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216 General techniques in mesenteric-based colorectal surgery
In placing a patient in a steep right or left lateral position,
some use side T-bars to prevent lateral slide (Figure16.8).
Soft padded gamgees are inserted between T-bars and bony
prominences to minimize risk of nerve injury. is is fur-
ther aided by positioning the patients hands with thumbs
in the upright position. To prevent the patient from sliding
superiorly (when in Trendelenburg position), soft cushioned
shoulder pads can be placed immediately above the shoul-
ders with gamgee padding interposed between shoulders
and pads. Some institutes utilize an inatable rubber mat
that does not slip if placed directly onto rubber. However,
this is not a fail-safe mechanism particularly in the obese
patient. To prevent the patient from sliding inferiorly (i.e.,
when in steep reverse Trendelenburg), a half-bottom table
and overlying wedge support can be used.
Prior to beginning any procedure patient position is tested
to ensure that the patient is secure in all positional extremes.
e patient should be carefully examined to ensure all pres-
sure points are padded and gaps are lled with supports. Only
then should the patient be draped. Safesetup for mesenteric-
based surgery can be quite time consuming and it is always
preferable that an experienced operating team is involved.
Displacing mesentery
In open, laparoscopic, and robotic colorectal surgery, the
surgeon must be able to mobilize mesocolon and mesentery
without damaging surface mesothelium. Minor bleeding is
inevitable following mesothelial breech, as there are small
blood vessels located immediately beneath. Although this
bleeding is usually minimal, it renders anatomic planes
indistinct. Mesofascial and retrofascial planes are easily
obscured by even the smallest amount of blood. If the meso-
thelium must be disrupted (i.e., during peritonotomy), this
is best done with a hemostatic sealant device that divides in
an hemostatic manner.
During mesenteric-based surgery, it is important to have
strateg ies that permit mesenteric retr action without mesothe-
lial damage. One approach is to grasp appendices epiploicae
using a a grasper with serrated jaws (Figure16.9). ese are
excellent in grasping and holding epiploicae without causing
bleeding. As they are attached to the colon, their retraction
is transmitted to the colon and mesocolon. In addition, epi-
ploicae are generally attached at a narrow pedicle, meaning
that they can be retracted in numerous directions.
Another means of retracting the mesentery is to utilize
an atraumatic tissue grasper placed directly on the meso-
thelium of the mesentery. is enables a more focused
retraction of the mesothelium but without tearing and
has the added advantage of permitting ne dissection
(Figure 16.10). Mesentery denuded of mesothelium should
never be directly grasped, as adipose tissue is soft and will
bleed extensively.
ere are several other methods to safely retract
the mesentery. Some tack appendices epiploicae to the
anterior abdominal wall. Other laparoscopic retractors
areavailable that can be placed underneath the mobilized
left mesocolon, used to lift this up, and expose the meso-
fascial interface. e mesentery can be maintained sepa-
rate from the underlying fascia using the open jaws of a
grasper or by placing a swab between the two.
PREPARATION OF THE OPERATIVE FIELD
Too oen, the junior or inexperienced surgeon hastily
plunges toward the operative fi ld intent on completing
the intestinal component of a resection. is invariably
leads to time wastage and can be damaging as, in an eff rt
to eff ct a resection, structures are hastily displaced in the
hope of identifying “something familiar.” It is essential,
particularly in mesenteric-based surgery, to fully pre-
pare the operative fi ld. e strategy used depends on the
region in question.
In the case of the rectum/mesorectum, it is important
to place the patient in Trendelenburg so that the small
bowel and associated mesentery fall away from the pelvis
(Figure 16.7). e same applies for a long redundant sig-
moid and mesosigmoid. In itself, the intestinal component
of a redundant sigmoid is not dicult to technically man-
age (it can be retracted by grasping an epiploica). Diculty
arises because of the associated mesosigmoid. As described
in Chapter 2, the base of the mesosigmoid is considerably
shorter than the intestinal margin. As a result, the mesen-
tery must narrow considerably from the intestinal to the
Surgical table supports
Surgical table
shoulder supports
Knee and body strap
Surgical table
lateral support
Arm board
Figure 16.8 Patient positioning is crucial to obtain access.
A variety of barriers can be used (including side T-bars
and shoulder pads) to facilitate adequate positioning and
prevent the patient from slipping.
