Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_869_Библиотеки_им_академика_М_И_Перельмана.pdf
32 A Roadmap tothePelvic Autonomic Nerves During Transanal Dissection
Table 32.2 Five key zones where autonomic nerves are at risk during transanal approach
Key
zone Level Nerve segments Dissection Depiction
1 Upper anal canal, at
dentate line
Terminal branches of the
IASN
Intersphincteric
337
2 Levator ani muscle IASN (Postero-) lateral at
3 Pelvic sidewall above
the level of the levator
ani muscle
4 Sacral nerve routes S4
and S3
5 Prostate/vagina IHP with its anterior parts
Posterior-inferior edge of
the IRP
PSN Posterolateral
and NVB
the 4 and 8 o’clock
lithotomy positions
Lateral at the 3 and 9
o’clock lithotomy
positions
Anterolateral at the
2–3 and 10–11
o’clock lithotomy
positions
IASN internal anal sphincter nerves, IRP inferior rectal plexus, PNS pelvic splanchnic nerves, IHP inferior hypogastric
plexus, NVB neurovascular bundles
during a partial intersphincteric resection. With
diameters of 0.1 mm, intersphincteric nerves are
barely visible, even when an incision is performed
at or below the dentate line, during an initially open
approach (Table32.2). The nerves are embedded in
fatty tissue and tend to course along the internal,
rather than the external, anal sphincter. Injections
to enhance tissue volume and careful preparation
seem to comprise the method of choice to optimize
nerve- preserving dissection [10, 18–20].
338
Internal Anal Sphincter Nerves
In the 1950s, Otto Goetze described tuft-shaped,
branched, ne bers that projected from the lowest section of the pelvic ganglion in a specimen
after abdominoperineal excision. He reasoned
that extrinsic IAS innervation could be spared
with a transanal, bottom-up approach, and he
stated that the lower the resection and the less
IAS nerve preservation, the worse the continence
outcome [18].
When an incision is performed above the dentate line or the IAS level, the transanal video
endoscope-assisted approach is suitable for verifying the internal anal sphincter nerves (IASNs)
[10]. The extrinsic IAS innervation approaches
the anorectal junction with a varying number
(two to six) of nerve fascicles bilaterally, from
the 5 and 8 o’clock location (with patients positioned dorsal lithotomy), at the level of the levator ani muscle. This nerve location might vary
somewhat, due to changes in the perspective,
according to different lengths of anal canal, the
angle of the anorectum (90–100°), and the position of the platform shaft (and the nerve displacement this may cause). Nevertheless, the initial
posterior dissection appears to be safe with
respect to this innervation. During the subsequent
bottom-up mesorectal dissection, the IASN can
be traced in the caudal to cephalic direction, and
it curves from a lateral to an anterolateral position [8–10, 15, 20].
Inferior Rectal Plexus
During the lateral dissection, tracing the IASN
within the triangle that lies between the anterolateral aspect of the rectum and the posterolateral
border of either the prostate or the vagina leads to
the inferior rectal plexus (IRP). The sub-plexus
of the inferior hypogastric plexus (IHP) is located
anterolaterally, along the pelvic sidewall, starting
at the 3 and 9 o’clock locations (lithotomy position), above the inferior medial level of the levator ani muscle (Fig.32.1). The areas revealed at
W. Kneis t
Fig. 32.1 Inferior rectal plexus (IRP) on the right pelvic
side in a male patient with taTME for rectal cancer
the 2–3 and 10–11 o’clock positions, at the level
of the distal rectum, have been reported to be
nerve-rich zones [10, 13, 15, 20, 21].
Neurovascular Bundles
During the anterolateral dissection, one must recognize the combined structure of cavernous
nerves and blood vessels – the neurovascular
bundles (NVB) of Walsh. A very low, strictly
anterior dissection of the perineal body does not
cause injury to these cavernous nerves. At the
beginning, the NVB should rst be identied by
locating paired pulsatile arteries anterolaterally.
To avoid injuries to the nerves, blood vessels,
vagina, prostate, or urethra, it is necessary to nd
an adequate plane of dissection. This plane is
behind the NVB of Walsh and anterior to the urogenital septum (Denonvilliers’ fascia in males).
