The Effect of Detrusor Instability on Detrusor Contractility in the Benign Prostatic Hyperplasia / 대한비뇨기과학회지

ABSTRACT

PURPOSE: The process of micturition is depend on the bladder contracton power and urethral resistance. The higher urethral resistance in the BPH, the greater power(W) is needed to open the urethra and keep it open during voiding. It has been known that the occurrence of unstable bladder did correlate with the degree of obstruction. Unstable detrusor will exhibit greater contraction power with more efficient voiding(evidenced by higher flow rate, less voiding time). We performed this study to define the differences of urodynamic voiding parameters including detrusor contractility between unstable and stable bladder in the BPH. MATERIALS AND METHODS: In all subjects bladder outlet obstruction was ascertained urodynamically and BPH was diagnosed by digital rectal examination and transrectal ultrasound. The patients were divided into 2 groups. Group 1 included 25 men chosen randomly among BPH patients with bladder outlet obstruction and detrusor instability. Group 2 consisted of 22 men chosen at random among BPH patients with stable obstructed bladders. For each subject a number of urodynamic parameters derived from pressure-flow study were evaluated. RESULTS: Obstructive findings were found in the pressure-flow study in the both groups. Patients ages were 64.1 in the unstable and 61.9 years old in the stable group. Peak flow rate, minimum urethral opening pressure, maximum detrusor pressure, detrusor pressure at peak flow, maximum external voiding power were 14.2ml/sec, 24.3cmH2O, 52.1cmH2O, 42.9cmH2O, 537.3mW, respectively in the unstable group and 11.6ml/sec, 17.5cmH2O, 45.3cmH2O, 34.1cmH2O, 388.2mWm in the stable group. Voiding time was shorter in the unstable group(41.9sec) than in the stable group(54.5sec). Maximum cystometric capacity was significantly greater in the stable group(434.2ml) than in the unstable group(287.5ml) (p<0.01). Maximum contraction power, peak flow detrusor power, opening contraction power were significantly greater in the unstable group(38.8+/-20.2microW/mm2, 34.0+/-18.5microW/mm2, 24.0+/-3.1microW/mm2, respectively) than in the stable group(14.2+/-7.4microW/mm2, 12.9+/-8.1microW/mm2, 11.2+/-1.6microW/mm2)(p<0.01). Voiding efficiency was significantly higher in the unstable population(68.6+/-28.9%) than in the stable one(47.5+/-31.3%)(p=0.02). There were significant positive correlations between opening contraction power with maximum detrusor pressure(r=0.45) and peak flow detrusor pressure (r=0.48) (p<0.01). CONCLUSIONS: In this study, there were more powerful micturition power and more efficient voiding in unstable bladder group. Conclusively, it seems that unstable bladder possibly works as an energy saving device thereby maintaining efficient voiding despite obstruction.