title: Is there a clinically significant change in pressure-flow study values after urethral instrumentation in patients with lower urinary tract symptoms?
abstract: OBJECTIVE
  To determine the effect of urethral instrumentation on pressure-flow study values and subsequent grading of bladder outflow obstruction (BOO) in men with lower urinary tract symptoms (LUTS) using suprapubic intravesical pressure monitoring.
  
  
  METHODS
  Seventy-two men with LUTS underwent pressure-flow study using suprapubic intravesical pressure monitoring. The urethra was then instrumented successively with a 12 F catheter and a 17 F cystoscope, and a further pressure-flow study recorded after each procedure. Standard pressure-flow variables were measured for the three recordings. The presence and degree of obstruction were determined using commonly recognized grading systems, i.e. the Abrams-Griffiths nomogram. the linear passive urethral resistance ratio (LPURR) and the urethral resistance algorithm (URA).
  
  
  RESULTS
  There were statistically significant differences in the detrusor pressure at maximum flow and detrusor opening pressure between the uninstrumented and instrumented studies (12 F and 17 F) but no difference in peak flow rates between the groups or in the Abrams-Griffiths number or URA value between studies. Using the LPURR, there was a tendency to a lower obstruction class after urethral instrumentation, ranking as 17 F > 12 F > no instrumentation.
  
  
  CONCLUSIONS
  The changes seen after urethral instrumentation represent no more than the biological intra-individual variation normally seen in pressure-flow studies and do not lead to a clinically significant change in obstruction class.
authors.affiliation: Department of Urology, Charing Cross Hospital, London, UK.
authors.forename: R M
authors.initials: RM
authors.lastname: Walker
authors.forename: A
authors.initials: A
authors.lastname: Patel
authors.forename: S
authors.initials: S
authors.lastname: St Clair Carter
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D008297:Male; D008875:Middle Aged; D011312:Pressure; D011470:Prostatic Hyperplasia / Q000150:complications* / Q000503:physiopathology / Q000628:therapy; D001748:Urinary Bladder Neck Obstruction / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy; D014546:Urinary Catheterization; D014554:Urination / Q000502:physiology; D014563:Urodynamics