A unifying pathogenetic mechanism in the etiology of intraperitoneal adhesions;

Post-Operative Adhesions: A Comprehensive Review of Mechanisms

Post-surgical adhesions are common in almost all surgical areas and are associated with significant rates of morbidity, mortality, and increased healthcare costs, especially when a patient requires repeat operative interventions. Many groups have studied the mechanisms driving post-surgical adhesion formation. Despite continued advancements, we are yet to identify a prevailing mechanism. It is highly likely that post-operative adhesions have a multifactorial etiology. This complex pathophysiology, coupled with our incomplete understanding of the underlying pathways, has resulted in therapeutic options that have failed to demonstrate safety and efficacy on a consistent basis. The translation of findings from basic and preclinical research into robust clinical trials has also remained elusive. Herein, we present and contextualize the latest findings surrounding mechanisms that have been implicated in post-surgical adhesion formation.

Advancement of Biomaterial-Based Postoperative Adhesion Barriers

Postoperative peritoneal adhesion (PPA) is a prevalent incidence that generally happens during the healing process of traumatized tissues. It causes multiple severe complications such as intestinal obstruction, chronic abdominal pain, and female infertility. To prevent PPA, several antiadhesion materials and drug delivery systems composed of biomaterials are used clinically, and clinical antiadhesive is one of the important applications nowadays. In addition to several commercially available materials, like film, spray, injectable hydrogel, powder, or solution type have been energetically studied based on natural and synthetic biomaterials such as alginate, hyaluronan, cellulose, starch, chondroitin sulfate, polyethylene glycol, polylactic acid, etc. Moreover, many kinds of animal adhesion models, such as cecum abrasion models and unitary horn models, are developed to evaluate new materials' efficacy. A new animal adhesion model based on hepatectomy and conventional animal adhesion models is recently developed and a new adhesion barrier by this new model is also developed. In summary, many kinds of materials and animal models are studied; thus, it is quite important to overview this field's current progress. Here, PPA is reviewed in terms of the species of biomaterials and animal models and several problems to be solved to develop better antiadhesion materials in the future are discussed.

Pathogenesis of Peritoneal Fibrosing Syndromes (Sclerosing Peritonitis) in Peritoneal Dialysis

Drawing from diverse sources including epidemiological and clinical data, surgical observations, histopathology, serosal healing responses to fibrin and fibrinolysis, tissue reaction to chronic exposure, and to exo and endotoxins, new information on mesothelial stem cells, autocrine and paracrine influences on their proliferation and collagen synthesis, and the effect of glucose on fibroconnective tissue, we have begun to piece together the pathogenetic jigsaw of fibrosis in continuous ambulatory peritoneal dialysis (CAPD).

The reaction of peritoneal mesothelium and stroma to the stress of continual dialysis results in a spectrum of alterations ranging from opacification through a tanned peritoneum syndrome to sclerosing encapsulating peritonitis (SEP). Any agent that causes irritation of the mesothelial layer and induces serositis, or single severe or multiple episodes of peritonitis resulting in mesothelial loss, predisposes the peritoneum to fibroneogenesis. An accurate definition of the histopathological changes of peritoneal thickening is a prerequisite for defining pathogenesis. This paper is the first attempt to create such a framework.

It is evident from many areas of study that fibrin deposition and fibrinolysis, hyalinization of the superficial stromal collagen possibly tanned through nonenzymatic glycosylation by dialysate glucose and the proliferative potential of mesothelial stem cells play an important and possibly interdependent role in excessive fibroneogenesis in certain patients on CAPD.

Many of the pieces of the jigsaw are obviously still missing, and the picture is most surely incomplete. Nevertheless, the outline of the pathologic and etiologic landscape should now be discernible.

Usefulness of Dialysate Fibrin Degradation Products and Lactic Dehydrogenase Isoenzyme Patterns in Assessing the Clinical Course of Peritonitis

Objective

To establish the usefulness of fibrin degradation products (FDP) and lactic dehydrogenase isoenzyme patterns (LDH isoenzyme) in assessing the clinical course of peritonitis.

Design

A retrospective study of patients with peritonitis who were divided into three groups according to their clinical course.

Setting

Single dialysis unit of a general hospital.

Interventions

Patients were treated by intraperitoneal and oral antibiotics.

Patients

Twenty-six patients with 34 episodes of peritonitis were studied. Group 1 consisted of 21 patients with 26 recoveries from peritonitis; Group 2 consisted of 5 patients with 5 relapsing episodes of peritonitis, and Group 3 consisted of 3 patients with 3 persistent episodes of peritonitis.

Main Outcome Measures

Concentrations of WBCs, FDP, LDH isoenzyme and microbiological culture of the dialysate were determined.

Results

In most of Group 1, WBCs, FDP, and LDH isoenzyme returned to normal within 2 weeks. In 4 patients of Group 1, who had complications (diverticulitis, cholecystitis, cystitis, and tunnel infection), WBCs, FDP, and LDH isoenzyme returned to normal gradually within 3 weeks. In Group 2, WBCs returned to normal, but FDP remained relatively high and LDH isoenzyme did not normalize. In Group 3, WBCs, FDP and LDH isoenzyme did not normalize.

Conclusions

Failure of normalization of FDP and LDH isoenzyme suggests an incomplete recovery from peritonitis. FDP and LDH isoenzyme are useful in assessing the course of peritonitis.