With a caudal to cephalic approach, the nerves
diverge from the lateral aspects of the perineal
body and follow the anterolateral surface of the
mesorectum. They pass along the inferior border
of the prostate– or along the lateral surface of the
vagina, at the level of the junction of the lower
and middle thirds of the vagina. Then, the nerves
can be traced to the lower anterior part of the IHP,
at the 2–3 and 10–11 o’clock locations (patient
positioned dorsal lithotomy) [8–10, 12–17]
(Fig.32.1).
32 A Roadmap tothePelvic Autonomic Nerves During Transanal Dissection
339
Pelvic Splanchnic Nerves
A cephalad posterolateral dissection enables
the identication of the pelvic splanchnic
nerves (PSNs). However, parts of these nerve
ber diameters are less than 150μm; thus, identication and preservation might be relatively
difcult. The sacral spinal nerves (mainly from
S3 and S4) course across the piriformis muscle.
A thin parietal fascial sheath covers these
routes. Approximately at the height of the transition from the lower third to the middle third of
the rectum, the PSN connects with the IHP in a
“bow”-shaped manner, particularly evident
from the taTME vantage point. With careful
preparation and pneumodissection, the PSNs
can be reected dorsolaterally, and then, they
can be traced to the anterior aspect. By following the autonomic nerves to the anterior aspect
and recognizing the S4 and the NVB, the prostate gland can be identied, and a central dissection of the perineal body can be performed
[10, 14–16].
Inferior Hypogastric Plexus
Described as a triangle, the IHP is located
between the leaves of the parietal fascia, and it
spreads over the lateral walls of the pelvis minor.
It contains nerves from different sources, including hypogastric nerves, pelvic splanchnic nerves,
sacral splanchnic nerves, the sympathetic chain,
and the mesenteric plexus.
A vertical organization of the IHP has been
described according to the pelvic organs and anatomical structures. The bladder lies at the superior
extent, the genital organs are in the medial region,
and the rectum is positioned at the inferiormost
extent. The length, width, and depth of the IHP are
approximately 40mm×10mm×3mm [22, 23].
The ganglion cell clusters are located lateral to the
urinary bladder, seminal vesicles, paracervix, and
middle rectum. Starting from the vesical plexus,
there are up to eight efferent branches, and from
the prostatic and rectal plexuses, there are up to six
efferent branches [24, 25]. In addition to efferent
nerves, the IHP also contains afferent bers.
Topographically, the dorso-cranial angle of
the IHP forms at the conuence of the internal
iliac vein. The ventro-caudal angle forms at the
lateral aspect of the prostate gland, or at the entry
point of the ureter into the uterine ligament, at the
base of the parametrium. During a down-to-up
TME dissection, the dorso-caudal angle of the
IHP could project to the fourth sacral region. As
described above, the PSN must be identied, and
during a lateral dissection, care must be taken to
avoid opening the parietal fascia (violations to
the fascia result in the so-called halo sign), due to
the risk of entering a false plane with subsequent
inadvertent total denervation of the hemi pelvis
autonomics. According to an international consensus statement, the lateral dissection should be
performed last, after dissecting the dorsal and
ventral parts, to minimize the risk of damaging
neurovascular structures (alternative approaches
may also be valid). The extra-mesorectal, avascular fat (“adipose pillars”), at 3 and 9 o’clock positions, at the level of the mid-rectum, represents
an important landmark, and these pillars, often
visible during taTME, must remain in the lateral
region as they are prone to medial displacement
[10, 14, 26, 27].
Hypogastric Nerve
After dividing the lateral rectal ligaments, a dissection along the “holy plane” (the plane between
the presacral fascia and the mesorectal fascia)
proceeds in a caudal to cephalic course, up to the
peritoneal reection, until reaching the level of
the sacral promontory. Originating in the IHP
within the parietal pelvic fascia, the hypogastric
nerves (HN) run medially from the ureter, internal iliac artery, and veins and could be identied
shining through in caudal-lateral to a craniomedial direction. The left HN is described as signicantly shorter (53.0± 1.0mm) and narrower
(1.7±0.2mm) than the right HN (73.8±19.4mm
and 1.9±0.0mm, respectively).
340
W. Kneis t
The risk of injury to the HN and the nerve segments above (i.e., the superior hypogastric plexus
and inferior mesenteric plexus) is lower than the
risk of injury to nerves in the pelvis minor.
