Increased mortality and altered local immune response in secondary peritonitis after previous visceral operations in mice

Postoperative peritonitis is characterized by a more severe clinical course than other forms of secondary peritonitis. The pathophysiological mechanisms behind this phenomenon are incompletely understood. This study used an innovative model to investigate these mechanisms, combining the models of murine Colon Ascendens Stent Peritonitis (CASP) and Surgically induced Immune Dysfunction (SID). Moreover, the influence of the previously described anti-inflammatory reflex transmitted by the vagal nerve was characterized. SID alone, or 3 days before CASP were performed in female C57BL/6 N mice. Subdiaphragmatic vagotomy was performed six days before SID with following CASP. The immune status was assessed by FACS analysis and measurement of cytokines. Local intestinal inflammatory changes were characterized by immunohistochemistry. Mortality was increased in CASP animals previously subjected to SID. Subclinical bacteremia occurred after SID, and an immunosuppressive milieu occurred secondary to SID just before the induction of CASP. Previous SID modified the pattern of intestinal inflammation induced by CASP. Subdiaphragmatic vagotomy had no influence on sepsis mortality in our model of postoperative peritonitis. Our results indicate a surgery-induced inflammation of the small intestine and the peritoneal cavity with bacterial translocation, which led to immune dysfunction and consequently to a more severe peritonitis.