A pneumoperitoneum perpetuates severe damage to the ultrastructural integrity of parietal peritoneum in gastric perforation-induced peritonitis in rats

Background: Minimal invasive surgery is increasingly used in conditions com plicated by peritonitis-e.g., peptic ulcer perforation. This study was devi sed to assess the effect of a pneumoperitoneum (PP) on the ultrastructural integrity of parietal peritoneum in perforation-induced peritonitis. Methods: Anesthetized rats were subjected either to standardized gastrotomy simulating gastric perforation (groups Ia-d; IIa-d) or to sham perforation (groups IIIa-d, IVa-d). Ln group I (a-d) and III (a-d), CO2 was insufflate d 12 h after gastrotomy for 60 min (P-ia 4 mmHg). Glutaraldehyde was admini stered intraperitoneally at the end of the PP period while the abdominal wa ll was still extended (group index a), as well as 30 sec (b), 2 h (c), and 12 h (d) after desufflation. Specimens were taken from the parietal periton eum of the left diaphragm for scanning electronic-microscopic (SEM) analysi s. In groups II (a-d) and IV (a-d), simple puncture of the abdominal cavity was performed, and specimens were taken at corresponding times. Results: In group Ia (gastric perforation with PP), distortion of the mesot helial cell layer with concomittant opening of stomata to the submesothelia l tissue was already observed in specimens harvested while the abdominal wa ll was still extended. Concomitantly, scarce microvilli, which appeared coa rse and thickened, were lying flat on top of the mesothelial cells. After d esufflation (groups Ib-c), a rapid process of mesothelial disintegration wi th disruption from the submesothelial layer and vanishing of microvilli occ urred. At 12 h after PP (group Id), complete deterioration of mesothelial c ell integrity was observed. In groups IIa-c (gastric perforation without PP ), microvilli appeared shrunk and coarse, while integrity of the mesothelia l cell layer remained intact up to 2 h after the abdominal puncture. At 12 h after abdominal puncture (group lid), the microvilli had nearly completel y vanished and the mesothelium was breaking apart into multiple soils. Conclsions: In SEM analysis of parietal peritoneum, premature distortion, a nd disintegration of the mesothelial cell layer was observed in animals exp osed to increased abdominal pressure in addition to gastric perforation-ind uced peritonitis.