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Omentum:

Good Cop or Bad Cop?

Omentum – Purpose?

• Hippocrates: formation and absorption of fluid

• Aristotle: protects the intestine against cold

• Vesalius: fixation ligament for the transverse

colon

• Ross (1890’s): protects the intestine against

injury “It is like a man-of-war ready to

sail to any port in which there is impending

trouble”

Sir Rutherford Morison

British Medical Journal 1906

• “A special protective agency…the

abdominal policeman. It travels

around the abdomen with

considerable activity, and is attracted

by some sort of information to

neighborhoods in which mischief is

brewing”

OmentumThe Policemen of the Abdomen

Omentum:

Good Cop or Bad Cop?

Omentum

• What is it and why does it exist?

• How does it work:

How does it move ?

How does it adhere ?

What is its role in malignancies ?

What is its role in bowel obstruction?

• What good is it?

Omentum

• How can we use it:

• Should we remove it?

Omentum - Structure

J. Pathology 1926 Florey, Walker and

Carleton

“The question of omental reaction resolves

itself into two questions: (1) through what

agency does the omentum get into contact

with an injured area or foreign body, and (2)

how does it attach itself thereto?”

How Does It Move?

• Intrinsic omental movement

o “chemiotaxis”

o Morison – moves like a jelly fish

o Cantacuzene – differences in electric potential

o Hertzler – leukocyte dependent “an individual’s

omentum is as smart as their leukocytes”

• Passive movement

– Diaphragmatic motion

– Peristalsis

– Gravity

Omentum - movement

Movements of the omentum were randomAllen MS, Surgery 1954

Omentum - Attachment

Omentum - Attachment

?

Omentum – What is its

function?Activated by:

– Infection

– Trauma

– Ischemia

– Foreign bodies

– Obesity

– Tumor metastases

Activation of the Omentum

One week after activation with foreign body:

• Milky spots expand 15 to 20-fold

• Blood vessel density increases 3-fold

• Increased production of:VEGF P-/ E- selectin bFGF

• Increased progenitor cells, marked by: – SDF-1α

– CXCR-4

– WT-1

Litbarg et al. Cell Tissue Res 2007

Boston: Officer O’mently

To The RescueSurgical Utility of Omentum

Plastic Surgical Applications

“The omental free flap is a valuable option

for reconstructive efforts in nearly all

anatomic regions. This is a result of its

inherent anatomy and vascularity, and its

angiogenic, immunogenic, and lymphatic

properties” Mazzaferro et al., J Reconstr

Microsurg 2018

Wound Bed Preparation

Omentum as Healer

• Vascularized Omental Lymphatic Transfer

(VOLT)

Omentum as Healer

• Anastomotic augmentation

– Duodenum

– Colon

– Esophagus

– Bronchus

Graham Patch

for perforated ulcer

Anastomotic Augmentation

Does Omentum Improve

Anastomotic Healing?• Dai et al. Surgery 2011 Prospective

randomized study esophageal cancer resections

(n=255)

– Anastomotic leaks:

• 1% with omentum wrap

• 6% w/o omentum wrap p< 0.05

– Strictures:

• 6% with omentum wrap

• 16% w/o omentum wrap p< 0.05

Does Omentum Improve

Anastomotic Healing?• Wiggins et al. Surgical Oncology 2015

Meta-analysis of esophageal and

colorectal anastomoses ( 9 studies, n= 2296)

– Esophageal leaks:

• 2.9% with omentum wrap

• 10.5% w/o omentum wrap p< 0.0001

– Colorectal leaks:

• 5.0% with omentum wrap

• 8.4% w/o omentum wrap NS

No difference in stricture or mortality

Anastomotic Healing

Bronchus in lung transplantation or lung

resection?

How Does Omentum Augment

Anastomotic Healing?• Neovascularity

– VEGF?

• Improved control of infection/ inflammation

– Milky spots

• Structural integrity

Omentum

Anastomotic Healing

Bronchus in lung transplantation or lung

resection?

Dog studies: omentum increases

capillary ingrowth to bronchus after auto-

transplantation

Early years of lung transplantation;

routinely used omental wraps -> now rarely

Anastomotic Healing

Bronchus in lung transplantation or lung

resection?

Pancreatic fistula prevention?

