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5-Nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) is a non-specific chloride channel blocker. Peritoneal adhesion is an inevitable complication of abdominal surgery and remains an important clinical problem, leading to chronic pain, intestinal obstruction, and female infertility. The aim of this study is to observe the effects of NPPB on peritoneal adhesions and uncover the underlying mechanism. The formation of postoperative peritoneal adhesions was induced by mechanical injury to the peritoneum of rats. MTT assay and wound-healing assay were used to evaluate proliferation and migration of primary cultured adhesion fibroblasts (AFB) respectively. Whole-cell chloride currents were measured using a fully automated patch-clamp workstation. Cell volume changes were monitored by light microscopy and video imaging. Our results demonstrated that NPPB could significantly prevent the formation of peritoneal adhesion in rats and inhibit the proliferation of AFB in a concentration-dependent manner. NPPB also reduced the migration of AFB cells with an IC 50 of 53.09 μM. A 47% hypotonic solution successfully activated the I Cl,vol in AFB cells. The current could be blocked by extracellular treatment with NPPB. Moreover, 100 μM NPPB almost completely eliminated the capacity of regulatory volume decrease (RVD) in these cells. These data indicate that NPPB could prevent the formation of postoperative peritoneal adhesions. The possible mechanism may be through the inhibition of the proliferation and migration of AFB cells by modulating I Cl,vol and cell volume. These results suggest a potential clinical use of NPPB for preventing the formation of peritoneal adhesions.

Formation of intraperitoneal adhesions after abdominal or pelvic surgery is a very common phenomenon. Although there is no universally accepted definition, they are bridges of scar tissue between the various organs of the peritoneal cavity as a result of a local repair process excessively. Adhesions can be congenital or acquired as a local inflammatory process. Some adhesions can be asymptomatic, but many of them can cause severe complications such as abdominal or pelvic pain, female infertility, and intestinal obstruction. Physicians and patients should be informed of the possibility of postoperative intraperitoneal adhesions and this possibility should be mentioned in the informed consent signed by the patient. The formation of adhesions has multiple proinflammatory mechanisms involved, many with a pathophysiology still incomplete understood. Laparoscopic procedures do not diminish much the possibility of developing postoperative adhesions.Diagnostic imaging is quite uncertain, and the possibilities of preventing with a poor final result. The use of correct surgical technique and avoidance of traumatic intraperitoneal organs maneuvers may help reduce postoperative adhesions incidence., (Celsius.)

A huge number of factors play a significant role in the process of adhesion formation, like bleeding, the presence of foreign bodies, tissue injury, tissue destruction, ischemia and hypoxia. Adhesions are present in 95% of the cases following abdominal surgery. As a result of adhesions a large number of postoperative complications can occur, such as abdominal pain, bowel motility disturbances and infertility. Hence, it is important to know the precise mechanism of adhesion formation process and establish a suitable animal model to investigate the underlying mechanisms. Molecules which play a part in the process of adhesion formation were collected from the international literature. Male Wistar rats were used to create the adhesion model. Bleeding, implantation of foreign bodies, creation of ischemic areas and tissue destructions were carried out. Within this experiment the tiny bleeding and ischemic areas did not result in adhesion formation. The adhesion formation due to foreign body implantation depends on the type of the materials. Due to the inhibitory mechanism of adhesion formation there was no adhesion detectable due to tiny peritoneal destruction. The most reliable model was the one when gross tissue destruction of the abdominal wall was applied and the resulting bleeding initiated the adhesion formation process. It is also extremely important to know the key participants in the complex process of adhesion formation. This reliable model can help to work out the proper method of prevention.

Background: Laparoscopic surgery has been incorporated into common surgical practice. The peritoneum is an organ with various biologic functions that may be affected in different ways by laparoscopic and open techniques. Clinically, these alterations may be important in issues such as peritoneal metastasis and adhesion formation., Methods: A literature search using the Pubmed and Cochrane databases identified articles focusing on the key issues of laparoscopy, peritoneum, inflammation, morphology, immunology, and fibrinolysis., Results: Laparoscopic surgery induces alterations in the peritoneal integrity and causes local acidosis, probably due to peritoneal hypoxia. The local immune system and inflammation are modulated by a pneumoperitoneum. Additionally, the peritoneal plasmin system is inhibited, leading to peritoneal hypofibrinolysis., Conclusion: Similar to open surgery, laparoscopic surgery affects both the integrity and biology of the peritoneum. These observations may have implications for various clinical conditions.

