Acoustic non-invasive diagnosis of urinary bladder obstruction

Elderly men are prone to developing Lower Urinary Tract Symptoms, such as a weak urinary stream, frequent (nocturnal) voiding and incomplete emptying of the bladder. The two most probable causes for these symptoms are a weakly contracting bladder muscle or Bladder Outlet Obstruction (BOO), frequently caused by Benign Prostatic Enlargement. The most frequently used urodynamic method to diagnose this condition is an invasive pressure-flow study: measurement of bladder pressure during voiding using a catheter inserted in the bladder via the urethra. In this thesis an alternative non-invasive diagnostic method is presented. This method is based on turbulence in the urinary stream, induced by an obstruction (enlarged prostate) in the urethra. This turbulence can be recorded using a simple microphone placed at the perineum (between scrotum and anus). In a realistic biophysical model of the urethra we have shown that the sound frequency spectrum (characterized by ! three parameters) was uniquely and monotonically related to the degree of the obstruction. In a population of healthy male volunteers the variability of perineal sound recording within volunteers was found to be smaller than between volunteers: volunteers can be distinguished on the basis of perineal sound recording. From these findings and the three parameters being uniquely and monotonically related to the degree of the obstruction it can be concluded that perineal sound recording is a promising method for a cheap, simple and quick non-invasive diagnosis of BOO and clinical validation is strongly indicated.

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