Conventional urodynamics and ambulatory monitoring in the definition and management of bladder outflow obstruction.

PURPOSE: We determined whether ambulatory urodynamics and new objective methods of defining bladder outflow obstruction might improve the classification of bladder outflow obstruction over conventional urodynamics (cystometrography), and whether such measures might improve prediction of the outcome of prostatectomy. MATERIALS AND METHODS: A prospective study was performed of 122 men undergoing prostatectomy for symptoms and low flow rates. Cystometrography and ambulatory urodynamics were performed before and 6 months after prostatectomy but did not influence selection for operation. Methods of classifying obstruction included the Abrams-Griffiths nomogram, Schäfer linear passive urethral resistance relation and Griffiths urethral resistance factor. RESULTS: The proportion of cases defined as obstructed did not differ on ambulatory urodynamics or cystometrography or when the Abrams-Griffiths nomogram was compared to the linear passive urethral resistance relation or urethral resistance factor. Significant improvements after prostatectomy were noted in flow rates (p < 0.001), residual urine (p < 0.001), voiding pressure (p < 0.001) and symptom scores (p < 0.001). Ambulatory urodynamics were more sensitive than cystometrography in detection of detrusor instability but detrusor instability did not correlate with outcome. Voiding pressures were greater during ambulatory urodynamics (p < 0.02). The outcome of obstructed cases (on Abrams-Griffiths nomogram during ambulatory urodynamics) was better (79% good outcome) than that of nonobstructed or equivocally obstructed cases (55% good symptomatic outcome, p < 0.05). CONCLUSIONS: Men proved to have obstruction on the basis of pressure and flow measurements applied to a nomogram have better outcomes after transurethral resection of the prostate but sophisticated or computer derived methods of classification of obstruction did not improve prediction.