MESENTRY

1. Kurdistan Board GEH/GIT Surgery J Club 2022
Supervised by Professor Dr. Mohamed Alshekhani.

2. Introduction:
 The mesentery is the organ in & on which all abdominal digestive organs
develop & remain connected to.
 It is the anatomical foundation of the abdomen & the fundamental order
at that level.
 Findings related to the shape & development of the mesentery have
illuminated its function, advancing our understanding of the pathobiology,
diagnosis& treatment of several abdominal& systemic diseases.
 Inclusion of the mesentery in surgical resections alters the course of benign
&malignant diseases.
 Mesenteric-based scoring systems can enhance the radiological
interpretation of abdominal disease.
 Emerging findings reconcile observations across scientific & clinical fields
& have been assimilated into reference curricula &practice guidelines.

11. Functions:
 During development,mesentery provides an incubatory support for abd
digestive organs,through the production of protein factors as bone
morphogenetic protein.
 Mesenteric lymph angiogenesis precedes intestinal lymph angiogenesis.
 The mesenteric organogenesis encapsulates the supportive & incubatory
relationship between the mesentery&abd digestive organs.
 The mesentery can sustain organs&organoids:Splenunculi are an
accessory form of spleen that occur in 10%& can arise anywhere in the
mesenteric frame.
 Heterotopic pancreata, ossification, mesenteric teratomas&ectopic
pregnancies identified in different mesenteric locations&int organoids
develop quicker in SI region of the mesentery than omental region.
 The mesentery provides a support frame for transport of energy substrates
& cellular migration.

12. Functions:
 Gonadal progenitor cells first arise in developing endoderm, then migrate
across the mesentery to the gonadal ridge.
 Neural crest cells migrate in the opposite direction to populate the
developing enteric nervous system&its failure is associated with
Hirschsprung’s disease & primary neuroendocrine tumours of the adult
mesentery.
 In Crohn’s disease, circulating fibrocytes extravasate from
intramesenteric vessels & migrate across the mesentery to the serosal
surface of adjoining intestine,all controlled by the topographical release of
trophic factors, including GDNF.
 The anatomical relationship between the developing intestine&adjoining
mesentery is a determinant of gut shape &function.

13. Functions:
 The intestine& mesentery continue to lengthen throughout the human
lifecourse&in Crohn’s, the mesentery encapsulates adjoining intestine as
so-called creeping fat (or fat wrapping)&mesenteric expansion in Crohn’s
induces a marked hyperplasia of neurological, connective tissue, lymphatic
&vascular components in the adjoining intestine.
 Mesenteric function varies by region in adults. The greater omentum
corresponds with the anterior wall of the upper region & adheres to areas
of intestinal inflammation, blocking these off &limiting spread of disease.
If an intestinal perforation occurs, it can be localised to the region in
question by adherence of the greater omentum,so greater omentum termed
policeman of the abdomen. This region of the mesentery & has
immunological / metabolic functions.
 The ileocaecal region of the mesentery corresponds with the periphery of
the mid-region fold & contains a substantive volume of lymphatic tissue.
This most commonly affected region in Crohn’s,frequently affected in
systemic viral infs (as SARS-CoV-2) &multiple/bacterial/parasitic infs.

14. Functions:
 The lymphatic mesentery has important immunological roles, including
the coordination of mucosal immune responses in adjoining intestine
&Sampling of environmental contents (ie, derived from the intestinal
lumen) occurs in the mesenteric interstitium&crucial to the orchestration
of local, regional&systemic immune responses.
 The functions of the mesentery, intestine, pancreas, spleen&liver are highly
integrated.

15. Pathologies:mapping metastatic LNs
 Lymph nodes draining digestive viscera are domain-specific,
intramesenteric in position&their distribution is aligned with the anatomy
of the mesentery.
 Knowledge of the regional anatomy of the mesentery provides the
pathologist with a simpler model to cross-reference when mapping nodal
depots, compared with the peritoneal model.

16. Pathologies: Tumor spread
 The interstitium is a connective tissue lattice in which nerves, blood vessels,
& lymphatics are integrated.
 It is a site of intense Toll-like receptor-based immunological activity.
 Tumour deposits can arise in the mesenteric interstitium, assisted by
cancer-associated fibroblastic activity.
 The mesenteric interstitium is continuous with that of the organs to which
the mesentery is directly connected.
 Mesenteric tumour deposits (including perineura& lymphovascular) are
interstitial & have a poorer prognosis than do lymph node metastases.

