Aims: To disclose the nature of the high-pressure voiding observed in small boys and to determine the influence of a transurethral catheter on voiding urodynamic parameters and reproducibility of these parameters.
Materials and methods: Video-urodynamic studies (V-UDSs) were repeated twice in a single session using two different sized, 18G (Ø1.15 mm) and 7.4Fr (Ø2.50 mm), catheters in 9 boys aged 7.3 months (2-17) and compared with the maximum voiding detrusor pressure (P(det max)) values. Separately, in 20 boys aged 8.9 (1-34) months, V-UDSs using an 18G catheter were repeated twice, and fluoroscopic images and UDS were continuously recorded during the whole voiding phase and analyzed.
Results: There was no significant difference between the mean P(det max) measured by the 18G and 7.4Fr catheters (102.0 +/- 22.5 vs. 94.7 +/- 25.6 cmH(2)O, P = 0.42). Intermittent interruptions of the urinary stream due to detrusor-sphincter dyscoordination were observed in 92.5% (37/40) of voiding cycles. The true maximum voiding detrusor pressure (T-P(det max)), the maximum detrusor pressure recorded only when the urinary stream was actually detected, on the first and second voiding cycles were 86.9 +/- 30.3 and 89.0 +/- 31.7 cmH(2)O, respectively. The mean difference between P(det max) and T-P(det max) was 5.6 +/- 11.4 cmH(2)O. The minimum detrusor pressure during voiding (33.6 +/- 18.4 and 30.8 +/- 16.3 cmH(2)O), the opening detrusor pressure and the number of stream interruptions were reproducible.
Conclusions: Small boys commonly void intermittently with a high detrusor pressure, which may be mainly due to detrusor-sphincter dyscoordination rather than the outflow obstruction caused by a transurethral catheter.
(c) 2007 Wiley-Liss, Inc