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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_869_Библиотеки_им_академика_М_И_Перельмана.pdf
Key Aspects of the Abdominal Dissection
Masaaki Ito
25
Introduction
Modern gastrointestinal surgery has changed
notably with respect to surgical modality since
the advent of endoscopic surgery. The introduction of endoscopic surgery in rectal cancer treatment has enabled “better visualization of
structures that could not be seen with conventional techniques,” especially in the deep areas of
the narrow pelvic cavity. Good surgical operation
under magnied vision that was not possible with
laparotomy became possible. As a result, laparoscopic total mesorectal excision (TME) has now
been standardized as a procedure for the treatment of rectal cancer. Several randomized comparative studies from around the world have
recently been published that have shown that
compared to laparotomy, laparoscopic surgery
for rectal cancer is associated with certain concerns regarding the technique’s application
toward curative-intent rectal resection [1–4]. This
shows that laparoscopic surgery is a complex surgical procedure requiring good surgical skills.
Even when a magnied view is obtained under
laparoscopic assistance, one cannot deny that
restrictions remain in the manipulation of forceps
and dissectors in the deep pelvic areas.
M. Ito (*)
National Cancer Center Hospital East, Department
of Colorectal Surgery, Kashiwa, Japan
e-mail: maito@east.ncc.go.jp
Under such pretext, transanal total mesorectal
excision (taTME) has emerged as a treatment
modality for rectal cancer [5, 6]. While TME surgery is conventionally performed from the abdomen, taTME is performed in the reverse direction
from the anus – i.e., the bottom-up approach.
Although the pelvic oor is the region most distal
from the abdomen and for which visibility and
dissection manipulations are difcult, the taTME
approach has enabled a direct and close-up view
of this area – which is the technique’s major
advantage.
In clinical practice, this surgery has several
advantages that account for its potential usefulness. In particular, the deep dissection layers
close to the tumor can be selected, and autonomic
nerves that should be left intact can be visualized.
Thus, an increased efcacy in curability and
function preservation could be realized. Rectal
cancer surgery, originally established amidst various constraints, is considered “a surgical procedure that is performed in the most distal area.”
However, when approached from the opposite
direction (as is the case with taTME), what was
the distal most region becomes the most proximal. Thus, taTME is a surgical procedure with
vast possibilities. This chapter reviews the important points on abdominal dissection while performing taTME.
© 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_25
263
264
M. Ito
Positioning of taTME in Abdominal Maneuvers
taTME is a surgical procedure whereby the critical portions of dissection, particularly the distal
and mid-mesorectal excision, are performed from
the anal side. Abdominal detachment maneuvers
are usually performed from the abdominal side.
taTME can be performed by two methods, either
a two-team surgery whereby the abdominal
maneuvers and perineal maneuvers are performed simultaneously, or as a single-team operation, in which the abdominal maneuvers and
perineal maneuvers are performed sequentially.
In the two-team arrangement, abdominal maneuvers are performed simultaneously with the perineal maneuvers; therefore, the perineal team
performs the majority of the TME dissection. For
that reason, the tasks that the abdominal maneuvers team must handle are primarily vascular
management and mobilization maneuvers from
the sigmoid colon through to the splenic exure.
On the other hand, in the single-team surgery,
the detachment maneuvers that must be performed from the abdominal side are often slightly
different depending on whether the intraperitoneal maneuvers or perineal maneuvers take precedence. The advantages and disadvantages of
the intraperitoneal maneuvers taking precedence
and those when the perineal maneuvers take precedence in the single-team surgery are summarized in Table25.1.
Laparoscopic TME is a commonly performed
surgical procedure, and there are no notable
problems associated with the anatomical understanding regarding the dissection procedures
from the abdominal side. However, the anatomical understanding for dissection procedures from
the perineal side is difcult, and such procedures
are not easy; therefore a certain amount of experience and familiarity are essential for adeptly
performing taTME. When taTME is to be performed, each institution must decide whether to
use the two-team or single-team approach and if
it is the single-team surgery, whether the abdominal procedures or perineal procedures would take
precedence. Such choices must be decided based
on the experience of the surgical team and the
Table 25.1 Above rst or below rst?
