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6 History
safe surgery, a factor that is likely to have aided in their
indoctrination in mainstream literature. Not surpris-
ingly, they were adopted comprehensively in most ana-
tomic, embryologic, and surgical texts and to the present
they form the basis of introductory chapters in reference
textbooks. It is remarkable that even today, case reports
continue to emerge describing the presence of a right or
left mesocolon (now known to be correct) as anomalous or
pathologic [1,5,6].
LIMITED SUPPORT FOR TOLDT’S
OBSERVATIONS
Toldt’s findings were supported by the observations of
Broesike (1891), Vecchi (1910), Vogt (1926), and Congdon
(1942) [12]. Gerota (1895) and Southam (1923) described
an “anterior renal fascia” (also referred to as the lat-
eroconal fascia or Gerota’s fascia) as being “fusional in
nature,” thereby touching on Toldt’s concept of adhe-
sion [13,14]. In a review of the topic in 1942, Congdon
noted that only a single reference anatomic text men-
tioned Toldt’s fascia, that is, Poirier and Charpy’s text
of anatomy [15]. Congdon also noted that at that time,
several anatomic texts including that of Waterston,
Last, Cunningham, and Grant omitted the fascia from
contained illustrations. Toldt’s observations received
little if any attention following Congdon’s corroboration
of them. It is not known why this occurred. Reference
in anatomic texts was, and to this day remains, scant.
Although surgical texts can be credited with a little more
emphasis, this has also remained limited [16]. The tide
may be turning however as the most recent edition of ref-
erence anatomic texts such as Gray’s Anatomy acknowl-
edge continuity of the mesentery, as well as the presence
of Toldt’s fascia between mesentery and the retroperito-
neum [4].
‘The mesocolon extends along the entire length
of the colon and is continuous with the small
bowel mesentery proximally and the meso-
rectum distally … Toldt’s fascia lies immediately
posterior to the mesocolon, where it is adherent
to the retroperitoneum of the posterior abdom-
inal wall’ (Culligan et al. 2014).
In the main, Treves’ arguments supporting discon-
tinuity were adopted in general and specialty literature
[5,6]. Mesenteric discontinuity meant that the right and
left mesocolon were, in general, considered absent in the
majority of adult humans. If they were present, then they
were regarded as abnormal or pathologic. In an attempt to
reconcile Treves’ descriptions with theories on the embry-
ologic development of the mesentery, two theories were
developed. ese were attempts at explaining mesenteric
regression or obliteration and were called the sliding and
regression theories [17–19].
RADIOLOGY
One of the best ways of appraising living anatomy in its undis-
turbed format is through radiologic imaging. Radiologists
continue to try reconciling the radiologic appearance of
the mesentery and associated peritoneum, with Treves’
descriptions. Not surprisingly, many articles on the topic of
mesenteric and peritoneal radiology open with a statement
asserting the complexity of the fi ld in general [20,21].
As mentioned earlier, and in keeping with other disci-
plines, radiologic appraisals of mesenteric anatomy adhere
to the descriptions of Treves. Earlier radiologic techniques
relied on the injection or consumption of radiopaque con-
trast to outline the intestinal lumen. ese provided lim-
ited information on structures outside the intestine, which,
for the most part, had to be inferred. e groundbreaking
development of computerized axial tomography (CT) and
magnetic resonance imaging (MRI) meant that structures
outside the intestinal tract could now be visualized. With
this development, radiologists attempted to reconcile CT
and MRI appearances of the mesentery, with classic ana-
tomic teaching, and diculty was again encountered.
To address this problem, Oliphant (1982) suggested that
the mesentery was continuous with the retroperitoneum
(Figure 1.6), leading to the concept of the “subperitoneal
space of Oliphant” (Figure1.6) [22]. In 1986, Dodd indi-
cated that the then current theories of mesenteric anat-
omy could not be correlated with the shapes observed on
CT imaging. Hesuggested that in order to reconcile both
fi lds (i.e., radiologic and anatomic), the mesentery was
best considered as being entirely extra-retroperitoneal
pcl
tm
srl
sim
im
dcl
hdl
lt
gsl
ghl
Figure 1.6 Schematic illustration demonstrating
Oliphant’s interpretation of the subperitoneal space.
