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298 Mesenteric component of exure mobilization
Ileocecal peritoneal re˜ec tion
(a)
component
component
Intact
Peritoneal
Peritoneal
Figure 20.3 (a) 2.5D image derived from a 3D digital model of the ileocecal exure. (b) The exure (including all components)
has been slightly displaced from adjacent structures to demonstrate continuity of each and contiguity between each.
mesentery (i.e., where the latter curves onto the posterior
abdominal wall and becomes adherent). Peritonotomy
of the ileocecal peritoneal reection is continued later-
component
(b)
intoview. By now, however, the entire ileocecal exure will
have been fully detached from the fascia and underlying
retroperitoneum.
Fascial
component
Mesenteric
component
Peritoneal
ally onto the right peritoneal reection (Figure 20.2b)
and medially onto the small bowel mesenteric reection
(Figure20.3c).
DUODENAL AND SIGMOIDAL FLEXURES
e principles of mobilization or detachment of the ex-
Colic and mesenteric components
ures are similar for all exures. e peritoneal component
is divided, which permits access to the mesenteric-fascial or
Once the peritoneal reection has been divided, only the
colo- and mesofascial interface remain attached. As earlier, the exure is best thought of in terms of radial and
longitudinal axes. e former extends from attached to
mesosigmoid-fascial plane. Mesenteric-fascial separation
above, below, and at the exure leads to mobilization along
both longitudinal and radial axes and completes exural
detachment.
nonattached intestinal mesenteric margin. e latter
includes the continuity between the small intestinal and
right mesocolon. is continuity has an apex at the ileoce-
FUTURE DIRECTIONS
cal junction.
Given that the ileocecal junction is generally mobile,
there is a short or limited colofascial plane in this region.
In cases where the intestinal component is attached, then
a colofascial interface will be encountered and the components are separated (Figure 20.3). e intestinal component
of the ileocecal junction is lied anteriorly, away from the
retroperitoneum, which places the latter under stretch and
e exures have traditionally been viewed as challenging from a technical standpoint. e above descriptions
provide a roadmap along which exural mobilization or
detachment may be conducted in a universally reproducible manner. As with other aspects of colorectal surgery, this
provides an anatomic basis for the international standardization of exural mobilization.
transmits traction to the interface. is exaggerates the
interface and the components may be separated either by
SUMMARY
peeling the mesentery o the fascia or by dividing through
the fascia.
At the right colon, colo- and then mesofascial separation is completed. At the small bowel mesentery, further mesofascial separation mobilizes the mesentery o
the retroperitoneum and the inferior vena cava comes
e exures can be understood as comprising four continuous and contiguous structures. Two of these, the peritoneum
and colon, are centered on a mesenteric conuence. In conceptualizing exures in these terms, exural detachment
and resection are greatly simplied and thus reproduced.
References 299
REFERENCES
1. Treves, F., Lectures on the anatomy of the intestinal
canal and peritoneum in man. Br Med J, 1885.
1(1264): 580–583.
2. Sehgal, R. and J.C. Coffey, Historical development of
mesenteric anatomy provides a universally applicable anatomic paradigm for complete/total mesocolic
excision. Gastroenterol Rep, 2014. 2(4): 245–250.
3. Culligan, K. etal., The mesocolon: A prospective
observational study. Colorectal Dis, 2012. 14(4):
421–428; discussion 428–430.
4. Culligan, K. etal., The mesocolon: A histological
and electron microscopic characterization of the
mesenteric attachment of the colon prior to and
after surgical mobilization. Ann Surg, 2014. 260(6):
1048–1056.
5. Coffey, J.C., Surgical anatomy and anatomic
surgery—Clinical and scientic mutualism. Surgeon,
2013. 11(4): 177–182.
6. Coffey, J.C. etal., Terminology and nomencla-
ture incolonic surgery: Universal application of
a rule-based approach derived from updates on
mesenteric anatomy. Tech Coloproctol, 2014.
18(9):789–794.
7. Coffey, J.C. etal., Mesenteric-based surgery exploits
gastrointestinal, peritoneal, mesenteric and fascial
continuity from duodenojejunal exure to the
anorectal junction—A review. Dig Surg, 2015. 32(4):
291–300.
