Historic Management of Rectal Cancer
“All carcinomas of the lower sigmoid and upper rectum are tabooed by all practical
surgeons on account of their anatomical inaccessibility. All are abandoned without
hope to linger on for a few months until death relieves them of their loathsome condition.”
H. W. Maunsell, The Lancet, 1892
The surgical management of rectal cancer has substantially evolved over the past 100
years, and continues to progress as we seek the best treatment. Rectal cancer was
historically an unsurvivable disease, with a poor understanding of the embryological
planes, lymphatic drainage, and a lack of standardized technique. In the early twentieth
century, patients underwent a perineal proctectomy as the standard of care, with poor
oncologic outcomes and high morbidity. The first moves to improve surgical outcomes
and standardize surgery for rectal cancer came from Dr. William Ernest Miles in 1908.
Recognizing the rampant recurrent disease and mortality after the perineal proctectomy,
Miles investigated and found tissue later termed mesorectum left in the pelvis, with
the lymphovasculature and mesorectal nodes by the iliac vessels; he called these areas,
“zones of upward spread,” and designed an operation to include the mesorectum and
its contents—the abdominoperineal resection (APR).[1]
[2] With the APR, Miles advocated for combined abdominal and perineal resections to
ensure completed resection of the mesorectum and clearance of the “zones of upward
spread.” The abdominal resection entailed dissection of the rectum, mesorectum, and
colostomy creations, and the perineal resection encompassed dissection and detachment
of the anorectum and levator complex from the ischiorectal fat and pelvic organs.[3] Miles found the APR reduced the recurrence rate from almost 100% to approximately
30%, with benefits limited from the use of blunt dissection.[4] His recognition of the necessity to remove the mesorectum in its entirety laid the
groundwork for the modern total mesorectal excision (TME) and continued improvement
of the curative rectal cancer resection. In his resection, Miles proposed a low tie
ligature of the inferior mesenteric artery (IMA); however, there was controversy over
what the best level of arterial ligation and division should be in a radical rectal
resection. Sir Berkeley George Andrew Moynihan advocated for a high vascular tie ligature
and division to complete the lymphadenectomy, stating that surgery of malignant disease
is really surgery of the lymphatic system, not solely the organs, the concept used
today.[5] In efforts to reduce complications and mortality rates after the APR, in 1921, Henri
Hartmann introduced the anterior resection of the rectum with a sigmoid colostomy
on the left flank, which preserved the distal third of the rectum and the anal sphincters.[6] While there was less morbidity and mortality with the “Hartmann procedure,” patients
still had a permanent stoma, and proximal rectal tumors were the primary indication
for this procedure. Better surgical technology was needed to completely resect lower
rectal cancers and restore continuity. Other techniques for radical proctectomy and
proctectomy with sphincter preservation were detailed by Dixon, Habr-Gama, Bacon and
Giambalvo, and Black, but lacked the standardization in technique and widespread use
of the APR.[7]
[8]
[9]
[10]
[11] The restorative low anterior resection (LAR) gained popularity with data from Goligher
et al that local tumor spread in rectal cancer did not exceed 2 cm from tumor margins
in most cases, and that a distal resection margin (DRM) of 5 cm was sufficient for
radical resection at that time.[12] The safe margin for a proper oncologic resection has since been advocated as 2 cm
below the level of the distal margin or 1 cm for cancers located at or below the mesorectal
margin or after neoadjuvant chemoradiotherapy.[13] The development of surgical staples in the 1970s, specifically the circular intraluminal
stapler, were a technology breakthrough which made a lower anastomosis universally
technically possible, with anastomotic leak rates with the stapler similar to that
of hand-sewn anastomoses.[14]
[15] The double stapling technique accelerated creation of the low colorectal anastomoses
for a restorative LAR, even in a narrow, fixed pelvis, minimizing issues in joining
bowel segments of different sizes and intraoperative contamination.[16] This new technology made the technical portions of the TME feasible, and permitting
further development of the procedure.
