Turbulent urinary flow in the urethra could be a causal factor for benign prostatic hyperplasia

Bladder Neck Angle Associated with Lower Urinary Tract Symptoms and Urinary Flow Rate in Patients with Benign Prostatic Hyperplasia

OBJECTIVE

To evaluate the effect of the funnel-shaped structure of the bladder neck in patients with benign prostatic hyperplasia (BPH), we investigated the correlation of the bladder neck angle (BNA) with the urinary flow rate and lower urinary tract symptoms (LUTS).

METHODS

The cohort comprised 281 first-visit patients. The anatomical prostatic parameters, including BNA, total prostate volume, prostate urethral angle, intravesical prostatic protrusion, and prostate urethral length, were measured by transrectal ultrasonography. The International Prostate Symptom Score (IPSS), postvoid residual urine volume, and uroflowmetric measurements were evaluated.

RESULTS

As revealed by multivariable linear regression analysis, BNA was independently associated with the peak flow rate (Qmax) and IPSS. The mean BNA significantly differed according to the severity of prostate symptoms and Qmax, and the mean BNA was 85.5°±17.4° and 89.84°±16.31° in patients with severe prostate symptoms and a Qmax<10 ml/s (P <0.001 and <0.001, respectively). The linear regression analysis showed that BNA was positively associated with the total IPSS (R = 0.718, P <0.001) and inversely associated with Qmax (R = 0.569, P <0.001). In addition, the mean BNA in patients with acute urine residual (AUR) was higher than that in patients without AUR (86.04°±16.36° vs 63.75°±15.14°, P <0.05).

CONCLUSION

BNA is significantly correlated with LUTS and urinary flow rate in patients with BPH. Our findings suggest that BNA could play an important role in the pathogenic mechanism of BPH and AUR.

Computational Tools for the Investigation of the Male Lower Urinary Tract Functionality in Health and Disease

Purpose

This paper aims to show the potentialities of computational bioengineering in the field of lower urinary tract pathophysiology. Engineering methods allow the investigation of urine flow in healthy and pathologic conditions and the analysis of urethral occlusion by means of artificial urinary sphincters.

Methods

Computational models of bladder and urethra were developed and exploited to investigate the lower urinary tract physiology in health and in disease. Average male morphometric configurations were assumed, together with typical properties of both biological tissues and fluids. The reliability of the models was assessed by the mutual comparison of results and the investigation of data from experimental and clinical activities.

Results

The developed models allowed to analyze typical situations, such as the micturition in health and in disease, and the lumen occlusion by external devices. The models provided information that clinical and experimental tests barely provide, as the occurrence of turbulent phenomena within urine flow, the shear stresses at the lumen wall, the external pressure that is strictly required to occlude the lumen.

Conclusions

The methods of bioengineering allow broadening and deepening the knowledge of the lower urinary tract functionality. More in detail, modeling techniques provide information that contributes to explain the occurrence of pathological situations, and allows to design and to optimize clinical-surgical procedures and devices.

Relationship between prostatic urethral angle and urinary flow rate: its implication in benign prostatic hyperplasia pathogenesis

OBJECTIVES

The prostatic urethra is a bent tube, and the clinical significance of the prostatic urethral angle (PUA) is poorly understood. We investigated the effect of the PUA on the urinary flow rate in men without benign prostatic obstruction.

METHODS

In a theoretical model, the urinary flow rate at the end of the prostatic urethra was formulated according to some principles of fluid dynamics, including the Navier-Storkes equation, Bernoulli's equation, and the loss of coefficient at bends. The change in the urinary flow rate according to the PUA was also calculated through mathematical simulations. In addition, the relationship between the PUA and the peak flow rate was evaluated in 65 healthy men without benign prostatic obstruction (age 50 to 59 years, prostate volume less than 30 cm(3), peak flow rate greater than 15 mL/s). The prostate volume and PUA were determined by transrectal ultrasonography.

RESULTS

Using the fluid dynamic model, the urinary flow rate increased in proportion to the urethral diameter and was inversely associated with the PUA. The mathematical simulations showed that the urinary flow rate decreased by more than 27% as the PUA increased from 35 degrees to 90 degrees. In the clinical setting, the peak flow rate was significantly associated with the PUA by linear regression analysis (R = 0.34, beta = -0.342, P = 0.005), but it was not associated with the total prostate volume (R = 0.18, beta = -0.181, P = 0.150).

CONCLUSIONS

The PUA was inversely associated with the urinary flow rate in this theoretical model and preliminary clinical study. This relationship could be an important factor in the pathogenesis of benign prostatic hyperplasia/lower urinary tract symptoms.

The overlooked cause of benign prostatic hyperplasia: prostatic urethral angulation

Benign prostatic hyperplasia (BPH) is one of the most common problems faced by aging men and can be associated with bothersome lower urinary tract symptoms that affect quality of life by interfering with normal daily activities and sleep patterns. Despite the clinical importance of BPH, its pathogenesis is still poorly understood. Previously, our understanding of BPH was centered on bladder outlet obstruction being secondary to benign prostatic enlargement. However, prostate size itself is not correlated with the urine flow rate and symptomatology. The prostatic urethra is a bend tube and the increased prostatic urethral angulation shows a higher bladder neck on cystoscopic examination. Although some urologists suspected that the higher bladder neck might be a causal factor for BPH, the clinical significance of prostatic urethral angulation was previously underestimated. In this study, we propose a new hypothesis that prostatic urethral angulation is a causal factor for BPH. By applying the concept of fluid dynamics to the process of urination in the prostatic urethra, we show that the energy loss in this bending tube (the prostatic urethra) can occur during micturition and it increases proportionally to prostatic urethral angulation; this energy loss results in a decrease of the urine velocity and accordingly, the urine flow rate is inversely associated with prostatic urethral angulation. We also propose that BPH involves prostatic urethral angulation as well as the classical BPH triad of prostatic enlargement, bladder outlet obstruction, and symptomatology. Our hypothesis suggests that prostatic urethral angulation is an overlooked cause of bladder outlet obstruction and is a causal factor of BPH, and provides novel insight into the pathogenesis of BPH. Ultimately, the relationship between prostatic urethral angulation and urine flow rate, and other clinical factors including urodynamic parameters, the symptomatology, the response to treatment, and disease progression, need to be investigated in a clinical setting.