Objective: To determine the acute effects of increased intra-abdominal pressure (IAP) on the biochemistry, morphology and contractility of the rat isolated urinary bladder using an experimental laparoscopy model. Methods: We divided 24 adult female Sprague-Dawley rats into three groups. The control group (group I) was not subjected to increased IAP. In groups II and III, IAPs of 10 and 20 mm Hg, respectively, were established by carbon dioxide pneumoperitoneum for 60 min. Thirty minutes after desufflation, the rat urinary bladder dome was removed for in vitro pharmacological investigation, measurement of malondialdehyde (MDA) levels and histopathological examination. Statistical comparisons between groups were performed. Results:Tissue MDA levels in groups II and III were significantly higher than in the control group. In group II, only the lamina propria was significantly damaged. However, the epithelium, lamina propria, and serosa were significantly damaged in group III. Acetylcholine potentiated contractions in both IAP groups. Increased responses to electrical field stimulation in the IAP groups were significant only in group II. Conclusions: In this experimental model, 10 and 20 mm Hg of IAP induced by pneumoperitoneum increased MDA levels and caused important changes in the morphology and contractile response of the urinary bladder. Copyright (c) 2006 S. Karger AG, Basel.