surgery. Tech Coloproctol. 2016;20(7):483–94. https://
doi.org/10.1007/s10151-016-1475-x. Epub 2016 May
17.
Conclusion
The critical anatomical landmarks encountered
when performing taTME have been described. It is
important to recognize the variability between
patients and also pathologies. The effect of radiotherapy and previous pelvic surgery can either alter
the anatomy or make the appearance of the anatomy slightly different. Finding the correct plane
and maintaining dissection in the correct plane are
the cornerstones to performing taTME.Adherence
to the principles described in this chapter and this
textbook will help the surgeon maintain a safe dis-
Atallah S, Mabardy A, Volpato AP, Chin T, Sneider J,
Monson JRT. Surgery beyond the visible light spectrum: theoretical and applied methods for localization
of the male urethra during transanal total mesorectal excision. Tech Coloproctol. 2017;21(6):413–24.
https://doi.org/10.1007/s10151-017-1641-9. Epub
2017 Jun 6.
Bernardi MP, Bloemendaal AL, Albert M, Whiteford M,
Stevenson AR, Hompes R.Transanal total mesorectal
excision: dissection tips using ‘O’s and ‘triangles’.
Tech Coloproctol. 2016;20(11):775–8. Epub 2016
Oct 1.
Knol J, Chadi SA. Transanal total mesorectal excision:
technical aspects of approaching the mesorectal plane
from below. Minim Invasive Ther Allied Technol.
2016;25(5):257–70. https://doi.org/10.1080/1364570
6.2016.1206572.
309
Urethral Injury: The New Challenge for taTME
Heather Carmichael and Patricia Sylla
30
Introduction
Transanal total mesorectal excision (taTME)
allows for improved exposure and visualization
of the distal rectum, improving the quality of
resection. However, there is a unique risk for iatrogenic injury to the male urethra due to the fact
that the prostate can be inadvertently mobilized
from below, but not from above, thus exposing
the prostatic urethra [1]. This risk is particularly
important given that, thus far, taTME has been a
preferred approach in men, given its benets in
approaching a narrow or deep pelvis [2], as demonstrated by data from the international taTME
registry (LOREC) showing that 1080 of 1594
cases (67.8%) were performed in male patients
[3]. Moreover, urethral injury has not been documented in other sphincter-preserving methods of
rectal resection (i.e., low anterior resection) and
is only a rare complication in abdominoperineal
resection, with reported incidence ranging
between 1.5% and 3.0% [4]. Specic training to
understand anatomic landmarks and risk factors
and prevent wrong-plane surgery will be neces-
H. Carmichael
Department of Surgery, University of Colorado,
Aurora, CO, USA
e-mail: heather.carmichael@ucdenver.edu
P. Sylla (*)
Division of Colon and Rectal Surgery, Icahn School
of Medicine at Mount Sinai, New York, NY, USA
e-mail: patricia.sylla@mountsinai.org
sary to avoid urethral injury as use of taTME
becomes more widespread.
Incidence of Urethral Injury
There is signicant variability in the rates of urethral injury reported in current case series, and
not all series reporting on the initial results of
taTME have documented complications including the incidence of urethral injury. To date, rates
of urethral injury have varied from 0% in several
large case series to 6.7% in a study of n=30 male
patients by Rouanet etal. [5]. A number of large
case series have reported no incidences of urethral injury including a study of n=140 patients
by de Lacy etal. [6], a study of n=80 patients by
Veltcamp Helbach etal. [7], and a study of n=50
patients by Chen et al. [8]. Three other series
have reported single cases of urethral injury, with
a rate of 2% in a study of n=50 patients by Burke
etal. [9], a rate of 5% in a study of n=20 patients
by Kang etal. [10], and a rate of 1% in a study of
n=100 patients by Perdawood etal. [11]. Results
from the voluntary international taTME registry
noted that of n = 1594 patients undergoing
taTME, 12 patients were documented to have a
urethral injury (0.8%), similar results to those
found in the initial publication including n=720
patients [3, 12]. Of note, most series report rates
that are not broken down by patient sex and
therefore do not report the incidence in males
© Springer Nature Switzerland AG 2019
S. Atallah (ed.), Transanal Minimally Invasive Surgery (TAMIS) and Transanal Total Mesorectal
Excision (taTME), https://doi.org/10.1007/978-3-030-11572-2_30
311
312
H. Carmichael and P. Sylla
alone [1]. This may partially explain the high rate
of injury noted by Rouanet etal. in their series of
male patients only. The rate of urethral injury in
all patients and in male patients only for large
case series (≥ 20 patients) are reported in
Table30.1.
