PERITONEAL HEALING

Micky Trent DVM DACVS

Peritoneal Structure

What are the histologic layers of normal peritoneum? Which vary by species?

Histologic Anatomy

Layers Mesothelial Cells Basement membrane Submesothelial

connective tissue Loose c.t. Species variation

Peritoneal Structure

What are the layers of peritoneum? What is the peritoneal space?

Gross Anatomy

Peritonal cavity Layers

Parietal Visceral

Peritoneal Structure

How is peritoneum innervated? Why should we as surgeons care?

Histologic Anatomy

Sensory Innervation Parietal Layer

Sharp & Deep pain, Stretch

Localizable Not blocked by local

or regional blocks Visceral Layer

Deep pain, stretch NO sharp pain Poorly localizable Can block with direct

application

Peritoneal Structure

What abdominal structures are considered retroperitoneal? Why should we as surgeons care?

Peritoneal Functions

List 4 critical functions that depend on the peritoneum.

Peritoneal Functions

Cell nutrition Peritoneal fluid production Maintain gliding surfaces Waste control

Peritoneal Functions

Cell Nutrition Diffusion

Produce Peritoneal Fluid Transudate from

blood Inflammation

changes volume and character

Peritoneal Functions

Maintain Gliding Surface Surface villi trap

fluid Peritoneal fluid Plasminogen

activators Mesothelial cells Fibrin break down Depressed with

peritoneal trauma

Removal of waste

How is waste removed from the peritoneal cavity? Low MW compounds? Cells? Foreign bodies?

Waste Control

Physical Removal Transmesothelial

Small molecules H20

Stomata/Lymphatics Peritoneal flow to

diaphragm 10 route Diaphram lymphatics Thoracic duct to vena

cava Larger molecules Particles/cells Fluid Omental alternative

Waste Control

Functional Removal Localization

Omental Trapping Fibrin Trapping

Phagocytosis PMNs Macrophages Bacterial kill

Waste Control

Functional Removal Localization

Omental Trapping Fibrin Trapping

Phagocytosis PMNs Macrophages Bacterial kill

Peritoneal Healing

How does the peritoneum respond initially (24hrs) to trauma? Vascular phase? Inflammatory cascade? Coagulation cascade? Link between inflammation and coagulation?

Vascular Response

Brief vasoconstriction Histamine, PGE2 release Local vasodilation & cell influx

Procoagulant factors Platelets adhere to wound bed

Alpha corpuscles degranulate Release PDGF, TGF-β, dense corpuscles

Release epinephrine, serotonin Contribute to PG & leukotriene release

Inflammatory Response

Local release of cytokines Cell migration to wound bed Platelet aggregation

Coagulation cascade activation Initial clot formation

Fibrin deposition Temporary matrix for signaling molecules &

inflammatory cells Temporary bridge between tissues

Coagulation Response

Close overlap with Inflammatory response

Two pathways converging to one Intrinsic pathway

BM damage & collagen exposure Factor XII (Hagemen factor)

Activation of factor II (prothrombin) Activation of factor IIa (thrombin precursor) Thrombin production

Link between coagulation and inflammation

Thrombin Cleaves soluble circulating fibrinogen into

insoluble fibrin clots Factor XII stimulates clot formation and

activation of the fibrinolytic system Fibrinolysis determined by:

tPA (mesothelial cells, leukocytes, tissue) PAI1&2

Peritoneal Healing

How does a peritoneal defect heal? What is the timing? Where do new cells come from? Are there differences in cells shed in a

dialysate? How is ECM formed?

Peritoneal Healing 12-24 hrs – PMNs 24 hrs + macrophages

Cytokine release Day 3

Mesothelial and fibroblast cells appear Area of lesion regresses

Day 7-10 Mesothelial layer reestablished

ECM follows cell migration

Peritoneal Healing

Species variation?

Species variation

tPA vs PAI baseline Human, horses, dogs – tPA high Cows – PAI high

Post-injury Most: tPA down, PAI up Cow: PAI up

Peritoneal Healing

Describe the steps in adhesion formation. What key enzymes are involved? How are these enzymes affected by trauma?

Post-Operative Adhesions

What is the incidence of post-op adhesions? In people? In horses?

Which structures are most commonly involved in identified cases in horses? Why?

Post-Op Adhesions

Humans 67%-93%

Horses 9%-32% Caveats?

Canine/Feline Low

Post-Op Adhesions

Equine SI procedures Regardless of procedure

SI Ventral incision Why??

Peritoneal Adhesions

Are there any beneficial effects of peritoneal adhesions?

Significance of Adhesions

Beneficial Effects Seal Breaks in

continuity Prevent visceral

leakage Neovascularization Stabilize mobile

viscera Bovine, canine,

equine

Significance of Adhesions

Beneficial Effects Seal Breaks in

continuity Prevent visceral

leakage Neovascularization Stabilize mobile

viscera Bovine, canine,

equine

Peritoneal Adhesions

What are common stimuli for adhesions?

Factors Promoting Adhesions

Suturing Peritoneum!!

Ischemia Serosal trauma

Drying Abrasion Others

Foreign bodies Bacteria

Peritoneal Adhesions

List preventative methods (and mechanisms) for reduction of adhesions

Steps to Minimize Adhesions

Avoid serosal trauma Reduce/avoid foreign bodies Minimize ischemic tissue Minimize bacterial contamination Consider protective coatings

Carboxymethyl cellulose most common Use of heparin debatable (little support)

Products/Approaches

Solid barriers Seprafilm (CMC & HA) Interceed (oxidized cellulose) Hyaluronate membranes

CMC Omentectomy(x) Antiticoagulants - Heparin (x) Fibrinolytics – tPA (cost) Antiinflammatories (~) Lavage (?) Antioxidants (?)

More new stuff

Fucoidan Chitosan dextran Hydrogel (PCEC) Aldehyde dextran Parecoxib Alginate gell Statins