Introduction of the Total Mesorectal Excision
Major improvements in recurrence, survival, and quality of life have resulted from
advances in preoperative staging, pathologic assessment, the development and timing
of multimodal therapies, and surgical technique.[11] However, the most significant contribution in advancing rectal cancer care may be
the standardization and widespread implementation of TME.
The concept of the TME and description of the anatomy and procedure dates far back
before the modern era. The first known description of the mesorectal concept was by
Romanian surgeon and anatomist Thoma Jonnesco in 1896, which he called “la gaine fibreuse
du rectum.”[17] While Jonnesco did not use the term “mesorectum,” he described the rectum as encapsulated
within this thin fibrous sheath, which separated it from the other pelvic organs and
allowed the rectum to be mobilized from the sacrum without damaging the presacral
vessels.[17]
[18] In 1899, Wilhelm Waldeyer described the fascia propria recti, referencing Jonnesco's
original observations, and adding his own observations on the lack of anterior peritoneal
component of the fascia.[18]
[19] Waldayer's description of the perirectal fascia and its components was translated
and published by Crapp and Cuthbertson in their 1974 article “The Book Shelf—William
Waldeyer and the Rectosacral Fascia.”[20] These concepts were incorporated into the TME procedure, which was first described
by Abel in 1931.[21] However, Professor Richard (Bill) Heald popularized and promoted the TME.[22] TME removes the rectal cancer with its primary lymphovascular drainage as an intact
package, by deliberate dissection under direct vision along embryologically determined
planes between visceral and parietal structures, which preserves the autonomic nerves
required for the maintenance of urinary and sexual function ([Fig. 1]).[23] Heald's insight was that rectal cancer is more apt to spread along the field of
active lymphatic and venous flow, not distally along the muscular tube. He described
that lymphatic extension of a rectal cancer created a “danger zone” in the mesorectum
around the visible and palpable tumor, and that incomplete and variable resection
of this “danger zone” might explain the extraordinarily wide variation in reported
local recurrence rates.[24] He described the proper surgical plane as the potential space along the avascular
interface between the mesorectum and the surrounding somatic structures—the holy plane—which
could be reproducibly created by dissection.[24] The importance of a proper TME in the “holy plane” is essential, as the plane of
surgery achieved remains the main prognostic factor for recurrence.[25]
[26] Pairing better surgical technology with his formal approach to proctectomy, widespread
training, and implementation, Heald revolutionized the way we manage rectal cancer,
standardizing the teaching and training, significantly reducing recurrence, and improving
survival, making the TME the gold standard for curative rectal cancer surgery worldwide.[22]
[27]
[28]
[29]
[30]
[31]
[32]
[33]
[34] Heightened awareness of the proper surgical techniques has created much interest
in the anatomy involved in TME surgery, with particular focus on the fascial planes
and their relationship to the surgical planes of excision.[35]
Fig. 1 Three-dimensional model: Anatomic state before total mesorectal excision (TME) (A);
risk of defect (D) in mesorectum (M) and parietal peritoneum (PP). Anatomic state
after introduction of TME (B): intact mesorectum (M) and nerve-sparing resection (N)
(Use VIPicture App).
Relevant Embryology and Anatomy of the TME Planes
“My personal story is of gradual realization that this midline gut tube can be redefined
with its intrinsic lymphovascular surround as a midline envelope recognizable for
surgeons by the spider's web of areolar tissue around it. The distal part of the envelope
is around the rectum and becomes the mesorectum, and the cobweb around it where the
surgeon dissects is the ‘holy plane’. The key hypothesis was that each part of the
envelope, if very carefully removed en bloc, might have a very good chance of enveloping
the whole primary field of spread of a cancer and thus curing all but the most advanced
cases.”
