EXPERIMENTAL BLADDER INSTABILITY FOLLOWING BLADDER OUTLET OBSTRUCTIONIN THE FEMALE RAT

Purpose: In rats, urethral obstruction was previously shown to lead to detrusor instability, but bladder instability in conscious animals ha s not been well characterized. The present study was designed to descr ibe the consequences of bladder outlet obstruction on urodynamic param eters in the conscious rat. A categorization of different types of bla dder instability in conscious rats is described. Materials and Methods : Cystometry was performed on conscious animals with chronically impla nted lines. Recordings of the micturition pattern and the bladder pres sure during the micturition cycle were made from normal female rats an d those with instability caused by infravesical outflow obstruction. R esults: In control rats, the peak micturition pressure was low (45.6 /- 2.5 cm. H2O) and only small pressure fluctuations occurred before o r after micturition. Rats with outlet obstruction exhibited bladder hy pertrophy, high micturition pressure (95.5 +/- 6.8 cm. H2O) as well as marked spontaneous activity throughout the micturition cycle. Accordi ng to the spontaneous activity profile we identified four main pattern s of abnormal micturition cycles. Conclusion: Urethral obstruction in rats leads to a significant increase in bladder weight and to altered micturition patterns which reveal clear similarities with features of the cystometric profiles performed in men with infravesical outflow ob struction. These modifications are not consistently correlated with an increase in bladder weight.