Results from the international taTME registry
showed only two (0.1%) HN divisions in 1594
cases, although this may be a gross under estimation and the true incidence remains unknown. On
the other hand, the risk of injury with the abdominal approach is also low. However, an uncoordinated, simultaneous operation from abdominal
and transanal can pose a risk in the pelvic autonomics. Finally, a well-rehearsed, two-team
approach can provide an additional dimension,
by perfecting the traction- countertraction strategy. Hence, autonomic nerve visualization and
preservation at the level of the sacral promontory
might be easier to achieve than it was before
[4, 7, 9, 12, 24, 28].
Future Aspects ofNerve-Sparing
taTME
is even more precise and rapid; this approach
could be used transanally in the future (Fig.32.3).
Fig. 32.2 Left-sided neurovascular bundle (NVB) demonstrated by the proctor and preserved by the participating
surgeons (taTME in cadaver courses [15])
Currently, cadaveric dissection is a recommended
key module in taTME training. Subperitoneal
autonomic nerve preservation can be studied in
detail in prepared didactics and other resources,
including this one, which help surgeons to understand the intricate nerve anatomy, as well as the
relevant evidence and pitfalls. Furthermore, anatomic specimens prepared for training and coursework should be used to demonstrate autonomic
nerve tissues, followed by a hands-on module
with formalin-xed pelvises. TaTME performed
in a cadaveric model should be used for teaching
visual identication and preservation of the different nerve segments [15] (Fig.32.2).
Intraoperative electrophysiological assessments (i.e., neuro-mapping) might provide new
insights into the complex issue of how to incorporate PANP into minimally invasive TME
approaches (laparoscopic, transanal, robotic,
hybrid, etc.). Indeed, during taTME, identifying
the IRP and its posterior branches (IASN) with
an electrophysiological assessment (80% accuracy) was more meaningful than with visual
assessment (45% accuracy), for both sides of the
pelvis. Fully robot-guided pelvic neuro-mapping
Fig. 32.3 Robotic-guided and transanal neuromapping.
Documentation of the innervation with EMG of the internal
anal sphincter and manometry of the urinary bladder [17]
32 A Roadmap tothePelvic Autonomic Nerves During Transanal Dissection
Fig. 32.4 Mixed reality
in taTME opens up
further possibilities [31]
341
Mixed reality technology and future developments in the eld will facilitate precision in
nerve-sparing surgery. Technological advances
will improve individualized planning, spatial
awareness, navigation, and the simultaneous display of rendezvous maneuvers, neuro- monitoring,
and staining results (Fig.32.4). In addition, better
visualization, electrophysiological measurements, postoperative specimen immunostaining,
MRI nerve status assessment, and retrospective
video analysis can improve quality control procedures to conrm the efcacy of PANP [11, 13,
17, 29–31].
References
1. Heald RJ, Husband EM, Ryall RD.The mesorectum
in rectal cancer surgery – the clue to pelvic recurrence? Br J Surg. 1982;69:613–6.
2. de Lacy AM, Rattner DW, Adelsdorfer C, Tasende
MM, Fernandez M, Delgado S, Sylla P, Martinez-Palli
G.Transanal natural orice transluminal endoscopic
surgery (NOTES) rectal resection: “down-to-up” total
mesorectal excision (TME)–short-term outcomes in
the rst 20 cases. Surg Endosc. 2013;27:3165–72.
3. Atallah S, Nassif G, Polavarapu H, deBeche-Adams
T, Ouyang J, Albert M, Larach S. Robotic-assisted
transanal surgery for total mesorectal excision (RATSTME): a description of a novel surgical approach
with video demonstration. Tech Coloproctol.
2013;17:441–7.
4. Heald RJ. A new solution to some old problems:
transanal TME.Tech Coloproctol. 2013;17:257–8.
5. Kauff DW, Wachter N, Bettzieche R, Lang H, Kneist
W. Electrophysiology-based quality assurance of
nerve-sparing in laparoscopic rectal cancer surgery–
is it worth the effort? Surg Endosc. 2016;30:4525–32.
6. Motson RW, Whiteford MH, Hompes R, Albert M,
Miles WF, Expert Group. Current status of transanal
total mesorectal excision (TaTME) following the
Second International Consensus Conference. Color
Dis. 2016;18:13–8.
7. Sylla P, Bordeianou LG, Berger D, Han KS, Lauwers
GY, Sahani DV, Sbeih MA, Lacy AM, Rattner DW.A
pilot study of natural orice transanal endoscopic
total mesorectal excision with laparoscopic assistance
for rectal cancer. Surg Endosc. 2013;27:3396–405.