8. Ellis, H. and V. Mahadevan, Clinical Anatomy:
Applied Anatomy for Students and Junior Doctors.
Wiley, Chichester, U.K., 2013, pp. 85–89.
9. Netter, F.H., Atlas of Human Anatomy. Elsevier
Health Sciences, Philadelphia, PA, 2014,
pp.263–268, 269–276.
10. Sinnatamby, C.S., Last’s Anatomy: Regional and
Applied. Elsevier Health Sciences, New York, 2011,
pp. 234–238, 247–259.
11. Standring, S., Gray’s Anatomy: The Anatomical Basis
of Clinical Practice. Elsevier Health Sciences, U.K.,
2015, pp. 1085, 1143
12. Coffey, J.C. etal., An appraisal of the computed
axial tomographic appearance of the human
mesentery based on mesenteric contiguity from
theduodenojejunal exure to the mesorectal level.
Eur Radiol, 2016. 26(3): 714–721.
13. Peirce, C. etal., Digital sculpting in surgery: A novel
approach to depicting mesosigmoid mobilization.
Tech Coloproctol, 2014. 18(7): 653–660.
Mesenteric considerations in resection
ofthetransverse colon
J. CALVIN COFFEY AND IAN LAVERY
21
Aim 301
Introduction 301
Laparoscopic/robotic mobilization and division of the
transverse colon 301
Laparoscopic/robotic mobilization of the greater
omentum 301
Laparoscopic/robotic mobilization of the splenic exure 302
Laparoscopic/robotic mobilization of the transverse
mesocolon 303
Identication of the mesenteric margin 303
Science is organised knowledge. Wisdom is
organised life.
Immanuel Kant
AIM
To demonstrate the mesenteric and peritoneal basis of
mobilization of the transverse mesocolon.
INTRODUCTION
Classical anatomic depictions of the transverse mesocolon
describe it as inserting directly into the posterior abdominal
wall along a linear attachment [1–7]. As per these descriptions, the line of attachment extends from the hepatic exure
across the upper abdomen to the splenic exure. According
to the current appraisal of mesenteric anatomy, the transverse mesocolon is formed by a coalescence of both hepatocolic and splenocolic mesenteric conuence, at the middle
colic adipovascular pedicle [1,2,7–10]. As such the transverse
mesocolon does not have a linear attachment to the posterior abdominal wall per se. Instead, it is mainly comprised
of mesenteric regions attached over a broad area. From this
Laparoscopic/robotic division of the middle colic
adipovascular pedicle 303
Open transverse mesocolic mobilization and division 305
Mobilizing the greater omentum from the
transversemesocolon 305
Mobilization from the left 305
Mobilization from the right 305
The mesenteric root region 305
Future directions 309
Summary 309
References 309
zone of mesofascial adhesion, the mesocolon extends to the
transverse colon itself. At the intestinal boundary, it elongates
considerably in tandem with the transverse colon.
e greater omentum is draped over the transverse mesocolon and focally adherent at several points. Furthermore,
a peritoneal reection occurs between the under surface of
the greater omentum and the upper margin of the transverse
colon and although an anatomic constant, it has yet to be
named. If one considers the transverse mesocolon in the
context of these anatomic arrangements, then its mobilization and division become a straightforward technical matter
that can be readily conducted in a reproducible manner.
LAPAROSCOPIC/ROBOTIC MOBILIZATION
AND DIVISION OF THE TRANSVERSE
MESOCOLON
Laparoscopic/robotic mobilization
ofthegreateromentum
In general, transverse mesocolic mobilization is conducted
either as part of an extended right or le mesocolectomy,
or total mesocolic excision. As the latter is more common,
this will be used as the platform to describe steps in its
301
302 Mesenteric considerations in resection ofthetransverse colon
retroperitoneum
Mesenteric componen
Splenic flexure
Omentomesocolic adhesions
omentum
upper surface
Entering lesser sac
Greater omentum
Omentomesocolic
adhesions
Figure 21.1 (See also QR 2d/10.) Laparoscopic view of the
greater omentumand the manner in which it is grasped
to enabledivision. Lateral to the gastroepiploic arcade
the omentum is not attached to the upper surface of the
transverse mesocolon. As a result, its division provides the
surgeon with direct and unimpeded access to the lesser sac.
mobilization. In total mesocolectomy, the le and right sides
are rst mobilized by some authors, while others commence
on the le and progress proximally around the transverse
mesocolon toward the right side.
