Detrusor hypocontractility evolution in boys with posterior urethral valves detected by pressure flow analysis

Purpose: We evaluated the natural evolution of detrusor voiding contractili ty in boys who underwent posterior urethral valve ablation using pressure f low analysis, which is a mathematical computerized analysis of pressure flo w studies. Materials and Methods: Among 30 boys with posterior urethral valves who wer e being prospectively followed, even if asymptomatic on serial pressure flo w studies, 11 were included in our study. These 11 patients had had at leas t 2 evaluations performed between ages 5 and 15 years, a minimum interval o f 4 years between the first and last examination, and all pressure flow stu dies records available for mathematical analysis of voiding contractility. The first examination had been done at ages 5 to 10 years (average 7 +/- 2. 04) and the last one at ages 9 to 15 (12.5 +/- 2.5), including 6 evaluated after puberty. All but 1 patient underwent valve endoscopic resection as a newborn and none received urinary diversion. Voiding symptoms, post-void re sidual, cystometric bladder capacity and bladder instability were considere d. Voiding phase maximal detrusor pressure and flow rate were evaluated and detrusor contractility was calculated by the pressure flow analysis parame ters of contraction velocity, detrusor contractile power expressed as watt factor and Schafer's nomogram. Contraction velocity and contractile power f actor were considered low if below 2 standard deviations of previously dete rmined normal values. True hypocontractility was diagnosed when at least 2 pressure flow analysis parameters were low. Results: True hypocontractility was detected in 3 of the 11 boys at the fir st examination and in 8 at the last pressure flow analysis. The remaining 8 and 3 cases of first and last examinations, respectively, were considered to have normal contractility even if 4 of the 8 and 1 of the 3 had 1 low pr essure flow analysis parameter (covert hypocontractility). Detrusor contrac tility worsened in B patients, hypocontractility was detected at the first pressure flow analysis in 2, hypocontractility changed to normal in 1 and p ressure now analysis remained normal in 2. Of the 6 boys followed through p uberty 5 had hypocontractility, including 3 with cystometric bladder capaci ty greater than 700 mi., high post-void residual and strained voiding. Of t he 11 patients 8 had detrusor instability, including 7 with urge symptoms, at first evaluation which was not found at last examination. Conclusions: Pressure flow analysis extensively used in men has been confir med as a useful tool to assess voiding contractility in children. The major ity of boys with posterior urethral valves have progressive impairment of d etrusor contractility at voiding many years after relief of obstruction. Th e pattern of hypocontractility, which is detected early on pressure flow an alysis, follows a prolonged phase of instability in many cases and leads to an over distended bladder in most patients followed after puberty. Questio ns arise if this evolution may be prevented by early (pharmacological or re habilitative) treatment and if it is partially determined by extensive use of drugs acting against unstable detrusor contractions.