8. Bertrand MM, Colombo PE, Alsaid B, Prudhomme
M, Rouanet P.Transanal endoscopic proctectomy and
nerve injury risk: bottom to top surgical anatomy, key
points. Dis Colon Rectum. 2014;57:1145–8.
9. Aigner F, Hörmann R, Fritsch H, Pratschke J, D’Hoore
A, Brenner E, Williams N, Biebl M, TAMIS TME
Collaboration Group. Anatomical considerations for
transanal minimal-invasive surgery: the caudal to
cephalic approach. Color Dis. 2015;17:O47–53.
10. Kneist W, Rink AD, Kauff DW, Konerding MA, Lang
H.Topography of the extrinsic internal anal sphincter nerve supply during laparoscopic-assisted TAMIS
TME: ve key zones of risk from the surgeons’ view.
Int J Color Dis. 2015;30:71–8.
11. Atallah S, Martin-Perez B, Larach S. Image-guided
realtime navigation for transanal total mesorectal excision: a pilot study. Tech Coloproctol. 2015;19:679–84.
12. Chouillard E, Regnier A, Vitte RL, Bonnet BV,
Greco V, Chahine E, Daher R, Biagini J. Transanal
NOTES total mesorectal excision (TME) in patients
with rectal cancer: is anatomy better preserved? Tech
Coloproctol. 2016;20:537–44.
13. Kneist W, Hanke L, Kauff DW, Lang H. Surgeons’
assessment of internal anal sphincter nerve supply
during TaTME—in between expectations and reality.
Minim Invasive Ther Allied Technol. 2016;25:241–6.
14. 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;20:483–94.
15. Kneist W, Stelzner S, Hanke LI, Wedel T.Inferior rectal plexus is no longer isolated in no man’s land. An
encouraging outlook with TaTME. Coloproctology.
2017;39:85–7.
16. Watanabe J, Ishibe A, Suwa Y, Suwa H, Momiyama M,
Ota M, Endo I.Surgical techniques for identication of
342
W. Kneis t
the prostate gland using the autonomic nerve as a landmark during transanal total mesorectal excision: secure
dissection of the male rectourethral muscle. Dis Colon
Rectum. 2018;61:999–1000.
17. Schiemer JF, Zimniak L, Grimminger P, Lang H,
Kneist W.Robot-guided neuromapping during nervesparing taTME for low rectal cancer. Int J Colorectal
Dis. 2018;33:1803–5. https://doi.org/10.1007/
s00384-018-3126-3.
18. Goetze O. Surgical observation on the vegetative
innervations of the pelvic organs, especially of the
sphincter ani. Dtsch Z Nervenheilkd. 1951;166:177–
88. [in German]
19. Hieda K, Cho KH, Arakawa T, Fujimiya M, Murakami
G, Matsubara A.Nerves in the intersphincteric space
of the human anal canal with special reference to their
continuation to the enteric nerve plexus of the rectum.
Clin Anat. 2013;26:843–54.
20. Stelzner S, Böttner M, Kupsch J, Kneist W, Quirke
P, West NP, Witzigmann H, Wedel T. Internal anal
sphincter nerves – a macroanatomical and microscopic description of the extrinsic autonomic nerve
supply of the internal anal sphincter. Color Dis.
2018;20:O7–O16.
21. Kinugasa Y, Arakawa T, Murakami G, Fujimiya M,
Sugihara K.Nerve supply to the internal anal sphincter differs from that to the distal rectum: an immunohistochemical study of cadavers. Int J Color Dis.
2014;29:429–43.6.
22. Mauroy B, Demondion X, Drizenko A, Goullet E,
Bonnal JL, Biserte J, Abbou C.The inferior hypogastric plexus (pelvic plexus): its importance in
neural preservation techniques. Surg Radiol Anat.
2003;25:6–15.
23. Mauroy B, Demondion X, Bizet B, Claret A, Mestdagh
P, Hurt C.The female inferior hypogastric (= pelvic)
plexus: anatomical and radiological description of the
plexus and its afferences–applications to pelvic surgery. Surg Radiol Anat. 2007;29:55–66.
24. He JH, Wang Q, Cai QP, Dang RS, Jiang EP, Huang
HL, Sun YP.Quantitative anatomical study of male
pelvic autonomic plexus and its clinical potential in
rectal resection. Surg Radiol Anat. 2010;32:783–90.
