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SECONDARY BLADDER NECK OBSTRUCTION (2°BNO) IN BOYS WITH A
HISTORY OF POSTERIOR URETHRAL VALVES - REVISITED
Andrew COMBS
1
, Kenneth GLASSBERG
2
and Mark HOROWITZ
3
1) Weill Cornell Medical College, Cornell University, Urology, New York, USA - 2) Columbia University, Urology, New
York, USA - 3) New York Hospital of Queens-New York Presbyterian, Urology, Flushing, USA
PURPOSE
The diagnosis of 2°BNO in boys with a history of posterior urethral valves (PUV) is complicated given that
radiographically the bladder neck typically appears narrow and uroflow parameters may appear grossly normal in the
face of a powerful detrusor contraction. We have been evaluating various combinations of uroflow and detrusor pressure
measurements to diagnose 2°BNO and herein wanted to test their usefulness.
MATERIAL AND METHODS
We analyzed the findings in 132 boys with a history of PUV who had undergone urodynamics and who were able to void
on command for a uroflow/EMG. The following 3 empirically developed combinations were used to determine the
presence of unequivocal 2°BNO: 1. Pdet>100cmH2O regardless of flow; 2. Pdet>80cmH2O and Qave<10cc/sec; and 3.
Pdet>60cmH2O and Qave<5cc/sec. Absence of 2°BNO was considered when voiding Pdet was <40cmH20,
Qmax>15cm/sec and Qave>10cm/sec. In between values were considered equivocal.
RESULTS
Based on the above criteria, 58 (44%) were categorized as unobstructed, 42 (32%) as equivocal and 32 (24%) as
unequivocal. 14 boys with unequivocal and 14 with equivocal obstruction were treated with alpha-blockers. Those
thought to have 2°BNO were placed on alpha-blockers. In the unequivocal group on alpha-blockers, mean voiding Pdet
decreased from 107.3 to 41.2cmH2O, Qave increased from 6.1 to 16.4cm/sec and Qmax from 12.5 to 24.7cm/sec.
Similar though less improvement occurred in the equivocal group.
CONCLUSIONS
Our findings not only identified dramatic and statistically significant improvement in pressure/flow studies with alpha-
blocker therapy thus validating the above cut-off values, they also help to confirm that 2°BNO is a real finding and that
improvement in pressure flow studies can be accomplished without bladder neck incision. The diagnosis of 2°BNO should
be considered in boys with a history of PUV who have persistent hydronephrosis, non-resolving LUTS, increased detrusor
voiding pressures, and/or impaired uroflow or emptying. While using combinations of values at first may appear
cumbersome, their value in predicting alpha-blocker therapy success makes them very useful.