The true incidence of urethral injury may be
underreported in these large case series. Indeed,
as many as 18 urethral injuries have been reported
to international registries, according to experts in
the eld, but only a handful have been documented in the surgical literature (Table 30.2)
[13]. Anonymous feedback from n=38 surgeons
who had undergone a formal cadaver-based
taTME training in North America demonstrated
that 20% of survey participants had experienced
at least one urethral injury in their experience
since course completion [14]. A recent international survey of urethral injury during taTME
Table 30.1 Large series of taTME with rates of urethral injury when complications were noted
Author Year Country N % male N urethral injury % total injured % male injured
de Lacy [33] 2013 Spain
Rouanet [5] 2013 France 30 100.0 2 6.7 6.7
Velthuis [34] 2014 Netherlands
Atallah [35] 2014 USA
Fernandez-Hevia [36] 2015 Spain
Veltcamp Helbach [7] 2015 Netherlands
Tuech [37] 2015 France
Muratore [38] 2015 Italy 26 61.5 0 0.0 0.0
de Lacy [6] 2015 Spain
Perdawood [39] 2015 Denmark
Buchs [40] 2015 UK
Chen [8] 2015 Taiwan 50 76.0 0 0.0 0.0
de’Angelis [41] 2015 France 32 65.6 0 0.0 0.0
Rink [42] 2015 Germany 24 75.0 0 0.0 0.0
Serra-Aracil [43] 2016 Spain 32 75.0 N/A
Burke [9] 2016 USA
Rasulov [44] 2016 Russia 22 50.0 0 0.0 0.0
Buchs [45] 2016 UK
Kang [10] 2016 China 20 60.0 1 5.0 8.3
Lelong [46] 2016 France
Perdawood [11] 2017 Denmark
Maykel [17] 2017 USA 40 60.0 0 0.0 0.0
Marks [47] 2017 USA 373 68.9 0 0.0 0.0
Caycedo-Marulanda
[48]
de Lacy [49] 2017 Spain
Penna [12] (registry) 2016 N/A 720 67.9 5 0.7 1.0
a–f
Indicate prospective cohorts with likely patient overlap
2017 Canada 27 51.9 0 0.0 0.0
a
c
a
d
a
f
c
f
d
a
20 55.0 0 0.0 0.0
b
25 72.0 N/A
20 70.0 0 0.0 0.0
37 64.9 0 0.0 0.0
b
80 60.0 0 0.0 0.0
56 73.2 0 0.0 0.0
140 63.6 0 0.0 0.0
e
25 76.0 0 0.0 0.0
20 70.0 0 0.0 0.0
50 60.0 1 2.0 3.3
40 80.0 0 0.0 0.0
34 67.6 N/A
e
100 72.0 1 1.0 1.4
186 63.4 N/A
reports a total of 34 urethral injuries that have
occurred during taTME; only 18 of these had
been reported to an international registry and
only 5 were included in published series, indicating that underreporting of this complication is a
serious concern (Sylla etal., manuscript submitted for publication) [15].
Furthermore, rates of injury may increase
with uptake of taTME unless surgeons are specically trained about the risk of male urethral
injury and how to avoid it. Rates of inadvertent
mobilization of the prostate (wrong-plane surgery) are high in reports on cadaveric trainees,
despite the fact that most trainees have extensive
rectal cancer experience. In one study, nearly
20% of cadaveric trainees unintentionally mobilized the prostate, and 2 out of 103 trainees accidentally completed a pelvic exenteration during
taTME training [14]. However, there is evidence
30 Urethral Injury: The New Challenge for taTME
Table 30.2 Descriptions of urethral injury during taTME reported in the surgical literature
Series
1 Rouanet
[5]
2 Rouanet
[5]
3 Burke [9] Low, anterior rectal tumor
4 Kang [10] Large, circumferential
5 Perdawood
[11]
Tumor and patient
characteristics Type and timing of injury
Bulky anterior rectal
tumor
Concurrent T4 prostatic
carcinoma
(<3cm from anal verge)
tumor 5cm from anal
verge in a patient with
benign prostatic
hypertrophy
Advanced low rectal
cancer, treated with
neoadjuvant
chemoradiation
Unspecied Noted intraoperatively,
Unspecied Noted intraoperatively,
Injury to posterior wall
of preprostatic urethra
that occurred during
mobilization of rectum
from prostate
Prostatic and urethral
injury accompanied by
massive hemorrhage
after dissection too far
anteriorly
Unspecied Managed
Management and
morbidity
suture repair with
TEO, no long-term
morbidity
suture repair with
TEO, no long-term
morbidity
Noted intraoperatively,
managed
nonoperatively, no
long-term morbidity
Conversion to
laparoscopic assistance
nonoperatively, no
long-term morbidity
313
Timing relative
to surgeon
experience
Beginning of
experience
Unspecied
Middle of
experience
Beginning of
experience
Unspecied
that this risk can be mitigated by training specic to urethral injury– the same group found
that the rate of prostate mobilization could be
decreased with additional training about landmarks and how urethral injuries occur, decreasing substantially from 20% to 3.3% after specic
training on urethral injury and anatomic landmarks was provided [14].