Richard J. Heald, Manual of Total Mesorectal Excision, 2013
A proper TME is inextricably linked with anatomy and embryology. The rectum is a hollow
muscular tube located at the end of the large intestine, where the epiploic appendages
are absent and the taeniae coalesce to form a complete lineal muscular layer. Although
not anatomically distinct, the rectum is segmented into upper (12–15 cm), mid (7–12 cm),
and lower rectal divisions (0–7 cm) from the anal verge; the rectum is actually variable
in length, but these approximate divisions are important when considering surgical
treatment of rectal cancer.[36] The majority of the rectum is extraperitoneal, although anteriorly and laterally
the upper rectum is covered by a layer of visceral peritoneum down to the peritoneal
reflection.[36] The peritoneal reflection lies approximately 7 to 9 cm from the anal verge anterior,
but its location is also highly variable and can be affected by gender and different
disease states.[37] The embryological hindgut mesentery is the mesorectum, connective tissue, and fat
housing the vascular and lymphatic supply ensheathed by a fascial system. The embryologic
fascial structures of the pelvis define the anatomy and surgical planes of dissection,
provide support, and may direct and limit the spread of malignant disease. Heald's
TME principles were based on the knowledge that the fascial plane surrounding the
mesorectum—the mesorectal fascia—is created by a separate embryological origin from
the rectum and mesorectum, which have the same embryological origin and are one distinct
lymphovascular entity ([Fig. 2]).[38] As the embryological delineation of the visceral from the somatic individuum, the
mesorectal fascia confers protection against tumor dissemination and confines the
main route of rectal cancer spread. An avascular, areolar tissue plane lies between
the mesorectal fascia and the parietal pelvic fascia. Appropriate traction on the
mesorectal fascia during surgery exposes this potential space, defined as the “holy
plane.” Meticulous, sharp dissection along this embryological plane will enable an
oncologically safe and complete removal of the rectal cancer with minimal neurovascular
damage or impact on urinary or sexual function. It also serves as a histopathological
landmark for comparison of quality of surgical resection.[23] The bulk of the mesorectum is posterior to the rectum, seen as two protruding bulges
(the “mesorectal cheeks”). It tapers at the anorectal junction, and extending the
surgical dissection plane downward around mesorectal fascia passes within the puborectalis
sling into the space between the external and internal anal sphincters.[23] Anteriorly, the mesorectum is thin and bordered by Denonvilliers' fascia, a tough
fibrous, double-layered tissue that separates the extraperitoneal rectum anteriorly
from the prostate and seminal vesicles in men or the posterior vaginal wall in women.[39] In females, Denonvilliers' fascia is less developed and the anterior mesorectum
less substantial.[36] Study has shown that Denonvilliers' fascia is more closely applied to the prostate
than the rectum, and lies anterior to the anatomic fascia propria plane in anterior
rectal dissection.[40] The pelvis is supported by the endopelvic fascia, which has two components: the
visceral layer (fascia propria of the rectum), a thin, transparent layer that lines
the rectum and maintains the integrity of the mesorectum, and a parietal layer (presacral
fascia), which runs posterior to the mesorectum follows the concavity of the sacrum
to cover the presacral veins and hypogastric nerves. The presacral fascia extends
caudally to the anorectal junction covering the anococcygeal ligament and laterally
to cover the piriformis muscle and upper coccyx, then becomes continuous with the
fascia propria of the rectum, contributing to the lateral ligaments of the rectum.
During a proper TME, the fascia propria is elevated sharply off of the presacral fascia,
which is left intact. Leaving the presacral fascia intact reduces the risk of exposing
the high-pressure presacral veins, a potential source of severe bleeding during the
mobilization of the rectum.[41] Inferiorly, between the levels of the third and fourth sacral vertebra, the mesorectum
and the presacral fascia fuse to form the retrosacral fascia or Waldeyer's fascia.
Waldeyer's fascia serves as an anchoring fascia of the rectum, and extends anteriorly
to join the posterior layer of the fascia propria proximal to the anorectal junction.[20] This layer is surgically relevant during posterior rectal mobilization because it
must be sharply divided to release the surrounding areolar tissue plane and for its
close relationship to the sympathetic hypogastric nerves and the inferior hypogastric
plexus.[42] Improper dissection can lead anteriorly to breach of the mesorectum and posteriorly
to tearing of the prefascia, with bleeding from the presacral veins. The lateral ligaments
of the rectum are trapezoid structures originating from the mesorectum and anchored
to the endopelvic fascia at the level of the midrectum. Heald did not describe these
ligaments in his description of the TME.[27] They do not contain middle rectal arteries or nerve structures of importance, but
the urogenital bundle runs just above the lateral ligament at its point of insertion
on the endopelvic fascia, the middle rectal artery runs posterior to it, and the nervi
recti fibers from the inferior hypogastric plexus course transversely under the lateral
ligament to the rectal wall[43]; thus, being mindful of these relationships is important during a pelvic dissection.