25. Baader B, Herrmann M. Topography of the pelvic
autonomic nervous system and its potential impact
on surgical intervention in the pelvis. Clin Anat.
2003;16:119–30.
26. Bernardi MP, Bloemendaal AL, Albert M, Whiteford
M, Stevenson AR, Hompes R. Transanal total mesorectal excision: dissection tips using ‘O’s and ‘trian-
27. Adamina M, Buchs NC, Penna M, Hompes R, St.Gallen
Colorectal Consensus Expert Group. St.Gallen consensus on safe implementation of transanal total mesorectal excision. Surg Endosc. 2018;32:1091–103.
28. Penna M, Hompes R, Arnold S, Wynn G, Austin R,
Warusavitarne J, Moran B, Hanna GB, Mortensen NJ,
Tekkis PP, International TaTME Registry Collaborative.
Incidence and risk factors for anastomotic failure
in 1594 patients treated by transanal total mesorectal excision: results from the international taTME
registry. Ann Surg. 2018; https://doi.org/10.1097/
SLA.0000000000002653. [Epub ahead of print]
29. Moszkowski T, Krüger T, Kneist W, Hoffmann
KP.Modeling the pelvic region for non-invasive pelvic intraoperative neuromonitoring. Curr Dir Biomed
Eng. 2016;2:185–8.
30. Wijsmuller AR, Giraudeau C, Leroy J, Kleinrensink
GJ, Rociu E, Romagnolo LG, Melani AGF, Agnus
V, Diana M, Soler L, Dallemagne B, Marescaux J,
Mutter D. A step towards stereotactic navigation
during pelvic surgery: 3D nerve topography. Surg
Endosc. 2018;32:3582–91.
31. Huber T, Hadzijusufovic E, Hansen C, Paschold M,
Lang H, Kneist W.Head-mounted mixed reality technology during robotic-assisted taTME. Dis Colon
Rectum. 2019;62:258–61.
Operative Vectors, Anatomic
Distortion, andtheInherent
Eects ofInsuation
SamAtallah, AlbertM.Wolthuis,
andAndréD’Hoore
33
Introduction
Prerequisite to taTME is a fundamental surgeon
skillset. This typically includes advanced
colorectal MIS experience as well as experience
with an advanced transanal platform– such as
for TAMIS or TEM – especially as applied
toward local excision of rectal neoplasia.
However, there are important aspects of taTME
that must be understood as this operation is not
simply a hybrid combination of minimally invasive laparoscopy and TAMIS. One reason for
this relates to how the workspace during taTME
is created and how this potential space is actualized by the pneumatic forces of insufation. To
some extent, the creation of this space and operation in this modality are more similar to the
techniques and viewpoint achieved during totally
extraperitoneal endoscopic surgery, such as is
the case for inguinal hernia repairs. Thus, taTME
radically differs from how workspace and operative eld exposure occurs during laparoscopy,
whereby transabdominal insufation almost
instantly creates a sustained workspace. Carbon
S. Atallah
AdventHealth Orlando, Oviedo Medical Center,
and University of Central Florida College of Medicine,
Orlando, FL, USA
A. M. Wolthuis · A. D’Hoore (*)
University Hospitals, Abdominal Surgery,
Leuven, Belgium
e-mail: andre.dhoore@uzleuven.be
dioxide insufation separates fusion planes during taTME pneumatically, thus insufation itself
is a crucial aspect of this complex operation. In
this chapter, focus is given to understanding
aspects germane to operation within the subperitoneal pelvis, to examining the important aspects
related to insufation, and to the peculiar effects
of gas ow observed during the transanal portion
of the taTME operation.
Operation intheSubperitoneal
Space
Commencing with the rectotomy (created after
purse-string application) until the point of peritoneal entry during the taTME operation, the dissection is created in an actualized, potential space
along the fascial fusion planes which surround
the mesorectal envelope circumferentially. This
is perhaps one of the most fundamental differences between the so-called up-to-down and
down-to-up approaches to TME. Hence, unlike
with laparoscopy where the operative eld and
workspace are dened immediately upon insufation of the peritoneal cavity, with taTME (during the down-to-up portion of dissection), the
space created is a potential space. This space is
gradually developed along embryonic fusion
planes by the combination of sharp and gas dissection as the eld is actualized. The dissection