Intra-Abdominal Adhesions and Their Prevention by Topical Tissue Plasminogen Activator

Recent work shows that a common pathway in adhesion production is a reduction in local plasminogen activator activity (PAA). This deficit permits deposited surface fibrin to become organized to fibrous adhesions. A rabbit model for adhesion formation was used to assess the effect of replacing the deficit with recombinant tissue plasminogen activator (rt-PA). Adhesions were produced by stripping peritoneum from corresponding parietal and visceral areas. One week later the adhesions were divided. Either rt-PA or placebo was applied to the divided adhesion. After a further week the animal was killed and the adhesions assessed. Sixty strips were performed. Fifty-five adhesions were produced (92%). Placebo gel was applied to 28 sides and rt-PA applied to 27. Twenty-two of the placebo group recurred (79%). Two of the rt-PA group reformed (7%, chi 2 = 20.883, P less than 0.001). Recombinant tissue plasminogen activator is an effective inhibitor of adhesion formation in the experimental animal.

Standard Biocompatibility Studies Do Not Predict All Effects of PVA/CMC Anti-Adhesive Gel in vivo

Purpose: PVA/CMC (polyvinyl alcohol/carboxymethyl cellulose) hydrogel fulfills various physiochemical properties required for an adhesion barrier and has shown good anti-adhesion properties in previous in vivo studies. In this investigation, we assessed the in vitro and in vivo biocompatibility of PVA/CMC gel and compared this to the functionality and promotion of wound healing for two surgical indications. Methods: Standardized ISO10993 in vitro and in vivo biocompatibility studies, comprising cytotoxicity, genotoxicity, acute systemic toxicity, delayed contact and maximization sensitization test, intracutaneous reactivity and local muscle implantation, were performed on PVA/CMC gel. In the functional studies, PVA/CMC gel was applied - on the one hand - to a rabbit abdominal wall model enforced with a polypropylene mesh for testing the anti-adhesion properties and - on the other hand - to an end- to-end anastomosis model that was selected for surveying potential influences of different dosages of PVA/CMC gel on anastomotic wound healing. Results: The ISO10993 methods indicated generally good biocompatibility properties, such as the absence of cytotoxic and mutagenic effects as well as no signs of systemic toxicity and sensitization potentials. No irritation effects were observed after the intracutaneous injection of lipophilic PVA/CMC sesame oil extract. However, the injection of hydrophilic PVA/CMC physiologic saline extract induced slight irritation. Following rabbit muscle implantation of the PVA membrane for 2, 4, 12, 26 and 52 weeks, a slight irritant effect was observed at 12 weeks due to the peak of phagocytosis. In the functionality tests, PVA/CMC gel showed good anti-adhesive effects in the abdominal wall model enforced with the mesh, with significantly lower and less tense adhesions compared to the untreated control. However, moderate signs of inflammation, especially in the spleen were observed after the intra-abdominal implantation of 3.3 ml PVA/CMC gel per kg body weight. In the end-to-end anastomosis model, PVA/CMC gel had no influence on wound healing. For dosages of 1-6 ml gel per treatment, no signs of intestinal leaks were detected, and tensile strength was equal to that of the untreated control, but again more moderate signs of inflammation in the spleen were observed at a dosage >3 ml. Conclusion: Comparing the standardized ISO10993 methods, anti-adhesive PVA/CMC gel displays good biocompatibility. However, those methods do not seem to be sensitive enough because the rabbit abdominal wall and the end-to-end anastomosis models display more effects with respect to the dosage and routes of the intra-abdominal resorption of PVA/CMC gel - with the recommended <2 ml PVA/CMC gel per kg body weight as a secure dosage.

Results of a prospective, randomized, controlled study of the use of carboxymethylcellulose sodium hyaluronate adhesion barrier in trauma open abdomens

INTRODUCTION

The open abdominal (OA) approach is a management strategy used in the most severely injured trauma patients. In addition to the morbidity and mortality, a major challenge is the gradual development of dense adhesions that make reoperations progressively more difficult. This randomized, prospective, proof-of-concept study was conducted to determine the effect of carboxymethylcellulose sodium hyaluronate adhesion barrier (CMHAB; Seprafilm, Genzyme Biosurgery, Bridgewater, NJ) on abdominal adhesions and wound characteristics in trauma open abdomens.

METHODS

A prospective, randomized, controlled study of wound and adhesion characteristics with or without CMHAB was conducted at 5 level I trauma centers. Consenting patients were randomized to either CMHAB or no adhesion barrier (NAB) groups. We evaluated patient demographics, injury characteristics/severity, reason for OA management, wound sizes (transverse/longitudinal), Zuhlke adhesion score, abdominal contamination score, hospital/intensive care durations of stay, morbidity, and mortality.

RESULTS

Thirty patients were enrolled (17 randomized to CMHAB; 13 randomized to NAB) with mean age of 40.3, Injury Severity Score of 30, Abbreviated Injury Score (AIS)-abdomen of 3.68, APACHE II score of 14.4, and 67% blunt trauma mechanism. The groups were well-matched with regard to age, sex, Injury Severity Score/abdominal AIS, penetrating/blunt injury rates, initial lactate/base deficit, mortality, OA indications, and contamination scores. There were no differences in nonabdominal or abdominal complications (ie, fistula, abscess, wound related) between the groups. Patients with CMHAB had shorter intensive care unit durations of stay (15 vs 22 days; P < .05). Intraoperative adhesion scores were not different during the first four operations but diverged significantly at the 5th operative intervention or after about 1 week of OA therapy. After the 5th operation, adhesion scores in the NAB group were 67% greater (approximately 1 Zuhlke point) than the CMHAB group. We did not note differences between wound sizes over time, closure types, or wound closure characteristics between CMHAB and NAB.