At the most distal part of the rectum, the mesorectum thins out and is virtually absent.
Distal rectal cancers are thus at greater risk of invading surrounding structures
at this level. A proper pelvic T2-weighted magnetic resonance imaging (MRI) is invaluable
to demonstrate the important anatomic landmarks, such as the mesorectal fascia, presacral
and posterior pelvic fascial planes, peritoneal reflection, and Denonvilliers' fascia.[35] With the clear visibility of these features, MRI is important for not only staging
the rectal cancer and selecting patients for preoperative neoadjuvant therapy, but
to assess resectability and surgical planning as part of the preoperative multidisciplinary
discussion.[44]
Fig. 2 Embryological development of the gastrointestinal tract (Use VIPicture App).
The blood supply and venous drainage of the rectum correspond to the hindgut embryology;
the blood supply is mainly from the superior rectal artery, arising as a main branch
from the IMA, and the venous drainage is primarily to the inferior mesenteric vein
(IMV) into the portal system.[36] Veins from the upper two-thirds by the superior rectal vein, which empties into
the portal circulation, while veins from the lower third drain into the internal iliac
veins and systemic via the middle and inferior rectal veins. The dual venous drainage
helps to explain separate patterns of pulmonary and hepatic metastases.[45] An extensive autonomic nervous system of sympathetic and parasympathetic fibers
supplies the rectum and genitourinary tract, controlling continence and sexual function.
Knowledge of the anatomy is essential in rectal surgery, as injury to these nerves
can lead to incontinence and sexual dysfunction. The sympathetic autonomic plexus
arises from T12–L2 lumbar sympathetic nerves, and pass anterior to the aorta and form
the superior hypogastric plexus, close to the origin of the IMA. The superior hypogastric
plexus enters the pelvis and divides into the left and right hypogastric nerves at
the level of the sacral promontory. The hypogastric nerves course posterolateral to
the mesorectum and join parasympathetic nerves from the pelvis plexus or nervi erigentes
to form the inferior hypogastric plexus. The parasympathetic nerves originate from
the S2–S4 sacral spinal nerve roots, and run laterally and anteriorly along the mesorectal
fascia before joining with the inferior hypogastric nerves to form the inferior hypogastric
plexus. The inferior hypogastric plexus is an extensive network with the paired sympathetic
hypogastric nerves and parasympathetic pelvic splanchnic nerves on the pelvic sidewall,
with the neurovascular bundle extending anterolaterally to the seminal vesicles, distal
ureters, vasa deferentia, urinary bladder, prostate and cavernous bodies in men, or
lower lateral wall of the vagina in women.[46] Functionally, the sympathetic autonomous system is responsible for urinary continence
and ejaculation. Damage to the sympathetic nerves during ligation of the IMA or during
mesorectal mobilization, can lead to urinary incontinence and retrograde ejaculation.
The parasympathetic system is responsible for micturition, erection, and lubrication.
Damage during the lateral or anterior dissection can lead to difficulty with erection,
urinary retention, and issues with sexual lubrication.
TME Technique
The indication for a TME is curative resection of rectal tumors of the middle and
lower thirds of the rectum, either as part of LAR or APR. For mid- to low-rectal cancer,
LAR with TME has been demonstrated to minimize locoregional recurrences.[27]
[47]
[48] For upper rectal cancer, or tumors more than 10 cm from the anal verge, where a
distal margin of 5 cm can be achieved, performing a tumor-specific mesorectal excision,
where the mesorectum and the rectum are divided at the same level, is sufficient and
is associated with outcomes similar to that achieved with TME.[13]
[48]
[49]
[50] A complete TME technique is defined as a “complete removal of the lymph node bearing
mesorectum along with its intact enveloping fascia.”[51] The three basic principles of the technique were described by Heald as recognition
of mobility between tissues of different embryologic origins, sharp dissection under
direct vision in good light, and gentle opening of the plane (between the visceral
and parietal pelvic fascia) by continuous traction with no actual tearing.[24] The dissection in this avascular embryologic “holy plane” allows for en bloc removal
of the cancer and surrounding mesorectum with an intact mesorectal fascia and preservation
of the autonomic nerves. This dissection is performed in a circumferential manner
down to the levator muscles to produce a globular, bilobed tissue block produced by
the midline indentation posteriorly of the anococcygeal raphe.[29] The two lobes reflect the paired concavities created by the levator ani muscles.