17. Pathologies: mesentery in malrotation
 Malrotation is one of the most common surgical emergencies in neonates, if
left unresolved, can lead to volvulus, intestinal necrosis,deathit& is
primarily a mesenteric pathology.
 The sides of the mid-region mesenteric fold normally switch position
(relative to the SMA) between central& peripheral zones.
 Before switching, the sides are aligned from central to peripheral zones;
however, after switching, they no longer align. Thus, if the switch fails to
occur, the sides remain aligned— ie, malrotated.
 In malrotation, the mesentery & intestine are abnormally mobile can twist
(ie, volvulus).
 Malrotation is corrected surgically by recapitulating the mid-region switch
in vivo, thus enabling placement of the intestine& mesentery in a normal
conformation,not just standard Ladd’s procedure, which aims to prevent
volvulus but does not correct the primary mesenteric pathology

18. Pathologies: mesentery in volvulus
 Volvulus is a twisting (or torsion) of the intestine& adjoining mesentery.
 As the intestine increases or decreases in length during&after peristalsis,
the adjoining mesentery smoothens & buckles in tandem.
 If the intestine continues to lengthen, then the shape of the intestine will
progress from a curve to a coil at a particular point.
 When coiling happens, the adjoining mesentery also changes shape from a
buckle to a spiral.
 The resultant coil–spiral complex of the intestine & mesentery is termed
volvulus.
 Normally, volvulus is prevented by adherence/ anchorage of the mesentery
to the posterior abdominal wall.
 If adhesion is inadequate, then the intestine & mesentery can readily
progress from a curve–buckle to a coil–spiral complex (ie, a volvulus).

19. Pathologies: looping during colonoscopy
 Volvulus can also apply to loop formation during colonoscopy,the most
common cause of colonoscopy failure.
 During loop formation, the intestine changes shape from a curve to a coil,
& the adjoining mesentery changes shape from a buckle to a spiral.
 Changes in conformation occur first at points where the intestine is
already curved(&the mesentery is already buckled).
 Understanding the intestinal–mesenteric basis of coil formation enables the
endoscopist to take preventative actions (eg, directed pressure or stiffening
of scope) or corrective actions (eg, limited withdrawal of the scope) to
prevent or reverse coil or spiral formation.

20. Pathologies: mesenteric ischemia
 Acute mesenteric ischaemia can quickly become life-threatening.
 The chronic form has a wasting effect that inexorably leads to marked
deterioration of the patient.
 These outcomes arise due to the fact that arterial inflow to the entire
mesenteric domain is limited to three vessels: the coeliac trunk, SMA&
inferior mesenteric artery,so narrowing or occlusion of the origin of any of
these vessels can become rapidly catastrophic.
 Venous drainage of the mesenteric domain is similarly limited, occurs via
the hepatic veins at the intersection between these veins&IVC.
 Given that venous drainage of the mesenteric domain occurs solely via the
hepatic veins, thrombosis of these veins (eg, Budd-Chiari syndrome) has
major implications for all abdominal digestive organs.

21. Pathologies: mesentery in multisystemic pathos
 The mesentery provides an anatomical frame on which multiorgan or
multisystem pathologies can develop (eg, multiorgan failure).
 The linkage mechanism provided by the mesentery becomes increasingly
important in systemic viraemia (eg, COVID-19).
 Mesenteric lymph nodes provide a relatively inaccessible niche and
potential reservoir site for viral pathogens (including HIV /SARS-CoV-2),
bacterial pathogens (eg, Mycobacterium tuberculosis), parasites (eg,
Trypanosoma brucei species).
 These pathogens can remain in mesenteric nodes, evading immunological
clearance& later re-emerge to exert systemic effects.
 Mesenteric manifestations, including mesenteric lymphadenitis, SMA
thrombosis& portal vein thrombosis, have been reported with COVID-19
& have particularly poor prognoses.

22. Pathologies: mesenteric sclerosis
 A debilitating disease with persistent deterioration in intestinal function,
despite medical & surgical efforts.
 In mesenteric panniculitis, the mesodermal mesentery is inflamed,
thickened, foreshortened, bleeds easily.
 In sclerosing mesenteritis, both sclerosing/ inflammatory abnormalities
are apparent.

23. Pathologies: Radiological assessment
 Mesenteric model vs peritoneal model provides a far simpler standard with
which the radiologist can cross-reference radio depictions of the abd&
contributed to the generation&validation of several radio scoring systems.
 Radiological software is available that enables the radiologist to
reconstruct regions of the mesentery from cross-sectional imaging datasets
 In turn, these tools facilitate the precise quantitation of mesenteric fat,the
single largest contributor to visceral adiposity&visceral adiposity correlate
with the development of multiple systemic dis;CAD,HT,DM, MS& stroke.
 Radiology characterise the shape/volume of the mesentery&is now possible
to establish the relationship between visceral adiposity& systemic dis.
 Combining U/S with colonoscopy (eg, endoscopic mesenterography)
relatively non-invasive means of identifying,sampling&trt the mesentery.
 Radiological localisation of the mesentery during endoscopy enables
transintestinal delivery of therapeutic agents directly into adjoining
mesentery&provides new therapeutics for benign conditions (eg, Crohn’s)
&malignant diseases (eg, mets from int primary tumours&NETs).