CONCLUSION

Although CMHAB did not eliminate adhesions in this proof-of-concept study, it limited their severity, particularly in abdomens left open >9 days or requiring ≥5 operations. There was no difference in wound sizes, overall or abdominal complications, or mortality between the groups. Further research is warranted to better delineate potential benefits of CMHAB, especially in the setting of reoperations in post-OA patients.

Can effluent matrix metalloproteinase 2 and plasminogen activator inhibitor 1 be used as biomarkers of peritoneal membrane alterations in peritoneal dialysis patients?

BACKGROUND

Peritoneal effluent contains clinically relevant substances derived from intraperitoneal production or transperitoneal transport, or both. The glycoproteinase matrix metalloproteinase 2 (MMP-2) cleaves denatured collagen and complements other collagenases in the degradation of fibrillar collagens. Elevated intraperitoneal levels of plasminogen activator inhibitor 1 (PAI-1) have been demonstrated to be present in patients with intra-abdominal adhesions. The aim of the present study was therefore to investigate the potential for effluent MMP-2 and PAI-1 to be used as markers of the development of peritoneal alterations. In addition, MMP-2 was analyzed in previously frozen effluent samples from a uremic rat model, in which data concerning the severity of peritoneal fibrosis were available.

METHODS

This prospective, single-center cohort study included 86 incident peritoneal dialysis (PD) patients. All patients were treated solely with biocompatible dialysis solutions and underwent a standard peritoneal permeability analysis (SPA). The presence of local MMP-2 and PAI-1 production and the relationships between those markers and peritoneal transport parameters were analyzed. Furthermore, effluent interleukin 6 was analyzed as a marker of local inflammation.

RESULTS

Median effluent levels of 21.4 ng/mL for MMP-2 and 0.9 ng/mL for PAI-1 were found. The median dialysate appearance rates were 218.8 ng/min for MMP-2 and 9.6 ng/min for PAI-1. Local peritoneal production averaged 90% of effluent MMP-2 concentration and 74% of effluent PAI-1 concentration. Furthermore, correlations between peritoneal transport parameters and MMP-2 and PAI-1 were observed. Longitudinal follow-up showed no change for MMP-2 (p = 0.37), but a tendency for PAI-1 to increase with the duration of PD (p < 0.001). In rats, a significant relationship was present between the extent of peritoneal fibrosis and the appearance rate of MMP-2 (r = 0.64, p = 0.03).

CONCLUSIONS

The foregoing data illustrate the potential of effluent MMP-2 and PAI-1 as biomarkers of peritoneal modifications, especially fibrosis; however, the components of peritoneal transport and local production should be clearly distinguished in every patient.

Practical implications of postoperative adhesions for preoperative consent and operative technique

Adhesions complicate most intra-peritoneal operations. Once adhesions have formed, patients are at life-long risk for complications that include small bowel obstruction, increased risks during subsequent operations and female infertility. This has two implications for the daily work of surgeons. On the one hand, surgeons need to include the risks from adhesions during pre-operative consent. On the other hand, surgeons need to use operative techniques that minimize adhesions. Therefore this review focuses on the practical implications of adhesions for preoperative consent and operative technique.

Local tissue ischemia is not necessary for suture-induced adhesion formation

BACKGROUND

We investigated the hypothesis that local tissue ischemia is responsible for suture-induced adhesion formation.

METHODS

A total of 160 interrupted sutures were placed in the parietal peritoneum of 20 Wistar rats. The animals were randomized into an ischemia group, where the sutures were pulled tight and a non-ischemia group, where the sutures were tied as loose loops with air knots to avoid any local ischemia. The midline laparotomy was closed with a running suture. On postoperative day 10, adhesions to the sutures were counted.

RESULTS

There was no statistically significant difference in the number of adhesions forming to sutures with local ischemia (n = 66/80) versus sutures without local ischemia (n = 69/80).

CONCLUSION

We conclude that local tissue ischemia is not necessary for suture-induced adhesion formation and propose an additional mechanical mechanism to explain how suture knots can predispose to adhesiogenesis.

Current status and practical use of effluent biomarkers in peritoneal dialysis patients

Long-term peritoneal dialysis therapy can lead to alterations in the function and morphology of the peritoneal membrane. Assessment of the peritoneal dialysis membrane usually is done by investigating the transport of small solutes and fluid. Assessment of morphologic alterations and their development would require repetitive peritoneal biopsies that usually are not feasible. Peritoneal tissues are bathed in dialysis solutions during peritoneal dialysis and may secrete or shed substances that can be recovered in peritoneal effluent. These molecular effluent biomarkers may give insight into morphologic changes. In this review, established and emerging candidate biomarkers in peritoneal dialysis are discussed. Additionally, requirements, challenges, and clinical applications of effluent biomarkers in peritoneal dialysis are addressed.

Current strategies and future perspectives for intraperitoneal adhesion prevention

INTRODUCTION

The formation of peritoneal adhesions still is a relevant clinical problem after abdominal surgery. Until today, the most important clinical strategies for adhesion prevention are accurate surgical technique and the physical separation of traumatized serosal areas. Despite a variety of barriers which are available in clinical use, the optimal material has not yet been found.