Laparoscopic and robotic surgery: The craft of colorectal surgery 7
[23]. e theory of Oliphant gained acceptance, while that
of Dodd went largely unnoticed until recently (see the
“Anatomic continuity: a simpler principle” section).
More recently still, Charnsangavej et al. exploited
vascular markings in order to identify mesenteric regions
on abdominal CT [20,21,24]. is approach is practical and
readily adopted, which likely explains its widespread use.
However, the sentiment expressed by Dodd (that the CT
appearance of the mesentery is dicult to correlate with
prevailing anatomic concepts) still holds.
RENAISSANCE IN FOCUS
ON THE MESENTERY
Interest in the mesentery increased with the realization
thatwhen the mesentery associated with the rectum (i.e.,the
mesorectum) was fully excised for rectal cancer, the inci-
dence of recurrent cancer decreased signifi antly. e con-
cept was termed “total mesorectal excision.” Although total
mesorectal excision had been conducted worldwide and
for decades, the anatomic basis for its success was a recent
discovery. In 1982, Heald etal. showed that a plane occurs
between the mesorectum and the pelvis and that dissection
in this plane, “the holy plane,” enabled a total mesorectal
excision (Figure1.7) [25,26]. Th s was a highly signifi ant
anatomic description as it provided surgeons with a fail-
safe anatomic roadmap, which, if adhered to, led to better
outcomes for patients with rectal cancer. Initial uptake of
the anatomic principle was begrudgingly slow, but it has
now gained worldwide acceptance. Surprisingly, Heald and
coworkers did not extrapolate the same anatomic basis to
the remainder of the colon and mesocolon.
LAPAROSCOPIC AND ROBOTIC SURGERY:
THE CRAFT OF COLORECTAL SURGERY
During the 1990s, the development of laparoscopic and
minimally invasive surgery (and subsequently robotic tech-
niques) revolutionized intestinal surgery by providing high
magnifi ation (greater than 20-fold) and high-resolution
anatomic imagery. Just as the principles of laparoscopic
and robotic intestinal surgery emerged, terminologies such
as “mesocolon” and “Toldt’s fascia” were increasingly uti-
lized. For laparoscopic and robotic colorectal surgery to be
safe and repeatedly successful, the surgeon must adhere to a
universally reproducible anatomic roadmap. Unfortunately,
the anatomic basis for laparoscopic and robotic intestinal
surgery was also sketchily developed [5,27]. Th s asser-
tion may be considered as unexpected, given surgeons for
decades practiced technically superb resections in the open
context. It is not surprising, however, when one considers
that descriptions of open, laparoscopic and robotic surgi-
cal techniques are hallmarked by limited reference to the
mesentery, the associated peritoneum and fascia.
A brief illustration of this point is important at this junc-
ture. e mesofa scial plane is a key plane throug hout colorec-
tal surgery. Access to it is universally gained by division of
the overlying peritoneal reection. Peritonotomy (i.e., divi-
sion) of the reection and separation of plane components
are core colorectal activities and are universally required
for colorectal resection. Despite being centrally important,
their anatomic basis has only recently been described.
Focus on the anatomic and surgical importance of the
mesentery increased further when Werner Hohenberger
described superb results for patients undergoing a “com-
plete mesocolic excision” for colon cancer (Figure 1.8)[28].
Figure 1.7 Professor R.J. (Bill) Heald, OBE, MChir,
FRCS(Ed)(Eng).
Figure 1.8 Professor Werner Hohenberger, MD, PhD.
8 History
In his 2009 article, he demonstrated that by applying
anatomic principles, one could achieve an R0 resection
(i.e., clearance of all microscopic disease) in 97% of cases.
Around the same time, West etal. demonstrated the eff cts
of anatomic dissection on colon cancer outcomes. eir
ndings suggested that by adopting a strictly anatomic
approach, one could enhance patients’ survival following
surgery for stage three colon cancer [29,30]. ese ndings
went a considerable distance in demonstrating the associa-
tion between anatomic surgery and better cancer-specic
outcomes.
Remarkably, however, a unifying anatomic principle
that could reconcile anatomic with established surgi-
cal approaches to the colon, rectum, and small bowel
remained elusive.
