Changes in bladder of rabbits subjected to elevation of intraabdominal pressures☆

Abstract 

Background/Purpose: An experimental study has been conducted to evaluate the effects of increased intraabdominal pressure (IAP) on the morphology of the bladder of rabbits. Methods: Experiments were performed on 20 adult male New Zealand rabbits. Six rabbits served as the control group (group I). Seven rabbits were subjected to increased IAP of 7 cm H₂O for 10 days through installing air into the abdominal cavity (group II). Increased IAP was maintained for 60 days in another group of 7 rabbits (group III). Bladders were removed and fixed in 10% formalin for routine process. Paraffin sections of 5 to 7 μm were stained with H & E for light microscopic evaluation. Histopathologic parameters were scored, and the mean scores according to groups were compared by 1-way analysis of variance (ANOVA). The mean values of groups were compared separately by Tukey-Kramer multiple comparison test. In these tests, P value less than .05 was considered statistically significant. Results: All of the bladder strips obtained from animals subjected to 10 days of pressure increase (group II) showed mild to severe degree of vacuolation and desquamation of urothelium. Both vacuolation and desquamation of urothelium were present in all of the strips obtained from rabbits with 60 days pressure increase (group III). Additionally, there were infiltration and congestion of the urothelium together with vacuolation, suburothelial edema, and desquamation in 4 group III rabbits. Moderate or severe congestion in the lamina propria was present in bladder strips of group II rabbits. The congestion of the lamina propria was advanced, and additional moderate to severe inflammation was present in 4 rabbits of group III. Mean histopathologic scores of urothelium (P < .00001) and lamina propria (P = .002) differed significantly among groups. When the groups were compared one by one, the differences between the group I and group II and group II and III were significant (P < .05). Although seroza appeared normal in both group I and II, moderate congestion and infiltration of the seroza was present in the bladder strips of group III (P < .05). Conclusion: Increases in IAP for even 10 days show damaging effects on the bladder. Extended period resulted in augmentation of the damage. J Pediatr Surg 36:995-999. Copyright © 2001 by W.B. Saunders Company.

Keywords:  Intraabdominal pressure, infection, voiding dysfunction, constipation, bladder