Background: Animal experiments have suggested that the laparoscopic peritoneal environment is hypoxic. This study aimed to investigate whether peritoneal tissue is hypoxic on a cellular level during a carbon dioxide (CO(2)) pneumoperitoneum at different intraperitoneal pressures (IPPs) and to determine the short-term effects of surgical injury on the hypoxia status of peritoneal tissue in the injured peritoneum and the distant noninjured peritoneum at cellular and molecular levels., Methods: Experiment 1: Mice were divided into five groups according to the following treatments: anesthesia alone, laparotomy, and CO(2) pneumoperitoneum at IPPs of 2, 8, or 15 mmHg. Over the course of each experiment, the peritoneal tissue-oxygen tension (PitO(2)) was continuously monitored. Experiment 2: On the first day, the mice were divided into three groups according to the following treatments: CO(2) pneumoperitoneum at an IPP of either 2 or 8 mmHg or laparotomy. The bilateral caudal epigastric arteries and uterine horns then were coagulated using a bipolar cautery device. On day 7, peritoneal tissue samples were collected for real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry. In both experiments, pimonidazole hydrochloride was used to detect tissue hypoxia at a cellular level., Results: Experiment 1: Peritoneal hypoxia at both tissue and cellular levels was detected only in the groups treated with an IPP of 15 mmHg (PitO(2): 5.2 ± 1.0 mmHg, mean ± SEM). Experiment 2: The percentage of pimonidazole immunostained mesothelial and stromal cells from the distant noninjured peritoneum was significantly higher in the group treated with an IPP of 8 mmHg than in the other groups. Hypoxia-inducible factor 1 alpha subunit mRNA expression in the distant noninjured peritoneum of the group treated with an IPP of 8 mmHg was significantly higher than in the control group (anesthesia alone)., Conclusion: The CO(2) pneumoperitoneum itself did not cause peritoneal hypoxia at either a tissue or a cellular level in a mouse model when a low IPP was used.

Purpose: The purpose of this document is to review the non-barrier methods to prevent postoperative adhesion formation in humans., Methods: A MEDLINE computer search was performed to identify relevant articles using the keywords "postoperative adhesion prevention" "abdominal" and "humans". Subsequent searches were performed using the keyword "non-barrier" to further supplement the information obtained. After careful review of the abstracts, 15 articles were selected for inclusion in the manuscript., Results: Many methods, drugs and materials have been demonstrated effective for reducing postoperative adhesion in animal models. Among them, four types of drugs have been clinically used in attempts to reduce postoperative adhesions: gonadotropin-releasing hormone agonists, anti-inflammatory drugs, humidified CO(2) and hydroflotation. Many clinical and meta-analyses revealed that hydroflotation materials do not increase adhesion-free outcome. GnRHa pretreatment using a standard clinical dose (3.75 mg monthly) before myomectomy do not decrease adhesion formation. The role of CO(2) on the reduction and/or prevention of postoperative adhesions have been reported only in cardiac surgery. None of them have been adopted for clinical standard therapy, despite positive reports in animals or preclinical applications., Conclusion: In contrast to the results from animal studies, there is no substantial evidence that the use of non-barrier materials reduces postoperative abdominal adhesions in humans.

Background: Adhesion formation remains an almost inevitable consequence of abdominal procedures, potentially resulting in significant morbidity and mortality. There is an ongoing need to evaluate current understanding of adhesion formation and products aimed at prevention. Failure to keep up to date with adhesion treatment may subject clinicians to a greater medico-legal risk., Design: Review of published studies exploring the problem of peritoneal adhesion formation. This encompasses the underlying processes of adhesion formation combined with general approaches to reduce formation. An overview of products trialled to prevent formation in both the animal model and clinical setting describes products of scientific interest and commercial success., Results: Advances in surgical technique, such as laparoscopic surgery, can help minimize the probability of adhesion formation. Currently barrier products, whilst reducing adhesion formation, have not been shown to reduce the risk of readmission with complications related to adhesions. Hybrid products may improve upon this situation., Conclusions: No single approach has been wholly satisfactory in reducing adhesions. Research into the processes driving adhesion formation is providing exciting new targets for therapeutic agents. It would seem plausible that with many promising avenues of research a revolutionary agent to reduce the incidence of adhesional small bowel obstruction may result., (Copyright © 2010 S. Karger AG, Basel.)

Background: To investigate whether surgical trauma in a rabbit adhesion formation model and the administration of normal saline (N/S), icodextrin (ID) and/or dimetindene maleate (DM) changes the permeability of the normal rabbit parietal peritoneum., Materials and Methods: A total of 45 female rabbits were operated on for adhesion formation and were euthanized 10 days later. In some rabbits, ID or N/S was instilled intraabdominally during operation, whereas in others DM was infused intravenously. In others, ID plus DM or no agent was used. Specimens were obtained postoperatively and were mounted between Ussing chambers. Amiloride was used to investigate Na(+) channels. Transmesothelial resistance (R(TM)) was determined as a permeability indicator., Results: Amiloride increased the R(TM) of both surfaces. Surgical trauma increased R(TM) and partially inhibited the effect of amiloride. ID and N/S increased R(TM) and inhibited the effect of amiloride. Use of DM did not change R(TM) and did not inhibit the effect of amiloride. Use of ID plus DM slightly increased R(TM), but the effect of amiloride was blocked., Conclusions: Surgical trauma impairs the permeability of the normal rabbit parietal peritoneum. ID or N/S surmounted this effect, but DM did not, suggesting that surgical trauma is a diffuse process. Antiadhesion measures influence peritoneal physiology., (Copyright © 2010 S. Karger AG, Basel.)

