title: What is normal bladder neck anatomy?
abstract: OBJECTIVE
  Functional anatomy of the bladder neck and proximal urethra has been studied extensively because of the belief that it is important for urinary continence. The aim of this study was to explore the limits of normality for pelvic floor ultrasound parameters of bladder neck and urethral mobility associated with stress urinary incontinence (SUI) and urodynamic stress incontinence (USI).
  
  
  METHODS
  A retrospective study was conducted on 589 women seen for urodynamic testing in a tertiary urogynaecology clinic. All women were assessed following a protocol including interview, clinical examination, flowmetry, urodynamic testing and 4D pelvic floor ultrasound. Volume data sets were analysed offline to assess for bladder neck descent (BND), urethral rotation and the retrovesical angle (RVA) on maximal Valsalva.
  
  
  RESULTS
  After excluding women with previous incontinence or prolapse surgery, 429 datasets were available. SI was significantly associated with the RVA (p = 0.033) and BND (p = 0.036); USI was associated with urethral rotation (p = 0.021) and BND (p < 0.001). On multivariate logistic regression analysis, controlling for confounders including age, BMI, parity, previous hysterectomy and maximal urethral pressure, the association between SUI and BND remained significant (OR [per 10 mm] = 1.23; 95 % CI: 1.01 to 1.51; p = 0.043), as did the association between USI and BND (OR [per 10 mm] = 1.58; 95 % CI: 1.3 to 1.91; p < 0.001). ROC statistics for BND suggested a cut-off of 25 mm in describing the limit of normality.
  
  
  CONCLUSIONS
  Measures of functional bladder neck anatomy are weakly associated with SUI and USI (with association between BND and USI being the strongest). It is suggested that a BND of 25 mm or higher be defined as abnormal ("hypermobile") on the basis of its association with USI.
authors.affiliation: Sydney Medical School Nepean, University of Sydney, Sydney, NSW, Australia. c_naranjoortiz@outlook.com.|Functional Urology and Rehabilitation Unit, Urología Madrid - Fisioterapia Pélvica Avanzada Madrid, Madrid, Spain. c_naranjoortiz@outlook.com.|Faculty of Health Sciences, Camilo Jose Cela University, Madrid, Spain. c_naranjoortiz@outlook.com.|Centro Universitario San Rafael-Nebrija, Paseo de La Habana, 70 bis / 28036, Madrid, Spain. c_naranjoortiz@outlook.com.
authors.forename: Cristina
authors.initials: C
authors.lastname: Naranjo-Ortiz
authors.affiliation: Sydney Medical School Nepean, University of Sydney, Sydney, NSW, Australia.|University of Western Sydney, Liverpool, NSW, Australia.
authors.forename: Ka Lai
authors.initials: KL
authors.lastname: Shek
authors.affiliation: NHMRC Clinical Trials Centre, University of Sydney, Sydney, Australia.
authors.forename: Andrew James
authors.initials: AJ
authors.lastname: Martin
authors.affiliation: Sydney Medical School Nepean, University of Sydney, Sydney, NSW, Australia.
authors.forename: Hans Peter
authors.initials: HP
authors.lastname: Dietz
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008875:Middle Aged; D012189:Retrospective Studies; D014463:Ultrasonography; D014521:Urethra / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D001743:Urinary Bladder / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D014550:Urinary Incontinence, Stress / Q000000981:diagnostic imaging*; D055815:Young Adult
keywords: Bladder neck descent; Functional anatomy; Stress incontinence; Urethral mobility; Urinary incontinence; Urodynamic stress incontinence