Urethral injuries, when they do occur, can
have exceedingly debilitating effects on urinary
and even sexual function. Of the 34 injuries documented by Sylla etal., 32 (94.1%) were identied intraoperatively [15]. Of these, 12 were
converted to a transabdominal approach or
unplanned APR or Hartmann’s procedure
(37.5%). Of 34 injuries, 9 patients (26.4%) went
on to develop complications from the repair
including stricture (n = 4), rectourethral stula
(n=3), urethral dehiscence (n=1), or urethraperineal stula (n=1). These patients with complications experienced a 30% rate of failed
urethral repair requiring permanent cystostomy.
Sexual function was assessed in 22 patients, with
13 (59%) noting erectile dysfunction.
Understanding the Anatomic Landmarks
Understanding the critical anatomic landmarks is
crucial to avoid wrong-plane surgery in taTME
and therefore prevent urethral injury [1, 9, 16,
17]. Atallah et al. have highlighted the impor-
tance of three key anatomic aspects that should
be recognized by the taTME surgeon [16]. The
rst is the paired neurovascular bundles of Walsh
which are located laterally between the rectum
and the prostate (at the 10 and 2 o’clock positions
during taTME dissection) and each include two
3–4mm paired arterial vessels [18]. The dissection in taTME should always be posterior (supercial) to these structures as well as the
rectoprostatic (Denonvilliers’) fascia [16, 19].
Secondly, the surgeon should recognize the
smooth, spherical, and symmetric shape of the
inferior lobe of the prostate, which is normally a
pale yellow in color [1, 16]. Unfortunately, rectoprostatic plane identication can be severely
complicated by dense postradiation brosis,
prostate enlargement, or plane distortion from
314
H. Carmichael and P. Sylla
bulky T4 anterior rectal tumors. Finally, the surgeon should be able to recognize the cylindrical
shape of the prostatic urethra in case the wrong
plane of dissection is entered [13, 16].
Another important anatomic landmark is the
rectourethral muscle (RUM), and understanding
the relationship between this muscle, the anterior
rectal wall, the posterior prostate, and other muscles of the pelvic oor is vital, although underappreciated until recently (Sylla etal., manuscript
submitted for publication) [15]. The RUM is a
dense band of smooth muscle bers that extends
from the muscular propria of the rectum anteriorly to the external urethral sphincter. The anatomic signicance of the RUM has been described
extensively in the urologic literature on radical
perineal prostatectomy [20, 21]. During taTME
for low rectal tumors (within 5–6cm of the anal
verge), the RUM must be divided in order to
access the plane between the anterior rectum and
posterior surface of the prostate. The RUM must
be divided close to the rectum, as division of this
muscle too far anteriorly leads to dissection along
the inferior lobe of the prostate in an anterior
direction, toward the membranous urethra [22]. If
unaware of these anatomic relationships, the surgeon may mistake the RUM for residual muscularis propria of the rectum and direct dissection
too far anteriorly in an attempt to avoid rectal
perforation (Figs.30.1 and 30.2).
a
c
Fig. 30.1 Near-miss injury to the prostatic urethra during
taTME. Transanal TME dissection initiated shortly after
complete intersphincteric resection was completed for a
very low rectal tumor. The anatomically correct plane
between the anterior mesorectum and posterior prostate
was difcult to identify. Fibers of the rectourethral muscle
are seen coursing anteriorly between the anterior rectal
wall and the apex of the prostate and should have been
divided close to the anterior rectal wall (a, blue arrow).
Instead, and out of concern of erring too close to the anterior rectal wall and risking anterior rectal wall perforation,
the dissection is inadvertently carried out too anteriorly (a,
white arrow). Dissection was erroneous and briey
b
d
extended close the apex of the prostate (b, white arrow),
but the surgeon quickly realized the error and corrected the
dissection back to the correct plane, more inferiorly and
closer to the anterior rectal wall (b, blue arrow). The prostate is nally visualized along its left lateral aspect (area
between the white and blue arrows, c), and dissection proceeds along the correct anatomic plane, close to the anterior rectal wall (c, blue arrow). After taTME is completed,
the prostatic urethra is visualized along with a small defect
in the surrounding urethral sphincter muscle (d, white
arrow). Fortunately in this near-miss case, the urethra
remains intact, as conrmed with intraoperative cystoscopy under transanal endoscopic perineal visualization