Background: Even with the advent of bioresorbable barriers, complications due to visceral adhesions following surgery continue to occur. The use of a homologous adhesive barrier such as human peritoneal membrane (HPM) could prevent adhesions formation and enhance wound healing. This study evaluates HPM as an effective adhesive barrier in a porcine model simulating a ventral hernia procedure., Materials and Methods: Through a midline laparotomy, meshes (10 cmx10 cm) were sewn onto the intact peritoneum of a pig, on each side of a midline incision in superior and inferior positions (4 randomized meshes/pig, n=9 pigs). The pigs were survived for 90 d. The meshes used were: HPM, compressed polytetrafluoro-ethylene (cPTFE), cPTFE+HPM, and polyester-collagen composite (PX). Exploratory laparoscopy was performed at 30 and 90 d to evaluate the extent of visceral adhesions. At necropsy, the extent and tenacity of visceral adhesions as well as material-abdominal wall integration were evaluated. Finally, host tissue response was assessed through scoring of inflammation, foreign body reaction, and mesothelialization., Results: HPM and PX led to the least extent and tenacity of visceral adhesions compared to cPTFE and cPTFE+HPM, but integrated less strongly within the adjacent abdominal wall. PX displayed the most robust foreign body reaction among all prosthetic materials, while HPM scored similarly to the native peritoneum. The extent of mesothelialization was similar throughout the materials tested., Conclusions: The HPM barrier which promotes long-term peritoneal remodeling could diminish postsurgical intraperitoneal adhesions following hernia repair.

To summarized the experiences from our basic experimental and clinical research on peritoneal dialysis. In the past 16 years, peritoneal fibrosis rat models and rabbit models of peritonitis were first established successfully in our laboratory in China. Peritoneal mesothelial cells were also separated and identificated. Besides, we assessed the biocompatibility of peritoneal dialysis fluid and analyzed the molecular mechanism of peritoneal mesothelial cell injury. We demonstrated the key role of transforming growth factor-beta1 (TGF-beta1), connective tissue growth factor (CTGF) and peroxisome proliferative activated receptor-gamma (PPAR-gamma) in the pathogenesis of peritoneal fibrosis, as well as their regulation of molecular mechanism. Furthermore, we transfected the plasmids encoding TGF-beta1-shRNA or pCTGF-shRNA into peritoneal cells and tissues by nanocarrier technologies. In clinical research, the positioning of peritoneal dialysis catheters, peritoneal dialysis treatment modalities and the prevention and treatment of its complications were studied. The characteristics and mechanism of solute transport in peritoneal dialysis was also explored.

Background: Peritoneal fibrinolysis is crucial in the peritoneal healing processes and subsequent adhesion formation. During conventional surgery, the peritoneal fibrinolytic system is rapidly disturbed. Short-term laparoscopy does not seem to affect peritoneal fibrinolysis. The aim of the present study was to assess the effect of prolonged laparoscopic surgery on peritoneal fibrinolysis., Methods: Twelve consecutive patients undergoing laparoscopic gastric bypass surgery for morbid obesity were included in the study. During the procedure, biopsies of the parietal peritoneum were taken at the start of the procedure and each 45 min afterward. Tissue samples were homogenized and tissue-type plasminogen activator (tPA) antigen, tPA activity, urokinase-type PA antigen, and plasminogen activating inhibitors type 1 antigen were measured using commercial assay techniques., Results: Both tPA antigen and its activity progressively decreased during the procedure, reaching significant levels after 90 min of surgery. The levels of uPA antigen and plasminogen activating inhibitors antigen did not significantly change throughout the procedure., Conclusions: As for conventional surgery, prolonged laparoscopic surgery causes a decreased fibrinolytic activity in the peritoneum due to decreased tPA levels.