The proof of a properly performed TME is the gross appearance of the specimen itself,
which is being increasingly recognized as a reliable predictor of an adequate rectal
cancer operation.
Prior to the TME dissection, the surgeon should perform high ligation of the IMA and
the IMV, mobilization of the splenic flexure, and division of the colon at the descending
sigmoid junction.[52] The basic components for a TME are sharp dissection in the avascular plane into
the pelvis anterior to the presacral fascia and outside the fascia propria or enveloping
visceral fascia, division of lymphatic and middle hemorrhoidal vessels anterolaterally,
and inclusion of all pelvic fat and lymphatic material at least 2 cm below the level
of the distal margin (1 cm for cancers located at or below the mesorectal margin or
after neoadjuvant chemoradiotherapy).[52] The initial step of TME involves finding the “pedicle package,” the clue to the
top of the “holy plane.” The key here is recognition of the shiny fascial-covered
surface of the back of the pedicle, found by lifting the sigmoid colon with its mesentery
forward to open the plane between the back of the pedicle package and the gonadal
vessels, ureter and preaortic sympathetic nerves. Depending on the operative platform,
this can be approached by dividing the right leaf of sigmoid mesocolon peritoneum
near its root in the midline above the aortic bifurcation (used in laparoscopic and
robotic approaches) or in a lateral to medial fashion, as in open surgery, first dividing
close to the white lines of congenital adhesions, and then working medially to open
the plane.[53] With the minimally invasive platforms, the pneumoperitoneum can pneumodissect and
facilitate opening the retrorectal plane anterior to the presacral fascia for identification
of structures at the pelvic brim. A basic principle is that the dissection here should
stay on “the yellow side of the white” cobwebs. The combination of forward traction
on the visceral package and countertraction on the nerve layer behind allows sharp
or diathermy dissection of the areolar tissue to open the plane widely. As the surgeon
works upwards in this space, the IMA becomes apparent, and the nerves splitting around
it are preserved. The dissection plane is extended downward into the pelvis. The traction
drawing the visceral mesorectal envelope away from the autonomic nerve plexuses allows
identification of the sympathetic bifurcation—the superior hypogastric plexus—into
the paired hypogastric nerves, which course around the mesorectum and down the lateral
pelvic sidewalls toward the inferior hypogastric plexus. Dissection is extended downwards
anterior to the curve of the sacrum on the surface of the mesorectal fascia. The continued
forward traction and countertraction will lift the midline mesorectal pedicle away
from the presacral fascia, and facilitate dissection through the angel hair/white
areolar plane in the potential space from the perivisceral fascia and parietal presacral
fascia.[53] Dissection should be predominantly from below upwards, allowing the hypogastric
nerves to drop away posterolaterally, and should remain in the posterior midline as
it descends further into the pelvis, where the visceral fascia on the back of the
mesorectum will fall away from the presacral fat and anterior fascia. Performing circumferential
mobilization with some dissection in the lateral and anterior planes is recommended
rather than proceeding too far posteriorly at this stage. The lateral dissection plane
is opened in the same manner, facilitated by retracting the rectum to one side at
a time. The dissection is carried down to the level of the levator ani muscle where
the two fascial layers fuse together as the rectosacral fascia ligament. This fascial
band is ligated and divided to fully open the retrorectal plane and complete the posterior
mobilization of the rectum. Posterior and lateral mobilization is easier once the
anterior dissection is completed. Anterior mobilization commences in the line of reflection
of the visceral peritoneum, where a small incision immediately posterior to the peritoneal
reflection will allow entry into the avascular rectovaginal or rectovesical plane.
