title: The comparative pressure-flow plot properties of radiological bladder neck and prostatic obstruction.
abstract: OBJECTIVE
  To test the hypotheses that: (i) significant differences should exist in pressure/flow data between radiologically determined bladder neck and prostatic obstruction; (ii) these differences should inform understanding of the pathophysiology of male outflow obstruction. The biomechanics of the voiding/pressure/flow plot imply that a urodynamic assessment trace should identify outflow obstruction and characterise the urethral viscoelastic properties. Micturating cystourethrograms (MCUG) images might provide a useful diagnostic dichotomy for testing these assumptions.
  
  
  METHODS
  The pressure/flow data from 71 men who also provided video-urodynamic imaging data that a radiologist could classify unequivocally as showing bladder neck obstruction (42) or prostatic obstruction (29) were analysed. The following variables were recorded: the detrusor pressure at initiation of voiding (P(det.open)); the detrusor pressure at the end of voiding (P(det.close)); the detrusor pressure at maximum flow rate (Q(max)), (P(det.)Q(max)), and Q(max). The urethral resistance relation (URR) was drawn onto the pressure-flow plot and the gradient of the URR, DeltaP(det)/DeltaQ, was calculated.
  
  
  RESULTS
  There were significant between group differences in P(det.open) (95% confidence interval of the difference 5.2-28.6, U = 352, P = 0.003); P(det.close) (0.2-15.0, U = 428, P = 0.034); P(det).Q(max) (0.0-18.9, U = 439, P = 0.05); Q(max) and DeltaP(det)/DeltaQ did not distinguish between the MCUG groups (95% confidence interval of the difference 2.3-18, U = 111; P = 0.004). The best-fit model from linear combinations of the data achieved an area under the receiver operator curve of 0.72 for discriminating between the MCUG groups.
  
  
  CONCLUSIONS
  The urodynamic assessment identified interesting and coherent biomechanical differences, and could distinguish between the obstructions with a moderate degree of accuracy.
authors.affiliation: Department of Surgery, University College Hospital, London, UK.
authors.forename: Sanjin
authors.initials: S
authors.lastname: Idriz
authors.forename: Samuel
authors.initials: S
authors.lastname: Bishara
authors.forename: Alex
authors.initials: A
authors.lastname: Kirkham
authors.forename: David
authors.initials: D
authors.lastname: Rickards
authors.forename: P
authors.initials: P
authors.lastname: Julian
authors.forename: R
authors.initials: R
authors.lastname: Shah
authors.forename: James
authors.initials: J
authors.lastname: Malone-Lee
mesh_terms: D000368:Aged; D004812:Epidemiologic Methods; D006801:Humans; D008297:Male; D008875:Middle Aged; D011312:Pressure; D053448:Prostatism / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011859:Radiography; D001748:Urinary Bladder Neck Obstruction / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014554:Urination / Q000502:physiology*; D014563:Urodynamics / Q000502:physiology*