Meta analysis w/ 2971 patientsTian Y et al. Hepatogastroenterology 2015

No reduction

Omentum as Healer

Subtotal nephrectomy model

Rat model of 5/6 nephrectomy

Control animals had omentectomy

Experimental animals polydextran gel

particles injected to activate omentum

Omentum as Healer

• After 12 weeks:

– Experimental rats had lower creat, BUN, less

glomerulosclerosis, thinner basement

membrane

– Stem cell Antigen-1, WT-1, and CD34

expression at the renal-omentum interface

Omentum slowed the progression of CKD, and

the repair of the injured kidney was associated

with stem cell activity derived from the omentum

Omentum as Healer

Subtotal nephrectomy model

Activated omentum preserves renal function

Intra-abdominal fistula management

Reduction of femoral artery aneurysm after

axillary- bifemoral by-pass

Myocardial perfusion

Neural injury/ scarring/ ischemia

©2005American Society of Plastic Surgeons. Published by Lippincott Williams & Wilkins, Inc. 2

Fig. 3

s of the Wrist: A Long-Term Follow-Up.Gbert; Steichen, James

Plastic & Reconstructive Surgery. 115(1):163-171, January 2005.DOI: 10.1097/01.PRS.0000138808.77038.D7

Fig. 3 . Omentum placed around the median nerve and microvascular anastomosis performed in the distal forearm.

Omentum as Healer- Infection

• Omental flaps for:

– Mediastinitis

– Vascular graft infections

65 patients 93% survival

Frautschi RS et al. Ann Plast Surg 2017

– Infected AAA

Infected Abdominal Aortic

Aneurysm

Omentum as Healer

• Treatment for CNS disease:

– Spinal cord injury

– TIA

– Stroke

– Alzheimer’s Disease?

Neurotrophic factors

Improved neovascularization – esp. MMD

Konieczny MJ et al. World Neurosurgery 2016

Omental Transposition for

Alzheimer’s Diseaes• Hypothesis: Decreased cerebral blood

flow is a cause of AD, not a consequence

of AD

• 9 of 25 patients treated with OT had

reversal of symptoms

• Theory: improved blood flow & VEGF,

stem cells, nerve growth factors

Omentum as Safe Harbor

• Tissue engineering “incubator”

Porcine Engineered Intestine

Grikscheit, CHLA

Engineered Intestine

Courtesy of T.

Grikscheit, CHLA

Omentum as Source of

Problems• Cysts

• Torsion

• Site of metastases

• Adhesive bowel obstruction

• Spontaneous bleeding

• “Engine of obesity”

Omentum - Obesity

Omentum: Role in Obesity

Omentum in Obesity

• Produces adipokines:

Resistin Adiponectin

MIP MCP-1

IL-6 TNFα

GRO TIMP-1

• Omental fat effects myometrial artery

contraction

Omentectomy as Rx for Obesity

• 2002 – 50 patients randomized to

omentectomy vs. no omentectomy with

adjustable gastric banding.

– Omentectomy associated with significantly

improved insulin sensitivity and glucose

tolerance at 2 years

• 2017 – 49 patients randomized to gastric

by-pass with and w/o omentectomy

– No significant improvement on weight, insulin

sensitivity, or hemodynamic profile

Omentum - metastases

• Intra-abdominal malignancies

Ovarian, gastric, colon

• Adipocytes: micro-environment favorable

to metastases

Omentum - metastases

• Intra-abdominal malignancies

Ovarian, gastric, colon

• Adipocytes: micro-environment favorable

to metastases

Chemokines Adhesion molecules

Growth factors

Omentum – To keep or

remove?• David Tapper – “get rid of that (damn)

omentum. If you don’t, it will always

(mess) you up.”

• “The greater omentum, a useless and

hazardous organ for the patient and

surgeon. Advantages of omentectomy in

all abdominal operations” Yodice in El Dia

Medico, 1963

Omentum – Role in Adhesions

Injury

Inflammation -> Fibrinous exudate

Decrease of t-PA

Overaccumulation of fibrin exudates

Increase of PAI-1

and PAI-2

Omentum – To keep or remove?

Peritoneal dialysis

Retention of omentum:

? Increased filtration

? Improved immunologic protection

? Increased obstruction

Phan et al.

J Ped Surg 2013: Lack of omentectomy associated

with 2-fold increased risk of infection and malfunction, and

higher mortality

Omentum – To keep or

remove?Ariake et al. Int. J. Surg 2015

Case:control study of 113 patients w/ ASBO

18 developed recurrence

95 no recurrence

Multivariate analysis: Omentectomy was

associated with 3-fold risk of recurrent

ASBO

Omentum – Good Cop or Bad

Cop?

Omentum

• Simple structure -> complex physiology

• Provides protection

• Versatile applications

• Central role in obesity

Must be treated with respect!

Omentum – Good Cop or Bad

Cop?

Good

Bad