Above rst Below rst
Surgical eld of
view
Difculty of
dissection in the
pelvis
Forceps
operation in the
pelvis
Understanding of
surgical anatomy
Evaluation of
intraperitoneal
tumor
progression
No touch
isolation
Risk of the
urethral injury
Autonomic nerve
preservation
Selection of
dissection plane
Familiar Takes time to get
Difcult Comparatively
Some
restrictions
Comparatively
easy
Possible Impossible
Possible Difcult
Rare Certain risk in
Possible Better visibility
As usual Possible
used to
easy
Less restrictions
Occasionally
difcult
the lower rectum
of NVB and
PSN
selection depend
on tumor depth
level of technical familiarity with dissection procedures from below. When there is no familiarity
with taTME procedures from the anal side, we
would recommend collaborative surgical procedures by a single-team or dual-team approach
whereby the abdominal portion of the operation
takes precedence.
Key Aspects for Performing TME from the Abdominal Side
Understanding the Perirectal Fascia Structure
A clear understanding of the perirectal fascia
structure is necessary for performing procedures
from the perineal side and even while performing
TME procedures from the abdominal side to
avoid pitfalls. The mesorectal envelope, the thin
fascial layer that covers the rectum and surrounding fat, is the most important landmark while performing TME.The mesorectum is surrounded by
a layer of pre-hypogastric nerve fascia. Preserving
Later
bundle
PSN;Pelvic splancnic nerve
Upward traction by assistant
Counter-traction by operator
25 Key Aspects of the Abdominal Dissection
265
this layer results in the preservation of the hypogastric nerves, the pelvic autonomic nerve plexus,
and the paired neurovascular bundles. The prehypogastric nerve fascia reaches the anterior wall
of the rectum, where it transitions into the
Denonvilliers’ fascia. The endopelvic fascia,
which lies further exterior to the pre-hypogastric
nerve, is present in the posterior wall of the rectum and covers the blood vessels running in the
anterior plane of the sacrum. The anatomical
understanding of these fascial layers becomes
critical during dissection around the rectum
(Fig.25.1).
While performing the TME procedure from
the abdominal side, the post-rectal space is
entered from the promontory angle to accurately
identify the mesorectum. In this area, there is a
potential space between the mesorectum and prehypogastric nerve fascia, which makes it easy to
identify the mesorectum. As a technique for
expanding the visual eld, the vicinity of the sigmoid colon is grasped with two forceps and
retracted upward, away from the pelvis. By doing
so, the mesentery of the sigmoid colon is pulled
to the peritoneal surface of the anterior abdominal wall (Fig. 25.2). The mesentery is incised
upwardly, at approximately 1cm from the root of
the sigmoid mesentery; it is then opened to the
left and right to enter the plane of the post-rectal
space (Fig.25.2b). By pulling the pre- hypogastric
nerve fascia dorsally (at the S2/3 level of the
sacrum) from the promontory angle, it becomes
easier to recognize the plane between the fascia
and the mesorectum, which is identied as a
thick, yellow membrane (Fig.25.3). If the mesorectum is not identied with absolute accuracy,
one cannot guarantee a proper TME dissection
layer.
The basic concept of TME is to identify the
mesorectum during surgery and then to perform
dissection along this fascia. For early-stage
lesions, such as T1 and T2 rectal cancers, radical
Fig. 25.2 Effective exposure entering the post-rectal
space
Fig. 25.1 Fascias
around the rectum
al ligament
Pelvic plexus
PSN
NVB
Seminal vesicle
Rectum
Hypogastrin nerve
Sacrum
Denonvillier’s fascia
Meso-rectum
Prehypogastric
fascia
Endopelvic fascia
NVB;Neuro-vascular
266
Prehypogastri
fasci
Fig. 25.3 Identication
of mesorectum
Fig. 25.4 Identication
of Denonvilliers’ fascia
covering the rectum in
anterior side of the
rectum
M. Ito
Mesorectum
cnerve
a
Denonvilliers’ fascia covering
the seminal vesicle
Mesorectum
resection is possible in the conventional TME
dissection plane. For T3 and T4 rectal cancer
lesions, selection of a more inclusive dissection
layer is sometimes necessary to ensure adequate
circumferential resection margin (CRM). In
these cases, the dissection layer intentionally
includes the pre-hypogastric nerve fascia which
is located more externally than the mesorectum.
The pre- hypogastric nerve fascia is a series of
membrane structures that include the hypogastric nerve and pelvic plexus on the lateral side
and Denonvilliers’ fascia on the anterior side.