Consequences and complications of postsurgical intra-abdominal adhesion formation not including small bowel obstruction and secondary infertility are substantial but are under-exposed in the literature. Inadvertent enterotomy during reopening of the abdomen or subsequent adhesion dissection is a feared complication of surgery after previous laparotomy. The incidence can be as high as 20% in open surgery and between 1% and 100% in laparoscopy depending on the underlying disease. Delayed postoperative detection of enterotomy is a particular feature of laparoscopy associated with significant morbidity and mortality. Adhesions to the ventral abdominal wall are responsible for the majority of trocar injuries. Both trocar injuries and inadvertent enterotomies result in conversion from laparoscopy to laparotomy in almost 100% of cases. There is a paucity of data on other organ injury, such as liver laceration or bladder perforation. Dissecting adhesions before executing the planned operation takes on average 20 min, being one-fifth of the total operating time in patients having had previous open colorectal surgery. There is some evidence that postoperative morbidity and mortality of patients who need adhesiolysis is higher than that of patients with a virgin abdomen. The necessity to dissect adhesions is associated with increased hospital stay. Postsurgical adhesions are considered a main reason for conversion from laparoscopy to laparotomy in many types of procedures including laparoscopic colonic resection. Adhesion formation is part of the innate peritoneal defence mechanism in peritonitis. Abscess formation and bleeding, organ injury and fistula formation at 'on demand' relaparotomies are well-known complications after surgery for intra-abdominal sepsis associated with fibrinous adhesions. The clinical magnitude hereof is poorly researched. Postsurgical adhesions may cause pain as evidenced by pain mapping clinical experiments. Filmy adhesions between movable organs and the peritoneum appear to be worse in terms of generating pain. The high caseload of gynaecological and some colorectal practices suggest an enormous impact of adhesion-related chronic abdominal and pelvic pain on patient's wellbeing and socio-economic costs. The significant risk of inadvertent enterotomy, conversion to laparotomy and trocar injury, and the associated postoperative morbidity and mortality and increased length of hospital stay warrant routine informed consent of adhesiolysis related complications in patients scheduled for abdominal or pelvic reoperation.

Adhesions perhaps should be considered to be the most frequent complication of abdominopelvic surgery. The incidence is well documented but the burden to the cost of healthcare is not given the recognition it deserves. For any other disease or operation, with a recognized complication with such a high incidence, a prophylactic therapy or preventative strategy would be recommended if not mandatory. Adhesions occur in over 95% of all abdominal operations and can account for up to 6% of all readmissions. The problem affects all ages and exists for the life of the patient.

The peritoneum is a serous membrane, which has a protective function for the contents of the abdominal cavity. It maintains homeostasis by allowing exchange of molecules and production of peritoneal fluid, thus providing an environment in which intra-abdominal organs can function properly. When traumatized, whether by surgery or due to inflammatory processes, a series of responses come into action to regenerate the injured part of the peritoneum. The inflammatory reaction causes influx of inflammatory cells but also activates resident mesothelial cells, ultimately leading to a fibrinous exudate. Depending on the severity of the trauma this exudate is transient due to fibrinolysis, or becomes more dense as a result of fibroblasts persisting, leading to fibrinous adhesions. A pivotal role is taken by the enzyme plasmin and its promotors and inhibitors; it is mainly the tissue-type plasminogen activator/plasminogen activator inhibitor ratio which determines the rate of fibrinolysis and therefore the rate of adhesion formation. The rate of injury determines the rate and extent of the inflammatory response to that injury; in its turn the inflammatory reaction determines the extent of adhesion formation. One should realize this when performing intra-abdominal surgery, which is in fact operating inside the peritoneal organ.

Aside from the normal 'ad integrum' peritoneal regeneration, the postoperative intraperitoneal adhesion formation process may be considered as the pathological part of peritoneal healing following any injury, particularly a surgical one. Despite a large body of clinical and experimental studies, its pathophysiology remains controversial. Moreover, a better understanding of the pathophysiological events and of the medical and surgical factors involved in the adhesion formation process is pivotal in any attempt to control this very frequent phenomenon and its serious consequences.

Damage to the peritoneum during abdominal surgery triggers a cascade of events aimed at repairing the damage. As part of this process, fibrin is deposited, which is the precursor to the formation of an adhesion between 2 damaged peritoneal surfaces. This can have a significant impact on morbidity and even mortality as well as large cost implications. Strategies to reduce adhesion formation include improving surgical techniques, optimizing laparoscopy conditions, using pharmacologic interventions targeted at the inflammatory response and/or fibrin deposition, and using agents that provide a physical barrier to adhesion formation. While these strategies have provided some success, none have yet proved totally successful in abolishing adhesions. Further research to ensure that adhesion prevention is optimal is therefore essential.

There are numerous approaches for exploring the lower lumbar vertebrae, and the anterior transperitoneal route is one of the most popular. Like all surgical techniques, this approach has advantages and disadvantages. It provides direct access to the target tissue through a small incision, exposes the anterior portion of the vertebrae well, and permits good visualization of the major vessels, thus reducing risk of vascular injury and life-threatening hemorrhage. However, compared to the extraperitoneal route, the transperitoneal approach carries higher risks for peritoneal complications. This article describes a new practical method for creating an extraperitoneal passageway or "window" during transperitoneal approaches to the lower lumbar vertebrae. Isolation of the peritoneal cavity and its contents with this technique can reduce peri- and postoperative abdominal complications.

Peritoneum is a serous membrane with a significant fibrinolytic potential, playing an important role in the abdominal response to trauma. Peritoneum takes part in the formation and degradation of postoperative adhesions. The sequence of changes during the adhesion formation is indispensable in the healing of peritoneal trauma. Presented paper describes the short historical update of mesothelial research and review of contemporary knowledge over the peritoneal function with special regard to its fibrinolytic activity. The factors influencing the fibrinolytic capacity of peritoneum were discussed, as well as present pathways of research on the prevention of postoperative adhesion formation.

