Adhesions between visceral organs and the abdominal wall are frequent sequelae of abdominal or pelvic surgery, causing complications such as small bowel obstruction or infertility [2, 8, 23]. Safe, efficient and easily to apply barrier measures are still missing. Hyaluronic acid carboxymethylcellulose films, oxidized regenerated cellulose and extended polytetrafluoroethylene film have been used to prevent adhesions after surgical trauma . The use of a PVA membrane gave quite promising results clearly better than other commercially available products . Membranes are not applicable in every surgical site. Therefore a gel or a liquid solution is preferred in the prevention of post surgical adhesions.
Anti-adhesion barriers basically fall under two main categories: macromolecular solutions (crystalloids, polysaccharide, hyaluronic acid, fibrin, polyethylene glycol, phospholipids) and mechanical devices (oxidized-regenerated cellulose, hyaluronic acid-carboxycellulose, expanded polytetrafluoroethylene and autologous transplants).
Crystalloid solutions are proposed to work by hydro-floatation to separate raw peritoneal surfaces. But they have a negative effect on post-operative adhesions , because the volume of the applied crystalloids are absorbed very rapidly . By hydro-floatation and siliconization of intra-abdominal structures with polysaccharide such as Dextran solutions a physiological separation occurs between peritoneal surfaces. Data of Dextran solution used as a barrier are discussed controversial. There are studies showing good anti-adhesive results but other studies failed to demonstrate any clinical improvement and instead showed severe side effects such as edema, ascites and coagulopathy [37, 38].
Carboxymethylcellulose (CMC) is a derviate of cellulose and works by separating raw surfaces and allowing independent healing of traumatized peritoneal surfaces [39, 40]. CMC showed a good anti-adhesive effect in experimental models but not in clinical trials. CMC in membranes together with hyaluronic acid and CMC membranes with polyethylene oxide and calcium chloride have also been reported as effective anti-adhesive agents in clinical trials .
Oxidized regenerated cellulose (ORC) is another barrier used for the prevention of adhesions . When applied to raw peritoneal surface, it gels within 8 h . Experimental and clinical models reported good preventive results by forming a barrier which physically separates the adjacent raw peritoneal surfaces. However poor results were noted in the presence of blood and probably also at coexisting infections . ORC is not widely used in general surgery today.
The experimental effects of a glucose polymer have been promising, reducing adhesions without obvious side effects [45, 46]. In a RCT it was shown that this polymer reduces the incidence of adhesions and that its application is safe and easy . However, a Meta-analysis report on pelvic adhesion, has not recommended this polymer for the prevention of intra-abdominal adhesions .
Hyaluronic acid (HA) is a naturally occurring glycosamin which is biocompatible, non immunogenic and bioabsorbable, therefore it seems to be well suited as an anti-adhesive agent . Compounds consisting of HA act as a barrier because they coat serosal surfaces and provide a certain degree of protection from serosal desiccation and other types of injury. But they have also been shown to have an anti-inflammatory effect [49–51]. The most popular product on the market is Seprafilm®, a combination of HA and CMC. Seprafilm® reduces adhesive formation, but it is very expensive . Its use increases the risk of anastomotic deshiscence, the formation of abscess  and inflammatory reaction .
In a previous randomized controlled trial the safety and efficacy of another anti- adhesive agent, Intergel® was evaluated in colorectal surgery . Intergel® is a hyaluronic based gel which is cross-linked with carboxylate groups by chelation with ferric (Fe3+) ions. The aim of the study was to reduce the occurrence of intestinal obstructions due to abdominal surgery using Intergel®. Patients who received Intergel® showed a high incidence of anastomotic dehiscence and a prolonged postoperative ileus in comparison to the control group treated only with distilled water. Furthermore, wound infections were observed more often in the Intergel® group. Due to this high incidence of adverse effects in the Intergel® treated group the study was prematurely terminated. The authors discouraged from the use of Intergel®, especially during intervention in which the gastrointestinal tract has been opened, because the application of Intergel® may interfered with the anastomotic wound healing process.
