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218 General techniques in mesenteric-based colorectal surgery
Direct grasping and retraction of mesentery
mesocolon
adipovascular
(b)
Atraumatic
grasper on
mesentery of
adipovascular
pedicle
(a)
Atraumatic
grasper to
deflect
mesentery
upward
Atraumatic grasper grasping middle
colic adipovascular pedicle
Lesser sac
Middle colic
pedicle
Figure 16 .10 (a) and (b) Intraoperative views of the means by which the mesentery may be directly grasped using an atrau-
matic grasper. Importantly, the mesentery can only be directly grasped when the covering mesothelium is still intact. If the
mesothelium is absent, then mesenteric fat is exposed. This tears and bleeds readily if grasped directly.
nonintestinal margin. is poses problems in retraction,
as it limits the distance over which the intestinal mesenteric margin can be manipulated. A similar phenomenon
occurs with the small bowel; although the base of the small
bowel mesentery is short, the mesentery fans out considerably at the intestinal margin. It is this expansion of the
mesentery that renders it and the small bowel so dicult
to eectively retract over its full length.
e dierential between the intestinal and nonintesti-
nal margin of the mesentery is a conformational property
that creates considerable diculty in setting up the operative eld and providing “mesocolic access.” ere remains
a strong clinical need to generate a system that would
automatically and reliably cater to these conformational
properties. Most retractors deal directly with the intestinal component of the small bowel and not with the mesenteric component. e optimal retractor would retract and
maintain both mesenteric and intestinal components of the
small intestine. At present, one is largely reliant on gravity
or additional ports and instruments to deect the bowel and
mesentery (in the laparoscopic context), or on large swabs
and separate retractors, in the open context.
In surgery on the upper rectum/mesorectum, sigmoid/
mesosigmoid or descending colon/mesocolon, it is an
absolute prerequisite that the le mesocolon be adequately
exposed. e inferior mesenteric artery and vein are contained in mesenteric adipovascular pedicles that require
mobilization and skeletonization (Figure 16.11). Robotic
and laparoscopic surgery is particularly challenging when
mesenteric access is inadequate. Prior to commencing any
laparoscopic or robotic procedure on the rectum, many surgeons insist on rst developing access to the le mesocolon
as far as the duodenojejunal exure. To do this, the patient
is placed head down (sometimes right shoulder down) and
any adhesions between serosal surfaces of the fourth part of
the duodenum and le (or transverse) mesocolon divided
(Figure 16.12). If access to the le mesocolon and mesosig-
moid cannot be obtained, despite the earlier maneuvers,
Transverse
Preparation of the operative eld 219
Inferior mesenteric artery and vein
(a)
(c)
(e)
Skeletonized inferior
mesenteric artery
Clipping of inferior
(b)
(d)
Clamping, division, and ligation
of inferior mesenteric artery
mesenteric vein
Figure 16 .11 (a) Intraoperative view of the inferior mesenteric artery after it has been isolated and skeletonized.
(b)Intraoperative laparoscopic view of the inferior mesenteric vein after isolation, skeletonization, and clip placement.
(c–e) Clamping, division, and ligation of the inferior mesenteric artery at open surgery.
then one should convert to an open operation. Conversion
should not be seen as a technical failure but rather a technical imperative in these contexts.
In the absence of anatomic knowledge of the mes-
entery and peritoneal reections, it is not possible to
dierentiate normal from abnormal anatomy, and thus it
is highly unlikely that the operative eld will be correctly
“set up”. An example of this occurs with adhesional complexes between diering mesenteric and intestinal structures. Adhesional complexes occur, even in the previously
unoperated abdomen, and it is important to have a crystallized view of mesenteric anatomy in order to be able
to dierentiate their components. An adhesional complex
frequently occurs between the small bowel mesentery
220 General techniques in mesenteric-based colorectal surgery
Adhesions between left mesocolon and duodenum
Left mesocolon
Mesenterotomy
pedicles
pedicle
Mesenterotomy
Duodenum
Congenital
adhesions
Duodenum
Figure 16 .12 Example of the adhesions that can occur
between the duodenum and left mesocolon, as observed
in open surgery.
