Functional Anatomy Of Female Urethra And Bladder And Its Influencing Factors:a MRI Study

Pelvic floor dysfunction(PFD)is a common chronie disease in middle-aged and elderly women,which seriously affects the quality of life and increases the financial burden.Among them,stress urinary incontinence and anterior vaginal wall prolapse are the most common,of which the pathogenesis related to the defects of the sphincter muscle system and supporting system of the urethra and bladder.Accurate assessment of the structure and function of the urethra and bladder is very important for site-specific repair.Some shortcomings need to be considered:First,there is a lack of generally accepted PFD animal models;Second,there is a shortage of cadaveric specimens for teaching;Third,clinical findings is always inconsistent with surgical findings;Forth,urodynamic study only represents the instantaneous function of the urethra and bladder,can not reflecting the anatomical defect,and it is also an invasive technique.Therefore,the use of imaging to assess the relationship between pelvic floor structure and function has become a common method.Imaging methods include X-ray radiography,ultrasound and MRI.Among then,MRI plays an important role in PFD evaluation because of its advantage of non-radiation,high resolution of soft tissues such as muscles,and not easily interrupted by the proficiency of the operator.Even so,the facial and the ligaments are too small to be seen directly and to be differentiated on MRI.Therefore,it is a good method to indirectly reflect the pelvic floor supporting structure and function of organs by observing the position,shape and mobility of pelvic organs,and the study of the relationship between structure and function is functional anatomy.With the development of technology,MRI can not only study the pelvic floor functional anatomy in two dimensions,but also carry out post-processing such as three-dimensional reconstruction.Combined with dynamic analysis,it can better reflect the mobility of organs and some potential defects that can not be found in static state.However,the current methods still have some drawbacks:First,definition and different reference lines are based on the two-dimensional X-ray and ultrasound sagittal plane;Second,dynamic measurements did not consider the bias originating from the pelvic tilt during Valsalva maneuver;Third,there is a lack of research method for the pelvic multi-level defects.Forth,the dichotomous classification of posterior bladder expansion is an oversimplification,making it difficult to evaluate the actual defects;Fifth,the occupying effect of the pelvic organs,volume and shape of bladder,volume and orientation of uterine can not be standardized and may have potential impact on the parameter measurements.In addition,multi-factors(such as bladder volume,uterine volume and orientation,demographics,obstetric characteristics,pelvic floor defects and operations that affecting the pelvic floor support)analysis is lacking to determine factors predispose women to developing PFD.Previous studies only analyzed the relationship between some of the above factors and the clinical manifestations of PFD.We aimed to carry out the following study based on the static and dynamic MRI database:First,using the static and dynamic MRI data of a cohort of young nulligravidae to explore imaging methods for functional anatomy study,focusing on the construction of a three-dimensional spatial coordinate system,correcting the bias that originating from the pelvic inclination during Valsalva maneuver individually,and exploring methods that can reflect the multi-level support of the pelvic floor(segmental urethral mobility and quantitative analysis of the posterior bladder expansion);Second,to explore what factors are mostly responsible for functional anatomy measurements by multiple linear regression analysis;Third,to explore changes before and after radical hysterectomy(RH).Part one Methodological study and reliability evaluation of functional anatomyof female urethra and bladder based on static and dynamic MRI data setsObjectivel,To create a pelvic floor coordinate system and pelvic inclination correction system based on the static and dynamic MRI data sets.2,To explore new methods for segmental urethral mobility and quantitative analysis of the posterior bladder expansion based on the pelvic inclination correction system,and to evaluate the reliability of the new index and commonly used functional anatomy parameters of female urethra and bladder.MethodsStatic and dynamic MRI data of patients attending to Nanfang Hospital