24. Trt issues: mesenteric-based surgery for cancer.
 Mesenteric-based approaches for resection of colon,rectal,pancreatic,
gastric&eso cancers are now standard practice.
 The mesentery is excised intact by identifying&following the
embryological plane between the mesenteric domain&non-mesenteric
domain (eg, the mesofascial plane).
 The benefits of mesenteric-based surgery derive from the fact that
tumours mostly develop &spread in a domain-specific manner& unusual
for them to extend beyond the domain of origin,providing a useful law to
direct surgical strategy&technique to remove a tumour by excising the
organ in which it originates & the adjoining mesentery.
 The structures in the adjacent non-mesenteric domain rarely require
excision for successful oncological clearance of tumours of the mesenteric
domain, except to in the relatively infrequent setting whereby a tumour of
the mesenteric domain penetrates into the non-mesenteric domain.
 short-term / long-term outcomes are generally better than in circumstances
in which these anatomical principles are not followed.

25. Trt issues: mesenteric-based surgery for cancer.
 Many spancreatic cancer are unresectable due to local invasion,to
overcome this challenge, pancreatic surgeons are increasingly adopting
either a mesenteric-based or ex-vivo approach,both approaches follow the
mesenteric model of abdominal anatomy.
 The mesenteric approach greatly simplifies even the most complex of
procedures, including multivisceral transplantation, Cattell-Braasch /
Mattox visceral rotation, fluoroscopic reconstruction in vivo&provides the
anatomical basis for post-mortem techniques, described by Rokitanski.

26. Trt issues: mesentery in CD.
 Mesenteric events exert, on balance, a net pathobiological effect in Crohn.
 Surgical techniques aiming to alter mesenteric inputs might ameliorate
disease progression.
 The benefits of stricturoplasty (in which the mesentery is retained) may fit
into a mesenteric-based disease framework.
 Resection or exclusion of the mesentery in patients undergoing surgery for
Crohn’s disease improved outcomes, such as surgical recurrence rates.
 Microbiome profiles in mesenteric lymph nodes can differentiate ulcerative
colitis from Crohn’s disease.
 During surgery, manifestations of mesenteric disease guide placement of
the proximal intestinal division.
 The radiological index of mesenteric disease severity, correlated with
severity of intestinal disease.
 Quantitation of mesenteric fat wrapping increases postop recurrence.
 The cellular, molecular, metaboli& immunological events are associated
with mesenteric abnormalities in patients with Crohn.

27. Trt issues: Multivisceral transplantation.
 A mesenteric-based technique, is increasingly practised for several
advanced pathologies (eg, locally advanced hepatobiliary cancer, intestinal
failure in Crohn’s disease, locally advanced desmoid tumours).
 Understanding the relationship between mesenteric&non-mesenteric
domains provides an intuitive & anatomical roadmap for the
transplantation surgeon, by reducing the technical complexities associated
with excision & re-implantation of individual organs.

28. Trt issues: targeting mesentery in syst diseases.
 The mesentery is a major site of C-reactive protein production,an
important component of glycaemic control.
 The pancreas develops in the mesentery&regions of the mesentery can
support heterotopic pancreata & pancreatic islet cell organoids,support
mesentery being relevant in metabolic physiology.
 Visceral adiposity corresponds to adipose tissue of the mesenteric domain
(ie, fat in the mesentery & conjoined organs).
 Levels of visceral fat correlate with severity of atherosclerosis&related
conditions&reducing mesenteric fat reverses insulin resistance.

29. Trt issues: mesenteric pharmacotherapeutics.
 Clarifying the development & shape of the mesentery allows for systematic
characterisation of mesenteric drug targets (eg, extracellular or
intracellular), techniques by which medications can be delivered to the
mesentery (eg, transintestinal, percutaneous, peritoneal-based), assessment
of mesenteric levels of therapeutic agents&response monitoring.
 Recognition of the mesenteric basis of disease, as well as development of
techniques to investigate this approach, are likely to lead to further
expansion of this nascent field.

34. Conclusion:
 Investigation of the mesentery over the past 5 years refutes the idea that
fundamental advancements in our understanding of nature can only be
made at cellular, molecular, or subatomic levels.
 Clarification of the macroscopic shape of the mesentery provides a new
definition of the mesentery & explains the anatomical foundation&
fundamental order of the abdomen.
 Emerging findings have led to the mesenteric model of abdominal anatomy
& the positional anatomy of all components within the abdomen (including
the peritoneum).
 Ultimately, the mesenteric model of abdominal anatomy is a novel
platform from which the abdomen can be systematically studied in health
&disease.