Adipovascular
pedicle
Mesenterotomy of
mesentery between
Figure 16 .13 Division of the mesentery (i.e., mesenterotomy) during laparoscopic left mesocolectomy.
Divided
adipovascular
Inferior
mesenteric vein
and mesosigmoid. Simple division of the adhesions (i.e.,
separation of the anatomic components) allows freeing
of the small bowel mesentery, mobilization of the small
bowel out of the pelvis, and permits access to the mesosigmoid. Other common examples include the adhesional
complexes formed by the greater omentum and colon or
mesocolon. In patients with a pelvic appendix, the mesoappendix and appendix can adhere to the right side of
the mesosigmoid or to the right pararectal peritoneal
reection.
DIVISION OF MESENTERY
(MESENTEROTOMY)
Once the mesentery has been mobilized (i.e., detached), it
needs to be divided up to the intestinal margin. is can
proceed in an anterograde (i.e., from adipovascular pedicle
to intestine) or retrograde manner (i.e., from the intestinal margin to the adipovascular pedicle). e anterograde
approach is favored in robotic and laparoscopic surgery
and is commenced once the adipovascular pedicle has been
hemostatically secured (Figure 16.13). In open surgery, the
intestinal tract is oen rst divided thereby exposing the
mesointestinal margin. In a retrograde approach, the mesentery can then be hemostatically divided toward the adipovascular pedicle (Figure 16.14).
enced by the degree of mesenteric thickness. Multifunctional tissue sealing devices can divide mesentery in a
e technique of hemostatic mesenterotomy is inu-
Figure 16 .14 Division of mesentery during open surgery.
hemostatic manner obviating suture ligation of mesenteric
stumps. Tissue sealant devices generally incorporate a cutting mechanism which allows tissue division aer fusion.
e means by which they achieve fusion diers. One type
employs bipolar electrical energy in conjunction with pressure. e high frequency and low voltage fuse collagen and
elastin in vessels up to 7mm in diameter [61]. Incorporated
feedback mechanisms mean the devices automatically stop
once a tissue seal has been obtained. Another mechanism
Division of mesentery (mesenterotomy) 221
Mesenterotomy (open) Crohn’s disease
ry
(a)
by which tissue fusion can be obtained (the harmonic
scalpel) exploits high-frequency ultrasound to denature
proteins. It is excellent when applied to vessel walls and
tissues measuring up to 5 mm thick, in which it creates
a hemostatic coagulum. Tissue sealant devices are available in dierent formats and sizes suitable for open, laparoscopic, or robotic surgery.
In the case of the harmonic scalpel, one must be mindful of the temperature the active blade reaches. It must
not be used to exert traction or retraction of the bowel.
e narrow blades of the harmonic can also be used to
divide peritoneal reections without violating underlying
mesentery. Adrawback of the harmonic, however, is the
shortness of the blades. is limits the amount of tissue
that can be divided. e blades of tissue sealant devices
that use electrical energy can be broader, and more tissue can be incorporated between them. is means they
can be used to good eect in thicker mesentery. is is
best done in a stepwise and gradual manner (i.e., avoiding incorporation of too much mesenteric tissue between
blades). e predominantly adipose composition of the
mesentery renders it ideally suited to division using these
devices [61].
e decision to conduct an intra- versus extracorporeal mesenterotomy is important and can make the dierence between continuing in a controlled manner or rapid
conversion to regain hemostasis. If adipovascular pedicles cannot be dierentiated (i.e., in the massively obese
patient), then it may be prudent to gain vascular control
in an extracorporeal manner (Figure 16.15). is situa-
tion is oen encountered in Crohn’s disease, where mesenteric disease manifestations mean that adipovascular
pedicles cannot be dierentiated from interpedicular
regions [62–64].
