The nature of high-pressure voiding in small boys and its relation with the influence of a transurethral catheter

Abstract

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 (Pdet 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 Pdet max measured by the 18G and 7.4Fr catheters (102.0 ± 22.5 vs. 94.7 ± 25.6 cmH2O, 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-Pdet 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 2O, respectively. The mean difference between Pdet max and T-Pdet max was 5.6 ± 11.4 cmH2O. The minimum detrusor pressure during voiding (33.6 ± 18.4 and 30.8 ± 16.3 cmH2O), 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. © 2007 Wiley-Liss, Inc.