As a rst step, many mobilize the greater omentum o
the transverse mesocolon, thereby gaining access into the
lesser sac. To do this, an assistant holds up the greater
omentum with the patient in the head up position while
the surgeon places countertraction on the greater omentum (Figure 21.1). e greater omentum is divided in a
hemostatic manner. e division commences distal to the
gastroepiploic arcade so as not to compromise the latter. Ingeneral, in this region, the greater omentum is not
attached to the underlying mesocolon, which means that
omentotomy here accesses the lesser sac proper. Once
opened in this region, the omental division is continued le
and laterally to the junction between right and le gastro-
epiploic vessels. Atthe lateral extreme of the lesser sac, the
omentum is adherent to underlying transverse mesocolon.
Adhesions here must be divided to fully expose the underlying mesocolon (Figure 21.2) [11–13].
Laparoscopic/robotic mobilization
ofthesplenicexure
At the exure proper, the omentum and splenocolic reection coalesce to a variable degree and oen it is not possible
to dierentiate either. Continued division of the omentum/
reection here will bring the surgeon around to the le
Lesser sac
Transverse mesocolon
Greater
Figure 21.2 Laparoscopic view of omentomesocolic
adhesions that are divided in order to fully separate the
omentum from the mesocolon. This activity is essential as
it later permits the surgeon fully isolate the middle colic
adipovascular pedicle.
Transverse
mesocolon
peritoneal reection. In general at this stage, and in particular if one retracts the splenic component of the exure
to the right iliac fossa, a mesofascial interface is identiable.
is is the interface between the splenic mesenteric conuence and Toldt’s fascia (Figure 21.3).
Coalescence of greater
omentum and
splenocolic reflection
of splenic flexure
Toldt’s fascia between
mesocolon and
Figure 21.3 (See also QR 2/5.) Robotic view of mesofascial
interface formed between the mesenteric component of
the splenic exure and underlying Toldt’s fascia. When the
transverse mesocolon is retracted toward the right iliac
fossa the fascia is placed under stretch and the interface
formed between it and the mesocolon becomes apparent.
t
Left (Toldt’s )
mesocolic fascia
Laparoscopic/robotic mobilization and division of the transverse mesocolon 303
Mesenteric margin
Middle colic adipovascular pedicle
transverse mesocolon
root region
Origin of middle colic
Mesenteric root region
Transverse mesocolon
Figure 21.4 (See also QR 1/6 and 7.) The mesenteric margin. This is created as a result of peritonotomy of the peritoneal reection at the right side of the mesosigmoid and
division of the inferior mesenteric adipovascular pedicle. It
is important to identify as it provides the starting point for
mesenterotomy of the transverse mesocolon and isolation
of the middle colic pedicle.
Left mesocolon
Laparoscopic/robotic mobilization
ofthetransverse mesocolon
Before describing mobilization of the transverse mesocolon,
it is important to describe the anatomy of the operative eld
(see Chapter 20 for details). e le mesocolon and colon
will have been mobilized. e le peritoneal and splenocolic
reection will have been divided, and the greater omentum
freed from the upper surface of the transverse mesocolon.
Finally, a mesenteric margin will have been created following division of the inferior mesenteric artery and vein, as
well as intervening mesentery (Figure 21.4). e divided
edge of the mesentery is a crucially important landmark
and provides the starting point for transverse mesocolic
mobilization and division [11–13].
Middle colic
adipovascular pedicle
To mesenteric
root region
Figure 21.5 Laparoscopic view of the transverse
mesocolon that has been spread and thereby “opened
up,” to expose the middle colic vascular pedicle.