Objective: To study the modulation of the inducible nitric oxide synthase/nitric oxide (iNOS/NO) expression system in fibroblasts isolated from human peritoneum and adhesion tissues by hypoxia., Design: Prospective experimental study., Setting: University medical center., Patient(s): Cultures of fibroblasts from both peritoneum and adhesion tissues of five patients., Intervention(s): Hypoxia treatment of the primary cultured fibroblasts., Main Outcome Measure(s): We used Western and Northern blots to determine whether iNOS mRNA and its protein were present in peritoneal and adhesion fibroblasts and whether this expression is modulated by hypoxia. Multiplex reverse transcription polymerase chain reaction (RT-PCR) technique was used to quantify type I collagen mRNA in response to NG-nitro-L-arginine methyl ester (L-NAME). A terminal deoxynucleotidyl transferase mediated dUTP nick-end-labeling (TUNEL) assay was used to quantify apoptosis in response to NO donor S-nitro-N-acetyl-penicillamine (SNAP) treatment. A Griess assay was used to measure NO levels., Result(s): Peritoneal fibroblasts have significantly higher NO levels than adhesion fibroblasts. Hypoxia decreased NO in peritoneal fibroblasts to levels observed for adhesion fibroblasts. In addition, hypoxia increased both mRNA and protein levels of the iNOS gene in peritoneal and adhesion fibroblasts. Augmentation of NO by SNAP treatment increased apoptosis in adhesion fibroblasts. In contrast, SNAP had no effect on apoptosis of peritoneal fibroblasts. Inhibition of NO by L-NAME treatment increased type I collagen mRNA levels in peritoneal fibroblasts., Conclusion(s): Our findings confirm that adhesion fibroblasts produce less NO than normal peritoneal fibroblasts; NO may be the mechanism responsible for the creation and persistence of the adhesion phenotype.

We have previously shown that fibroblasts obtained from adhesions produce greater amounts of transforming growth factor-beta 1 (TGF-beta1) and extracellular matrix (ECM) molecules than normal fibroblasts isolated from normal peritoneum. The purpose of the current studies was to examine the effect of Tisseel (Baxter Healthcare Corporation, Glendale, CA), a fibrin sealant containing fibrinogen, aprotinin (a protease inhibitor), thrombin, and CaC1(2), on TGF-beta1 and ECM production by human peritoneal mesothelial cells, normal peritoneal fibroblasts, and adhesion fibroblasts. Multiplex reverse transcription-polymerase chain reaction using beta-actin as a housekeeping gene was used to determine mRNA levels of TGF-beta1 and ECM in these cells at 6, 12, 24, and 48 hours under normoxic conditions in the following treatment groups : fibrin sealant (Tisseel) alone; fibrin sealant with the two components diluted 1 : 2; fibrin sealant with the sealer protein component reconstituted without aprotinin (a protease inhibitor); fibrin sealant with the sealer protein component reconstituted without aprotinin (and both components diluted 1 : 2); fibrin sealant components diluted to physiologic concentrations; and control (culture media). The test compositions had little effect on TGF-beta1 mRNA expression in mesothelial cells and normal peritoneal fibroblasts, but resulted in a marked reduction of TGF-beta1 from adhesion fibroblasts. Expression of type I collagen by human peritoneal mesothelial cells was not detected; the compositions reduced type I collagen mRNA expression by both types of fibroblasts. Type III collagen was detected at six hours, and increased approximately 50 percent by culturing for 48 hours. Tisseel at full strength and with both components diluted 1 : 2 initially increased type III collagen mRNA levels; in contrast, type III collagen mRNA levels were reduced in mesothelial cells by the fibrin sealant without aprotinin at both concentrations and at physiologic concentrations. In both types of fibroblasts, the Tisseel compositions reduced type III collagen mRNA expression. Fibronectin mRNA were transiently reduced at six hours by approximately 50 percent in the presence of the Tisseel components, but then returned to control levels. Fibronectin mRNA levels were not altered in normal peritoneal fibroblasts, but were reduced by all but the physiologic concentration in adhesion fibroblasts. Tisseel may modulate human peritoneal mesothelial cell, normal peritoneal fibroblast, and adhesion fibroblast function. These results suggest that fibrin sealant prepared from the Tisseel kit without aprotinin has the ability to reduce ECM and TGF-beta1 mRNA levels, especially from adhesion fibroblasts, which may indicate a role in reduction of postoperative adhesion development.