ANATOMIC CONTINUITY: A SIMPLER
PRINCIPLE
In 2012, a study was performed involving collaboration
between the Department of Surgery in University Hospital
Limerick, Ireland, and the Department of Colorectal Surgery
at the Digestive Diseases Institute at e Cleveland Clinic, in
which the anatomic structure of the small and large intestinal
mesentery was formally clarifi d (Chapter2) [31]. Crucially,
the authors demonstrated that the small intestinal and colonic
mesenteries are dierent regions of the same anatomic struc-
ture and that the mesentery itself spans the intestinal tract
from the duodenum to the junction between the rectum and
anus (Figure 1.9). Th s was a considerable departure from
the classic depictions as it meant that the mesenteric organ is
asubstantive and continuous structure, and not fragmented
or discontinuous as was generally described [32,33].
e newer appraisal was far simpler than the classic
description. Recognition of continuity led to similar obser-
vations on the peritoneal refl ction and Toldt’s fascia. Itis
now accepted that Toldt’s fascia is continuous from the origin
of the mesenteric organ (at the superior mesenteric artery)
to its termination at pelvic fl or. Similarly, the peritoneum
is draped in a contiguous manner over intraperitoneal struc-
tures from the root region to the so-called anterior refl ction
in the pelvis [32,33].
FUTURE DIRECTIONS
Anatomic continuity and contiguity of mesentery, fascia,
peritoneal reection, and gastrointestinal tract has major
implications at numerous levels and across multiple special-
ties (clinical and nonclinical). ese form the basis and con-
tent of this book. For the surgeon, continuity and contiguity
mean that the same anatomic technical elements can be uni-
versally used to perform a safe intestinal resection [33]. For
the abdominal radiologist, they enable a clearer understand-
ing of the type and extent of intraperitoneal disease [33].
Perhaps most importantly, identication of continuity and
clarication of anatomy now permits the systematic (i.e., sci-
entic) study of the mesentery and associated structures [33].
SUMMARY
ere are numerous incidents in the history of medicine
where an inaccurate understanding of structure was dog-
matically integrated in literature. William Osler wrote that
“the greater the ignorance the greater the dogma.” Recent
clarication of mesenteric structure has presented a far sim-
pler structure than heretofore thought. e following chap-
ters will describe the scientic opportunities that stem from
this clarication. In addition, it will explain the mesenteric
basis of clinical practice.
REFERENCES
1. Treves, F., Lectures on the anatomy of the intesti-
nal canal and peritoneum in man. Br Med J, 1885.
1(1264): 580–583.
2. McConnell, A.A. and T.H. Garratt, Abnormalities
of xation of the ascending colon: The relation of
symptoms to anatomical ndings. Br J Surg, 1923. 10:
532–557.
3. Netter, F.H., Atlas of Human Anatomy. Elsevier
Health Sciences, Philadelphia, PA, 2014, pp. 263–276.
4. Standring, S., Gray’s Anatomy: The Anatomical Basis
of Clinical Practice. Elsevier Health Sciences, London,
U.K., 2015, Chapter 62, pp. 1098–1111, 1124–1160.
5. Coffey, J.C., Surgical anatomy and anatomic
surgery—Clinical and scientic mutualism. Surgeon,
2013. 11(4): 17 7–182 .
Transverse
colon
Right
mesocolon
Right
colon
Mesosigmoid
Mesorectum
Sigmoid colon
Rectum
Anorectal
junction
Transverse
mesocolon
Left
mesocolon
Figure 1.9 (See also QR 1 and 7.) The mesenteric organ.
The illustration is of a model of the mesentery generated
using a 3D printer. Pan-mesenteric continuity is demon-
strated (from the duodenum to the anorectal junction).
References 9
6. 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.
7. Toldt, C., Bau und wachstumsveranterungen
der gekrose des menschlischen darmkanales.
Denkschrdmathnaturwissensch, 1879. 41: 1–56.
8. Toldt, C., An Atlas of Human Anatomy: For Students
and Physicians, Vol. 6: Primary Source Edition.
BiblioBazaar, 2013.
9. Toldt, C. and A.D. Rosa, An Atlas of Human Anatomy
for Students and Physicians. Macmillan, New York,
1926.
10. Cohen, M.M., Jr., Further diagnostic thoughts about the
Elephant Man. Am J Med Genet, 1988. 29(4): 777–782.
11. Treves, F., Discussion on the subsequent course and
later history of cases of appendicitis after operation.