Thisactivity is crucial in identifying the transverse
mesocolon and permitting its division.
from mesenteric
root region
Lesser
sac
Transverse
mesocolon
Undersurface of
Transverse
mesocolon
Identication of the mesenteric margin
e patient is placed in a slight head up position. e greater
omentum attached to the stomach is deected up under the
le hemidiaphragm. e le colon (just distal to the splenic
exure) is lied toward the anterior abdominal wall and to
the le. e transverse colon (just proximal to the splenic
exure) is lied toward the anterior abdominal wall and to
the right. e tension created is transmitted to the mesocolon that is “opened out” (Figure 21.5). ese activities expose
the divided margin of the mesocolon (Figure 21.6). e
mesocolon can be directly divided at this point because the
greater omentum has been dissected o the upper surface of
the transverse mesocolon (see earlier). Mesocolic division
using a tissue sealant device is continued until the middle
colic adipovascular pedicle is reached near the midline.
Mesenteric
Figure 21.6 (See also QR 1/8.) Laparoscopic view differentiating avascular mesenteric regions on either side of the
middle colic adipovascular pedicle.
Lesser sac
Laparoscopic/robotic division of the
middlecolic adipovascular pedicle
e middle colic vessel originates from the superior mesenteric artery at the mesenteric root region (Figure 21.7).
is relationship is important to bear in mind. If dissection
304 Mesenteric considerations in resection ofthetransverse colon
n
Skeletonization of middle colic vessel
Lesser sac
T
Middle colic artery
Clipping and division of middle colic vessels
Root of mesentery
(a)(b)
c
Superior
mesenteric
artery
Middle
colic
artery
Superior
mesenteri
artery
Middle
colic
artery
Figure 21.7 (See QR 1/4.) Digital image demonstrating the relationship between the middle colic adipovascular pedicle
and the mesenteric root region. (a) View from the right side. (b) View from the left side.
of the middle colic is too low, then the superior mesenteric
artery could be compromised. To avoid this, the middle
colic is best divided high up along its mesenteric pedicle.
e approach is based on the presence of avascular mesenteric regions occurring on either side of the middle colic
vascular pedicle (Figure 21.8).
e avascular mesentery, on either side of the pedicle,
is divided using a tissue sealant device such as the harmonic scalpel. is isolates the pedicle for further dissection. efat of the pedicle is slowly dissected through in
a stepwise and gradual manner under high magnication.
Given that the greater omentum was already freed from the
upper surface of the mesocolon, the middle colic vessel can
be skeletonized circumferentially. Once exposed, it can be
securely clipped (or stapled) and divided (Figure21.9).
Where there is an artery there is a vein and so care
must be taken to identify this and manage it using the
same approach (Figure 21.9). At the right side of the
middle colic adipovascular pedicle, a further interpedicular mesocolic region occurs between the right (present in 25%) and middle colic vessels. This again can be
directly divided as the greater omentum was separated
off the transverse mesocolon as described earlier. This
completes laparoscopic transverse mesocolic mobilization [11–13] .
Middle colic vessel
Transverse mesocolo
Figure 21.8 Laparoscopic isolation of the middle colic
pedicle by dividing avascular mesocolic regions on
eitherside.
ransverse mesocolon
Middle colic vein
Transverse mesocolon
Lesser sac
Figure 21.9 Laparoscopic view of middle colic vein after
skeletonization and clip application.
Open transverse mesocolic mobilization and division 305
Greater omentum
Omentocolic reflection
Omentocolic reflection (open surgery)
OPEN TRANSVERSE MESOCOLIC
MOBILIZATION AND DIVISION
e principles here are identical to that of laparoscopic/
robotic mobilization of transverse mesocolon and, similarly,
are entirely mesenteric and peritoneal based. It is usually conducted as part of total mesocolectomy. In keeping with this,
the splenic exure has been detached, the inferior mesenteric
adipovascular artery, and vein divided. As for laparoscopic/
robotic mobilization, a mesenteric margin will be apparent,
which serves as a starting point for transverse mesocolic
mobilization (see the “Mobilization from the le” section).