Objective: To develop a laparoscopic mouse model to evaluate the hypothesis that mesothelial hypoxia during pneumoperitoneum is a cofactor in adhesion formation., Design: Prospective randomized trials., Setting: Academic research center., Animal(s): One hundred thirty female Naval Medical Research Institute (NMRI) mice., Intervention(s): Adhesions were induced by opposing monopolar lesions in uterine horns and pelvic side walls during laparoscopy and evaluated after 7 or 28 days under microscopic vision during laparotomy. The following pneumoperitoneum variables were assessed: duration (10 or 60 minutes), insufflation pressure (5 or 15 cm of water), insufflation gas (CO(2) or helium), and addition of oxygen (0-12%)., Main Outcome Measure(s): Adhesions were scored quantitatively and qualitatively for extent, type, and tenacity., Result(s): Scoring of adhesions 7 or 28 days after laparoscopic surgery was comparable. Adhesions increased with duration of pneumoperitoneum and with insufflation pressure and decreased with the addition of oxygen. Half-maximal reduction of adhesions was obtained at 1.5% oxygen, whereas a maximal reduction required only 2%-3%. The effect of CO(2) and helium was similar., Conclusion(s): These data demonstrate the feasibility of the intubated laparoscopic mouse model and confirm previous observations in rabbits, indicating that mesothelial hypoxia plays a key role in adhesion formation.

Objective: To determine the response of adhesion and peritoneal fibroblasts to hypoxia., Design: Prospective experimental study., Setting: University medical center., Patient(s): Primary cultures of fibroblasts established from the peritoneal and adhesion tissues of the same patients (n = 2) to minimize genetic variations., Intervention(s): Hypoxia treatment of the primary cultured fibroblast., Main Outcome Measure(s): Analyze the expression of extracellular matrix (ECM) components, metalloproteinases and their tissue inhibitors, growth factors, and cytokines in adhesion and peritoneal fibroblasts under normal and hypoxic conditions by reverse transcriptase/polymerase chain reaction analysis., Result(s): Compared to peritoneal fibroblasts, adhesion fibroblasts had a significant increase in the basal mRNA levels for collagen I, fibronectin, MMP-1, TIMP-1, TGF-beta 1, TGF-beta 2, and IL-10. Hypoxia resulted in a further increase in collagen 1, fibronectin, TIMP-1, TGF-beta 1, TGF-beta 2, IL-10, and IFN-gamma mRNA levels in both peritoneal and adhesion fibroblasts. The increase was more profound in adhesion fibroblasts., Conclusion(s): Hypoxia induces molecular changes in both peritoneal and adhesion fibroblasts, creating a milieu that favors adhesion development. The effect of hypoxia was more profound on adhesion fibroblasts.

Study Objective: To investigate the effects of peritoneal exposure to carbon dioxide (CO2) on peritoneal microcirculation and free radical scavenger (FRS) metabolism, and its role in potential adhesion formation after operative laparoscopy., Design: Randomized, controlled study (Canadian Task Force classification I)., Setting: University-affiliated hospital., Patients: Twenty-eight women undergoing operative laparoscopy for adnexal masses., Intervention: For each patient, a 1 x 1-cm sidewall peritoneal flap was excised at the end of laparoscopy and numbered randomly. Similar flaps obtained from 24 women immediately after entering the abdomen during laparotomy served as controls., Measurements and Main Results: Changes in glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) levels were studied in homogenized peritoneal tissues. The duration of CO2 exposure and amount of CO2 used were correlated with levels of free radical scavengers and compared with controls. Mean CO2 exposure, amount of CO2 used, and CO2 pressure (15 mm Hg) was similar between low irrigation and irrigated laparoscopy (118.3 +/- 25 and 39.2 +/- 8.81 min and 125 +/- 20 and 44.5 +/- 6.81 min, respectively). The change in FRS levels was significantly correlated with duration and amount of CO2 exposure (r = -0.92). Levels of GSH-Px, SOD, CAT, and GSH were significantly lower in the CO2 exposure group than in controls (0.57 micro mol, 1.8 ng, 48.5 micro mol, 1.5 nmol vs 0.8 micro mol, 2.6 +/- 0.4 ng, 79 micro mol, 3.6 nmol, respectively)., Conclusion: Exposure to CO2 has adverse effects on peritoneal microcirculation and cell-protective systems, which are proposed mechanisms in adhesion formation. Avoiding long CO2 exposure and copiously irrigating the abdominal cavity throughout surgery may lessen these effects. The potential role of the peritoneal FRS system on postoperative adhesion formation and its relation to estrogen status mandates further studies.

