Impairment of the Peritoneal Surface as a Decisive Factor for Intestinal Adhesions in Intraperitoneal Onlay Mesh Surgery - Introducing a New Rat Model

Abstract

Background: Meshes implanted intraperitoneally are known to cause adhesions potentially resulting in complications such as chronic pain, enterocutaneous fistula, or mesh infection. This study introduces a model for investigation of intestine-to-mesh adhesions and evaluates as to whether missing of visceral peritoneum is causative.Methods: In 18 rats, rectangular 1.5 x 2 cm patches of an uncoated polypropylene mesh (Ultrapro®) were sewn to the inner abdominal wall next to the cecum. Additionally, a meso-suture ensured contact between cecum and mesh. Rats were assigned to 2 groups: in 8 rats the peritoneum was left intact, in 10 the cecum was depleted from peritoneum with abrasion. Sacrifice was on day 7. Macroscopic evaluation used two adhesion scores. Specimens were evaluated microscopically, statistical analyses employed student's t-test.Results: On day 7, rats with mesh implantation combined with locally de-peritonealization by cecal abrasion mostly showed severe cecum-to-mesh agglutination (mean Lauder score 92%, mean total Hoffmann score 90%), whereas meshes of most animals without cecal abrasion only had some coverage with intraabdominal fat (33%, 24%; p = 0.0002). Histological work-up showed adequate wall ingrowth of mesh in all rats. In animals with cecal abrasion, meshes were mostly adhesive with cecal wall. However, when the peritoneum of cecum was unimpaired, abdominal wall above the mesh as well as cecum usually revealed sub-peritoneal tissue and a mono-layer cell coverage as seen in normal peritoneum.Conclusion: This study introduces a model mimicking a clinical situation of e.g. hernia repair by intraperitoneally implanted meshes when mesh has contact with normal and with de-peritonealized intestine. The model might be useful for testing mesh types and coatings as well as other devices for their efficacy in adhesion prevention. The high adhesion scores of rats with local de-peritonealization compared with the low scores of animals with intact peritoneum indicate that the integrity of intestinal peritoneum is a decisive factor for adhesion formation.

Adhesion Prevention Efficacy of Composite Meshes Parietex®, Proceed® and 4DryField® PH Covered Polypropylene Meshes in an IPOM Rat Model

“…Recent studies showed that not only the foreign material or making of mesh but also the impairment of visceral peritoneum is a co-decisive factor for the development of intestine-to-mesh adhesions 18, 25, 26. This especially accounts for areas where intestine has been dissected from the hernia sac.…”

“…In the present study our recently described rat model was used 18. General anaesthesia was achieved by intraperitoneal injection of 80 mg/kg body weight ketamine and 5 mg/kg xylazine.…”

“…Recently published data of 10 rats using the same testing conditions but UPM without anti-adhesive treatment were used as a control (CT) group 18, data of 20 rats using the same testing conditions but UPM combined with 4DF gel for adhesion prevention were used for further comparison 19.…”

“…Original data of CT published in 18, original data of UPM/4DF premixed gel and UPM/4DF in-situ gel in 19.…”

“…Recently, we introduced a new rat model mimicking clinical IPOM situation with a direct contact of the mesh to impaired intestinal peritoneum, as found in the center of a hernia sac in terms of a hernia operation 18. Using this challenging model it could be shown that the application of a barrier gel basing on the polysaccharide 4DryField ® PH (4DF; PlantTec Medical GmbH, Germany), even with use of uncoated Ultrapro ® polypropylene mesh (UPM), significantly reduced adhesion formation 19.…”