may or may not proceed along the correct plane,
© 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_33
343
344
taTMEWork space volume dv
taTME dissection time dt
Change in taTME workspace volume as a function of time
S. Atallah et al.
Rectotomy
Fig. 33.1 The actualized workspace volume increases as
a function of time during the transanal portion of taTME
and then can be mathematically expressed as
∆v
/∆t
taTME
sents the change in volume and ∆t
tion time. The rate of change in workspace volume (e.g.,
the viewable surgical eld) is not constant and is depen-
or simply dv/dt, whereby ∆v
taTME
Extra-peritoneal taTME dissection
repre-
taTME
equates to dissec-
taTME
however, and it is well known that with taTME,
especially laterally and posteriorly, as the plane is
developed by pneumatic dissection, it is possible
dent on the phase of dissection. The subperitoneal workspace is negligible during rectotomy but increases
exponentially during taTME dissection. Finally, upon rendezvous with the abdominal cavity, which usually occurs
anteriorly along the peritoneal reection, the abdominopelvic cavity becomes one common space
operative eld’s workspace is a function of time
and can be mathematically expressed as
∆v
taTME
After peritoneal entry
/∆t
taTME
or simply dv/dt (Fig.33.1) [6].
to actualize deep planes that lie beyond the scope
of dissection. When the correct plane is achieved,
however, pneumatic dissection augments sharp
Operative Vectors
dissection in the TME plane in accordance to the
standards set forth by Professor RJ Heald.
In some regards, actualizing the subperitoneal
space during taTME is similar to extraperitoneal
surgery – such as for endoscopic totally extraperitoneal hernia repair [1, 2]. However, in those
approaches, typically a balloon is used to actualize the potential space prior to proceeding with
dissection, creating a constant workspace for the
entire procedure. In contradistinction, with
taTME, the workspace volume changes in rela-
tion to dissection time – since this space is not
established with balloon dissection but rather
with sharp, meticulous dissection in accordance
with the principles of TME surgery [3–5]. Thus,
the more the dissection progresses, the more the
workspace volume (and thus the eld of view)
increases. Therefore, the change in volume of the
With standard multiport laparoscopy or robotic
abdominal surgery, gas ow delivery can be
arranged by connecting inow tubing to any trocar
in any quadrant. Most often the choice of which trocar to use is arbitrary, although may surgeons prefer
to insufate through a trocar not occupied by the
camera lens as this can increase lens fogging leading to diminished optic clarity. Because of the large
volume of the abdominal cavity, however, the direc-
tion of gas ow into the cavity is generally not clinical relevant. That is, there is no distortion of target
anatomy and only symmetric doming of the anterior
abdominal wall can be appreciated. However, during taTME, the direction and magnitude of gas ow
and the resultant effect on the surgical eld during
operation, including the effect this imparts on the
process of dissection itself, are quite relevant.
33 Operative Vectors, Anatomic Distortion, andtheInherent Eects ofInsuation
345
Ta TME CO2 insufflation vector
Fig. 33.2 The insufation “vector” can be thought of as
the force of insufation together with its direction. With
abdominal minimally invasive surgery, insufation vectors have no appreciable effect on the operative eld and
With transanal access, insufation has a specic direction and specic force or magnitude. In
physics, the magnitude of a force together with
its direction denes a vector. Thus the force of
CO2 gas insufation plus the direction of gas
delivery can be dened as an insufation vector
[6]. The insufation vector achieved with taTME
(Fig. 33.2) results in a compounded effect that,
on the one hand, greatly facilitates sharp dissection by pneumatically delineating surgical planes
and maintaining what can be a remarkably pristine operative view; on the other hand, the taTME
insufation vector poses new challenges. Most
notable of these challenges are the following: (a)
exposure of false planes beyond the TME envelope, (b) lifting and “standing up” of pelvic autonomic nerves, creating a potential for their injury
if not recognized, and (c) in the event of pelvic
venous bleeding during dissection, introducing a
vehicle for CO
venous embolization.
2
Gas Flow Mechanics
Gas kinetics and the physics of Newtonian uid
dynamics within a closed system have been well
studied, but not as it pertains to insufation systems and the effect such systems impart on
human anatomy during operation. Thus, little is
known about how precisely Newtonian uids
Abdominal CO
Pelvic cavity
anatomy, but with taTME, the direction of insufation has
very specic effects on the target anatomy and the fascial
envelopes that surround the rectum and mesorectum
(such as exogenous CO
insufflation vectors
2
) effect anatomy, and
2
much of what can be learned is based on observational data and known physical principles of continuum mechanics [7–11].