Prior to the development of hemostatic sealant devices,
a variety of techniques were utilized to divide mesentery.
esimplest involved placing artery clips on mesentery, with
division between these. ereaer, the mesenteric stump
was ligated. Although 2-0 Vicryl® sutures can be used for
most cases, larger stumps should be suture ligated in a looplike manner using a thicker suture (i.e., 0 Vicryl). For large
mesenteric vessels, the simplest approach for division (aer
skeletonization) is between Kelly clamps (Figure 16.11).
Importantly, the mesentery should be divided closer to the
side being removed, thereby creating a mesenteric ange
on the side remaining. e ange facilitates suture ligation
and ensures that the stump (with vessel contained) does not
retract and become inaccessible.
Division of a severely thickened mesentery is challeng-
ing and oen required in conditions of severe inammation
such as Crohn’s or diverticular disease. e surgeon must
have a fail-safe approach to hemostatic mesenterotomy as
bleeding ca n be life threatening in these settings. Hemostatic
sealant devices should not be used as they cannot manage
the full thickness of the mesentery. Ifused, residual bleeding from the mesenteric margin can be extensive.
A reliable technique was devised in the Cleveland Clinic
by Rupert Turnbull and popularized by Victor Fazio, Ian
Lavery, and James Church. Kocher clamps are placed across
the mesentery, clamped rmly, and the mesentery is divided
between them (Figure 16.15). A Kocher clamp is applied
along the next segment of mesentery but (importantly)
overlapping the tip of the previous Kocher clamps. A Kocher
clamp is placed on the side of the mesentery to be removed
and the mesentery between clamps divided. is process
is repeated until the entire mesentery has been divided.
If bleeding occurs aer mesenteric division, it means the
clamp has not been fully secured.
Fat wrapping
Mesente
clamped
Figure 16.15 (a and b) Division of the mesentery in Crohn’s disease. The mesentery is grossly thickened and highly vascular.
Particular techniques must be adopted to ensure it is divided in as hemostatic manner as possible. (Continued )
between
Kocher's
clamps
222 General techniques in mesenteric-based colorectal surgery
(b)
Hemostatic
division of
mesentery
Figure 16 .15 (Continued ) (a and b) Division of the mesentery in Crohn’s disease.
Next, a 0-0 suture (e.g., Vicryl) on an adequately sized
needle, is passed through the mesentery beneath the tip of
the rst Kocher clamp (i.e., at the free margin of the mesentery). It is returned to the starting side of the mesentery
beneath the tip of the next clamp. is creates a loop that
hemorrhage from minor mesenteric vessels. Aggressive
traction by inexperienced assistants can lead to extensive
damage to the mesentery. Placing a 10 × 10cm swab over
the mesentery and retracting on this rather than handling the
mesentery directly can avoid this.
includes mesenteric vessels. As the clamp is removed, the
suture is securely tied. A square knot is absolutely required
as a slip knot here will lead to severe hemorrhage. is pro-
CLEARING MESENTERY FROM
THEINTESTINAL MARGIN
cess is repeated at the next Kocher clamp and again taking
care to return the suture back under the tip of the next,
successive, Kocher. e net eect is a continuous chain of
overlapping hemostatic suture loops across the divided
margin of the mesentery (Figure 16.16). Residual bleeding
at the mesenterectomy edge is rare but can occur. is can
be controlled by pinching the mesentery (i.e., by applying pressure) and then placing another suture in a gure
sis along the cut edge of a mesentery. Failure to do so can
lead to the formation of a mesenteric hematoma that may
place tension to an anastomosis or impair ow across an
anastomosis.
e consistency of mesocolon and mesentery varies
considerably in the same individual and between individuals. In some individuals (i.e., in the diabetic or massively
obese), mesenteric adipose tissue is conspicuously so
in consistency. In these settings, it is not dicult during
retraction to inadvertently disrupt the mesothelial surface,
imprint ones ngers in the mesentery proper, and cause
In order to create an anatomically safe intestinal anastomosis, it is necessary to dierentiate serosal, submucosal, and
mucosal layers of the intestinal tract. is is not possible
at the mesenteric margin unless the mesentery has been
partially cleared. equestion arises as to the optimal and
safest distance along which the mesentery can be cleared
while maintaining bowel viability. In clearing mesentery,
of the intestinal tract is important. is is the distance that
remains vascularized, if the mesentery is cleared. To be certain of adequate blood supply, this distance is divided by
two, and the mesentery is removed back as far as the new
measurement. In this manner, one can safely assume that
the bowel will continue to receive a blood supply, despite
having been cleared of mesentery (Figure 16.17).
