PREDICTION OF PROSTATIC OBSTRUCTION WITH A COMBINATION OF ISOMETRIC DETRUSOR CONTRACTION PRESSURE AND MAXIMUM URINARY FLOW-RATE

Objectives, Because isometric detrusor contraction pressure (P-iso) in creases with outlet obstruction and maximum urinary flow rate (Qmax) t ends to decrease with obstruction, we hypothesize that specific criter ia consisting of a combination of high P-iso and low Qmax may be able to differentiate obstructive from nonobstructive voiding dysfunction b etter than either parameter alone. Methods, Two hundred five men with lower urinary tract symptoms underwent uroflowmetry and videourodynami cs, including cystometry, continuous outlet occlusion test, and mictur itional urethral pressure profilometry. Combined threshold values of Q max of less than 12 mL/s and P-iso of 100 cm H2O or greater were used to predict obstruction, whereas threshold values of Qmax of at least 1 2 mL/s and P-iso less than 100 cm H2O were used to predict nonobstruct ion. Results. Of the 205 patients, 103 (50%) were significantly obstru cted and 102 (50%) were only mildly obstructed or nonobstructed. Of th e total population, 151 patients (74%) were categorized by the combine d flow and contractility criteria. Of the categorized patients, 141 (9 3%) were correctly diagnosed with regard to infravesical obstruction ( sensitivity 89%, specificity 97%, positive predictive value 97%, and n egative predictive value 91%). Conclusions. A combination of Qmax and P-iso criteria can predict obstructive and nonobstructive voiding dysf unctions with high positive and negative predictive values in most pat ients with lower urinary tract symptoms. Combining the results of urof lowmetry and isometric tests may help to guide treatment strategies th at may improve the outcome of selected therapeutic options compared wi th strategies based on symptoms or uroflowmetry alone. Furthermore, th is approach forms a basis for interpreting various noninvasive methods that have recently been introduced for the purpose of diagnosing blad der outlet obstruction. Copyright 1996 by Elsevier Science Inc.