Urethral Cross-sectional Area Research Articles

Influence of transurethral catheters on urine pressure-flow relationships in males: A computational fluid-dynamics study

Background and ObjectiveIn the field of urology, the pressure-flow study (PFS) is an essential urodynamics practise which requires the patient's transurethral catheterization during the voiding phase of micturition to evaluate the functionality of the lower urinary tract (LUT) and reveal the pathophysiology of its dysfunctionality. However, the literature evidences confusion regarding the interference of the catheterization on the urethral pressure-flow behaviour. MethodsThe present research study represents the first Computational Fluid-Dynamics (CFD) approach to this urodynamics issue, analysing the influence of a catheter in the male LUT through case studies which included the inter-individual and intra-individual dependence. A set of four three dimensional (3D) models of the male LUT, different in urethral diameters, and a set of three 3D models of the transurethral catheter, diverse in calibre, were developed leading to 16 CFD non-catheterized either catheterized configurations, to describe the typical micturition scenario considering both urethra and catheter characteristics. ResultsThe developed CFD simulations showed that the urine flow field during micturition was influenced by the urethral cross-sectional area and each catheter determined a specific decrease in flow rate if compared to the relative free uroflow. ConclusionsIn-silico methods allow to analyse relevant urodynamics aspects, which could not be investigated in vivo, and may support the clinical PFS to reduce uncertainty on urodynamic diagnosis.

Web-Based Yoga-Pilates: A Prospective Cohort Study.

There are limited data to determine the change in severity, efficacy, and mechanism of action of yoga-Pilates in the treatment of stress urinary incontinence (SUI). The primary objective was to evaluate the effect of an 8-week web-based home yoga-Pilates exercise program on SUI severity and to evaluate the potential mechanism of action through ultrasound examination of the urethral rhabdosphincter cross-sectional area. This was a prospective cohort study of women with SUI. Participants underwent visits pre- and post-intervention, completed quality of life/severity surveys, and underwent pelvic examination and 3-dimensional transperineal ultrasonography to determine the urethral cross-sectional area. Pre- and post-intervention 24-hour voiding diaries were also collected. The intervention was an 8-week online yoga-Pilates video that tracked and prompted participation. Sixty women completed the study; they were predominantly premenopausal (67%) and vaginally parous (65%) and had done yoga (76%) and/or Pilates (44%). Seventy-three percent performed the exercises ≥3 times per week. For the primary outcome, the International Consultation on Incontinence Questionnaire-Urinary Incontinence Short Form score improved from 9.5 (95% confidence interval [CI], 8.7-10.4) to 7.1 (95% CI, 6.3-7.9) (P < 0.001). The median (interquartile range) number of incontinence episodes per 24 hours decreased from 1 (1-3) to 1 (0-1) (P < 0.001). The Brink pelvic floor strength score improved from 7.1 (95% CI, 6.6-7.7) to 7.7 (95% CI, 7.2-8.2) (P = 0.01). Eighty-three percent reported that they were "better" on Patient Global impression of Improvement. There were no significant changes in urethral measurements. Although it did not meet the minimal clinically important difference, this 8-week web-based yoga-Pilates exercise program improved SUI symptoms and decreased the number of incontinence episodes in women with SUI.

Changes in Morphology of the Urethral Rhabdosphincter Postpartum.

The aim of the study was to determine the effect of pregnancy on urethral rhabdosphincter cross-sectional area (CSA) and any association of CSA to urinary symptoms. Nulliparous women planning pregnancy (N = 135) underwent standardized evaluations (symptom and quality of life [QOL] questionnaires, magnetic resonance imaging, ultrasonography, and neurophysiologic testing) between January 2008 and December 2013 (V1). The participants who became pregnant and gave birth underwent the same evaluations at 6 weeks (V2) and 6 months postpartum (V3). Participants who had magnetic resonance imaging data from both V1 and V3 were selected. We measured urethral rhabdosphincter CSA from high-resolution axial MRIs in a masked fashion. The mean CSA for each participant was calculated. The change from V1 to V3 was assessed. Sixty-eight women were evaluated. There was a significant decrease of 0.05 cm2 (interquartile range, -0.03 to 0.16 cm2; P = 0.002) in the median sphincter CSA between V1 and V3. There was a significant increase in the median Urinary Distress Inventory (UDI) subscore of the Pelvic Floor Distress Inventory (PFDI) from V1 to V3 (median increase of 0 [IQR, 0 to 8.3]; P = 0.033), but this was not significantly correlated with the change in the urethral CSA (Spearman correlation, 0.199; P = 0.107). Increasing fetal weight was correlated with a decrease in CSA postpartum after vaginal birth (Spearman correlation, -0.340; P = 0.017). There is a decrease in urethral rhabdosphincter CSA with worsening Urinary Distress Inventory scores from prepregnancy to postpartum, but these two do not correlate in this cohort with low symptom levels. Among women who give birth vaginally, decrease in rhabdosphincter CSA is correlated with increasing fetal weight, perhaps with ramifications to be seen later in life.