A further technical issue arises when using a circular stapling device in creating an anastomosis. When the
anvil has been placed and the colon secured using a purse
string suture, mesentery will be pulled into the purse
Clearing mesentery from theintestinal margin 223
Technique of dividing mesentery in Crohn’s disease
12
45
7
89
3
10
6
Figure 16.16 Schematic diagram illustrating technique of dividing mesentery in Crohn’s disease. See main body of text for
explanation of the steps involved. The aim of the process is to create an overlapping sequence of suture loops that contain
all mesenteric tissue and vessels. The overlapping property means mesenteric division is hemostatic.
stringcomplex. Inmost cases, this is not an issue as cutting and stapling activities are still eective. ese may be
compromised when a considerable amount of mesentery is
interposed between serosal surface of proximal and distal
intestine. In this context, the mesentery should be cleared to
assist in transintestinal division and stapling. Oneapproach
is to gently insinuate the tip of a mosquito hemostatic forceps
between the mesentery and serosa. Although mesentery
and serosal tissue are cross connected via a connective tissue bridge, it is usually possible to position a mosquito tip
224 General techniques in mesenteric-based colorectal surgery
Middle colic adipovascular pedicle
root region
Demonstrating the level to which the intestine can be
cleared of mesente
and simultaneously retain a blood supply
ry
x
x
x
Figure 16 .17 Schematic diagram demonstrating the level
to which the intestine can be cleared of mesentery and
simultaneously retain a blood supply.
between them. e jaws of the mosquito are opened and the
mesentery between diathermied divided to expose underlying serosa. A col lar of mesentery then surrounds the anvil and
can be trimmed away using a dissecting scissors. Appendices
epiploicae should also be trimmed o the serosal surface.
ese are tougher in consistency than normal mesentery and
are more likely to compromise transintestinal stapling.
Anatomic subdivision of mesentery into adipovascular
pedicles and avascular interpedicular regions is technically relevant (Figure 16.18). e surgical approach to the
Lesser sac
Mesenteric
Figure 16 .18 Intraoperative (laparoscopic) view of middle
colic adipovascular pedicle.
Middle colic vessel
vascular pedicle diers markedly to that used in division of
avascular mesenteric regions. At the vascular pedicle, vessels, nerves, lymphatics, and connective tissues coalesce.
Itis possible to apply clamps directly across these and divide
between. However, this approach leaves a considerable mesenteric stump onto which adhesions can form. It is generally
preferable to skeletonize the major vessel within a pedicle
and then divide this alone. In the open setting, skeletonization can be achieved by sharp dissection of adipose tissue of
the vessel. Some use a right angled forceps and divide tissue
between the open jaws of this. Sometimes heavy bleeding
may be encountered if the major vessel within the pedicle is
opened. However, this is readily controlled by pinching the
pedicle between thumb and index nger.
In the minimally invasive (i.e., laparoscopic and robotic)
setting, the adipovascular pedicle can be dissected under
x
2
high magnication. is enables one to dissect perivascular
fat without damaging the vessels contained. e anterior and
lateral aspects of the vessel are rst dissected free. is leaves
the posterior (“far side”) remaining. e 30° lens should
be turned to visualize the fat of the far side. e fat is then
divided through thereby fully freeing the vessel for division.