DISCUSSION

Mesothelial cells play a crucial physiological role in friction less gliding of the serosa and the maintenance of anantiadhesive surface. The formation of postoperative adhesions results from a cascade of events and is regulated by various cellular and humoral factors. Therefore, optimization or functionalization of barrier materials by developments interacting with this cascade on a structural or pharmacological level could give an innovative input for future strategies in peritoneal adhesion prevention. For this purpose, the proper understanding of the formal pathogenesis of adhesion formation is essential. Based on the physiology of the serosa and the pathophysiology of adhesion formation, the available barriers in current clinical practice as well as new innovations are discussed in the present review.

Intra-abdominal adhesions: cellular mechanisms and strategies for prevention

Postoperative intra-abdominal adhesions represent a serious clinical problem. In this review, we have focused on recent progress in the cellular and humoral mechanisms underpinning adhesion formation, and have reviewed strategies that interfere with these pathways as a means to prevent their occurrence. Current and previous English-language literature on the pathogenesis of adhesion formation was identified. As the burden of surgical disease in the world population increases, and the frequency of reoperation increases, prevention of adhesion formation has become a pressing goal in surgical research.

Pathogenesis of postoperative adhesion formation

Background

Current views on the pathogenesis of adhesion formation are based on the ‘classical concept of adhesion formation’, namely that a reduction in peritoneal fibrinolytic activity following peritoneal trauma is of key importance in adhesion development.

Methods

A non-systematic literature search (1960–2010) was performed in PubMed to identify all original articles on the pathogenesis of adhesion formation. Information was sought on the role of the fibrinolytic, coagulatory and inflammatory systems in the disease process.

Results

One unifying concept emerged when assessing 50 years of studies in animals and humans on the pathogenesis of adhesion formation. Peritoneal damage inflicted by surgical trauma or other insults evokes an inflammatory response, thereby promoting procoagulatory and antifibrinolytic reactions, and a subsequent significant increase in fibrin formation. Importantly, peritoneal inflammatory status seems a crucial factor in determining the duration and extent of the imbalance between fibrin formation and fibrin dissolution, and therefore in the persistence of fibrin deposits, determining whether or not adhesions develop.

Conclusion

Suppression of inflammation, manipulation of coagulation as well as direct augmentation of fibrinolytic activity may be promising antiadhesion treatment strategies.

Intraperitoneal adhesions--an ongoing challenge between biomedical engineering and the life sciences

Peritoneal adhesions remain a relevant clinical problem despite the currently available prophylactic barrier materials. So far, the physical separation of traumatized serosa areas using barriers represents the most important clinical strategy for adhesion prevention. However, the optimal material has not yet been found. Further optimization or pharmacological functionalization of these barriers could give an innovative input for peritoneal adhesion prevention. Therefore, a more complete understanding of pathogenesis is required. On the basis of the pathophysiology of adhesion formation the main barriers currently in clinical practice as well as new innovations are discussed in the present review. Physiologically, mesothelial cells play a decisive role in providing a frictionless gliding surface on the serosa. Adhesion formation results from a cascade of events and is regulated by a variety of cellular and humoral factors. The main clinically applied strategy for adhesion prevention is based on the use of liquid or solid adhesion barriers to separate physically any denuded tissue. Both animal and human trials have not yet been able to identify the optimal barrier to prevent adhesion formation in a sustainable way. Therefore, further developments are required for effective prevention of postoperative adhesion formation. To reach this goal the combination of structural modification and pharmacological functionalization of barrier materials should be addressed. Achieving this aim requires the interaction between basic research, materials science and clinical expertise.

Visceral mobilization can lyse and prevent peritoneal adhesions in a rat model

OBJECTIVE

Peritoneal adhesions are almost ubiquitous following surgery. Peritoneal adhesions can lead to bowel obstruction, digestive problems, infertility, and pain, resulting in many hospital readmissions. Many approaches have been used to prevent or treat adhesions, but none offer reliable results. A method that consistently prevented or treated adhesions would benefit many patients. We hypothesized that an anatomically-based visceral mobilization, designed to promote normal mobility of the abdominal contents, could manually lyse and prevent surgically-induced adhesions.

MATERIAL AND METHODS

Cecal and abdominal wall abrasion was used to induce adhesions in 3 groups of 10 rats (Control, Lysis, and Preventive). All rats were evaluated 7 days following surgery. On postoperative day 7, unsedated rats in the Lysis group were treated using visceral mobilization, consisting of digital palpation, efforts to manually lyse restrictions, and mobilization of their abdominal walls and viscera. This was followed by immediate post-mortem adhesion evaluation. The rats in the Preventive group were treated daily in a similar fashion, starting the day after surgery. Adhesions in the Control rats were evaluated 7 days after surgery without any visceral mobilization.

RESULTS

The therapist could palpate adhesions between the cecum and other viscera or the abdominal wall. Adhesion severity and number of adhesions were significantly lower in the Preventive group compared to other groups. In the Lysis and Preventive groups there were clear signs of disrupted adhesions.

CONCLUSIONS

These initial observations support visceral mobilization may have a role in the prevention and treatment of post-operative adhesions.

Intra-abdominal healing: gastrointestinal tract and adhesions

The abdominal cavity represents one of the most active areas of surgical activity. Surgical procedures involving the gastrointestinal (GI) tract are among the most common procedures performed today. Healing of the GI tract after removal of a segment of bowel and healing of the peritoneal surfaces with subsequent adhesion formation remain vexing clinical problems. Interventions to modify both the responses are myriad, yet a full understanding of the pathophysiology of these responses remains elusive. Different aspects of GI and peritoneal healing, with associated factors, are discussed in this article.