Med Chir Trans, 1905. 88: 429– 610.
12. Congdon, E.D., R. Blumberg, and W. Henry, Fasciae
of fusion and elements of the fused enteric mesenter-
ies in the human adult. Am J Anat, 1942. 70: 251–279.
13. Chesbrough, R.M. etal., Gerota versus Zuckerkandl:
The renal fascia revisited. Radiology, 1989. 173(3):
845–846.
14. Amin, M., A.T. Blandford, and H.C. Polk, Jr., Renal
fascia of Gerota. Urology, 1976. 7(1): 1– 3.
15. Poirier, P. and A. Charpy, Traité D’Anatomie Humaine
Publié Sous la Direction de P Poirier et a Charpy.
BiblioBazaar, Charleston, SC, 2010.
16. Goligher, J., Surgery of the Anus Rectum and Colon.
All India Traveller Book Seller, 1992.
17. Moore, K.L., T.V.N. Persaud, and M.G. Torchia, The
Developing Human: Clinically Oriented Embryology.
Elsevier Health Sciences, Philadelphia, PA, 2015,
pp.210–239.
18. Sadler, T.W., Langman’s Medical Embryology. Wolters
Kluwer Health, Philadelphia, PA, 2011, pp.208–232.
19. Schoenwolf, G.C. etal., Larsen’s Human Embryology.
Elsevier Health Sciences, Philadelphia, PA, 2014,
pp.341–374.
20. Charnsangavej, C. etal., CT of the mesocolon.
Part1. Anatomic considerations. Radiographics,
1993. 13(5): 1035–1045.
21. Charnsangavej, C. etal., CT of the mesocolon.
Part2. Pathologic considerations. Radiographics,
1993. 13(6): 1309 –1322.
22. Oliphant, M. and A.S. Berne, Computed tomography
of the subperitoneal space: Demonstration of direct
spread of intraabdominal disease. J Comput Assist
Tomo g r, 1982. 6(6): 112 7–113 7.
23. Dodds, W.J. etal., The retroperitoneal spaces revis-
ited. Am J Roentgenol, 1986. 147(6): 1155 –1161.
24. Coffey, J.C. etal., An appraisal of the computed
axial tomographic appearance of the human mes-
entery based on mesenteric contiguity from the
duodenojejunal exure to the mesorectal level.
EurRadiol, 2016. 26(3): 714 –721.
25. Heald, R.J., The “Holy Plane” of rectal surgery.
JRSoc Med, 1988. 81(9): 503–508.
26. Heald, R.J., E.M. Husband, and R.D. Ryall, The
mesorectum in rectal cancer surgery—The clue
to pelvic recurrence? Br J Surg, 1982. 69(10):
613 – 616.
27. Coffey, J.C. etal., Terminology and nomencla-
ture in colonic surgery: Universal application of
a rule-based approach derived from updates on
mesenteric anatomy. Tech Coloproctol, 2014. 18(9):
789–794.
28. Hohenberger, W. etal., Standardized surgery for
colonic cancer: Complete mesocolic excision and
central ligation—Technical notes and outcome.
Colorectal Dis, 2009. 11(4): 354–364; discussion
364–365.
29. West, N.P. etal., Pathology grading of colon cancer
surgical resection and its association with survival:
A retrospective observational study. Lancet Oncol,
2008. 9(9): 857–865.
30. Coffey, J.C. and P. Dockery, Colorectal cancer:
Surgery for colorectal cancer—Standardization
required. Nat Rev Gastroenterol Hepatol, 2016.
13(5): 256–257.
31. Culligan, K. etal., The mesocolon: A prospective
observational study. Colorectal Dis, 2012. 14(4):
421–428; discussion 428–430.
32. Coffey, J.C. etal., Mesenteric-based surgery exploits
gastrointestinal, peritoneal, mesenteric and fas-
cial continuity from duodenojejunal exure to the
anorectal junction—A review. Dig Surg, 2015. 32(4):
291–300.
33. Coffey, J.C. and D.P. O’Leary, The mesentery:
Structure, function, and role in disease. Lancet
Gastroenterol Hepatol. 1(3): 23 8 –2 47.
