The Vital Role of the Distal Urethral Segment in the Control of Urinary Flow Rate

Gleason, Donald M.; Bottaccini, Manfred R.

doi:10.1016/s0022-5347(17)62498-4

Cited by 24 publications

(11 citation statements)

References 9 publications

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“…Fluoroscopic measures of the urethra in female children have reported values similar to those we observed [Gleason and Bottaccini, 1968]. Measurements from four subjects showed an average urethral diameter of 1.8 mm.…”

Section: Discussionsupporting

confidence: 84%

“…Turbulence has been estimated previously to cause energy losses of 10^30% in the urethra of women [Ritter et al, 1964;Spangberg et al, 1989]. However, the tapering shape of the bladder neck and proximal urethra as well as the short urethra in women minimizes viscous losses and facilitates laminar £ow in the urethra [Gleason and Bottaccini, 1968], making the assumptions in Bernoulli's formula reasonable ones to model voiding. If the model presented here were to include energy losses due to turbulence, the areas based on urodynamic data would be larger than predicted from Bernoulli's formula.…”

Section: Discussionmentioning

confidence: 99%

“…Previous studies using visual examination of the external urethral meatus or X-ray techniques during voiding to visualize the shape and con¢guration of the urethra have demonstrated that it is not actually circular in cross-section [Gleason and Bottaccini, 1968;Pullan et al, 1982;Fonda et al, 1985]. However, the dual assumptions of steady £ow and circular crosssectional area of the urethra on average give relatively accurate predictions for urethral area [Gleason and Bottaccini, 1968;Backman, 1971]. Tubes with circular cross-sectional area have the greatest area to perimeter ratio, allowing the highest £ow for the least stretch of elastic tissue.…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Predicting urethral area from video‐urodynamics in women with voiding dysfunction

Rao

Walter

Jamnia³

et al. 2003

Neurourology and Urodynamics

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Section: Discussionsupporting

confidence: 84%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Predicting urethral area from video‐urodynamics in women with voiding dysfunction

Rao

Walter

Jamnia³

et al. 2003

Neurourology and Urodynamics

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“…Flow dynamical assessment, especially vorticity formation in the urine stream, is an undeveloped approach to LUT function. More than 50 years ago, Gleason and Bottaccini [26][27][28][29] investigated the association between flow dynamics and LUT function or urethral shape. However, technological limitations may have been obstacles in the development of flow dynamical assessment of LUT function.…”

Section: Discussionmentioning

confidence: 99%

Vorticity in lower urinary tract can be assessed and associates with urinary tract morphology in men

Minagawa

Tezuka

Ogawa

et al. 2019

Neurourology and Urodynamics

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Objectives: The aim of this study is to develop a method to evaluate the fluid dynamics of urine flow in the lower urinary tract (LUT), especially that of vorticity. Materials and Methods:This investigation included three sub-studies to demonstrate urine flow in the entire LUT. First, we attempted to observe vorticity generation in the urinary bladder during spontaneous voiding using transabdominal color Doppler ultrasonography (CDUS). Second, we performed transrectal CDUS to evaluate the vorticity of urine flow in the prostatic urethra. Patients with prostate cancer were enrolled before robotic surgery and divided into the vorticity and nonvorticity groups based on CDUS findings for comparisons of longitudinal urethral diameter and prostatic urethral angle. Third, the vorticity of the voided urine stream was observed using a high-speed video-camera. Micturition was done in a standing position while synchronously monitored for urine flow using uroflowmetry.Results: Vorticity formation could be dynamically demonstrated in the urinary bladder and prostatic urethra using CDUS. The prostatic urethral angle of the vorticity group was more than that of the non-vorticity group. High-speed video recording could clearly capture vorticity and spiral shape generation in voided urine. The distance from the external urethral orifice to the first twist changed in accordance with urine flow rate. Conclusions: In a series of sub-studies, this investigation proved vorticity generation in the LUT and voided urine. Vorticity was detectable in the LUT and in voided urine using CDUS and a high-speed video-camera. Vorticity generation might be associated with urethral morphology. K E Y W O R D S fluid dynamics, lower urinary tract, urodynamics, vorticity Abbreviations: CDUS, color Doppler ultrasonography; LUD, longitudinal urethral diameter; LUT, lower urinary tract; PUA, prostatic urethral angle; Qmax, maximum urine flow rate; US, ultrasonography; VFM, vector flow mapping.