In women, the dissection starts with identification of the peritoneum over the pouch
of Douglas. Meticulous dissection is necessary to avoid damaging the thin-walled vagina
as it is separated from the rectum. In men, dividing the peritoneum just anterior
to the fold to avoid entering the rectal wall best enters the plane. The seminal vesicles
are identified, and dissection continues in a plane posterior to the seminal vesicles.
In most cases, dissection should remain on the fascia propria in the usual anatomic
plane; by not excising Denonvilliers' fascia, postoperative urinary, sexual, and oncologic
outcomes will not be affected. However, for anterior tumors, deep dissection anterior
to Denonvilliers' fascia of the anterior extraperitoneal rectum is appropriate.[40] After the completion of the dissection circumferentially, the rectal tube is ready
for division. Digital examination is recommended, with or without proctoscopy, to
verify the dissection has proceeded past the tumor with appropriate margins for resection.
The rectum is divided at the appropriate level. At this level in the low pelvis, there
is no further mesorectum, and the rectum is essentially a muscular tube. After division,
an anastomosis is created to the rectum either as a straight end-to-end, a small reservoir
end-to-side colorectal anastomosis, or as a colonic J-pouch, per the surgeon's preference.
In females, special care is taken to distract the rectum from the vagina while stapling
to ensure the back wall of the vagina is not accidentally incorporated. Following
creation of the anastomosis, an air leak test is performed to validate the integrity
of the anastomosis. Per-surgeon preference, a proximal diverting loop ileostomy can
be performed.
Beyond TME
Although TME remains the gold standard for curative rectal resection, recently much
attention has been given to further improving oncological results by implementing
new techniques. The literature to date shows that much gain can be achieved for the
dissection of the most distal third of the rectum, an area with the highest risk of
threatening the completeness of the circumferential resection margin.[54] Quality of the resection and the specimen are mainly determined by maneuverability
deep down in the pelvis. In male patients, who require the majority of rectal resections,
the mid pelvis is often the narrowest part of the bony structures, resulting in an
hourglass-shaped working space ([Fig. 3]).[55]
[56]
Fig. 3 The hourglass-shaped pelvic working space, with easy (green) and difficult (red)
resection planes noted.
While measuring distances within the bony pelvis gives an impression of access to
the pelvic floor, many other factors contribute to reducing the working space, like
size of the tumor, volume of the mesorectum, and size of the prostate in male patients.
Other factors that contribute to an increasing level of difficulty of low pelvic dissection
are high body mass index, time interval after radiotherapy, anterior location of the
tumor, and distance between lower border of the tumor and anorectal junction ([Fig. 4]).[57]
[58] When all of these factors are present, an optimal dissection is challenging, requiring
an expert in rectal cancer surgery, optimally trained in different techniques and
performing each on a regular base.
Fig. 4 Factors contributing to increasing levels of difficulty during total mesorectal excision
(TME) dissection. RT, radiotherapy.
Compared with the traditional open technique, laparoscopy resulted in better short-term
outcomes with comparable oncologic results, even in well-trained surgeons.[59] The results from two recently published randomized trials could not demonstrate
that laparoscopic rectal cancer surgery was not inferior to open TME when considering
a composite pathological endpoint.[60]
[61] Although the COREAN and COLOR II trials showed noninferiority when comparing laparoscopic
to open TME, this still results in conflicting data with no clear favor for one of
the approaches.[62]
[63] From a technical point of view there remain some limitations to the laparoscopic
approach, mainly related to limitations in articulating instruments and stapler devices.[64] These limitations and the differences in traction and countertraction required in
laparoscopy compared with an open approach implicates a risk to manipulate the tumor
site and mesorectum multiple times and to cone into the specimen on the distal rectum,
requiring great expertise in more difficult cases ([Fig. 5]). Also, the anterior dissection below the level of the seminal vesicles is hard
to visualize when the camera is introduced through an umbilical trocar, as used in
a standard setup. The conversion rate of around 10% reflects the difficulty of the
laparoscopic TME procedure.[60]
[61]
[62]
[63]
Fig. 5 Three-dimensional (3D) model: Risk of coning (C) into the mesorectum (M) while performing
laparoscopic total mesorectal excision (TME) in narrow male pelvis with large prostate
(P) (Use VIPicture App).