11
2
Mesenteric and peritoneal anatomy
J. CALVIN COFFEY, PETER DOCKERY, BRENDAN J. MORAN, AND BILL HEALD
There is pleasure in recognising old things from
a new viewpoint.
Richard Feynman
AIM
e aim of this chapter is to summarize mesenteric and
peritoneal structure in light of recent advancements in
our understanding of both. A second aim is to indicate the
relevance of both to current clinical practice.
INTRODUCTION
e magnication aff rded by endoscopic techniques
coupled with the resolution of modern displays has revolu-
tionized our appraisal of living anatomy. Nevertheless, ref-
erence anatomic and embryologic texts continue to present
classic anatomic descriptions. In keeping with this, classic
descriptions of mesenteric and peritoneal anatomy continue
to dominate reference texts. Sir Frederick Treves compre-
hensively described the human mesentery and peritoneum
in a study spanning 100 cadavers in 1889 (Figure 2.1) [1].
His descriptions were rst presented in a series of classic lec-
tures and thereaer integrated in most reference anatomic,
embryologic, surgical, and radiologic texts [1–11]. Treves laid
down his understanding of mesenteric and peritoneal anat-
omy at a time when anatomic descriptions were providing a
formal basis for safe and anatomic surgery (Figure 2.1) [1,9].
Treves correctly described the small intestinal mesentery
as having a “mesenteric root” at the origin of the superior
mesenteric artery. According to his descriptions, the small
intestinal mesentery then fans out from the duodenum to
terminal ileum. At the gastrointestinal margin, the mes-
entery elongates considerably. is contrasts considerably
with the length of the “attachment” to the posterior abdom-
inal wall. As per Treves, the mesenteric attachment extends
across the posterior abdominal wall from duodenojejunal
exure to ileocecal level. As it does so, it obliquely traverses
the aorta and inferior vena cava (Figure 2.2a and b) [1,12].
Treves described the right and left mesocolon as being
absent in the majority of cases. If an anomalous right or le
mesocolon was present, then this would be seen to attach
in regions corresponding closely to the attachment of the
right or left colon (Figures 2.1 and 2.2a,b). For example, the
attachment of the right mesocolon corresponds to that of
Aim 11
Introduction 11
Mesenteric anatomy 14
Mesenteric root region 14
Mesentery in the right iliac fossa 14
Small intestinal mesentery 14
Right mesocolon 16
Adipovascular and avascular mesentericregions 16
Hepatic exure 17
Transverse mesocolon 20
Relationship between transverse mesocolon and
greater omentum 20
Middle colic adipovascular pedicle 20
Splenic exure 20
Left mesocolon 20
Inferior mesenteric adipovascular pedicle 22
White line of Toldt 22
Mesosigmoid 25
Mesosigmoid: Transverse axis 25
Mesosigmoidal angles 25
Congenital adhesions 26
Mesorectum 28
The peritoneal reection 28
Flexural anatomy 34
Duodenojejunal and ileocecal exures 34
Hepatic exure 34
Splenic exure 38
Colosigmoid and rectosigmoid exures 38
Mesenteric conformation ingeneral 38
Future directions 38
Summary 38
References 38
12 Mesenteric and peritoneal anatomy
Attachment
of left colon
(i.e., left
mesocolon)
Attachment of
mesosigmoid
Attachment
of small
intestinal
mesentery
Attachment
of right colon
Mesenteric attachments: classic teaching
Attachment
of transverse
mesocolon
Figure 2.1 Schematic demonstrating the attachments of the mesentery as depicted by Treves. The small intestinal
mesentery attaches along a diagonal line crossing the posterior abdominal wall from the fourth part of the duodenum
tothe ileocecal junction.
Mesentery and attachments: classic vs. current
Mesentery:
classic teaching
(a) (b)
Right
mesocolon
Left
mesocolon
Mesosigmoidal
attachment
Transverse
mesocolon
Mesosigmoid
Vestigial
lef
t mesocolon
Mesenteric attachments:
classic teaching
Figure 2.2 (a) Schematic summarizing Treves’ descriptions of the attachment of the mesentery and mesocolon (red region).
