title: Effect of bladder volume, gender and body position on the shape and position of the urinary bladder.
abstract: OBJECTIVE
  The optimal design of bladder volume-monitoring equipment, e.g. regarding transducer design and software algorithms, depends greatly on the shape and position of the bladder or on potential changes due to body position and bladder volume. The purpose of this study was to study the influence of body position, bladder volume and gender on the shape and position of the bladder.
  
  
  METHODS
  MRI scans of 11 young volunteers were performed during changes in posture. Images were recorded in the transverse and frontal planes and repeated four to six times through the bladder-filling cycle from empty to full. The position of the bladder midpoint was measured in the three planes. Moreover, to account for shape, the compactness of the cross-section of the bladder was calculated based on its perimeter and area. The effect of body position and gender was analyzed using repeated-measures ANOVA and the independent samples t-test, respectively.
  
  
  RESULTS
  No significant effect of body position on bladder position or shape was found. Gender was shown to have a significant impact on both the position and shape of the bladder: the female bladder was positioned more caudally and was less compact in the transverse plane than the male bladder. Furthermore, there was significant cranial-dorsal movement of the bladder during filling.
  
  
  CONCLUSIONS
  No significant changes in the position or shape of the bladder were observed during changes in body position in young subjects, regardless of bladder volume or gender. However, changes in both parameters were found due to bladder filling.
authors.affiliation: Clinical Institute, Aarhus University Hospital, Skejby Sygehus, Aarhus, Denmark. niels.kristiansen@ki.au.dk
authors.forename: Niels Kristian
authors.initials: NK
authors.lastname: Kristiansen
authors.forename: Steffen
authors.initials: S
authors.lastname: Ringgaard
authors.forename: Hans
authors.initials: H
authors.lastname: Nygaard
authors.forename: Jens Christian
authors.initials: JC
authors.lastname: Djurhuus
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009068:Movement / Q000502:physiology; D011187:Posture / Q000502:physiology*; D012016:Reference Values; D012727:Sex Characteristics; D001743:Urinary Bladder / Q000033:anatomy & histology* / Q000502:physiology*; D014554:Urination / Q000502:physiology