from September 2010 to January 2019 were retrospectively analysed,38 nulligravidae were included for analysis after excluding the PFD and potential confounding factors.Static MRI data of 25 young asymptomatic volunteers were recruited as control group.l,Mimics 10.01 was used for three-dimensional reconstruction,UG software was used for constructing coordinate system and individual pelvic inclination correction system to decline bias originating from pelvic inclination during Valsalva maneuver.2,Functional anatomy parameters:2.1 Two-dimensional parameters:thickness of urethral striated muscle,bladder neck funneling,thickness of bladder wall,symmetry of the periurethral structures.2.2 Three-dimensional parameters:position of the bladder neck and external urethral meatus,posterior urethrovesical angle,distance of pubic to bladder neck.2.3 New explored parameters:segmental urethral mobility and quantitative analysis of posterior bladder expansion.Resultsl,Three-dimensional models of pubic and pelvic organs were successfully constructed,with a realistic shape and stereoscopic viewing.The inferior portion of the symphysis pubis was used as the origin of the coordinate system,X-axis pointing to the left of the body,Y-axis pointing dorsally,and Z-axis pointing cranially.According to the coordinates of the organ indication points on the Y axis,the ventral-dorsal position of the points can be determined,and the position of the organ indication points on the Z axis can be determined relative to the longitudinal axis of the human body.The left-right inclination angle was 0.1±2.3 degree,and the inclination angle in the mid-sagittal plane was 3.5±2.0 degree,variations of inclination angles were compensated by corrections individually.2,The urethral trajectory was divided into six equal segments automatically by seven equidistant point from bladder neck(point 1)to the external urethral meatus(point 7),and then point to point measurement was performed.The mobility of bladder neck(9.0±7.8 mm)was larger than the external urethral meatus(6.5±4.4 mm).The maximum value of right lateral,midline,and left lateral posterior bladder expansion was measured on the 3-D axial viewing,with the premise that a paravaginal defect would make the bladder base drop on the side of the defect.The posterior bladder expansion was irregular,and the right side is obvious,there are significant increase of posterior bladder expansion during Valsalva maneuver(less than 4 mm,P<0.05).3,Significant decrease of the bladder neck and external urethral meatus position was found during Valsalva maneuver in normal subjects.Significant increase of posterior urethrovesical angle was found during Valsalva maneuver in normal subjects.Significant increase of the width of bladder neck funneling was also found.No significant difference of static functional anatomy parameters was found between nulligravidae and volunteers.4,The intrarater reliability varied from 0.624 to 0.998,and interrater reliability varied from 0.673 to 0.997.Reproducibility of parameters such as position,length,mobility,and bladder expansion was good and reproducibility of parameters such as small numerical parameters and angles are not so good.ConclusionsMethodologies for measuring the functional anatomy of female urethra and bladder are feasible.Quantitative analysis of urethral segmental mobility and paravesical bulge based on pelvic floor space coordinate system and pelvic inclination correction system can reflect different levels of pelvic floor support.Reproducibility of parameters such as position,length,mobility,and bladder expansion based on correction system was good and reproducibility of parameters such as small numerical parameters and angles are not so good.Part two Multiple linear regression analysis of influencing factors on themeasurement of the functional anatomy of female urethra and bladderObjectiveTo explore influential factors of functional anatomy of female urethral and bladder,and demonstrate how these factors(bladder volume,uterine volume and orientation,demographics,obstetric characteristics and pelvic floor defects)affects measurements of functional anatomy.MethodsData of patients attending to Nanfang Hospital from September 2010 to January 2019 were retrospectively analysed,620 subjects were included for multiple linear regression analysis after excluding the PFD.Dependent variables including posterior bladder expansion,posterior urethrovesical angle,segmental urethral mobility,position of the bladder neck and external urethral meatus,width and depth of bladder neck funneling,distance of pubic