Nitric oxide synthetase and Helicobacter pylori in patients undergoing appendicectomy

Background: This study was designed to determine whether Helicobacter pylor i forms part of the normal microenvironment of the appendix, whether it pla ys a role in the pathogenesis of acute appendicitis, and whether it is asso ciated with increased expression of inducible nitric oxide synthetase (iNOS ) in appendicular macrophages. Methods: Serology for H. pylori was performed on 51 consecutive patients un dergoing emergency appendicectomy. Appendix samples were tested for urease activity, cultured and stained for H. pylori, graded according to the degre e of inflammatory infiltrate, and probed immunohistochemically for iNOS exp ression. Results: The mean age of the patients was 21 (range 7-51) years. Seventeen patients (33 per cent) were seropositive for H. pylori but no evidence of H . pylori was found in any appendix specimen. However, an enhanced inflammat ory cell infiltration was observed in seropositive patients (P < 0.04) and the expression of macrophage iNOS in the mucosa of normal and inflamed appe ndix specimens was increased (P < 0.01). Conclusion: H. pylori does not colonize the appendix and is unlikely to be a pathogenic stimulus for appendicitis. Priming effects on mucosal immunolo gy downstream from the foregut may occur after infection with H. pylori.