Preparation of the operative eld 217
Grasping appendices epiploicae
Greater
omentum
Lesser sac
T
ransverse colic
appendices
epiploicae
Toothed
grasper on
epiploicae
Atraumatic
grasper to
stabilize
epiploicae
Toothed, ratcheted grasper
(a)
(b)
(c)
Figure 16.9 (a) Intraoperative view of the retraction afforded by grasping an appendices epiploicae using a toothed
grasper. Although the latter is traumatic, the consistency of the epiploicae means that it will not tear or bleed. The
same cannot be said for the mesentery and any attempt to directly grasp the mesentery with a traumatic grasper will be
followed by hemorrhage. (b) Grasper being used to grasp an appendices epiploicae. (c) Blades of traumatic grasper.
218 General techniques in mesenteric-based colorectal surgery
nonintestinal margin. is poses problems in retraction,
as it limits the distance over which the intestinal mesen-
teric 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 consid-
erably at the intestinal margin. It is this expansion of the
mesentery that renders it and the small bowel so dicult
to eff ctively retract over its full length.
e diffe ential between the intestinal and nonintesti-
nal margin of the mesentery is a conformational property
that creates considerable diculty in setting up the opera-
tive fi ld 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 intesti-
nal component of the small bowel and not with the mesen-
teric 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 left mesocolon be adequately
exposed. e inferior mesenteric artery and vein are con-
tained 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 sur-
geons insist on rst developing access to the left 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 left (or transverse) mesocolon divided
(Figure 16.12). If access to the left mesocolon and mesosig-
moid cannot be obtained, despite the earlier maneuvers,
Direct grasping and retraction of mesentery
Atraumatic
grasper on
mesentery of
adipovascular
pedicle
Atraumatic
grasper to
deflect
mesentery
upward
Atraumatic grasper grasping middle
colic adipovascular pedicle
Lesser sac
Transverse
mesocolon
Middle colic
adipovascular
pedicle
(a)
(b)
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.
Preparation of the operative eld 219
then one should convert to an open operation. Conversion
should not be seen as a technical failure but rather a techni-
cal imperative in these contexts.
In the absence of anatomic knowledge of the mes-
entery and peritoneal reections, it is not possible to
diffe entiate normal from abnormal anatomy, and thus it
is highly unlikely that the operative fi ld will be correctly
“set up”. An example of this occurs with adhesional com-
plexes between diffe ing mesenteric and intestinal struc-
tures. Adhesional complexes occur, even in the previously
unoperated abdomen, and it is important to have a crys-
tallized view of mesenteric anatomy in order to be able
to diffe entiate their components. An adhesional complex
frequently occurs between the small bowel mesentery
Inferior mesenteric artery and vein
Skeletonized inferior
mesenteric artery
(a)
(c)
(e)
(d)
(b)
Clamping, division, and ligation
of inferior mesenteric artery
Clipping of inferior
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.
220 General techniques in mesenteric-based colorectal surgery
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 meso-
sigmoid. Other common examples include the adhesional
complexes formed by the greater omentum and colon or
mesocolon. In patients with a pelvic appendix, the meso-
appendix 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 intesti-
nal 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 mes-
entery can then be hemostatically divided toward the adipo-
vascular pedicle (Figure 16.14).
e technique of hemostatic mesenterotomy is inu-
enced by the degree of mesenteric thickness. Multi-
functional tissue sealing devices can divide mesentery in a
hemostatic manner obviating suture ligation of mesenteric
stumps. Tissue sealant devices generally incorporate a cut-
ting mechanism which allows tissue division aer fusion.
e means by which they achieve fusion diffe s. One type
employs bipolar electrical energy in conjunction with pres-
sure. 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
Adhesions between left mesocolon and duodenum
Congenital
adhesions
Left mesocolon
Duodenum
Figure 16 .12 Example of the adhesions that can occur
between the duodenum and left mesocolon, as observed
in open surgery.
Mesenterotomy
Adipovascular
pedicle
Mesenterotomy of
mesentery between
pedicles
Divided
adipovascular
pedicle
Figure 16 .13 Division of the mesentery (i.e., mesenter-
otomy) during laparoscopic left mesocolectomy.
Mesenterotomy
Inferior
mesenteric vein
Duodenum
Figure 16 .14 Division of mesentery during open surgery.
Division of mesentery (mesenterotomy) 221
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 avail-
able in diffe ent formats and sizes suitable for open, lapa-
roscopic, or robotic surgery.
