Chapter / Urodynamics and LUTS 47 Urodynamics and the Evaluation of Male Lower Urinary Tract Symptoms J Quentin Clemens, MD, MSCI CONTENTS INTRODUCTION UROFLOWMETRY PRESSURE-FLOW STUDIES VIDEOURODYNAMICS CYSTOMETRY SYMPTOMS AND URODYNAMIC FINDINGS PREDICTIVE VALUE OF URODYNAMICS INDICATIONS FOR URODYNAMIC STUDIES IN MEN WITH LUTS CONCLUSION REFERENCES INTRODUCTION The purpose of urodynamic testing is to reproduce the patient’s symptoms in a controlled laboratory setting A variety of measurements (bladder and urethral pressures, urine flow rate, fluoroscopic imaging) are made, and based on these observations and the clinical acumen of the examining physician, a diagnosis can be found that explains the patient’s complaints In men with lower urinary tract symptoms (LUTS), the primary urodynamic question is whether or not there is bladder outlet obstruction A variety of urodynamic techniques may be used to address this question From: Management of Benign Prostatic Hypertrophy Edited by: K T McVary © Humana Press Inc., Totowa, NJ 47 48 Clemens Fig Siroky nomogram for evaluation of uroflow results The peak flow rate (vertical axis) and total bladder volume (voided volume plus residual volume, horizontal axis) are plotted as a single point on the nomogram The shaded zone indicates values that occur in < 2.5% of the normal male population UROFLOWMETRY Uroflowmetry is an attractive test for both clinician and patient because it is simple to perform and noninvasive The most clinically useful measurement is the maximum urinary flow rate (Qmax), which is measured in milliliters per second Other information that may be obtained includes the flow pattern (continuous or intermittent), average flow rate, shape of the flow curve, flow time, and time to maximum flow Postvoid residual bladder volume may also be assessed with ultrasonography after the void Uroflowmetry may be done with the patient in the standing or supine position to best mimic normal voiding patterns at home In general, Qmax of < 10 mL/s is considered abnormal; Qmax of > 15 mL/s is normal; and Qmax of 10–15 mL/s is equivocal (1,2) It is advisable to perform multiple measurements because intraindividual variation for this test is high (3) Interestingly, the variability appears to be increased in men with LUTS as a result of benign prostatic hyperpla- Chapter / Urodynamics and LUTS 49 sia (BPH) when compared with asymptomatic controls (4) At very low voided volumes (< 150 mL), uroflow results are quite inaccurate, and results from such voiding episodes should be viewed with a high degree of skepticism (5) Furthermore, it must be remembered that normal flow-rate parameters vary with voided volume and with age The progressive decrease in Qmax observed with age does not appear to be caused by an increased incidence of bladder outlet obstruction (6,7) A variety of nomograms with volume- and/or age-adjusted normative flow rate calculations have been published The Siroky nomogram is one of the most commonly used (Fig 1) (8) The urinary flow rate is a product of both detrusor contractility and urethral resistance A low flow rate may be caused by anatomic obstruction (BPH, urethral stricture), dynamic obstruction (incomplete external sphincter relaxation), poor detrusor contraction, or a combination of these factors Similarly, a normal or supranormal flow rate may occur in the face of significant outlet obstruction by strong detrusor contraction It is, therefore, not surprising that uroflowmetry results alone not differentiate obstructed from unobstructed patients (9–11) Nevertheless, the technique may have some merit as a screening test for obstruction, because in general, those with a low flow rate (