Pelvic Adhesions....
From: Helen Dynda (olddad66@runestone.net)
Wed Jun 14 20:59:49 2000
This article may be a little technical for many of you; however, I think
that many of you will be able to understand the difficulties which pelvic
adhesions present - to both the surgeon and the patient.
** Pelvic Adhesions **
Despite multiple alterations in operative technique, and the recent
induction of various adhesion barriers, the issue of adhesion prevention
remains at the forefront. All surgeons must deal with the potential for
formation of adhesions during surgery, as well as the sequelae of adhesions
from previous surgery which may markedly alter the difficulty of a
particular surgery.
Post-surgical adhesions often occur following pelvic and abdominal surgery.
Data has suggested that 67% to 93% of patients will develop adhesions
following abdominal surgery and 55% to 100% of patients will develop
adhesions following gynecologic surgery. These issues become critically
important from a standpoint of reproductive potential. Additionally,
adhesions may be associated with issues such as pelvic pain, as well as
abnormalities of bowel function and small bowel obstruction.
** Definitions **
Several definitions of adhesions exist. De novo or new adhesions may form
at a site of direct surgical trauma such as a myomectomy incision or an
ovarian incision at the time of ovarian cystectomy. De novo adhesions may
also develop remote from the site of surgery, such as when adhesions
develop surrounding the adnexa at the time of a cesarean section.
Adhesions may also reform following adhesiolysis or adhesiectomy.
While three general types of adhesions exist - filmy, vascular, and
cohesive, the underlying pathophysiology is similar. The American
Fertility Society has attempted to classify disease according to the
location and type of adhesions. We have additionally suggested
modifications in this standard assessment in an effort to increase
reproducibility between surgeons, as well as provide greater levels of
information when surgeons communicate.
** The Peritoneum **
An understanding of the anatomy of the peritoneum and the response of the
peritoneum to injury is important in understanding how we might prevent
adhesion formation. The peritoneum is composed of multiple layers, the
mesothelium being the innermost layer, a layer of connective tissue which
contains the vascularity and a basement membrane. When the peritoneum is
injured (which is inevitable during surgery), during direct incision or
indirectly such as with desiccation, there is an inflammatory response.
During this initial phase, inflammatory mediators and histamine are
released from mast cells and leukocytes. Capillaries located within the
connective tissue dilate and an increased permeability is noted. This
allows leukocytes, red blood cells and platelets to become concentrated at
the site of an injury. A fibrinous exudate is thus formed at the site of
injury. Multiple factors such as prostaglandins, lymphokines, bradykinin,
serotonin, transforming growth factor and other chemotactic agents are
present within the exudated material.
At this point in time the fibrinous exudate may be cleared through
fibrinolysis. In order for this to occur plasminogen must be converted to
plasmin by tissue plasminogen activator (t-PA). There is a constant
balance in the system between tissue plasminogen activator and plasminogen
activator inhibitors. Unfortunately, surgical trauma may have an inherent
ability to decrease tissue plasminogen activity while increasing
plasminogen activator inhibitors. Under normal circumstances plasmin
breaks down exudated fibrin. If this does not occur, the fibrinous exudate
is converted into an organized adhesion and fibers of collagen are
deposited. Following this, blood vessels begin to form allowing
organization of the adhesion.
This process occurs over a one to seven day period of time. In general, at
seven days the quantitative development of adhesions is complete.
Qualitative changes continue over the next several months with
adhesions becoming more dense and vascularized.
Our efforts at adhesion reduction have thus been an attempt to alter the
previously described process. These may generally be described as:
1.) minimizing peritoneal injury during surgery,
2.) reducing the local and inflammatory response,
3.) inhibiting the coagulation cascade and promoting fibrinolysis, and
4.) using barriers for separation of surfaces at high risk for adhesion
formation.
** Micro and Macro Techniques for Adhesion Reduction **
Various techniques and disease states have been suggested to predispose to
adhesion formation. Many studies have been performed to document this.
They include incomplete hemostasis, foreign bodies, tissue injury, type of
suture utilized, amount of crushing and tissue destruction from
instrumentation, tissue desiccation, and underlying infection. Many
practical techniques may be utilized to minimize aberration from optimal
techniques.
The use of gauze and minimally moistened dry sponges may cause significant
peritoneal denudation and surface injury. The use of frequent irrigation
has been recommended to limit tissue desiccation and keep
tissues moistened. Micro- surgical techniques have been developed in an
effort to achieve less tissue destruction during surgery while maintaining
precise hemostasis in an effort to decrease subsequent fibrin layering and
the potential for adhesions. The use of the most acceptable minimally
reactive sutures and an effort to not suture unless necessary helps avoid
both tissue reaction and subsequent tissue ischemia from suture placement.
