The Effects of Bladder Diverticulum on the Pathophysiology of Bladder Outlet Obstruction: An Experimental Study in Guinea Pigs

Objectives: This study is the first to urodynamically and histopathologically evaluates the effects of bladder diverticulum (BD) secondary to bladder outlet obstruction (BOO). Methods: Guinea pigs (n=32) weighing 900–1,000 g were divided randomly into four groups: Sham, BD, BOO, and BD combined with BOO. All guinea pigs in the four groups underwent urodynamic evaluation preoperatively and at 1 month postoperatively. The bladders were removed and examined histopathologically. Results: The post-operative filling detrusor pressure was lower in the Sham group (7.1±1.6 cm H2O) than in the BD (21.4±5.6 cm H2O) and BD with BOO groups (23.6±9.3 cm H2O) (p<0.05). There was no difference between the Sham and BOO (9.5±4.0) groups. Post-operative bladder compliance was better in the Sham group (2.3±0.8 ml/cm H2O) than in the BD (0.9±0.22 ml/cm H2O) and BD with BOO groups (0.6±0.3 ml/cm H2O) (p<0.05). Involuntary detrusor contraction was not observed in the Sham or BOO groups, but was observed in 37.5% of subjects in the BD and BD with BOO groups. On histological examination, the bladder wall was thicker (3.75±0.68 mm) (p=0.601), and the connective tissue volume was significant increased (p=0.046), in the bladder muscularis mucosa in the BD groups compared to the BOO group. Conclusion: Physiological and histopathological changes in the bladder with BD combined with BOO are more evident than with BOO alone.