Changes in urethral sphincter size following rehabilitation in older women with stress urinary incontinence.

The purpose of this study was to evaluate the effects of a pelvic floor muscle (PFM) rehabilitation program on the striated urethral sphincter in women over 60 years with stress urinary incontinence (SUI). We hypothesized that the PFM rehabilitation program would also exercise the striated urethral sphincter and that this would be demonstrated by hypertrophy of the sphincter on magnetic resonance imaging (MRI). Women with at least weekly episodes of SUI were recruited. Participants were evaluated before and after a 12-week group PFM rehabilitation intervention with T2-weighted fast-spin-echo MRI sequences recorded in the axial plane at rest to assess urethral sphincter size. Data on SUI symptoms and their bother were also collected. No control group was included. Seventeen women participated in the study. The striated urethral sphincter increased significantly in thickness (21%, p < 0.001), cross-sectional area (20%, p = 0.003), and volume (12%, p = 0.003) following the intervention. The reported number of incontinence episodes and their bother also decreased significantly. This study appears to demonstrate that PFM training for SUI also trains the striated urethral sphincter and that improvement in incontinence signs and symptoms is associated with sphincter hypertrophy in older women with SUI. These findings support previous ultrasound (US) data showing an increase in urethral cross-sectional area following PFM training and extend the previous findings by more specifically assessing the area of hypertrophy and by demonstrating that older women present the same changes as younger women when assessed using MRI data.

In Vivo Biomechanical Assessment of Anterior Rabbit Urethra After Repair of Surgically Created Hypospadias

We studied the in vivo biomechanical properties of the anterior urethra in a rabbit hypospadias simulation model at long-term followup after urethroplasty. A total of 38, 9-week-old white New Zealand male rabbits were randomized into active treatment and control groups. The active treatment group included hypospadias-like simulation and acute repair (sham, mobilization and advancement, tubularized incised posterior urethral plate). After 23 weeks all groups underwent biomechanical investigation using impedance planimetry. Cross-sectional area pressure measurements during bag distention were conducted at 3 different positions along the urethra, and biomechanical (tension-strain) relations were computed. The biomechanical parameters studied were urethral luminal dimension (cross-sectional area pressure relation) and its deformability to luminal pressure (tension-strain relation). The urethral cross-sectional area was significantly larger in the mobilization and advancement group compared to the tubularized incised plate group (p <0.001), shams and controls at the distal distention site (p <0.05), and other groups at the intermediate distention site (p <0.05). The strain-tension curves were not significantly different between the groups. All groups showed a nonlinear cross-sectional area pressure and circumferential wall tension-strain relationships in the 3 distention sites. The urethras exhibited a decreasing ability to be distended with increasing pressures, indicating self-protection against damage. At long-term followup no differences in tension-strain relations were found between groups, despite the fact that the mobilization and advancement group had enlarged urethras. Our hypospadias simulation animal model could be useful to test commonly used or new urethroplasty techniques and their functional (biomechanical) long-term results before clinical use.

Simultaneous measurement of urethral opening pressure and urethral cross-sectional area during voiding cystometry.

To assess a new technique for measuring urethral opening pressure and urethral cross-sectional area during the course of routine voiding cystometry. Twenty-eight male patients were studied, 24 of whom had cystometric evidence of bladder outlet obstruction, the other four being unobstructed. Urethral opening pressure was measured using an adapted fluid bridge test and urethral cross-sectional area was measured using the method described in the preceding paper. The mean urethral opening pressure in the obstructed patients was 68 cm/H2O (range 38-124) against a mean of 19 cm/H2O (range 16-22) in the unobstructed group. The mean urethral cross-sectional area in the obstructed group was 2.6 mm2 (range 0.9-7.9) compared with a mean of 14.2 mm2 (range 10.8-19.9) in the unobstructed patients. This technique allows measurement of the parameters of bladder outlet obstruction described by Schäfer during routine voiding cystometry, without specialized equipment. This provides a simple method for quantification of urinary outflow obstruction and should prove useful in the assessment of new treatment modalities.