Unfortunately, while the use of such microsurgical techniques are important
in and of themselves, they will not completely decrease the risk of
adhesions. Indeed, studies have suggested that de novo adhesion rates in
patients undergoing laparotomy may be greater than 90% when large numbers
of sites are evaluated at the time of second look laparoscopy.
** Risk Factors for Adhesion Formation **
Multiple risks factors have been identified for the formation of adhesions.
In one study performed at the time of autopsy the authors reported a 90%
incidence of adhesions in patients with multiple previous surgeries, 70%
incidence of adhesions in patients with previous gynecologic surgery, a 50%
incidence of adhesions with previous appendectomy, and interestingly, a
greater than 20% incidence of adhesions in patients with no surgical
history. Of even greater interest, a recent publication suggested that
myomectomy with a posterior uterine incision may have an incidence of
greater than 90% of adhesions from the incision line to bowel, omentum. or
the adnexa. Additionally, there has been great interest in the amount of
adhesion reformation following lysis of adhesions for laparotomy vs.
laparoscopy, as well as the incidence of de novo adhesion formation in
laparotomy and laparoscopy.
Compilation studies have suggested that there is a 70% incidence of
adhesion reformation with laparotomy and greater than 50% de novo adhesion
formation. While adhesion formation has not been found to be significantly
altered by laparoscopy, the amount of de novo adhesion has been reported in
various studies to be only 10%.
** Pharmacologic Agents in Adhesion Reduction **
In an effort to decrease the adhesions in patients, multiple different
methodologies have been utilized. Installation of crystalloid, such a
lactated ringers, has been performed. While several animal studies
demonstrated a significant reduction in adhesions, multiple studies which
utilize crystalloid in control patients, demonstrated no significant
effect.
Thirty-two percent Dextran-70 (Hyskon) has been evaluated in multiple
studies. The affect of Hyskon to draw fluid into the peritoneal cavity
conceptually allows hydro-floatation of viscous structures. It was
thought that the separation of viscous structures would not allow fibrin
bands to form, thus reducing the risk of adhesion formation. Multiple
studies have presented conflicting results from ineffective to
statistically effective. In general, it is presently felt that if such
therapy is effective, the dependent area of the pelvis may be most
positively affected.
Corticosteroids, antihistamines, and non steroidal anti-inflammatories have
all been used by various routes in an effort to decrease adhesion
formation. The classic regimen of a steroid with antihistamine has been
shown to be ineffective in a well done study.
** Barriers for Adhesion Reduction **
Most recently, barriers have been suggested as a means to decrease
adherence of one peritoneal structure to another. Presently, two such
surgical membranes are marketed in the United States - a Gore-tex surgical
membrane composed of expanded polytetrafluoroethylene and Interceed
(Johnson and Johnson Medical, Inc. Arlington, TX). The Gore-tex surgical
membrane has been used for a number of years and was initially approved for
cardiovascular work. This membrane is non-absorbable, non-inflammatory,
and because of the small pore size of less than one micron, does not allow
infiltration into this sheath. Placement of a surgical membrane requires
immobilization by either suture or staple. Several studies have recently
demonstrated the efficacy of this membrane. Unfortunately, it is currently
recommended that the membrane be removed in patients desiring subsequent
fertility.
Interceed barrier is an oxidized regenerated cellulose compound. The
exposure of Interceed to peritoneal fluid causes subsequent breakdown and
formation of a gelatinous coating over the applied tissue. It is felt that
this coating decreases the formation of fibrin bridges which may lead to
adhesion formation. Multiple studies have evaluated Interceed as a barrier.
In a study of pelvic sidewall adhesions, applications of Interceed
prevented adhesion formation in 51 % of patients vs. 24% of controls where
only good surgical technique was utilized. Multiple studies presently
exist to document the efficacy in additional procedures, such as
endometriosis and in ovarian surgery. It is critically important in the
application of Interceed that complete hemostasis be assured. The barrier
is then applied, subsequently moistened, and does not require suturing. It
is helpful to remove all irrigation fluid by placing the patient in severe
reverse Trendelenberg prior to application of these barriers.
Most recently, efforts have been directed to evaluate a solution, film, and
gel composed of hyaluronic acid. While initial studies were discouraging,
reformulation of the compound have demonstrated excellent results in animal
trials. We are presently completing a multicenter randomized double blind
study to evaluate both the solution and film. It is hoped that, in the
future, applications will obviate the difficult application of membranes,
or the need to return for second-look laparoscopy to remove non- absorbable
membranes. However, this work remains to be clinically documented.
It remains to be elucidated what the most effective substance will be for
adhesion prevention. It is likely that a multifaceted approach, which
includes minimization of trauma to tissue, tissue hydration, use of
the least reactive sutures, and application of various barriers may yield
the best results.
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