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

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.