to bladder neck.Independent variables including bladder volume,uterine volume and orientation,demographics,obstetric characteristics and pelvic floor defects.ResultsFactors that affecting the dependent variables and the affect size was shown as follows,the minus sign represent the negative affect.1,Posterior bladder expansion(static):defect of periurethral ligaments,defect of levator ani muscle,bladder volume,-uterine volume.Posterior bladder expansion(dynamic):defect of periurethral ligaments,bladder volume,uterine orientation,-uterine volume.2,Posterior urethrovesical angle(static):defect of levator ani muscle,-bladder volume,-bladder neck tunneling,-posterior bladder expansion,-uterine volume.Posterior urethrovesical angle(dynamic):uterine orientation,defect of levator ani muscle,body mass index.3,Segmental urethral mobility:Point 1:parity,defect of periurethral ligaments.Point 2 to point 4:parity.Point 5:parity,bladder volume.Point 6:parity,bladder volume.Point 7:bladder volume,parity.4,Bladder neck position(static):-transvaginal delivery,-defect of levator anm muscle,uterine orientation.Bladder neck position(dynamic):-defect of levator ani muscle,-uterine orientation,-defect of periurethral ligaments.5,External urethral meatus position(static):-defect of levator ani muscle,uterine orientation,-defect of periurethral ligaments,parity,-transvaginal delivery.External urethral meatus position(dynamic):-defect of levator ani muscle,parity,-defect of periurethral ligaments,-bladder volume.6,Width of bladder neck funneling(static):defect of periurethral ligaments,-bladder volume,uterine orientation,-uterine volume.Depth of bladder neck funneling(static):-bladder volume,parity,nulliparous,defect of periurethral ligaments.Width of bladder neck funneling(dynamic):uterine orientation,defect of periurethral ligaments,-bladder volume.Depth of bladder neck funneling(dynamic):-bladder volume,uterine volume,parity.7,Distance of pubic to bladder neck(static):defect of levator ani muscle,uterine volume,uterine orientation.Conclusions1,When measuring the functional anatomy of female urethra and bladder,we need to consider the influence of confounding factors,such as bladder volume,uterine volume and orientation.2,The main influencing factors of functional anatomical parameters were levator ani muscle defect and periurethral ligament defect.3,Parity is the major influencing factor of urethral mobility,body mass index has little effect on the functional anatomical parameters.4,Age can not be considered as a factor affecting the functional anatomical parameters of urethra and bladder in this study.Part three Impact of radical hysterectomy on the functional anatomy of femaleurethra and bladderObjectiveTo explore impacts of Q-M C2 type radical hysterectomy on the functional anatomy of female urethra and bladder.MethodsPreoperative and postoperative MRI data of 29 cervical cancer patients attending to Nanfang Hospital from December 2016 to January 2019 were prospectively analysed,functional anatomy parameters were compared.Results1,We observed a decrease in segmental urethral mobility that reached significance for 5 of the 7 points,and the change of bladder neck is the most obvious.2,We observed a significant posterior bladder expansion after RH(average increase on the right side was 6.9 mm,P?0.005,midline 10.6 mm,P?0.000,left side 9.0 mm,P=0.002).Post-RH defects of cervical level,basal level of bladder and Retzius space level increased obviously(P<0.001).3,The postoperative width of bladder neck funneling was a few millimeters higher than preoperatively(average increase 1.3 mm,P?0.O00).4,A significant shortening of the urethra is seen after RH(average shortening 3.0 mm,?0.003),5,There is a posterior-inferior displacement of the bladder neck and a anterior-superior displacement of the external urethral meatus.6,We observed a significant decrease of posterior urethrovesical angle after RH(average decrease 7.7 degree,P=0.037).7,The thickness oft bladder wall and the urethral striated muscle shows no difference before and after RH.Conclusions1,The position,shape and mobility of female urethra and bladder changed in varying degrees,mainly above the perineal membrane,but the degrees of changing are small.2,Increased posterior bladder expansion at different levels one year after RH suggests decreased bladder support,but long-tenn observation is needed to determine whether it increases the risk of POP.3,The functional anatomical changes of the urethra and bladder alter RH provide a basis for elucidating the mechanism of lower urinary tract dysfunction after RH.