Prevention of intra-peritoneal adhesions in gynaecological surgery: theory and evidence

Post-operative adhesions are a significant complication of all abdominal surgical procedures. The major strategies for adhesion prevention in gynaecological surgery are focused on the optimization of surgical technique and use of anti-adhesive agents, which fall into two main categories: pharmacological agents and barriers. Surgical technique that minimizes peritoneal trauma can reduce, but cannot prevent post-operative adhesion formation. Various local and systemic drugs that can alter the local inflammatory response, inhibit the coagulation cascade and promote fibrinolysis have been evaluated. Limited data support the administration of post-operative corticosteroids in addition to systemic intra-operative corticosteroids for the prevention of adhesions after gynaecological surgery. None of the remaining pharmacological agents have been found effective for the reduction of post-operative adhesions. Barriers are currently considered the most useful adjuncts, which may reduce adhesion formation. They act by separating the traumatized peritoneal surfaces during the healing period. The separation can be achieved by solid barriers or fluids. There is limited evidence from randomized clinical trials that support the beneficial effect of most of these barrier agents in the prevention of intra-peritoneal adhesions after gynaecological surgery. However, the evidence is not adequate for definite conclusions to be drawn and further research in this field is warranted.

Use of barrier products in the prevention of adhesion formation following surgery

Postoperative adhesion formation is a significant health-care problem with no universally accepted method of prevention. Barrier methods of prevention have been extensively tested and licensed, and this article examines the evidence.

Peritoneal adhesions: facing the enemy

BACKGROUND

Postsurgical adhesions severely affect the quality of life of millions of people worldwide. Numerous attempts have been made to prevent or reduce the incidence of peritoneal adhesions, but with limited success.

DATA SOURCES

An extensive Medline search, textbooks, scientific reports and scientific journals are the data sources. We also reviewed reference lists in all articles retrieved in the search as well as those of major texts regarding postsurgical intraperitoneal adhesion formation.

CONCLUSIONS

A multifactorial approach including minimizing tissue injury, prophylactic antibiotic usage to reduce infectious morbidity, and biochemical agents with or without biomechanical barriers will reduce the amount and severity of adhesions. However, further research is needed to establish the safety, effectiveness and also the cost/benefit ratio of these substances in human subjects.

The Role of Simvastatin on Postoperative Peritoneal Adhesion Formation in an Animal Model

AIM

The aim of this study is to show the effect of simvastatin on intra-abdominal adhesion formation.

METHOD

Adhesion formation was achieved by scratching the cecum and anterior abdominal wall following median laparotomy. Three different groups of 10 rats each were formed. In group I, 0.57 mg/kg/day simvastatin was injected intraperitoneally right after the operation and for 5 days thereafter. In group II, an equal dose of simvastatin to that used in group I was given via gavage. A physiological saline solution was given to group III for the same period of time. On the 6th and 14th day, blood samples were taken and peritoneal lavage was performed to measure the tissue-type plasminogen activator (t-PA) activity. Adhesions were graded via re-laparotomies on the 14th day after the first operation.

RESULTS

The adhesion scores were 1.40 +/- 0.22, 1.50 +/- 0.26, and 2.90 +/- 0.34 in groups I, II, and III, respectively (p = 0.007), and the score was higher in group III than in the other groups (p = 0.005, p = 0.011).

CONCLUSION

Intraperitoneal simvastatin application decreases adhesion formation by increasing the t-PA level in abdominal surgery.

Effect of Sirolimus in the Prevention of Adhesions Around Intraabdominal Prosthetic Graft

BACKGROUND

Adhesions due to the reactions caused by the grafts used in primary vascular operations can lead to various problems when a secondary operation is necessary. These problems include bleeding, injuries to neighboring organs, and complications occurring due to a prolonged operation. We investigated the effects of sirolimus, which has antiproliferative features, on vascular adhesions.

METHODS

The abdominal aorta of rats was explored and abrasions applied. Following the fixation of a polytetrafluoroethylene (PTFE) graft on the abdominal aorta, sirolimus (rapamycin) is applied (in powdered form) onto the grafts of the study group. Eight weeks later a laparotomy was repeated and any adhesions were evaluated.

RESULTS

In the study group the adhesions were determined to be fewer in number and milder in severity. Severe cases of adhesion were determined in the control group.

CONCLUSIONS

Therefore, sirolimus applied around the prosthesis in vascular operations was determined to be effective at preventing possible adhesions.

Closure vs. nonclosure of the peritoneum at cesarean delivery

OBJECTIVE

To compare the frequency and severity of celiac adhesions following cesarean sections performed with and without closure of the parietal and visceral peritoneum.

METHODS

A retrospective cohort study involved 612 women who underwent their second lower-segment transverse cesarean section.

RESULTS

Nonclosure of the parietal peritoneum at the time of the first cesarean section was associated with significantly more visceral adhesions than closure (16.2% vs. 8.1%; P=0.003), and closure of the visceral peritoneum had a similar effect (16.1% vs. 6.7%; P=0.02). However, the difference in rates of severe adhesions was not statistically significant (12.9% vs. 17.6%; P=0.12). After controlling for confounding variables, it was found that closure of the parietal peritoneum reduced the rate of visceral adhesions 2.7-fold. Trial of labor before and fever after surgery increased the risk of severe adhesions 6.1-fold and 5.6-fold, respectively.

CONCLUSION

Nonclosure of the peritoneum at primary cesarean section is associated with a significantly increased risk of visceral adhesions.