As per Treves, when an anomalous right mesocolon is present, it attaches along a vertical trajectory from the right iliac fossa
to the hepatic exure. The transverse mesocolon attaches along a horizontal line that traverses the upper part of the abdo-
men. When an anomalous left mesocolon is present, it attaches along a vertically oriented region, while the mesosigmoid
attaches along a v-shaped line. The attachment of the mesorectum was not dened by Treves. (b) 2.5D snapshot from a
3Ddigital sculpture of the mesocolon (yellow) as depicted by Treves. The small bowel and associated mesentery have been
conceptually removed for clarity. The right and left mesocolon are vestigial or near absent, while the transverse and sigmoid
regions are substantial. The mesorectum is absent. Overall, the mesentery is fragmented and discontinuous. (Continued)
Introduction 13
the right colon, extending along a vertical orientation from
the right iliac fossa to the subhepatic region. e attachment
of the left mesocolon corresponds to that of the left colon,
extending from the subsplenic region to the left iliac fossa
(Figures2.1 and 2.2a, b) [1]. To the present, many reference
texts continue to describe these regions as the attachments
of the right and left olon or mesocolon [3–5,13,14].
Treves’ description of the transverse and sigmoid meso-
colon was similar to that of the small intestinal mesentery.
He described the transverse mesocolon as being “attached”
along a horizontal trajectory to the upper part of the posterior
abdominal wall (Figure 2.2a andb). He described the meso-
sigmoid as attaching to the posterior abdominal wall in the le
iliac fossa. e attachment followed an inverted V shape, with
the apex of the “V” providing an important landmark overly-
ing the left ureter (where this crosses the bifurcation of the
common iliac artery) (Figure 2.2a and b) [2,4,6,14,15].
e mesosigmoid, transverse mesocolon, and small
intestinal mesentery were described as mobile, while the
right and left mesocolon were described as absent (or vesti-
gial) [4,6,8,9,13,14]. According to this, the mesenteric organ
is fragmented (present in some regions, absent in others).
If this description were correct, then one would expect to
identify start and end points for each mesenteric region.
ese were never described, a point that is explained by
their absence in the rst place [10].
A question arises as to how Treves’ generated his fi dings.
His descriptions can be explained if one were to conceptu-
ally slice through the posterior region of the abdomen in a
coronal plane, that is, (1) posterior to the right and left colon
and (2) at the level where the small intestinal mesentery
attaches to the posterior abdominal wall (Figures 2.1 and
2.2b). Doing this would generate the impression of a series of
mesenteric insertions for the small intestine, transverse, and
sigmoid mesocolon [10,16,17]. In addition, it would fail to
identify the right and left mesocolon as well as the attached
region of the mesosigmoid and mesorectum.
In 2012, our group refuted the findings of Treves
demonstrating mesenteric continuity from small intes-
tinal mesentery to mesorectal level (Figure 2.2c and d)
[10]. This led to a general overhaul of our understand-
ing of mesenteric anatomy [2]. We found that the small
intestinal mesentery attaches to the posterior abdomi-
nal wall and extends laterally as the right mesocolon
(Figures 2.2c, d, 2.3, 2.4). Along the line of attachment,
a peritoneal reflection extends from the small intestinal
mesentery to the posterior abdominal wall and bridges
the gap between the two. The line along which the small
intestinal mesentery attaches to the posterior abdomi-
nal wall (and continues laterally as the right mesocolon)
extends diagonally from the duodenojejunal junction to
the ileocecal level.
Right mesocolic
and small bowe
l
mesenteric
attachment
Left
mesocolic
attachment
Mesosigmoidal
attachment
Left
mesocolon
Mesosigmoid
Mesorectu
m
Mesenteric attachments:
current teaching
Mesentery:
current teaching
(d)(c)
Figure 2.2 (Continued ) (c) Schematic summarizing the attachment of the mesocolon (yellow region) as described by
Toldt. The right mesocolon is always present and attaches over a broad region on the right side of the posterior abdomi-
nal wall. Theleft mesocolon is always present and attaches over a similarly broad region on the left side of the abdomen.
Themesosigmoid is a distal continuation of the left mesocolon. (d) (See also QR 1/1.) 2.5D snapshot from a 3D digital
sculpture of the mesocolon (yellow) as it is currently understood. The distal small bowel and associated mesentery have
been retained in the illustration. The right and left mesocolon are substantial and continuous with adjacent regions of mes-
entery. The right mesocolon is continuous withthe small intestinal mesentery medially and with the transverse mesocolon
at the hepatic exure. On the left, the left mesocolon, mesosigmoid, and mesorectum are similarly continuous. Overall,
the mesentery is continuous from root region to the mesorectum.
