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

Abstract

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.

Keywords: Bladder diverticulum; partial bladder outlet obstruction urodynamic study.

Figure 1.

Bladder Diverticulum model.

Figure 2.

Partial bladder outlet obstruction model.

Figure 3.

Urodynamic testing was performed on animals in Sham group. Postoperative filling detrusor pressure values were normal range in sham group and involuntary detrusor contraction was not observed.