More recently, robotic surgery and transanal surgery have been developed to overcome
the limitations of conventional laparoscopic surgery for rectal cancer. Compared with
laparoscopic surgery, the robotic system has theoretical advantages of being a stable
optic platform, with all moves fully controlled by the surgeon with articulating instruments.
These features potentially allow better visualization and maneuverability, even in
the lower pelvis, possibly resulting in a better dissection. The anatomical structures
are approached as in any other technique from above, with known embryological-derived
surgical planes. Difficulties stapling remain an issue, as the robotic stapler reaches
a maximum angulation of less than 55 degrees, thus perpendicular stapling of the distal
rectum is still difficult in the limited working space. As for all techniques from
above, judgment on the DRM is imprecise, and can only be evaluated by a digital rectal
exam or the use of a proctoscope before and after introducing the linear stapling
device during a robotic procedure. For robotic surgery, there is an ongoing discussion
on investment in equipment and costs per procedure, plus time needed for setup and
docking.[64]
[65] The future launch of different robotic systems might lower the price to make the
platform more competitive to costs of conventional laparoscopic surgery. As in all
advanced surgical procedures a whole learning curriculum is required with proctoring
during first cases and still with a high initial conversion rate.[66]
[67]
[68] All techniques from above encounter the anatomical structures in a same sequence
(in time), and choice between them is mainly based on surgeon's preference, although
maneuverability within the pelvis and visualization of structures are important issues.
Transanal TME (taTME) is a recently popularized different concept to treat mid and
low rectal cancer.[69]
[70] The difference with pure transabdominal techniques is that dissection of the distal
third of rectum and mesorectum, the most difficult part of the TME procedure, is performed
through the anus. The biggest gain is probably achieved in patients with multiple
factors that contribute to an increasing level of difficulty of the pelvic dissection.
The procedure is optimally started by the abdominal team to exclude metastatic pathology
and to mobilize the splenic flexure. The patient is secured in the Trendelenburg position,
and the abdominal team performs a standardized mobilization of the upper rectum, while
a second team can start the transanal portion of the procedure in a synchronized way.
After introduction of a rigid or flexible platform into the anus, the level of purse-string
suturing should be chosen, considering enough distance to clear the lower border of
the tumor. An airtight purse-string suture, washout of the rectal lumen, and recognition
of full rectal wall dissection are crucial steps before advancing the perimesorectal
dissection in a cylindrical way and toward the team dissecting from above. When both
teams connect, traction and countertraction can be optimized, most difficult areas
can be tackled together, and the light from the other team can help in recognizing
the right plane of dissection. Appreciation of steep angulation during initial posterior
dissection, and optimal use of CO2 insufflation are aspects to focus on during initial experience when guided by a proctor.[71]
[72]
[73]
Main benefits of the taTME are better visualization of the anterior part of distal
rectal dissection, more precise judgment on DRM, avoidance of imperfect stapling of
the distal rectum, and less manipulations of tumor containing rectum and mesorectum.
Because taTME differs in many aspects from the transabdominal techniques, a validated
training pathway has to be followed, including cognitive and psychomotor skills training.[74]
[75] Much attention has to be given on recognition of anatomical structures from below,
as well as on pitfalls specifically for the technique; triangles and “O”'s indicate
dissection into a different plane of dissection, while bleeding and dissection on
bare striated muscle are warning signs of going into a wrong plane.[76] Specifically in male patients, the urethra is at risk when full-thickness dissection
is started below the level of the prostate and aimed too much anteriorly. At the end
of the procedure, there is an open rectal stump on which either a purse-string suture
and stapling or hand-sewn anastomosis has to be performed.[77] After completing the training pathway, it is crucial to be proctored during initial
experience. Finally, registration of data in a registry is necessary with feedback
on individual results for continuous quality improvement with the new approach.[78]
[79]
