Cold knife valvulotomy for posterior urethral valves using novel optical urethrotome

Mechanical Ablation of the Posterior Urethral Valve Omitting Thermal Energy: A Brief Report

Management of the posterior urethral valve (PUV) is a clinical challenge in pediatric urology. We report the results of a modified valve ablation method without using a pediatric resectoscope and thermal energy. Patients were selected from children with PUV who were referred to the pediatric urology clinic of Shahid Labbafinejad Hospital, Tehran, Iran, and have undergone endoscopic valve ablation surgery between May 2019 to May 2021. Ten male patients with PUV underwent mechanical valve ablation without the use of the conventional pediatric resectoscope, and thermal energy was replaced by a 6F semi-rigid urethroscope and 3Fr ureteral catheter. Patients were assessed both pre-and postoperatively using serum creatinine, urinary tract ultrasound imaging, and voiding cystourethrography. The mean age was 23.88±30.13 months (range= 25 days to 8 years). Four out of 10 patients (40%) had elevated serum creatinine, and seven had unilateral or bilateral hydroureteronephrosis (70%). No major complications were reported according to Clavien-Dindo Classification System. The level of serum creatinine, the grade of hydroureteronephrosis, and the ratio of the prostatic urethra to anterior urethra diameter in postoperative voiding cystourethrography were decreased. A decrease in serum creatinine level occurred in patients after valve ablation, but this decrease was not statistically significant (P=0.059). The decrease in hydroureteronephrosis grade on the right (P=0.006) and left (P=0.022) was statistically significant. There was no evidence of urethral stenosis or need for repeating resection. It can be concluded that our mechanical valve ablation method might be a safe and effective technique for PUV ablation.

Computational fluid dynamics modeling approaches to assess lower urinary tract hydraulic dynamics in posterior urethral valve before and after endoscopic valve ablation: a pilot study

PURPOSE

Computational fluid dynamics (CFD) has been used successfully in cardiovascular system research to analyze the physiological processes inside vessels. We evaluated the hydraulic information of urine through the lower urinary tract in a patient with posterior urethral valve (PUV) before and after valve ablation by CFD.

METHODS

A set of models of the lower urinary tract were developed based on geometrical data obtained by cystoscopy and voiding cystourethrography. Simulated assumptions and conditions were applied according to prior studies and urodynamic results. We used Fluent CFD 19.0 (Ansys Inc., USA) to compute the velocity and pressure of the fluid regions. The simplification of Bernoulli's formula was applied afterward to calculate the hydraulic energy of different positions.

RESULTS

The urine flow rates of the NORMALst, the PUVst, and the POSTst at 5000 Pa were 18.08 ml/s, 11.14 ml/s, and 12.16 ml/s, respectively. Precipitous pressure change was observed around the valve in the PUVst, and the abnormal change was concentrated in the dilated urethra in the POSTst. Major energy dissipations were generated around the valve and the dilated urethra in the PUVst. The energy loss that occurred in the dilated urethra did not improve after the operation.

CONCLUSIONS

Our findings are probably indicative of the hydrodynamics changes in the dilated urethra in PUV and need to be confirmed through more improved CFD models in the future. CFD may revolutionize pediatric urologists' perception in the management of urinary disease.

The changes of urethral morphology recognized in voiding cystourethrography after endoscopic transurethral incision for posterior urethral valve in boys with intractable daytime urinary incontinence and nocturnal enuresis

PURPOSE

Endoscopic transurethral incision (TUI) of posterior urethral valve (PUV) can improve daytime urinary incontinence (DUI) and nocturnal enuresis (NE). However, the underlying mechanism has not been elucidated. In this study, we retrospectively examined the mobility of the urethra before and after TUI by measuring the urethral angle with voiding cystourethrography (VCUG), to clarify the effects of TUI on the morphology of the urethra during voiding.

METHODS

Between July 2010 and December 2014, 29 boys with intractable DUI and/or NE were diagnosed as PUV and underwent endoscopic TUI. VCUG during voiding phase was performed at sequential radiographic spot images (1 image per second) at a 45° angle in oblique standing position. The point at which the angle of the urethra was the smallest during urination was regarded as the minimum urethral angle. The maximum urethral angle during early voiding phase was compared with the minimum urethral angle, and the percentage by which this angle changed was calculated as the flexion rate. Then changes in minimum urethral angle and flexion rate were analyzed before and 3-4 months after TUI.

RESULTS

After TUI, the minimum urethral angle on VCUG became more obtuse (before vs. after TUI, respectively: 112.7 vs. 124.5°, p < 0.001), the flexion rate decreased (before vs. after TUI, respectively: 11.8 vs. 4.1%, p < 0.001).

CONCLUSIONS

This study demonstrated a significant difference in the degree of change. The findings may contribute to understanding of the mechanism of improvement in symptoms after TUI in patients with PUV.