Establishment of an animal model of underactive bladder induced by obstruction in rats

Abstract

Objective To establish and evaluate a rat modle of bladder outlet obstruction (BOO) induced underactive bladder (UAB). Methods Male Sprague-Dawley rats were randomly divided into sham operation group, BOO6 week group and BOO12 week group. The UAB animal model was constructed by ligation of the bladder outlet by compression. At 6 and 12 weeks, animal models were evaluated by urodynamics, muscle tone measurement and Masson staining. Results 2 rats died after operation. The incidence of UAB was 43% and 100% at 6 and 12 weeks after operation. At the 6th week, the maximum bladder capacity (MBC), post-void residual urine volume (PVR), and micturition time (MT) of UAB rats were (2.52±0.16) ml, (0.87±0.08) ml, (109.59±1.00) s, respectively, which were higher than that of sham group (0.98±0.08) ml, (0.01±0.01) ml, (50.19±0.19) s, and the maximum pressure (Pmax) was (39.83±0.85) cmH2O (1 cmH2O=0.098 kPa), which was lower than that of sham group [(61.53±0.68) cmH2O]. The difference was statistically significant (t=21.221, 25.721, 101.001, 34.531, P<0.05). At the 12th week, the MBC, PVR and MT of UAB rats were (3.87±0.05) ml, (1.33±0.14) ml, (154.44±1.99) s, respectively, which were higher than that of the sham group (1.33±0.08) ml, (0.01±0.01) ml, (50.80±0.29) s. The Pmax was (27.68±0.83) cmH2O less than sham group [(66.53±1.68) cmH2O], and the difference was statistically significant (t=27.041, 23.741, 89.261, 35.891, 60.891, P<0.05). At 6 and 12 weeks, the bladder detrusor contractility of UAB rats was significantly lower than that of sham group. The wet weight of bladder at 6 and 12 weeks was (356.67±42.74) mg and (464.67±7.58) mg, respectively, which was significantly higher than that of sham group [(166.67±22.51) mg and (183.83±8.38) mg]. The collagen deposition rate was significantly higher than that of sham group, and the difference was statistically significant (t=9.635, 60.891, P<0.05). Conclusion UAB animal models can be successfully established by ligation of the bladder outlet and can be assessed using urodynamics, muscle strip tension measurements, and Masson staining. Key words: Bladder outlet obstruction; Underactive bladder; Urodynamics; Muscle tone