Occasionally, it may not be possible to fully clear the far
side of fat in this manner. A strategy in this setting involves
the use of the curved retraction blade with a blunt tip. is
instrument consists of a retractable and gently curved blade
with a protected tip. ese features permit a gentle dissection
of the posterior surface of the vessels without tearing. When
the tip is introduced around the surface of the vessel, mesenteric fat on the nonvisible surface in separated. Once the tip of
the curved retraction device is visualized around the posterior surface of the vessel, it can be gently swept along the vessel to further clear it of fat. Alternatively, careful dissection
using the laparoscopic right angle, or Maryland dissector
permits clearing of fat from the posterior surface of the vessel.
ere are several laparoscopic strategies for vessel divi-
Transverse colic peritoneal reflection
omentum
-mesocolic
Omento-mesocolic adhesions
mesocolon
sion. One involves application of an endoscopic stapling
device. As the stapler is red, it places rows of titanium
staples and simultaneously divides the tissue between the
rows. It is important to select the appropriate stapler for its
length and the closed height of the staples aer it has red.
e length selected should be the minimum required to
cross the pedicle, usually 30 or 45 mm. is will reduce the
risk of inadvertent stapling of adjacent structures. Fordividing mesenteric vessels, a closed staple height of 2.0–2.5 mm
is typically adequate, although needs to be tailored to the
thickness of the pedicle.
Once the stapler has been introduced, the jaws are
opened and it is articulated into an orientation that permits
easy division of the vessels. e thin blade should be placed
posterior to the vessel (it causes less trauma to overlying
mesentery). Once secured in position, it is closed, clamped
and slowly red. Some would delay ring or opening the
instrument for 30 seconds to theoretically reduce the edema
in tissue or provide compression hemostasis of small residual mesenteric vessels. Even aer safe and successful ring of
the stapling device, staple line bleeding can occur. is can
be controlled with placement of a clip diagonally across the
staple line or placing a ligature around the vascular pedicle.
Greater omentum 225
Peritoneal
reflection
Transverse colon
GREATER OMENTUM
Current thinking holds that the greater omentum, like the
mesentery, is derived from the dorsal mesentery. However,
it is structurally and topographically very dierent from
mesentery. It is highly relevant from a surgical perspective given its variable adherence to the upper surface of the
transverse mesocolon. It also adheres to the upper surface of
the peritoneal reection at the hepatic and splenic exure.
Adhesion of the omentum to the hepato- and splenocolic
reection occurs to variable degrees and can complicate
dissection in this region.
In mesenteric-based surgery, it is important to have an
anatomic-based strategy for clearing the omentum from
the mesocolon. Separation of the greater omentum from
mesocolon permits access to the lesser sac. Perhaps more
importantly, however, it also frees the mesocolon to allow
the surgeon to circumvent the middle colic vessel when the
latter is to be divided (e.g., in total mesocolectomy).
is can be achieved in a number of manners. In open
surgery, one approach is to li the greater omentum
anteriorly or superiorly and the transverse colon inferiorly.
is places the peritoneal reection between these under
stretch (see earlier discussion) (Figure 16.19). e latter
is then divided using either diathermy on coagulation, or
cutting. Alternatively, it can be divided with the LigaSure
or Harmonic scalpel. Diathermy division of the reection is
ner and also allows separation of adhesions at the omento-
mesocolic interface (Figure 16.20). ese adhesions obliter-
ate the space between the greater omentum and transverse
mesocolon creating a complex lattice of spaces that may be
misinterpreted as the lesser sac proper. However, continued
Greater
Figure 16.19 Intraoperative (open surgery) of the peritoneal reection between the greater omentum and
transverse colon.
Greater omentum
Transverse
Figure 16.20 Intraoperative view of omento-mesocolic
adhesions between the greater omentum and underlying
transverse mesocolon.
Omento
adhesions
226 General techniques in mesenteric-based colorectal surgery
Lesser sac
mesocolon
Stomach
Lesser sac
Figure 16.21 Intraoperative view of the lesser sac after
dividing the greater omentum to gain access.
Greater omentum
Transverse
division of omento-mesocolic adhesions eventually disrupts
the adherence between the greater omentum and mesocolon
suciently to permit entry into the lesser sac proper. Liing
the stomach superiorly and following the transverse mesocolon toward the pancreas will demonstrate short adhesions
between the mesocolon and either the pancreas or stomach.