With the regular TME dissection layer,
Denonvilliers’ fascia is recognized as the fascia
that covers the seminal vesicle (Fig. 25.4).
Meanwhile, if the selected dissection plane is
one layer deeper than the regular TME dissection layer, then Denonvilliers’ fascia becomes
the dissection layer in the anterior wall, while on
the lateral side of the rectum, it is the pre-hypo-
Seminal vesicle is directly
exposed by resecting the
Denonvilliers’ fascia
Mesorectum
Fig. 25.5 External dissection plane in anterior side of the
rectum
gastric nerve fascia that becomes the dissection
layer to be selected for the resection. If the
Denonvilliers’ fascia is resected together with
the rectum, for males, the layer that exposes the
seminal vesicles is where the dissection will take
place (Fig. 25.5). However, for females, the
same fascia is usually thin and may not be accu-
Traction of the rectum
Mesorectum
a
1
25 Key Aspects of the Abdominal Dissection
267
rately recognizable. When dissection occurs in
the layer that includes the hypogastric nerve,
neurovascular bundle (NVB), and pelvic plexus
in the vicinity of the resection site, caution must
be taken to avoid injury to these structures as urinary and sexual dysfunction may likely be
induced postsurgically.
However, on the lateral side of the rectum, an
adequate plane between the hypogastric nerve
and pelvic plexus is acquired by pulling the
mesorectum inward, and cutting that peak yields
nerve preservation (Fig.25.6). If the TME procedure is continued unmodied in the vicinity of
the anal canal, which is the endpoint of the TME,
the intersphincteric space (ISR) is identied
behind the NVB, and dissection of the ISR is initiated (Fig.25.7).
If taTME is performed from the anal side,
there are mainly two choices for the dissection
Dissection point to preserve
nerves
Mesorectum
Pelvic plexus
layer in the posterior wall of the rectum: these are
the dissection layer of the abdominal side or that
of the posterior side of the endopelvic fascia
(Fig. 25.7). In taTME, due to the presence of
recto-sacral ligament with fusion of several fascial layers in the vicinity of the S2–3 sacral vertebrae, then isolation of this ligament is necessary.
In this region, if the dissection proceeds in a
direct line with no change toward the peak of the
curve of the L-shaped sacrum, caution is required
to avoid injury to the blood vessels located in the
anterior surface of the sacrum. The direction of
the dissection shifts upward after the recto-sacral
ligament is resected; this results in dissection that
conforms to the shape of the sacrum. In contrast,
typical perirectal dissection from the abdomen
involves the dissection layer between the mesorectum and pre-hypogastric nerve fascia.
However, as with taTME, resection of the rectosacral ligament in the region of the S2–3 vertebrae is necessary.
Figure 25.8 presents a case where the surgery was performed from the perineal side,
with the dissection layer lies behind the endopelvic fascia for T3 lesions of the posterior wall
of the rectum. Such difference of the dissection
planes from the abdomen to those from the
perineum is occasionally found in two-team
taTME procedures.
Fig. 25.6 Dissection between mesorectum and the pelvic
plexus in lateral side of the rectum
Fig. 25.7 Identication of the intersphincteric space
behind the neurovascular bundle
NVB
Intersphincteric plane
2
Pre-hypogastric nerve fasci
3
Endo-pelvic fascia
1 2 3
RECTUM
Anal
canal
Recto-sacral fascia
Fig. 25.8 Fascias in posterior side of the rectum
Sacrum
268
Le
NVB
plane from below
Caution During the Dissection in the Neurovascular Bundle (NVB)
M. Ito
In TME procedures approached from the peritoneal side, the dissection procedures of the anterolateral region of the rectum are particularly
challenging. The anterolateral region of the rectum
is in close proximity to the NVB, where bleeding
can be readily triggered. Moreover, if the surgeonselected dissection plane is slightly exterior, autonomic nerve injury may occur. We have often
experienced cases of voiding dysfunction and sexual dysfunction occurring because of this injury.
In males with a narrow, android pelvis, dissection procedures in the vicinity of NVB may be
difcult as forceps maneuvers are restricted. In
cases where the tumor mass is located anterolaterally and where the depth of tumor invasion is
≥T3, a dissection plane where a part of the NVB
is also resected has to be chosen. However, even
when the rectal cancer is T1 or T2, dissection
manipulations in this region are not always easy
due to restriction of the bony pelvis. One of the
important and recently recognized advantages of
the taTME procedure is good visibility of NVB
from the perineal side. In taTME, NVB is known
as a bundle structure of a certain length.
