Comparison of two experimental models of urodynamic evaluation in female rats Comparação de dois modelos experimentais para avaliação urodinâmica em ratas

Purpose: Urodynamic studies in small animals can be performed through urethral sounding or cystostomy. Objective: To compare the two methods of urodynamic evaluation in female rats. Methods: Ten female rats weighing on average 250g, under anesthesia with urethane (1,25 mg/kg) were submitted in three repeats to an urethal catheter of 0,64 mm in external diameter for cystometric measurements of vesicle pressure(VP1) and contraction time (CT1). The catheter was extracted at a constant velocity of 0.05 cm/minute until complete exteriorization and determinations of maximal urethral pressure (UP1) and functional urethral length (FUL1). This was followed by a cystostomy with catheter PE50 and a new determination of the vesical pressure (VP2). After bladder denervation, a new cystometric record indirectly infered the maximum urethral closure pressure (UP2). The peak urethal pressure (UP3) and the functional urethral length (FUL2) were determined in another urethral sounding. The pressure registration system consisted of a continuous infusion pump regulated to a flow of 0.1 ml/minute connected both to the cystostomy catheter (PE-50) or the urethal catheter (0.64mm) and the polygraph Narco-Biosystem. Statistical analysis employed the Wilcoxon non-parametric test Results: Mean VP1= 48,2 mmHg (11,8 SD); Mean VP2 = 38,2 mmHg (9,0 SD) “p” (VP1 X VP2) = 0,0039. Mean CT1=30,2 s (21,5 SD); Mean CT2=20,0 s(7 SD) p (CT1 X CT2) = 1,28. Mean UP1 = 47,2 mmHg (6,5 SD); Mean UP2 = 21,3 mmHg (6,6 SD), mean UP3 = 40,7 mmHg(13,3 SD) p (UP1 X UP2) = 0,002; “p” (UP1 X UP3) = 0,084; p (UP2 X UP3) = 0,002. Mean FUL1=14,2 mm (1,9 SD); Mean FUL2= 14,1mm (1,9 SD); p (FUL1 X FUL2) = 0,64. Conclusions: The methods employed to evaluate vesical and urethral pressures are different. The presence of the urethral catheter may be an obstructive factor. Surgical denervation up to the bladder neck level does not compromise urethral function.