14 Mesenteric and peritoneal anatomy
MESENTERIC ANATOMY
Mesenteric root region
e following is a description of mesenteric anatomy as it
is currently understood. Before commencing, it is impor-
tant to dene the terms “attachment” and “suspension.”
“Attachment” refers to the attening of the mesentery
against the posterior abdominal wall so the mesentery
becomes apposed to the retroperitoneum. As will be seen
from the following, the mesentery does not “insert” into
the posterior abdominal wall in any location. “Suspension”
refers to the suspension of the mesentery to the posterior
abdominal wall at vascular points of suspension.
e mesentery fans out from the “root region” where
the superior mesenteric artery suspends it to the posterior
abdominal wall. is was correctly described by Treves [1].
From this point, the mesentery expands, like a Chinese fan.
In some regions, it is mobile while in others it is attached
to (i.e., attened against) the posterior abdominal wall. e
continuous mesentery spans the intestine from duodenoje-
junal to anorectal junction.
Mesentery in the right iliac fossa
In the right iliac fossa, the mesentery tapers toward an apex
at the ileocecal junction. Th s region of mesentery can be
arbitrarily called “the ileocecal mesenteric conuence,”
a term that is descriptively useful (see section “Flexural
anatomy”). A fatty appendage (the mesoappendix) extends
from the under surface of the ileocecal mesenteric conuence
(Figure 2.5a throughc). Retromesenteric origin of the meso-
appendix explains how the appendix oen occupies a retroce-
cal location (the clinical relevance of this will be expanded
on in Chapter 7) (Figure2.5a through c). Treves correctly
described the mesoappendix as originating from the under-
surface of the mesentery in the ileocecal region [1,12].
e ileocecal mesenteric conuence is a substantive tissue
mass separated from the retroperitoneum by Toldt’s fascia.
When the abdomen is rst entered, the conuence is obscured
from direct view by a peritoneal reection. isis an extension
of the peritoneal reection at the base of the small intestinal
mesentery. Regions of the peritoneal reection are of surgical
and pathobiologic importance, as mobilization of the mesen-
tery requires their division to permit access to surgical planes.
In addition, they act as a mechanical barrier to the spread of
submesenteric disease (see Chapters 6 and 7) [18].
Small intestinal mesentery
ough the base of the small intestinal mesentery (i.e.,
whereit continues as the right mesocolon) is short, the intes-
tinal margin of the small intestinal mesentery is approxi-
mately 4 ft in length [10,18]. As a result, the mesentery
Mesentery
(d)(c)
Mesentery and intestine
Peritoneum, mesentery,
fascia, and intestine
(a)
Mesentery,
fascia, and intestine
(b)
Legend
Mesentery PeritoneumColonFascia
Figure 2.3 (a) (See also QR 2/1.) 2.5D snapshot from a 3D digital sculpture of the mesentery, associated peritoneal reec-
tion, and large bowel. Just as the mesentery is contiguous so too is the peritoneal covering and associated large bowel.
(b) Same model as in (a) but with peritoneum removed. (c) Same model as in (b) but with peritoneum and fascia removed.
(d) Same model as in (c) but peritoneum, fascia, and colon removed.
Mesenteric anatomy 15
Small
intestional
mesenter
y
Ascending colon
Transverse
colon
Transverse mesocolon
(a)
(c)
(d)
(b)
Right
mesocolon
Right
mesocolon
Small intestinal
mesentery
Small intestional
mesentery
Right
mesocolon
Small intestinal mesentery and right mesocolon
Figure 2.4 (a) (See also QR 3/1.) 2.5D snapshot of a 3D digital sculpture of the small bowel mesentery and right
mesocolon. The model has been sectioned and the point of view is looking from above downward. The small intestinal
mesentery is continuous with the right mesocolon. (b) (See also QR 4/1.) The model used in (a) has been sectioned
through at the same level, but the point of view now is from below upward. The small intestinal mesentery is continuous
with the right mesocolon. (c) Cadaveric demonstration of continuity between the small bowel mesentery and right
mesocolon. (d) Intraoperative image depicting mesenteric and mesocolic continuity.