Therefore, a dissection at the superior aspect of
the NVB will not result in nerve injury (Fig.25.9).
Even in our experience, the incidence of voiding
dysfunction has been less in patients in whom
nerve preservation was done during
taTME. Therefore, when taTME is performed
from the perineal rather the abdominal side,
selective dissection procedures can be performed
Dissection plane from above
Rectum
Prostate
Fig. 25.10 Difference of dissection point between from
above and from below
Pelvic plexus
NVB
Dissection
under good NVB visibility. As shown in
Fig.25.10, when the TME is performed from the
abdominal side, there exists a potential to injure
the nerves located toward the central side of the
NVB.In taTME, dissection in the periphery (i.e.,
in a plane too lateral) is quite possible. Therefore,
even from the viewpoint of nerve preservation, it
is preferable to obtain a certain level of familiarity before performing dissection procedures in
TME.Thus, when one senses that dissection in
the region of the NVB by the abdominal approach
to TME would be difcult, it is better to select a
dissection layer in this area that would work
cooperatively with the perineal (taTME) technique, so as to optimize correct-plane surgery
and subsequent patient outcomes.
Pubis
vator ani muscle
䚽
Prostate
Rectum
Coccyx
㽢
Endo-pelvicfascia
Key Aspects for Adequate Blood Flow Preservation in the Colon
While performing taTME, regardless of it being
executed in single-team or dual-team fashion–
the team performing the abdominal dissection is
responsible for blood vessel management in the
vicinity of inferior mesenteric artery (IMA) and
Fig. 25.9 Neurovascular bundle from below
the mobilization of the colon. The important
25 Key Aspects of the Abdominal Dissection
269
issues in abdominal procedures are (1) preservation of adequate colonic blood ow and (2) mobilization of the colon that is long enough to avoid
tension in the anastomotic site.
In case of high anastomotic sites following low
anterior resection (LAR), the branching site of the
left colic artery (LCA) can be easily preserved with
a comparatively low level of ligation. However, if
an anastomotic site is predicted to become a lowlevel anastomosis in the vicinity of the anal canal, it
is essential for the abdominal dissection team to
perform the mobilization of the splenic exure, so
as to assure ample length, with care to preserve the
intrinsic vascular arcades to the colon and conduit.
To accomplish this, three things must be performed: (1) high division at the root area of IMA,
(2) complete mobilization of the splenic exure,
and (3) division of the inferior mesenteric vein
(IMV) at the inferior margin of the pancreas. By
completing these three procedures, an adequate
mobility of the colon can be obtained, and an anastomosis using the colon with good blood ow
becomes possible. Other steps include mobilization of the descending and sigmoid mesentery,
division of the White Line of Toldt, and intracorporeal division of the marginal artery at the site
selected for proximal bowel division. The latter is
particularly important to perform, especially prior
to transanal extraction of the specimen, since the
blood supply (especially the marginal artery) is
prone to shear during this process.
In particular, the evaluation of blood ow during surgery by indocyanine green (ICG) uorescence imaging has recently become available.
Consequently, through real-time perfusion angiography utilizing ICG intraoperatively, it is possible to mitigate the risk of using a colon with
inadequate blood ow– such as when due to the
presence of Sudeck’s point which is an anastomotic site in the sigmoid colon susceptible to
ischemic colitis.
in the pelvic cavity needs to be maintained.
Therefore, it is desirable that the dissection layers
of the abdominal procedures and perineal procedures are not connected in the early phase of the
surgery. In particular, the rendezvous point is
commonly the peritoneal reection. Therefore,
during the abdominal dissection with two teams
(top and bottom), it is preferable not to dissect
the peritoneal reection located in the anterior
wall of the rectum until both teams are ready to
carry out the rendezvous. Similarly, during the
dissection of the posterior wall of the rectum, it is
better not to connect the dissection plane between
the abdominal space and the perineal space just
close to the recto-sacral ligament. Once the
abdominal and perineal sides are connected, the
abdominal air pressure on the perineal side and
that on the peritoneal side must be the same; otherwise the subsequent abdominal procedures will
be affected.
After all the dissections are completed, the
rectal cancer mass (en bloc with the rectum and
mesorectal packet) is excised and extracted.