Induction and assessment methods used in experimental adhesion studies

Infertility and intestinal obstruction are well-known complications, arising from adhesion formation after intra-abdominal operations. Basic principles of adhesion formation have been found through animal studies. In addition, examination of agents for the prevention of adhesions can be easily made using experimental studies. However, lack of uniformity in study design makes assessment of the efficacy of any prophylactic regimen difficult. In this review, the material and methods used in experimental studies designed for adhesion formation or prevention were evaluated in detail, with experimental studies published in the literature from 1960 to 2003 being evaluated. Several methods for adhesion induction have been described in the literature. Severity of the adhesion varies from method to method, with the main problem being the lack of uniform expression of study results. Extensive use of complex adhesion classification systems should be used to resolve this discordance between experimental studies.

Current Management of Small-Bowel Obstruction

The most significant advances in the management of small-bowel obstruction are developments in imaging modalities available to assist in the diagnosis itself, as well as to possibly assist in the early identification of those cases requiring urgent operative decompression. The most marked of these have been in the use and interpretation of contrast-enhanced CT. This has decreased the use of barium studies and has largely supplanted ultrasound and magnetic resonance imaging in the management of these patients. Diagnostic and therapeutic laparoscopic techniques are also growing in both capability and popularity. Laparoscopic adhesiolysis and the adjuvant of bioresorbable membranes each hold promise but have yet to become established as standard treatment. Further progress is needed in the detection of early, reversible strangulation. As a consequence, the fundamentals of the surgical management of small-bowel obstruction have evolved little over the past 15 years. With our persistent inability to detect reversible ischemia, a substantial risk of progression to irreversible ischemia remains when surgery is delayed, particularly in the setting of suspected complete obstruction.

Electron microscopic alterations of the rat's pleura after experimental haemothorax

The initial signs of pleural reactivity and the subsequent mechanisms of pleural healing still remain unsolved. The visceral and parietal (costal and diaphragmatic) pleura were investigated following an experimental haemothorax (EH) by transmission electron microscopy. Young-adult Wistar rats were divided in five groups and survived 6 hours, 1, 3, 8 and 15 days respectively after EH. Six hours after EH the mesothelial cells had a more prominent lysosomal system and electron-dense material in the vesicles, as in the dilatated intercellular spaces. On the 1st day of the EH the mesothelial cytoplasm formed a thin interrupted band. The extravasal cells built multiple layers over the basal lamina, leading to a thicker submesothelial layer, occupying the superficial position toward the pleural cavity. The activated mesothelial cells covered both pleural sheets on the 3rd day after EH. Eight days after EH different membrane bodies, large apical evaginations, elastic-like formations, an extensive vesicular and cytofilamentous systems characterized the mesothelium. The wider elastic membrane showed thickenings, protrusions, bifurcations and double course. Fifteen days after EH larger zones in both pleural sheets displayed thinner basal lamina, remnants of elastic membrane and a thicker submesothelial layer. In conclusion, different newly formed structures (reversible and stable) retain the tendency of enlargement of the pleural surface in all investigated periods. Simultaneous intercellular and transcellular transport, as an increase of the lysosomal system characterize the passing of the electron-dense material through the mesothelium. The early period (until 3rd day after EH) is characterized by more prominent mesothelial changes, involving activated cells. The initiation of the late period (on the 8th day after EH) begins with the appearance of lamellar bodies and newly formed elastic membrane. The following late changes (on the 15th day after EH) concern predominantly the components of the connective tissue layer, such as collagen accumulations and blood capillaries. The present data suggest that the alterations over the entire pleura are irregular and asynchronous, showing significant morphological differences in both pleura sheets, some of them are diffuse in character, the final ones appear to be stable and ensure incomplete pleural restoration.

Regulation of expression of tissue plasminogen activator and plasminogen activator inhibitor-1 by dichloroacetic acid in human fibroblasts from normal peritoneum and adhesions

OBJECTIVE

As part of our ongoing studies to understand the biologic mechanisms of wound repair that lead to postoperative adhesions, we have identified characteristics of an adhesion phenotype that differs between fibroblasts that are obtained from human normal peritoneum and adhesions. In this study, we sought to examine whether stimulation of aerobic metabolism would alter differential expression of tissue plasminogen activator and plasminogen activator inhibitor-1, thereby creating a milieu likely to be less favorable to postoperative adhesion development. To examine this issue, we used a compound, dichloroacetic acid, that stimulates the pyruvate dehydrogenase complex, which causes pyruvate to be metabolized in the Kreb's cycle rather than being converted into lactate, thereby switching anaerobic to aerobic metabolism.

STUDY DESIGN

Human fibroblasts from normal peritoneum and adhesions were cultured in the absence or presence of dichloroacetic acid (100 microg/mL) for 24 hours, under normal and hypoxic (2% O(2)) conditions. Real-time reverse transcriptase-polymerase chain reaction of tissue plasminogen activator, plasminogen activator inhibitor-1, and a housekeeping gene beta-actin was performed with messenger RNA that was extracted from all treatment points.

RESULTS

Dichloroacetic acid stimulated normal peritoneal fibroblast tissue plasminogen activator messenger RNA expression under hypoxic conditions. In adhesion fibroblasts, dichloroacetic acid treatment enhanced tissue plasminogen activator messenger RNA expression under both normoxic and hypoxic conditions. Plasminogen activator inhibitor-1 messenger RNA expression was unaltered by dichloroacetic acid in normoxic normal peritoneal fibroblasts; but during culture under hypoxic conditions, dichloroacetic acid reduced plasminogen activator inhibitor-1 messenger RNA expression. Similarly, in adhesion fibroblasts, dichloroacetic acid reduced plasminogen activator inhibitor-1 messenger RNA expression under both normoxic and hypoxic conditions. As a result, in normal peritoneal fibroblasts under hypoxic conditions and in adhesion fibroblasts under normoxic and hypoxic conditions, dichloroacetic acid greatly increased the tissue plasminogen activator/plasminogen activator inhibitor-1 ratios.