If surfaces are damaged, another way to prevent adhesion formation is the application of phospholipids. Experimental results have been effective using phospholipids, mainly phospatidylcholine, both in models with peritonitis and under normal conditions. No negative effects were seen on wound healing or anastomosis safety [45, 54]. However no clinical studies have been performed so far.
Polyethylene glycol has also been used as a barrier to prevent post surgical adhesions. Experimental studies showed good results and clinical trials reported an adhesion-preventing effect in gynaecological surgery. Additionally, no effect has been noted on pregnancy rates after treatment . In contrast, a Meta-analysis failed to demonstrate the evidence for the use of polyethylene glycol in the prevention of post surgical adhesions .
Fibrin sealant are compounds of fibrinogen and thrombin. They have the advantage of decreasing bleeding and increasing the production of plasminogen activator (PA) and plasminogen activator inhibitor-1 (PAI) which may be beneficial in the prevention of adhesions . But experimental results are diverging and no clinical data are available [56, 57].
Non-dissoluble membranes of expanded polytetrafluoroethylen (ePTFE) have been used successfully to reduce adhesions. But these membranes are difficult to apply and must be fixed in place usually with sutures. In addition they are non biodegradable and should be removed at a later time raising the possibility of damage and subsequent adhesion formation during this surgical episode . One clinical study has been conducted, showing a reduction in postoperative adhesions . But ePTFE is not widely used as a barrier in surgery at present.
No clinical data are available for the use of collagen films as a barrier but experiments reported an effect against adhesion formations . Transplantation of an autologous mesothelial cell sheet has recently shown positive experimental results and offers also a new interesting platform for future development.
None of these agents mentioned above have been proven to be uniformly efficacious and safe under all surgical conditions. Despite initial promising results in postoperative adhesion prevention, none of them have become a standard application. Therefore there is still the need of a barrier that is safe and efficient in reducing the incidence and the extent of surgical adhesion occurring after general abdominal surgical procedures.
A-Part® Gel consists of PVA and CMC and shows no cytotoxity, no allergenic reactions, no systemic toxicity and no genotoxicity . Physical properties such as viscosity and adherence to the wound have also been tested with good results .
In this study A-Part® Gel is used as a physical barrier between the injured peritoneal surface to prevent post surgical adhesions. Animal studies have shown high efficiency in the prevention of adhesions [26, 27, 60, 61]. Wound healing and anastomosis healing were not negatively affected by the application of A-Part® Gel in these animals.
To explore the efficacy of A-Part Gel® in reducing adhesion in humans, adhesion to the abdominal wall will be assessed by ultrasound examination. The gold standard of evaluating adhesion formation by second look assessment is only possible in surgical procedures that require a planned re-operation. However, as this limitation would reduce the amount of eligible patients this assessment is not being chosen, especially as there would be no benefit for the primary objective of this trial as a safety study. Assessment of adhesion development will be done by ultrasound examination. Sigel et al. as well as Steitz et al. [62, 63] described a technique for non-invasive ultrasound examination to detect and map abdominal adhesions. The findings that identify abdominal wall adhesions are based on the presence or restriction of ultrasonically observed movement of abdominal viscera in reference to abdominal wall. Sliding is the result of forces applied by respiratory excursions or by manual ballottement of the abdominal wall and is referred to as viscera slide. In brief, examination of spontaneous visceral slide with ultrasound scanning, provide information on the presence or absence of adhesions. Normal and abnormal visceral slide can be distinctly defined by simple measurement of excursion distance. Restricted visceral slide has been defined as reduced movement at a given point on the abdominal wall during ultrasound scanning of spontaneous visceral slide produced by regular and deep respirations or during longitudinal and transverse scanning of induced viscera slide produced by manual compression. It is strongly correlated with the presence of abdominal adhesions as several authors confirm. Most studies report a sensitivity of 90% and a specificity between 86-93% [62–64]. The method has only minor shortcomings in the lower third of the abdomen and may not detected a long thin adhesion or adhesions to the movable omentum, probably because this type of adhesion would not cause a significant restriction of viscera movement . For assessment at the laparotomy scar spontaneous visceral slide is the most sensitive indicator of adhesions [62, 63, 66].