Biomechanical Research Of The Bladder Outflow Obstruction

The urethral obstruction has become a high incidence and high risk disease after hypertension and heart disease,which have a high incidence in the middle and old age population,especially for the male,benign prostatic hyperplasia is one of the main causes of urethral obstruction.Most of the detection methods for urethral obstruction are based on pressure,flow rate and other urodynamic tests nowadays,this kind of detection can obtain more accurate lower urinary tract related data by compared to the means of CT and MRI,however it was invasive to human people.On the one hand,these methods will be affected by the psychological state of patients,who require patients to avoid coughing,sneezing and other violent behaviors which will disturbing the result during the measurement.On the other hand,invasive testing may cause some physiological and psychological effect on patients.Therefore,the demand for non-invasive detection of lower urinary tract obstruction is more and more urgent at present.To explore the response mechanism of multiple urodynamic parameters in lower urinary tract obstruction diseases,this paper build four finite element models of lower urinary tract which based on male urinary tract collodion embedding continuous slice images,including normal male lower urinary tract model,bladder neck outlet obstruction model,prostatic urethral obstruction model and urethral sphincter obstruction model.Subsequently,the corresponding material parameters were given to several groups of lower urinary tract model organs,and the bladder pressure was set as a dynamic pressure curve during the period of urination,and the lower urinary tract models were simulated by two-way flow solid coupling simulation.The validication of the results was verify by the ICS nomogram and micturitional urethral pressure curve after the calculation,and the parameters of lower urinary tract deformation,urethral pressure,stress and urine flow rate were analyzed.The result of the normal male lower urinary tract model shows that the urinary flow rate and the internal wall shear stress reach their peak vaules at the same time in the urethral sphincter,and the reasons for the easy occurrence of relaxation of the urethral sphincter in aging males are explained.Besides,the time-Von Mises stress curve in different observation points of urethra showed a positive correlation with the urinary bladder pressure curve during the urination period,and there was a delay about one second in the curve peak time,which was consistent with the clinical classic conclusion.From the lower urinary tract obstruction model,we know that the rate of urine flow is higher than others urethra during the period of urethral obstruction.After analyzing the distribution characteristics of Von Mises stress in the lower urinary tract,it is found that the stress at the urethral stricture appears to have a decline and a rapid rise,bringing a large stress difference and the location of stress difference is the same as the area where obstruction occurs.In this paper,the lower urinary tract model of male lower urinary tract normal model and three other groups of different types of obstruction was established based on the images of adult men's collodion.After adding material parameters and constraints to the model,the dynamic pressure curve during urination is applied to the bladder,and the fluid-structure coupled simulation is performed.After validating the validity of the results,relevant parameters of the normal group lower urinary tract model and other groups of obstructive models were extracted and compared.This paper lays a foundation for further research on the response mechanism of urodynamic parameters such as deformation and urine flow rate in the model of lower urinary tract obstruction,and provides a theoretical basis for the research t of noninvasive urodynamic testing technology.