Extraction can be done by two different routes–
transabominal or transanal. Each route has its
own advantages and disadvantages. In patients
whose tumor volume is relatively small, and the
mesentery is not overly bulky, extraction of the
specimen via the anus is a reasonable option.
However, when the tumor size is large or the
mesentery bulky due to visceral obesity, there is a
risk of injury to the mesenteric blood vessels and
shearing of the mesentery itself. Hence, a transabdominal route is preferred in this setting.
Another advantage of the transabdominal route is
that the surgeon can check whether the marginal
vessels are correctly preserved. In particular, for
cases of ISR and in cases of low-level anastomosis, the colon must be fully mobilized so that
adequate colon length and good blood ow are
preserved.
Caution for the Abdominal Dissection Team in the Dual-Team taTME
There are several points that the abdominal dissection team of the two-team approach must be
cautious about. In taTME, abdominal air pressure
Summary
taTME is a surgery procedure that is performed
from the perineal side, which is the reverse of the
conventional TME. This technique has demonstrated many advantages compared to conventional TME, especially in the treatment of male
270
M. Ito
patients with a narrow pelvis and in patients with
visceral obesity. In properly selected patients, it
may be superior to TME in terms of resection
quality and patient outcomes.
In this chapter, the salient points pertaining to
the abdominal dissection have been highlighted.
The abdominal portion of taTME is critical for
assuring safe and proper conduct of the taTME
operation. Coordination and dual-team orchestration is important, as is the anatomical understanding of the structure of the membranes
surrounding the rectum is necessary.
References
1. Bonjer HJ, Deijen CL, Haglind E, COLOR II Study
Group. A randomized trial of laparoscopic versus open surgery for rectal cancer. N Engl J Med.
2015;373(2):194.
2. Jeong SY, Park JW, Nam BH, etal. Open versus lapa-
roscopic surgery for mid-rectal or low-rectal cancer
after neoadjuvant chemoradiotherapy (COREAN
trial): survival outcomes of an open-label, non-
inferiority, randomised controlled trial. Lancet Oncol.
2014;15(7):767–74.
3. Stevenson AR, Solomon MJ, Lumley JW, et al.
Effect of laparoscopic-assisted resection vs open
resection on pathological outcomes in rectal cancer: the ALaCaRT randomized clinical trial. JAMA.
2015;314(13):1356–63.
4. Fleshman J, Branda M, Sargent DJ, etal. Effect of
laparoscopic-assisted resection vs open resection
of stage II or III rectal cancer on pathologic outcomes: the ACOSOG Z6051 randomized clinical
trial. JAMA. 2015;314(13):1346–55. Martin-Perez
B, Andrade-Ribeiro GD, Hunter L, Atallah S.A systematic review of transanal minimally invasive surgery (TAMIS) from 2010 to 2013. Tech Coloproctol.
2014;18:775–88.
5. De Lacy AM, Rattner DW, Adelsdorfer C, Tasende
MM, Fernandez M, Delgado S, etal. 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.
6. Atallah S, Martin-Perez B, Albert M, deBeche-Adams
T, Nassif G, Hunter L, etal. Transanal minimally invasive surgery for total mesorectal excision (TAMISTME): results and experience with the rst 20 patients
undergoing curative-intent rectal cancer surgery at a
single institution. Tech Coloproctol. 2014;18:473–80.
Zen andtheArt
ofthePurse-String
AndrewR.L.Stevenson
26
Introduction
Just like a storybook, every surgical procedure
has a beginning, middle and an end. Each part of
the operation requires careful attention, but perhaps the most important part of transanal total
mesorectal excision (taTME) surgery is the
beginning – the purse-string. The creation of a
sound and perfect purse-string sets the foundation for successful surgery to follow. This chapter
is largely based on personal experience with
observations made by myself and colleagues
conducting workshops from around the globe.
This is often found to be a time-intensive exercise
for novice surgeons, who typically require multiple attempts to achieve the goal of a water- and
airtight purse-string.
It has been through these various workshops
that I was reminded of the cult book from the
1970s, Zen and the Art of Motorcycle Maintenance
by Robert M.Pirsig. This has become a classic
book on modern philosophy in which the author
explores both the meaning and concept of “qual-
A. R. L. Stevenson (*)
University of Queensland, Brisbane, QLD, Australia
Colorectal Surgery, Royal Brisbane Hospital,
Herston, QLD, Australia
ity” through his own dynamic personal quest for
quality and value. It is this same pursuit of excellence that is required of surgeons to create the
perfect purse-string in an efcient and reproducible manner. Taking the time to slow down, reect
and allow yourself to become totally absorbed in
the task– a state of ow– a highly focused mental state as described by eminent psychologist
Mihaly Csikszentmihalyi.