Elimination of the influence of intravesical pressure on the micturitional urethral pressure profile by calculation of urethral cross-sectional area: an experimental study.

To determine whether it is possible to eliminate the influence of intravesical pressure on the pressure drop recorded between the bladder and prostatic urethra during the micturitional urethral pressure profile (MUPP). An experimental study using an artificial bladder/urethral model and computerized urethral pressure profile measurement system. By simultaneous measurement of the flow rate and MUPP it is possible to calculate a theoretical cross-sectional area, based on Griffiths' theory of flow through distensible tubes. The calculated cross-sectional area for a given constriction remains the same despite changes in the driving pressure. The effect of changes in intravesical pressure on the MUPP can be eliminated by calculation of the urethral cross-sectional area. This parameter forms part of the Schäfer model of obstruction and this technique may therefore be useful in quantifying bladder outlet obstruction.

Urodynamic measure of urethral cross‐sectional area: Application for obstructive uropathy

A conductance formula was developed based on pressure (P) and flow (Q) data collected from rigid tubes with a cross-sectional area in the range of the flow controlling zone of the urethra. Curve fitting of data resulted in an exponential formula and a simple proportionality constant related tube of differing cross-sectional area. The resulting formula estimates cross-sectional area based on P and Q data and is in the form of a conductance ratio because Q is in the numerator and P is in the denominator. The formula is AEFm = 3.5 Q/P0.58, where AEFm is the area equivalent factor-male and Q is measured in ml/sec and P is cm H2O. To further introduce the estimate of cross-sectional area, urodynamics were retrospectively reviewed from 19 males over the age of 50 with complaints of prostatism. The AEFm was plotted on standard urodynamic records much like P and Q data. The onset of voiding was characterized by a rapid increase in urethral area. Maximal cross-sectional area obtained at maximal flow was 2.9 +/- 1.4 mm2. The maximal urethral area per unit of applied detrusor pressure, an estimate of urethral compliance, was 0.06 +/- 0.6 mm2/cm H2O. This latter measure may help to compare patients with widely different detrusor pressures. The urodynamic data from two young adult males is also presented for comparison. Their average maximal urethral cross-sectional area was 7.1 mm2. Their average area per unit of applied detrusor pressure was 0.15 mm2/cm H2O. These larger values contrast sharply with the BPH group. The AEFm clearly shows urethral function in terms of the principal factor regulating the urine flow rate, the urethral cross-sectional area.

Urodynamic measure of urethral cross‐sectional area: Application for obstructive uropathy

Urodynamic measure of urethral cross‐sectional area: Application for obstructive uropathy

Urodynamic Norms in Women. I. Normals Versus Stress Incontinents

Urodynamic statistics for normal women were compared to similar norms for stress incontinent women. It was concluded that 1) the reduction of flow rate in stress incontinent patients appears to be the result, with high probability of pathologic changes in the function of the distal urethra, 2) stress incontinence does not affect the combined effects of bladder pressure and the proximal urethral resistance during voiding as reflected in velocity, 3) the distal urethral cross-sectional area appears to be under neuromuscular control and 4) the distal urethra of stress incontinent women appears to be incapable of opening as widely as the distal urethra of normal women. It is not currently possible to assign anatomical or physiological causes to the observed phenomena.

A signal-processing system for real-time ultrasonic measurement of urine flow parameters.

An application of a signal-processing system to the urethra is described which allows for real-time measurement of the average velocity of the urine at a particular location along the urethra during voiding through measurement of the average frequency in ultrasonic return from scatterers in the flowing urine. In addition, this comparatively simple system provides, without additional instrumentation, the relative urethral cross-sectional area at this location and the relative urine flow rate as functions of time throughout the voiding period. Tests indicate its potential as a valuable transcutaneous diagnostic aid in the detection, study, and treatment of various disorders and diseases of the lower urinary system. The key element of the system is a circuit having a voltage transfer function magnitude proportional to the square root frequency.