In the case of the harmonic scalpel, one must be mind-
ful 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 tis-
sue can be incorporated between them. is means they
can be used to good eff ct in thicker mesentery. is is
best done in a stepwise and gradual manner (i.e., avoid-
ing 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 extracorpo-
real mesenterotomy is important and can make the diffe -
ence between continuing in a controlled manner or rapid
conversion to regain hemostasis. If adipovascular pedi-
cles cannot be diffe entiated (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 mes-
enteric disease manifestations mean that adipovascular
pedicles cannot be diffe entiated 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 loop-
like 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 bleed-
ing 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.
Mesenterotomy (open) Crohn’s disease
Fat wrapping
Mesente
ry
clamped
between
Kocher's
clamps
(a)
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 )
222 General techniques in mesenteric-based colorectal surgery
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 mes-
entery). It is returned to the starting side of the mesentery
beneath the tip of the next clamp. is creates a loop that
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-
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 eff ct 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 apply-
ing pressure) and then placing another suture in a gure
of eight conformation. It is essential to obtain hemosta-
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 individu-
als. 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
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.
CLEARING MESENTERY FROM
THEINTESTINAL MARGIN
In order to create an anatomically safe intestinal anastomo-
sis, it is necessary to diffe entiate 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,
the distance between mesenteric and antimesenteric border
of the intestinal tract is important. is is the distance that
remains vascularized, if the mesentery is cleared. To be cer-
tain 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 circu-
lar 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
(b)
Hemostatic
division of
mesentery
Figure 16 .15 (Continued ) (a and b) Division of the mesentery in Crohn’s disease.
Clearing mesentery from theintestinal margin 223
string complex. In most cases, this is not an issue as cut-
ting and stapling activities are still eff ctive. 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 tis-
sue bridge, it is usually possible to position a mosquito tip
Technique of dividing mesentery in Crohn’s disease
12
3
45
6
7
10
89
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.
224 General techniques in mesenteric-based colorectal surgery
between them. e jaws of the mosquito are opened and the
mesentery between diathermied divided to expose underly-
ing 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 off 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 techni-
cally relevant (Figure 16.18). e surgical approach to the
vascular pedicle diffe s markedly to that used in division of
avascular mesenteric regions. At the vascular pedicle, ves-
sels, nerves, lymphatics, and connective tissues coalesce.
Itis possible to apply clamps directly across these and divide
between. However, this approach leaves a considerable mes-
enteric 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, skeletoniza-
tion 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
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, mesen-
teric fat on the nonvisible surface in separated. Once the tip of
the curved retraction device is visualized around the poste-
rior surface of the vessel, it can be gently swept along the ves-
sel to further clear it of fat. Alternatively, careful dissection
permits clearing of fat from the posterior surface of the vessel.
Middle colic adipovascular pedicle
Lesser sac
Middle colic vessel
Mesenteric
root region
Figure 16 .18 Intraoperative (laparoscopic) view of middle
colic adipovascular pedicle.
Demonstrating the level to which the intestine can be
cleared of mesente
ry
and simultaneously retain a blood supply
x
x
x
x
2
Figure 16 .17 Schematic diagram demonstrating the level
to which the intestine can be cleared of mesentery and
simultaneously retain a blood supply.
Greater omentum 225
ere are several laparoscopic strategies for vessel divi-
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. Fordivid-
ing 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 fi ed. Some would delay fi ing or opening the
instrument for 30 seconds to theoretically reduce the edema
in tissue or provide compression hemostasis of small resid-
ual mesenteric vessels. Even aer safe and successful fi ing of
the stapling device, staple line bleeding can occur. Th s can
be controlled with placement of a clip diagonally across the
staple line or placing a ligature around the vascular pedicle.
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 diffe ent from
mesentery. It is highly relevant from a surgical perspec-
tive 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).
Th s can be achieved in a number of manners. In open
surgery, one approach is to lift the greater omentum
anteriorly or superiorly and the transverse colon inferiorly.
Th s places the peritoneal refl ction 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 refl ction is
fi er 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
Transverse colic peritoneal reflection
Peritoneal
reflection
Transverse colon
Greater
omentum
Figure 16.19 Intraoperative (open surgery) of the peri-
toneal reection between the greater omentum and
transverse colon.
Greater omentum
Omento
-mesocolic
adhesions
Omento-mesocolic adhesions
Transverse
mesocolon
Figure 16.20 Intraoperative view of omento-mesocolic
adhesions between the greater omentum and underlying
transverse mesocolon.