Mobilizing the greater omentum from the
transverse mesocolon
e greater omentum is attached to the transverse colon and
mesocolon at four points. ese include (1) the omentocolic
reection, (2) focal adhesions between the undersurface of
the omentum and the cephalad surface of the mesocolon,
fusion with the (3) hepatocolic peritoneal reection and
(4) the splenocolic reection. Most surgeons commence
mobilization in the midline with division of the omentocolic
reection.
e greater omentum is lied upward placing tension
on the reection between it and the upper surface of the
transverse colon (Figure 21.10). e reection is divided
through and adhesions between the greater omentum and
the cephalad aspect of the transverse mesocolon divided.
Oen the degree of fusion between greater omentum and
underlying mesocolon can hamper identication of the
correct plane of dissection here. If there is doubt, then it is
important to err toward the greater omentum and not into
mesocolon. ere may be some bleeding, but this is usually controlled with artery clips. If one digresses into an
intramesocolic plane then bleeding is more extensive and
dicult to control. Sometimes nonanatomic dissection
is impossible to avoid. Notwithstanding this one should
always aim to return to the correct plane of dissection as
quickly as is feasible.
Due to the coalescence of greater omentum with the
hepatocolic reection on the right and the splenocolic
reection on the le, it can sometimes be dicult to
identify a plane in these regions. is region of anatomy
is poorly understood and represents an area for future
development.
Mobilization from the left
In general, the surgeon will be approaching from the le side
of the midline, as in a total mesocolectomy. In this case, the
divided edge of the le mesocolon will be apparent and is
an important starting landmark for division (Figure21.11).
einferior mesenteric vein (IMV) may be apparent and
can be isolated, clipped, divided, and ligated. Isolation of
the IMV again depends on the presence of avascular mesentery on either side of it (Figure 21.11). Such is the relative
importance of the free margin of the mesentery on the le
that an illustration from an alternative view point (i.e., from
below to up) is provided in Figure 21.12.
Transverse colon
Figure 21.10 Intraoperative view of the omentocolic
reection and its division, thereby partially separating the
greater omentum from the upper surface of the transverse mesocolon.
Mobilization from the right
e hepatocolic reection has usually been divided up to
the point at which the greater omentum adheres to it. In
general, coalescence of the two structures is such that they
cannot be separated and the surgeon divides through the
greater omentum. is exposes the upper surface of the
transverse mesocolon. e later is simply detached from
the underlying fascia by mesofascial separation in this
region. is is continued from lateral to medial until further detachment is impeded by the mesenteric root region
where the superior mesenteric artery comes through the
pancreas (Figure 21.13).
The mesenteric root region
All that remains for complete mobilization and separation
of the transverse mesocolon is for its division at the mesenteric root region. Here, the middle colic pedicle arises
from the superior mesenteric pedicle and passes toward the
transverse mesocolon. e middle colic vessel can give o
the right colic, when this is present (Figure 21.14a), before
it divides into its main branches. In general, it is usually
safest to divide the main branches rather than the middle
306 Mesenteric considerations in resection ofthetransverse colon
Skeletonization of inferior mesenteric vein
vein pedicle
(b
my
t
Left
mesocolon
Peritonoto
margin of lef
mesocolon
Duodenum
under
retraction
(a)
mesocolon
Inferior
mesenteric
)
Left
Duodenum
under
retraction
Figure 21.11 (a) The free margin of the left mesocolon as observed from above (i.e., from the head) to below (to the feet).
The inferior mesenteric vein is apparent. (b) The inferior mesenteric vein after its isolation and skeletonization.
Open transverse mesocolic mobilization and division 307
in left mesocolon
Free margin of the left mesocolon (alternate view)
Transverse colon mobilized off the pancreas
ry
(a)
Left mesocolon
Duodenum Mesenteric free margin
Figure 21.12 (See also QR 2/10.) The free edge of the left mesocolon as viewed from below superiorly.
Second part
of duodenum
Head of
pancreas
Root region
of mesente
Figure 21.13 (a) The second part of the duodenum and head of pancreas are exposed once the transverse mesocolon has
been mobilized off via mesofascial separation. This process is impeded at the mesenteric root region where the superior
mesenteric artery comes through from behind the head of the pancreas. (Continued)