Impact of urethral catheterization on uroflow during pressure-flow study

Voiding efficiency in children is significantly impaired by the presence of the urethral catheter during pressure-flow studies

BACKGROUND

Little is known about the effect of catheterization during pressure-flow studies (PFS) on voiding efficiency in children. Our objective was to determine the effect of urethral catheterization on Qmax and flow index (FI) during PFS compared to the free flow of uroflowmetry (UF).

METHODS

We retrospectively reviewed 63 consecutive children who underwent UF and PFS at our center on the same day (2019-2022). Voiding data was available for 46 patients. Patients first underwent a UF with full bladder, then PFS after urethral catheter insertion. Patients with urethral pathologies (n = 6), on clean intermittent catheterization (CIC) (n = 2) and with major comorbidities (n = 2) were excluded. Indications for UF/PFS were LUTS, recurrent UTIs, incontinence or neurosurgical pre-operative evaluation. Data was collected from the UF and the PFS and compared using paired t-test. The idealized Qmax and flow index (FI) were calculated for UF and PFS using the formulas described by Franco et al.: Male Qmax = 11.26 + 0.0701(TBC [total bladder capacity]) - 0.0000513(TBC); Female Qmax = 10.723 + 0.073(TBC) - 0.0000423(TBC), FI = Actual Qmax/Expected Qmax (Franco and et al., 2016; Franco et al., 2018; Franco and et al., 2016).

RESULTS

Median age was 7 years old (IQR 5-11). Twenty-one (40%) patients were male and 32 (60%) patients were female. Of the 53 patients, 3 boys and 4 girls (n = 7; 13%) were unable to void with the catheter in place during PFS but able to void after its removal. Of the remaining 46 cases, the Qmax during PFS was 5 mL/s slower than the Qmax recorded on the UF without catheter, representing a decrease of 29% (12.3 vs 17.3 mL/s; p < 0.0001). The impact of urethral catheter during PFS was more important in males vs females (Qmax decreased by 7.7 vs 3.3 mL/s, or 45 vs 19%). The mean FI during PFS was 44%, which was a 30% reduction compared to the 74% FI obtained with UF (p < 0.00001). In males, the FI decreased by 37% on PFS, whereas it decreased 26% in females, similar to the Qmax decrease.

CONCLUSIONS

Voiding efficiency, as assessed by Qmax and FI, is decreased during PFS compared to uroflow studies. Our data documents for the first time the impact of urethral catheterization on pediatric voiding efficiency. Abnormal flow rates and elevated PVRs should be used to guide patient management only if obtained by uroflow. Prospective validation comparing free flow with PFS studies will help characterize the impact of urethral catheter relative to bladder pathology, age, gender and catheter size used.

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

BACKGROUND AND OBJECTIVE

In 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.

METHODS

The 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.

RESULTS

The 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.

CONCLUSIONS

In-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.

Defining bladder outlet obstruction and detrusor underactivity in females with overactive bladder: Are we forgetting about the free uroflowmetry?

INTRODUCTION

Both detrusor underactivity (DU) and bladder outlet obstruction (BOO) can coexist in patients with overactive bladder. Definitions of both DU and BOO are based on pressure-flow study (PFS) data. However, invasive urodynamics study can differ from a natural micturition, in fact, discrepancies between free uroflowmetry (UFM) and PFS have been largely described. Our goal is to assess the correlation of free-flowmetry and PFS among patients with OAB and to evaluate how different definitions of DU/BOO are able to discriminate patients with different free UFMs.

METHODS

A retrospective review of urodynamics performed at a single institution was conducted. Females with OAB who voided more than 150 mL in both UFM and PFS were included. Parameters from both voiding episodes were compared with nonparametric test. Two definitions of DU were applied; PIP1: Pdet@Qmax+Qmax < 30 and Gammie: Pdet@Qmax < 20 cmH₂ O, Qmax < 15 mL/s, and BVE < 90% (Bladder voiding efficiency). Also, two definitions of obstruction were chosen; Defretias: Pdet@Qmax ≥25 cmH₂ O and Qmax ≤ 12 mL/s and Solomon-Greenwell female BOO index ≥ 18. Patients who matched with each definition were compared to those who did not, to assess if any definitions were able to discriminate different noninvasive uroflowmetries.