CONCLUSION

These findings confirm that fibroblasts from adhesions are characterized by reduced tissue plasminogen activator and increased plasminogen activator inhibitor-1 production. These observations are extended to show the stimulation of oxidative metabolism by dichloroacetic acid increases tissue plasminogen activator expression under hypoxic conditions. Dichloroacetic acid reduces plasminogen activator inhibitor-1 production by hypoxic normal peritoneal fibroblasts and adhesion fibroblasts under hypoxic conditions. The resultant increases in the tissue plasminogen activator/plasminogen activator inhibitor-1 ratios would favor the development of a fibrinolytic milieu, which would be expected potentially to limit postoperative adhesion development. Thus, regulation of metabolic activity of peritoneal cells may provide a target for future interventions for the reduction of the development of postoperative adhesions, particularly as intervention relates to the healing of peritoneal sites that previously had adhesions. (eg, sites of potential adhesion reformation).

Prevention and treatment of gastrointestinal adhesions

As with many aspects of clinical medicine, there is yet to be a single or definitive cure for postoperative adhesion formation. Current methods of prevention target risk factors predisposing horses to adhesion formation. Systemic pharmacologic therapies, such as antimicrobials, nonsteroidal anti-inflammatory drugs, Salmonella antiserum, and hyperimmune plasma, help to reduce abdominal inflammation and minimize the effects of endotoxemia. Intra-abdominal or systemic heparin aids in enhancing peritoneal fibrinolysis. Prokinetic therapy promotes early postoperative return of intestinal motility, minimizing the propensity for adhesion formation between apposing adynamic segments of intestine. Mechanical separation of potentially adhesiogenic serosal and peritoneal surfaces is commonly achieved with use of abdominal lavage, protective coating solutions, and barrier membranes. Ongoing and future research is directed toward a better understanding of the local effects of intestinal trauma and the corresponding response of the fibrinolytic system. Recognition of horses at high risk for adhesion formation helps to guide the equine surgeon to an appropriate perioperative and intraoperative plan for adhesion prevention, including good surgical technique and a combination of adjunct therapies.

Prevention of intraperitoneal adhesion formation using beta-glucan after ileocolic anastomosis in a rat bacterial peritonitis model

BACKGROUND

To investigate the effects of beta-glucan on intraabdominal abscess and adhesion formation after ileocolic anastomosis in a rat bacterial peritonitis model.

METHODS

Sixty male Wistar rats were used in this study. Bacterial peritonitis was induced by performing a cecal ligation and puncture (CLP). On the first day, abdomen was reopened and peritoneal fluid samples were taken for microbiological examination. Thereafter, cecum was resected and ileocolic anastomosis was made. Group 1 rats were given 1 mL of normal saline as a placebo. Group 2 and group 3 rats were given beta-D-glucan 2 mg/kg by intramuscularly; 1 mg of beta-1,3-D-glucanase was administered to group 3 rats just after the use of beta-D-glucan. Half of each group were killed at day 7 and at day 21, respectively. Adhesions were scored and the presence of intraabdominal abscesses was noted.

RESULTS

One day after CLP, microbiological examination showed polymicrobial bacterial peritonitis. Five (8%) of the 60 animals died owing to sepsis. One week after CLP, in two rats in each group developed abscess formation. Three weeks after CLP, abscess formation was observed in only one rat in each group. The rats treated with the beta-glucan had significantly lower adhesion scores than did the saline-treated rats (P = 0.008 at one week; P = 0.001 at 3 weeks). Administration of beta-glucanase inhibited beta-glucan activity and resulted in more adhesions (P = 0.022 at 1 week; P = 0.006 at 3 weeks).

CONCLUSIONS

Although the use of beta-glucan after ileocolic anastomosis in rats with experimentally developed intraabdominal sepsis does not have any significantly effect on mortality and abscess formation, beta-glucan is capable of reducing the frequency of adhesion. This effect of beta-glucan has been prevented with beta-glucanase

Plasminogen activator/plasminogen activator inhibitor-1 and cytokine modulation by the PROACT System

OBJECTIVE

To examine the effects of the PROACT treatment on the fibrinolytic system and inflammatory cytokines in human peritoneum.

DESIGN

Controlled clinical study.

SETTING

University hospital.

PATIENT(S)

Nine subjects undergoing laparotomy had peritoneal samples taken at the incision.

INTERVENTION(S)

The PROACT applicator was inserted through the peritoneal incision, and treatment of peritoneum was performed twice. A peritoneal sample was taken from one treated area. At closure, the second treated sample and an additional control sample were taken. All four samples were snap frozen in liquid nitrogen. Samples were homogenized and protein content extracted.

MAIN OUTCOME MEASURE(S)

Concentrations of total and active transforming growth factor-beta 1 (TGF-beta1), tumor necrosis factor-alpha (TNF-alpha), tissue-type plasminogen activator (t-PA), urokinase plasminogen activator (uPA), and plasminogen activator inhibitor 1 (PAI-1) were obtained.