It is known that, because the insufated gas is
delivered via a closed cylinder (the transanal
platform’s access channel), that gas ow is governed by laws which dene uid movement in
such a cylinder. In particular, there are two important laws pertaining to gas ow. First, the HagenPoiseuille Law [12] denes the rate of ow of
CO2 as it is transmitted through the taTME access
channel. Essentially, this states that there is a
variable rate of ow through the channel, whereby
the highest ow velocity is observed at the center
of the access channel, while the lowest ow
velocity is at the periphery. Thus, there exists a
velocity gradient which effects the target anatomy is a specic way. Based on observational
data, this tends to create a concavity of the mesorectal envelope during the posterior taTME dissection, thus contributing the classic anatomic
distortion observed. It also produces a central
“forward compression” of the mobilized anatomy. Second, although of lesser importance,
Bernoulli’s Law [13] states that energy is conserved, and as CO
gas is transmitted from the
2
narrow radius of the insufation tubing and trocar to the much larger diameter access channel,
the overall gas rate of ow is constant, although
346
CO2 gas flow physics as applied to taTME
Hagen-poiseuille equationBernoulli equation (conservation of energy)
S. Atallah et al.
Velocity flow rate 2
CO2 flow velocity gradient
taTME access channel
inflow
CO
2
V
= V
rate 1
A1V1 = A2V
r2V1 = r2V
ππ
rate 2
A
Insufflation trocar
1
Velocity flow rate 1
2
2
Cannula
Cannula
P
1
A
2
Fig. 33.3 The principles of uid mechanics that govern
CO
ow through the taTME apparatus are illustrated.
2
Conceptually, two laws of physics should be understood.
First, the Hagen-Poiseuille Law states that pressure
diminishes along the forward direction of gas ow,
thereby creating a pressure gradient, ∆P (P
– P2).
1
Furthermore, this law states that gas ow velocity is highest at the center of the cylinder and lowest at its periphery,
thereby creating a velocity gradient. Bernoulli’s Law is
synonymous with the Law of Conservation of Energy, and
thus velocity ow rate is constant, as gas ows faster in a
smaller diameter cylinder (such as a trocar or insufation
P
2
outflow
CO
2
to surgical field
8µLQ
DP =
4
π
R
tubing) and slower in a large cylinder such as the taTME’s
access channel, but the overall ow rate remains the same
due to the larger cross-sectional areal of the apparatus. ∆P
pressure differential; P
access channel; P
, pressure at the outer rim of the
1
, pressure at the end of the access chan-
2
nel near the surgical eld; μ, dynamic (shear) viscosity
coefcient; L, cylinder length; Q, volumetric ow rate; R,
radius of cylinder; A
A
, taTME access channel’s cross-sectional surface area;
2
V
, velocity of CO2 within trocar; V2, velocity of CO2
1
, trocar cross-sectional surface area;
1
within taTME access channel
the velocity is decreased (Fig. 33.3).
Understanding gas kinetics helps one to understand the observed pneumatic effects and the
classic anatomic distortion (see later) that is often
evident during taTME dissection.
Cyclic Billowing
Since the introduction of TAMIS for local excision via endoluminal surgery [14] and subsequent use of this technique for taTME [15–19],
an important operative limitation has been overcome. Initially, both TAMIS and TAMIS-based
taTME relied on laparoscopic insufation systems designed for abdominal access surgery, and
not transanal surgery or limited space, subperitoneal pelvic surgery. This was at the time believed
to be an advantage of the technique of TAMIS
and taTME via TAMIS, because no specialized
equipment was required [14–16] (as is the case
with rigid platforms, which have unique and specically designed insufation systems as component of the apparatus). While currently TAMIS
and even taTME can be performed with standard
laparoscopic insufators, when available alternate modes of insufation are often advocated to
resolve the nuisance problem of cyclic billowing
and smoke accumulation with loss of visual eld
stability.
Cyclic billowing is dened as the sudden,
periodic collapse of the workspace – including
the lumen of the rectum in the case of TAMIS and
the actualized subperitoneal workspace of the
pelvis during taTME.Cyclic billowing is sometimes referred to as “pelvic breathing” due to the
rhythmic collapse of operative workspace during
transanal surgery. Advanced transanal surgery
such as TAMIS and taTME mandates a sustained
pneumatic dissection that is not volatile and is