The increased incidence of postoperative adhesions and their complications have refocused attention on our understanding of adhesions, their clinical consequences and prevention. Postsurgical adhesions have four major negative impacts on health care outcomes. First, adhesions cause significant morbidity, including intestinal obstruction, infertility and pelvic pain. Second, adhesions are associated with multiple surgical complications. Third, these complications lead to greater surgical workload and utilization of hospital and other health care resources. Fourth, all these negative impacts result in significant economic burden to society. The complexities of adhesion formation and limitations in their understanding and research have hampered the development of satisfactory preventive treatments. Adhesions are highly differentiated, formed through an intricate process and associated with a complex organ, the peritoneum. The surface lining of the peritoneum is the key site in adhesion formation and prevention. Two unique properties of the peritoneal surface play key roles in these processes: its delicacy and its uniform, relatively rapid rate of re-epithelialization, irrespective of the size of injury. A suitable barrier that separates damaged peritoneal surfaces for the entire five to seven days of re-epithelialization is likely to prove effective in reducing adhesion formation. Postsurgical peritoneal repair begins with coagulation, which releases a variety of chemical messengers that bring about a cascade of events. Some of the principal cellular elements in this cascade are leukocytes, including polymorphonuclear neutrophils and macrophages, mesothelial cells, and fibrin. Following surgical injury, macrophages exhibit increased phagocytic, respiratory burst and secretory activity, and after day 5, are the major component of the leukocyte population. Macrophages also recruit new mesothelial cells onto the surface of the injury. These cells form small islands throughout the injured area which proliferate into sheets of mesothelial cells and accomplish re-epithelialization, usually five to seven days after surgical injury. The progenitor to adhesions is the fibrin gel matrix which develops in several steps. These include the formation and insolubilization of fibrin polymer and its interaction with fibronectin and a series of amino acids. Protective fibrinolytic enzyme systems of the peritoneal mesothelium, such as the tissue plasminogen activator (tPA) system, can remove the fibrin gel matrix. However, surgery dramatically diminishes fibrinolytic activity. This occurs in at least two ways: first, by increasing levels of plasminogen activator inhibitors and second, by reducing tissue oxygenation. Peritoneal re-epithelialization and adhesion formation thus can be seen as alternative pathways following peritoneal injury. The pivotal events determining the pathway are the apposition of two damaged surfaces and the extent of fibrinolysis. Development of strategies to separate damaged peritoneal surfaces and to foster an appropriate degree of fibrinolysis appears to be among the most promising avenues of adhesion prevention research. Hopefully, these efforts will lead to adhesion-free peritoneal healing following abdominal surgery.

Processes that result in either normal peritoneal tissue repair of fibrous adhesion formation have until recently been largely unexplored at the molecular level. Our group is investigating the molecular events underlying peritoneal healing and hypothesizes that peptide growth factors, cytokines, and their receptors, which are expressed by various cell types at the site of injury and are present in the peritoneal fluid, play key roles in regulating tissue repair processes. This regulation is highly complex, involving the individual action of and/or synergistic interactions among many substances. These include various members of the growth factor family, such as transforming growth factors alpha and beta (TGF-alpha and TGF-beta), and of the cytokine family. These growth factors and cytokines are synthesized and released by activated macrophages in the peritoneal fluid and in the wound and by other major cell types in the wound, suggesting that they have a role in an autocrine/paracrine mechanism. For normal peritoneal healing to occur, the availability of these signaling substances must be optimal, precise, and synchronized. Inhibition, interruption, or excess expression of these signals seems to be responsible for failure in normal healing, either impairment (nonhealing) or excess tissue formation (adhesion development). Evidence of the key role of TGF-beta in peritoneal healing and adhesiogenesis falls into four main categories: 1) the characteristics of TGF-beta in other settings; 2) the presence and 3) activity of TGF-beta and/or its receptors in peritoneal wounds and fluid; and 4) the effects of the application of excess TGF-beta and anti-TGF-beta antibody on adhesion formation. TGF-betas are chemotactic for fibroblasts and inflammatory cells and promote cell proliferation and differentiation and angiogenesis. They also regulate the expression of various components of extracellular matrix. In mice, subcutaneous TGF-beta induces the formation of granulation tissue, and in several animal models and in humans, excess TGF-beta activity has been linked to the development of kidney and liver fibrosis. TGF-betas and their receptors are expressed by various cells in peritoneal wounds and fluid and are present at higher levels in injured compared with uninjured tissues. In vitro studies in peritoneal wounds and fluid show that TGF-beta 1 significantly upregulates its own expression and the expression of several extracellular matrix components and of tissue inhibitors of matrix metalloproteinases (TIMPs) but downregulates the expression of matrix metalloproteinases (MMPs). Following uterine horn injury, rats given TGF-beta daily for five days developed adhesions in significantly greater number and severity than did untreated controls. Although anti-TGF-beta neutralizing antibody in rats failed to significantly reduce adhesion formation, it did reduce cellularity of fibrous tissue. Antisense oligonucleotides to TGF-beta effectively blocked macrophage expression of TGF-beta, indicating the possible use of this technique in adhesion prevention. Another potential clinical application of some of our findings includes targeted delivery of an anti-TGF-beta preparation by means of a suitable biodegradable barrier during the first five to seven days following peritoneal injury.