RESULT(S)

Total TGF-beta1 at opening was 30% less in treated samples. At closure, active TGF-beta1 increased significantly (163%) in control samples and not in treated samples. Tumor necrosis factor alpha was detectable only in control samples at closure. During surgery, tPA levels showed a marked decrease in control samples vs. a small increase in treated samples. Levels of uPA increased significantly only in the control samples. In control samples, tPA/PAI-1 ratio was two thirds of treated sample ratio.

CONCLUSION(S)

Heating of the peritoneum with the PROACT System modulates the biologic tissue response to induce effects that would be consistent with inhibition of postoperative adhesion development.

Risk of small bowel obstruction after the ileal pouch-anal anastomosis

OBJECTIVE

To determine the incidence of small bowel obstruction (SBO), to identify risk factors for its development, and to determine the most common sites of adhesions causing SBO in patients undergoing ileal pouch-anal anastomosis (IPAA).

METHODS

All patients undergoing IPAA at Mount Sinai Hospital were included. Data were obtained from the institution's database, patient charts, and a mailed questionnaire. SBO was based on clinical, radiologic, and surgical findings. Early SBO was defined as a hospital stay greater than 10 or 14 days because of delayed bowel function, or need for reoperation or readmission for SBO within 30 days. All patients readmitted after 30 days with a discharge diagnosis of SBO were considered to have late SBO.

RESULTS

Between 1981 and 1999, 1,178 patients underwent IPAA (664 men, 514 women; mean age 40.7 years). A total of 351 episodes of SBO were documented in 272 (23%) patients during a mean follow-up of 8.7 years (mean 1.29 episodes/patient). Fifty-four patients had more than one SBO. One hundred fifty-four (44%) of the SBOs occurred in the first 30 days; 197 (56%) were late SBOs. The cumulative risk of SBO was 8.7% at 30 days, 18.1% at 1 year, 26.7% at 5 years, and 31.4% at 10 years. The need for surgery for SBO was 0.8% at 30 days, 2.7% at 1 year, 6.7% at 5 years, and 7.5% at 10 years. In patients requiring laparotomy, the obstruction was most commonly due to pelvic adhesions (32%), followed by adhesions at the ileostomy closure site (21%). A multivariate analysis showed that when only late SBOs were considered, performance of a diverting ileostomy and pouch reconstruction both led to a significantly higher risk of SBO.

CONCLUSIONS

The risk of SBO after IPAA is high, although most do not require surgical intervention. Thus, strategies that reduce the risk of adhesions are warranted in this group of patients to improve patient outcome and decrease healthcare costs.

The effectiveness of systemic antibiotics in preventing postoperative, intraabdominal adhesions in an animal model

OBJECTIVE

Postoperative intraabdominal adhesions can be prevented by antibiotic lavage. We assessed whether systemic antibiotics could prevent adhesion formation in a rat model.

METHODS

Cecal abrasion was performed in the peritoneal cavities of 40 Wistar albino rats. Twenty rats were treated with a 5-day course of cefepim and metronidazole; the remaining animals were given saline injections. The animals were sacrificed 14 days after surgery. Adhesion severity scores and histopathologic findings were compared.

RESULTS

The median adhesion severity score was 2 (0-3) in the antibiotic group and 2.5 (1-4) in the controls (P = 0.03). In tissue specimens from controls, the adhesions were marked by mature collagen bundles. In treated rats, the adhesions were immature, characterized by early inflammatory cells, less collagen formation, and no collagen bundles.

CONCLUSIONS

Postoperative systemic antibiotics slow adhesion formation and reduce the severity of the adhesions.

Infections in patients undergoing peritoneal dialysis

Considering experience acquired in the past years, it seems as though physicians have reached a plateau in the frequency of peritonitis. A peritonitis rate of 1 every 2 patient years may be acceptable. Further reduction of this peritonitis rate will require inordinately large efforts on all fronts. One will have to consider what are the acceptable costs and risks of peritonitis in patients on peritoneal dialysis. New developments in catheter technology, improved connections, better understanding of patient selection and training programs, improved diagnostic and therapeutic methods in the management of peritonitis, and understanding of the infectious and immune processes are eagerly awaited developments.

The influence of intraoperative complications on adhesion formation during laparoscopic and conventional cholecystectomy in an animal model

BACKGROUND

The aim of this study was to evaluate the extent of postoperative adhesion formation after laparoscopic and open cholecystectomy.

MATERIALS AND METHODS

Qualified surgeons performed 60 experimental laparoscopic cholecystectomies (LC) in dogs with the aim to acquire the laparoscopic technique. To assess the relation between the complications during the operation (bleeding, laceration of the liver bed, or gallbladder perforation) and the formation of adhesions, surviving animals were divided into four groups according to the type of complication occurred. Assessment of the results was made by second-look laparoscopy 4 weeks after LC using the adhesion index (AI; score range, 0-4). The animals then were killed so the extent of adhesion formation could be measured. As a control, open cholecystectomy was performed in 15 dogs without intraoperative complications. The Mann-Whitney rank-sum test and Dunn's method were used for statistical analysis.

RESULTS

No adhesion formation or intraoperative complications were registered in the laparoscopic group I. In all the cases wherein bleeding or laceration of the liver bed occurred and was managed with electrocoagulation, adhesions formed. Adhesion formation in these groups was significantly higher than in "ideal LC" or cases of gallbladder perforation alone (p < 0.01). All the animals in the control group developed significantly more adhesions than those in the experimental group (p < 0.05).

CONCLUSIONS

It seems that LC has a lower rate of adhesion formation than the conventional open technique. Complications such as bleeding or laceration of the liver bed during LC can enhance adhesion formation. No adhesion formation can be mentioned in relation to gallbladder perforation during LC.