The perfect purse-string is the beginning and
also the end of many taTME operations. This
chapter will provide the surgeon with the knowledge and helpful tips in their own personal quest
for quality and the perfect taTME.
The Setup
There is basically two ways that a purse-string
can be created. This will largely depend on the
height of the tumour from the anal verge or anorectal junction. The purse-string can be placed
either by using retractors and placed transanally
under direct vision or placed endoscopically via
the chosen transanal endoscopic platform.
Most surgeons will be more familiar with
transanal placement of purse-string with skills
that may have been developed when performing
stapled hemorrhoidectomy or similar procedures.
As with all steps of any operation, the key is adequate retraction, exposure and illumination.
© 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_26
271
272
A. R. L. Stevenson
Retraction can begin with eversion of the distal
anal canal either with sutures or using proprietary
retractors such as Lone Star retractor (Cooper
Surgical, Incl). Various proctoscopes can then be
employed to demonstrate the lower edge of the
tumour. If the lesion is higher than the anorectal
junction, the operating platform anoscope can be
inserted to provide exposure. However, for
tumours that are close to the anorectal junction or
into the upper anal canal, the purse-string would
need to be inserted using a proctoscope only,
before insertion of the operating platform and
endoscopic equipment. Illumination is best provided by means of a surgeon’s headlight or selfilluminating proctoscope. As the operating
theatre becomes crowded with all the equipment
required for these complex operations, the use of
a battery-powered headlight can be quite helpful,
if available. Long needle holder and forceps can
facilitate access to the distal rectum via the
proctoscope.
For tumours that are situated higher in the
rectum, it is more desirable to place the pursestring endoscopically using the chosen platform
for taTME. Good-quality laparoscopic needle
holders will be required for placement of the
purse- string. The preferred suture is an 0-Prolene
on a 26mm, semi-half circle (SH) needle. This is
less likely to break when tying the suture or during the TME dissection, and the smaller-diameter needle is both easier to use in a small space
and also less likely to take too much tissue at
once.
If the operation is being performed as a synchronous procedure with two teams, it is important for the perineal surgeon to have good access
and appropriate ergonomics to be able to perform
the perfect purse-string. It is important for the
abdominal surgeon to also appreciate the importance of this step of the operation and allow the
position or height of the patient to be adjusted to
suit the perineal surgeon. Although I prefer to
perform the taTME dissection in a standing position (with elbows slightly extended and assistant
camera holder standing or sitting comfortably
next to me), I will usually perform the purse-
string whilst seated but raising the operating table
for head-down tilt as required, to gain perfect
access.
Purse-String Principles
Generally, the purse-string is placed 1cm distal
to the lower edge of the tumour, and the rectotomy performed 1cm distal to the purse-string;
thus the rectotomy is created 2cm distal to the
inferior extent of the tumour. Depending on the
height of the tumour and its position in relation
to the anorectal junction, the distance below the
tumour at which the purse-string is placed may
be slightly greater to or less than 2cm. When
the purse-string has been tightened and tied, the
ideal appearance is a centrally placed knot with
a number of shallow radial folds extending out
towards the periphery from the central knot
(Fig.26.1).
The perfect purse-string is achieved by assuring equal needle placement and taking equal
size radial bites, typically 8–12 bites depending
on the width of the rectum. It is important that
the sutures are placed evenly and not too far
apart, not too close together, but “just right”.
The needle should enter the tissue just a few
millimetres along from where the needle exits
the tissue of the previous bite. When the pursestring is tightened and secured, this will invert
the rectal wall evenly, providing a good platform around which the rectotomy can be made.
It is vital that the purse-string is centrally secure
to prevent the egress of bowel content or, or
potentially, exfoliated malignant cells to enter
the operative eld. Whether the purse-string is
performed “open” via proctoscope or endoscopically via the chosen platform, it is advisable to
have minimal amount of the suture within the
rectum. This will help to prevent looping and
excess suture affecting visibility or forming
inadvertent knots.
There are no hard and fast rules about the best
position to start the purse-string (I typically start
at the three o’clock position), but it is often useful