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“…Several investigators proposed Reynolds numbers for non-obstructed urethral flows. For example, Gleason and Bottaccini [1968] reported (using radiologic evidence) Reynolds numbers of 1,000-3,000 within the upper urethra, implying laminar/ transitional flow, whereas Backman [1971] reported Reynolds numbers ranging from 10,000 to 20,300 (with a mean of 14,000), implying turbulent flow. Sterling et al [1983] proposed Reynolds numbers ranging between 10 3 and 10 4 , suggesting flows that may be laminar, transitional, or turbulent.…”

Section: Discussionmentioning

confidence: 99%

The flow regimes and the pressure-flow relationship in the canine urethra

et al. 1999

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Classical fluid dynamics predicts that the pressure difference Δp between any two points along a fully developed, viscous flow stream is linearly proportional to the flow rate Q (the Poiseuille relation). However, the passive urethral resistance relationship (PURR) widely used in modern urodynamics describes the pressure difference Δp between two points along the urethra as linearly proportional to the flow rate squared (Q2). It is our hypothesis that this functional dependence may have its origins in the developing flow field within the urethra. That is, rather than being fully developed hydrodynamically, urethral flow is more likely representative of flow within the entry length of a rigid conduit. In our study, we used a canine model of the lower urinary tract to investigate the possibility of entrance effects. Although the most rigorous model of urethral fluid mechanics would include the elastic properties of the urethra into its configuration, the solutions from such a model would be unnecessarily complex and not readily lend themselves to the analysis of clinical data. Therefore, we chose to model the canine urethra at each instant in time as a rigid tube, and characterized its instantaneous flow using viscous flow theory for a rigid tube. All urodynamic analyses were performed on a surgically exposed urinary tract. Solid state pressure transducers were used to measure the intravesical and distal urethral pressures, whereas an ultrasonic flowmeter was used to obtain a simultaneous measure of the urinary flow rate. Detrusor contractions were induced using bilateral electrical stimulation of the pelvic nerves. Varying degrees of outlet obstruction were created using an inflatable sphincter cuff secured around the bladder outlet. The experimental data were evaluated using the well‐known laminar entry length model of Atkinson and Goldstein. The peak Reynolds numbers under nonobstructed R pe non‐obs and obstructed R pe obs outlet conditions ranged between 500 < R pe non‐obs < 1,500 and 300 < R pe obs < 1,700, respectively. Under non‐obstructed outlet conditions, the urethral diameters D and total lengths lT ranged between 1.5 mm < D < 2.5 mm and 75 mm < lT < 95 mm, respectively, whereas the peak entrance lengths L pe non‐obs ranged between 55 mm < L pe non‐obs < 215 mm. These data suggest that flow in the canine urethra under both non‐obstructed and obstructed outlet conditions is typically laminar. The data further support the hypothesis that non‐obstructed flows are predominantly entry length in nature. Entry length flows are fluid dynamically described by a quadratic pressure‐flow relationship, thus suggesting a physiological basis for Schäfer's quadratic pressure‐flow relationship, and therefore, for the PURR. Neurourol. Urodynam. 18:521–541, 1999. © 1999 Wiley‐Liss, Inc.

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The Vital Role of the Distal Urethral Segment in the Control of Urinary Flow Rate

Cited by 24 publications

References 9 publications

Predicting urethral area from video‐urodynamics in women with voiding dysfunction

Predicting urethral area from video‐urodynamics in women with voiding dysfunction

Vorticity in lower urinary tract can be assessed and associates with urinary tract morphology in men

The flow regimes and the pressure-flow relationship in the canine urethra

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