RESULTS

A total of 195 patients were included. Overall, mean age was 55 ± 12 years, 90.8% had mixed urinary incontinence, and 39% complained of at least one voiding symptom. Globally, Qmax and BVE correlated poorly between UFM and PFS, showing that most of the variation corresponded to a systematic error. Twenty-two individuals were found to have DU, they had a difference of 13 mL/s on both maximum flows. Fifty-four patients showed BOO, with a difference between their Qmax of 19 mL/s. Among the four definitions analyzed, only PIP1 and Defreitas were able to discriminate patients with actually a lower Qmax on the free UFM.

CONCLUSIONS

Patients with overactive bladder seem to have a systematic discordance between the urine flow of the free and invasive studies. Current definitions of DU and BOO, which are based on the PFS parameters, are not consistently able to discriminate patients who actually void deficiently on the free UFM.

Transurethral versus suprapubic catheterization to test urethral function in rats

Transurethral and suprapubic catheterization have both been used to test urethral function in rats; however, it is unknown whether these methods affect urethral function or if the order of catheterization affects the results. The aim of this cross-over designed experiment was to compare the effects of catheterization methods and order on leak point pressure (LPP) testing. LPP and simultaneous external urethral sphincter electromyography (EUS EMG) were recorded in anesthetized female virgin Sprague-Dawley rats in a cross-over design to test the effects of transurethral and suprapubic catheterization. There was no significant difference in peak bladder pressure during LPP testing whether measured with a transurethral or suprapubic catheter. There was no significant difference in peak bladder pressure between the first and second catheter insertions. However, peak EMG firing rate, as well as peak EMG amplitude and EMG amplitude difference between peak and baseline were significantly higher after the first catheter insertion compared to the second insertion, regardless of the catheter method. Our results suggest that route of catheterization does not alter urethral function, e.g. create a functional partial outlet obstruction. Either catheterization method could be used for LPP and/or EUS EMG testing in rats.

Transurethral resection of the prostate with preservation of the bladder neck decreases postoperative retrograde ejaculation

Introduction

Even though transurethral resection of the prostate (TURP) is the standard surgical treatment for benign prostatic hyperplasia (BPH), there is a high rate of postoperative retrograde ejaculation.

Aim

To evaluate the effectiveness of TURP with preservation of the bladder neck in comparison with that of standard TURP.

Material and methods

This is a retrospective study. 137 men with BPH were divided into two groups: TURP with preservation of the bladder neck and standard TURP were performed respectively in group A and group B. The patients were evaluated preoperatively and at 3, 6 and 12 months after surgery by International Prostate Symptom Score (IPSS), health-related quality of life (HRQL) score, maximum urinary flow rate (Qmax), postvoid residual urine volume (PVR) and the rate of complications including retrograde ejaculation.

Results

There was no statistically significant difference between groups in terms of the operative duration, catheterization period, hemoglobin decrease, and hospital stay. At the 3-month follow-up, the rates of incontinence and retrograde ejaculation in group A were lower than those in group B. At the 6- and 12-month follow-ups, the difference in the frequency of retrograde ejaculation remained constantly stable whereas the incontinence rates were similar in both groups. The IPSS, HRQL score, Qmax, PVR and the rate of complications including hematuria, clot retention, urinary tract infection, urethral stricture, and bladder neck contracture evaluated at 3, 6 and 12 months also displayed a very similar response in the two groups.

Conclusions

Comparable with standard TURP, TURP with preservation of the bladder neck appears to provide a satisfactory clinical outcome in decreasing early postoperative incontinence and lowering the rate of retrograde ejaculation.