The Measurement of Minimal Urethral Opening Pressure (Pmuo) in Patients with Benign Prostatic Hyperplasia

Lee, Jong Won; Kim, Ha young

Abstract

The prevalence rate of benign prostatic hyperplasia is about 50 percent of all men after 50 years of age and the rate rises steadily up to 80 percent of men older than 80. Therefore, when a man after 50 years of age complains voiding dysfunction, benign prostatic hyperplasia must be ruled out. But 25 percent of benign prostatic hyperplasia diagnosed by current standard diagnostic work-up including patient's history, symptoms, digital rectal examination, volumetry by ultrasonography, uroflowmetry and residual urine determination did not show any significant change in voiding function after surgery. These data show that the standard procedures lead to a diagnosis of prostatic obstruction when the voiding problem is caused by detrusor dysfunction. Moreover, when the prostate is minimally or moderately enlarged by rectal examination the diagnosis of benign prostatic hyperplasia is puzzling. Generally, voiding is accomplished by detrusor contraction and urethral relaxation concomitantly so as to increase the intravesical pressure and decrease the external urethral sphincter pressure. The urine begins to leak from the moment when the intravesical pressure is the same level as the external urethral sphincter pressure. The pressure is known as the minimum urethral opening pressure( Pmuo). It is known that the minimum urethral opening pressure( Pmuo) is elevated to higher than 25 cmH2O when the bladder is obstructed by benign prostatic hyperplasia. Herein, to study the usefulness of the minimum urethral opening pressure(Pmuo) in the diagnosis of benign prostatic hyperplasia in patients with voiding dysfunction who had minimally or moderately enlarged prostate by rectal examination, I evaluated the symptoms 4 weeks after surgery on 12 patients who were diagnosed as benign prostatic hyperplasia due to higher than 25 cmH2O of the minimum urethral opening pressure( Pmuo) and anticholinergic medication on 5 patients who were diagnosed as detrusor dysfunction due to less than 25 cmH2O of the minimum urethral opening pressure (Pmuo). Ten out of 12 benign prostatic hyperplasia patients and 4 out of 5 detrusor dysfunction patients were cured or improved. So, the sensitivity and specificity of minimum urethral opening pressure(Pmuo) in the diagnosis ofbenign prostatic hyperplasia is 83% ( 10/12 ) and 80% (4/5), respectively. In conclusion, the measurement of the minimum urethral opening pressure (Pmuo) is a useful method in the diagnosis of benign prostatic hyperplasia especially in the patients with minimally or moderately enlarged prostate by rectal examination.