Postsurgical abdominal adhesions and their sequelae continue to present major clinical and medicoeconomic problems. A complex network of mediators and responses affecting at least five interrelated biological systems, including the fibrinolytic system, are involved in the pathogenesis of postsurgical adhesions. The fibrinolytic system degrades fibrin through the action of the enzyme plasmin, which is stored as the inactive substrate plasminogen. Fibrinolysis, by mediating fibrin degradation, appears to play a pivotal role in adhesiogenesis. Tissue-type plasminogen activator (tPA) is the chief plasminogen activator in the blood, but its activity is restricted by plasminogen activating inhibitors type 1 (PAI-1) and type 2 (PAI-2). Inadequate peritoneal fibrinolysis may result from decreased tPA, increased PAI-1 and PAI-2, or both. The causal relationship between a reduction in fibrinolytic capacity and the formation of adhesions has been demonstrated in animals. In human studies, plasminogen activator activity (PAA) was significantly reduced in peritoneal biopsies from patients with peritonitis compared with those from normal patients. During surgery, PAA declined significantly in both normal and inflamed peritoneum. tPA was responsible for about 95% of PAA. Reduced fibrinolysis in human peritoneum associated with peritonitis and abdominal surgery correlates with increased adhesion formation and may thus be an important early biochemical event leading to adhesion formation. The regulation of plasmin-mediated fibrin degradation in the peritoneal cavity is poorly understood. However, new insights in the cellular distribution of fibrinolytic components in peritoneal tissue suggest that the mesothelium appears to have a principal role in fibrin regulation in the peritoneal cavity and in the early formation of adhesions.

This article summarizes the discussions of the faculty and chairpersons on four major topics on postsurgical adhesions examined at the symposium, "Adhesions: Pathogenesis and Prevention". These topics are: 1) clinical significance; 2) pathogenesis; 3) research status and directions; and 4) recommendations for reduction or prevention. Abdominal postsurgical adhesions develop following trauma to the mesothelium, which is damaged often by surgical handling and instrument contact, foreign materials such as sutures and glove dusting powder, desiccation, and overheating. Postoperative adhesions occur after most surgical procedures and can result in serious complications, including intestinal obstruction, infertility, and pain. A long-term and unpredictable problem, postoperative adhesions impact the surgical workload and hospital resources, resulting in considerable health care expenditures. Although understanding of the pathogenesis of adhesions has improved recently, the molecular mechanisms involved continue to be delineated. Adhesions result from the normal peritoneal wound healing response and develop in the first five to seven days after injury. Adhesion formation and adhesion-free re-epithelialization are alternative pathways, both of which begin with coagulation which initiates a cascade of events resulting in the buildup of fibrin gel matrix. If not removed, the fibrin gel matrix serves as the progenitor to adhesions by forming a band or bridge when two peritoneal surfaces coated with it are apposed. The band or bridge becomes the basis for the organization of an adhesion. Protective fibrinolytic enzyme systems of the peritoneum, such as the plasmin system, can remove the fibrin gel matrix. However, surgery dramatically diminishes fibrinolytic activity. The pivotal events determining whether the pathway taken is adhesion formation or re-epithelialization are therefore the apposition of two damaged surfaces and the extent of fibrinolysis. Research in postsurgical adhesion formation and prevention abounds in a variety of avenues of investigation, including: 1) identification on a molecular level of the components involved in adhesiogenesis and their interactions; 2) clarification of the role of fibrin and fibrinolysis in adhesion formation; 3) standardization of design in preclinical and clinical studies of adhesion formation and prevention; 4) delineation of the relationship between adhesion formation and adhesive complications; and 5) elucidation of efficient, site-specific methods of prophylactic drug delivery. Currently, it seems logical to focus preventive research on development of barriers, fibrinolytic drugs, and selected agents such as phospholipids. The major strategies for adhesion prevention or reduction are adjusting surgical practice and applying adjuvants. Surgeons should adjust their major practices by: 1) becoming aware of the potential adhesive complications of a procedure; 2) minimizing the invasiveness of surgery; and 3) minimizing surgical trauma, ischemia, exposure to intestinal contents, introduction of foreign material into the body, and the use of talc- or starch-containing gloves. Available adjuvants include a newly developed by hyaluronic acid-phosphate-buffered saline solution applied intraoperatively to protect peritoneal surfaces from indirect surgical trauma and three mechanical barriers. One of these, a bioresorbable membrane consisting of hyaluronic acid and carboxymethylcellulose, has demonstrated efficacy and safety in both general and gynecological surgery. The other two barriers, one made of expanded polytetrafluoroethylene and one developed from oxidized regenerated cellulose, are indicated only for use in gynecological surgery.

Adhesion formation to the peritoneal scar was investigated in 108 white Wistar rats which had undergone midline laparotomy under ether anaesthesia. In 92 rats a microtrauma was produced by rubbing the intraperitoneal organs with dry gauze. After this procedure in 46 rats the abdominal cavity was closed by suturing the peritoneum and fascia, and in another 46 rats the peritoneum was left untouched. In the remaining 16 rats a sham operation was performed. The rats were sacrificed after 7, 14, 30 and 60 days and adhesion formation to the peritoneal scar was studied microscopically and macroscopically. It was found that in rats in which the peritoneum layer was sutured a significantly higher amount of adhesion to scar developed. The results of the sham operation proved that the method of abdominal-wall closure is responsible for the adhesion formation to scar after laparotomy.