Idzenga, T.

Response to the future of urodynamics: Non-invasive ultrasound videourodynamics (Letter To Editor)

2010-07-01T00:00:00Z

Acoustic non-invasive diagnosis of urinary bladder obstruction (Doctoral Thesis)

2008-04-16T00:00:00Z

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.

Fluid perfused urethral pressure profilometry and Valsalva leak point pressure: A comparative study in a biophysical model of the urethra (Article)

2007-08-01T00:00:00Z

In patient studies the correlation between maximum urethral closure pressure (MUCP) and Valsalva leak point pressure (LPP) is meagre at best (r = 0.22-0.50). We therefore studied the relation between MUCP and LPP in a flexible and extensible model urethra. We applied differently sized pressure zones and different degrees of resistance to a biophysical model urethra by stepwise inflating three types of blood pressure cuff placed around the model. At each degree of resistance we measured detrusor LPP, an in vitro equivalent of Valsalva LPP. Subsequently, we recorded the Urethral Pressure Profile using a water-perfused 5F end-hole catheter at four withdrawal rates and five perfusion rates and calculated MUCP. We tested the dependence of LPP on pressure zone length and MUCP on perfusion rate, withdrawal rate and pressure zone length using analysis of variance. We tested the correlation between LPP and MUCP using Pearson's correlation coefficient and Linear Regression. LPP did not significantly depend on the pressure zone length (P = 0.80) and increased linearly with increasing cuff pressure. MUCP also increased with increasing cuff pressure, however, MUCP significantly depended (P < 0.01) on perfusion rate, withdrawal rate and pressure zone length. MUCP increased with increasing perfusion rate, and decreased with increasing withdrawal rate. In our model urethra MUCP only accurately reflected urethral resistance for a very limited number of combinations of perfusion rate and withdrawal rate. LPP reflected urethral resistance independent of the type of pressure zone.

Accuracy of maximum flow rate for diagnosing bladder outlet obstruction can be estimated from the ICS nomogram (Article)

2007-06-30T00:00:00Z

Fluid perfused urethral pressure profilometry and Valsalva leak point pressure: a comparative study in a biophysical model of the urethra (Article)

2007-06-20T00:00:00Z

Is the impaired flow after hypospadias correction due to increased urethral stiffness? (Article)

2006-05-18T00:00:00Z

Purpose: A low flow rate without clinical symptoms is commonly found in boys after hypospadias correction. Urethral calibration usually shows no abnormalities. We investigated whether this flow rate impairment might be caused by increased neo-urethral wall-stiffness. Methods: From Polyvinyl Alcohol cryogel two models of the urethra were made, a hypospadias model and a control model. Both models had a constant and equal inner diameter and equal compliance. The hypospadias model had a less compliant distal segment mimicking the distal neo-urethra after hypospadias correction. In both models flow rate was recorded as a function of bladder pressure. To test whether the length of the less compliant segment had an effect on the flow rate, both models were shortened by cutting off 1 cm segments. Results: In a physiological range of bladder pressures (10 - 130 cmH2O) the mean flow rate(± 1sem) in the hypospadias model was 2.8± 0.3 ml/s, significantly lower (p < .05) than in the control model (5.4 ± 0.6 ml/s). Shortening of the hypospadias model showed some increase in flow rate, however not statistically significant. In the control model there was also no significant variation in flow rate. Conclusion: We showed that a low compliant segment of a urethral model reduces the flow rate. Extrapolating these results to asymptomatic boys with a low urinary flow rate after hypospadias repair might justify a watchful waiting policy.

A Biophysical Model of the Male Urethra: comparing viscoelastic properties of PolyVinyl Alcohol urethras to male pig urethras. (Article)

2006-04-12T00:00:00Z

Aims: We aim at developing a non-invasive method for grading and diagnosing urinary bladder outlet obstruction, based on noise recording with a perineal contact microphone during voiding. We found that the noise production during voiding depends amongst others on the viscoelastic properties of the urethral wall. To further test our method, we need a realistic biophysical model of the male urethra. Methods: We made various model urethras with different viscoelastic properties from a 10% aqueous solution of PolyVinyl Alcohol cryogel. We measured the viscoelastic properties of each model and compared them to those of the male pig urethra. The male pig urethra was used, as it is physiologically comparable to the human male urethra. The viscoelastic properties of both model and pig urethras were measured by applying strain to the urethral wall in a stepwise manner and recording the pressure response. We fitted the step-response of a mechanical model to this pressure response and derived the viscoelastic properties from the coefficients of this response. Results: A uniform model urethra that was freeze-thawed three times, with a Y-shaped flow channel was found to best represent the male pig urethra. Conclusion: We consider the three times freeze-thawed model urethra with a Y-shaped flow channel the best model of the human male urethra. And we therefore use this model urethra for studying the relation between noise recording during urine flow and the degree of bladder outlet obstruction.

Variation in noise recorded distally to a urethral obstruction related to cross-sectional area and flow pattern (Article)

2006-01-01T00:00:00Z

Perineal noise recording as a non-invasive diagnostic method of urinary bladder outlet obstruction: a study in polyvinyl alcohol and silicone model urethras (Article)

2005-05-10T00:00:00Z

AIMS: At present, an invasive pressure flow study is recommended to diagnose urinary bladder outlet obstruction. This method induces the risk of urinary tract infection and urethral trauma. We studied perineal noise recording as an alternative, non-invasive diagnostic method in three flexible/extensible model urethras and two silicone tubes. METHODS: The flexible/extensible model urethras were made of a 10% aqueous solution of polyvinyl alcohol (PVA) and differed in wall- stiffness, the silicone tubes differed in diameter and wall-thickness. Three degrees of obstruction were applied by inflating a cuff placed around the PVA-urethras and by compressing the silicone tubes with an adjustable clamp. Noise, produced during flow, was recorded at three positions distal to the obstruction using a piezoceramic contact microphone. RESULTS: The average amplitude of the noise and the essential frequency of the power spectrum of each noise recording depended significantly on the degree of obstruction, the position of the microphone and the wall-stiffness in PVA-urethras and the diameter in silicone tubes. CONCLUSIONS: Based on the results of this study perineal noise recording shows good potential as an alternative method for diagnosing bladder outlet obstruction