Although these should also be divided one must bear in mind
that dissection here brings one down onto the true root of the
mesentery (i.e., the origin of the superior mesenteric artery).
e principles of robotic and laparoscopic separation
of the mesocolon and greater omentum are the same,
although the approach is dierent. It is however possible
to adopt a similar approach in laparoscopic separation, by
grasping the transverse colon and liing the greater omentum in the opposite direction. is will identify the reection between the two and permit its division. An alternative
approach isto grasp the greater omentum just distal to
the greater curvature of the stomach, with traction in one
direction and with counter-traction exerted by the assistant in the opposite direction. e intervening omentum
is then divided until the lesser sac is entered (Figure 16.21).
Omental division is continued to where the right and le
contributions to the gastroepiploic arcade occur, when the
direction of dissection changes angle toward the splenic
exure. While this process separates the greater omentum o the transverse mesocolon, a bulk of omentum will
remain attached to the colon. is is useful, however, and
can in turn be exploited during retraction. Retraction of
the colon toward the right iliac fossa places the fascial
attachment of the mesocolon under stretch. Alternatively,
the patient can be placed in the steep right shoulder down
position, and the resultant eect of gravity on omentum
and colon means that the colo- and mesofascial interfaces
at the splenic exure are easily identied, accessed, and
separated (see Chapter 20).
COLO- AND MESOFASCIAL INTERFACE
One of the key techniques in colorectal and intestinal
surgery is identication of the interface formed between
mesocolon (or colon) and Toldt’s fascia (Figure 16.22).
Inmost reference texts, authors highlight the white line of
Toldt as the landmark at which to commence mobilization.
Peritonotomy in this region is very useful, but only when
one keeps the concept of colo- and mesofascial planes in
mind. If not, the retrofascial plane is frequently entered
(Figure 16.23) and the retroperitoneum dissected. To avoid
this, some surgeons emphasize peritonotomy one centimeter medial to the white line of Toldt. e problem here is
that in the case of the right and le colon, “one centimeter
medial” brings one directly onto the colonic surface.
e key point to keep in mind is that peritonotomy
provides access to the colo- or mesofascial plane. In keeping with this, peritonotomy medial to the white line of
Toldtshould be done with a view to identifying this plane.
Aer peritonotomy, the colon is placed under traction away
from the posterior abdominal wall. Traction is transmitted
to the plane and the interface between colon or mesocolon,
and fascia, is apparent. is principle is universally applicable (Figure 16.24). As such, this concept will be reiterated
throughout this book (Figure 16.25).
GRAVITY
e eects of gravity on tissue form a useful adjunct
in laparoscopic and open surgery. In fact, in laparoscopic surgery, it is crucial to exploit gravity in keeping
the greateromentum and small bowel/mesentery o the
mesocolic operative eld.
Countering the eects of gravity is also centrally impor-
tant. It must be overcome in liing mesentery o the retroperitoneum to place the meso- or colofascial interface
under stretch. It is only by placing this plane under stretch
that one identies the interface. Examples of this occur on
the right and le sides where the mesocolon is lied o the
retroperitoneum.
SPECIMEN EXTRACTION
is is a technical activity that generally receives little
attention. Injudicious extraction leads to tissue trauma,
mesenteric devascularization and can signicantly compromise an operation. It is particularly relevant in laparoscopic
and robotic surgery where a port site is elongated to permit
exteriorization. Provided mesenteric mobilization is complete, the length of an extraction site can remain minimal.
emain reason for this lies in the fact that mesentery is
malleable and will conform in shape to that of the extraction
site. us, an ordinarily bulky greater omentum or mesentery or colon can be removed through a small extraction site.
(c)
mesocolic fascia
Mesofacial plane
operitoneum
(a)
Specimen extraction 227
Mesocolon
Toldt’s fascia
Retr
Toldt’s
fascia
(b)
Mesosigmoid
Right
mesocolon
Mesosigmoid
mesocolon
Figure 16.22 (a) Schematic illustration of the mesofascial plane. (b) Intraoperative (laparoscopic surgery) demonstration of
the mesofascial plane. (c) Intraoperative (open surgery) view of the mesofascial plane.