Urodynamics: prediction, outcome and analysis of mechanism for cure of stress incontinence by periurethral collagen

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Abstract
To assess the role of urodynamics in the prediction and assessment of outcome and analysis of the mechanism of cure for stress incontinence using periurethral collagen as our treatment model. Prospective longitudinal study. A teaching hospital tertiary referral centre. Sixty women with genuine stress incontinence. The objective cure rate was 54% (n = 54) at 12 months. Subtracted cystometry, urethral electrical conductivity and bladder neck excursion measurements did not predict cure. A low pre-injection maximum urethral closure pressure adversely affects outcome (31 cmH2O (success) vs 19 cmH2O (failure), P = 0.004); all women with a maximum urethral closure pressure > 39 cmH2O were rendered dry. Urethral pressure profilometry can analyse mechanism of cure. Total profile length, stress maximum urethral closure pressure, stress functional urethral length and pressure transmission ratio in the first quarter of urethral length were increased in successful cases (P < 0.05), and rest maximum urethral and maximum urethral closure pressures, area under rest profile and pressure transmission ratio in the second quarter of urethral length were increased in failed cases (P < 0.02). In successful cases the increased area and pressure transmission ratio in the first quarter of the functional urethral length suggest that collagen placement occurs at the bladder neck or proximal urethra. Cure appears to be due to prevention of bladder neck opening during stress and not obstruction. In addition the cephalad elongation of the urethra caused by collagen probably accounts for the increased abdominal pressure transmission in the first quarter of the urethra. In failures, there is an increased length and increased area to peak pressure suggesting collagen is deposited more distally. This study confirms the role of certain urethral pressure profilometry variables in the prediction and analysis of mechanism of cure.