Impact of urethral catheterization on voiding efficiency in children
Ioana Fugaru, MD, MSc, Lysanne Campeau, MD, PhD, Lina di Re, RN, Marika Edvi, RN, John-Paul Capolicchio, MDCM.
McGill University, Montreal, QC, Canada.
BACKGROUND: Pressure-flow studies (PFS) allow for in-depth assessment of the voiding phase. In adults, the presence of a urethral catheter during the voiding phase decreases the maximal urine flow (Qmax) compared to the free flow produced during uroflowmetry (UF). It has been hypothesized that the presence of a transurethral catheter causes obstruction and/or local irritation. However, little is known about the effect of catheterization during PFS on the Qmax in children, whose urethra is smaller than that of adults. The objective of this study was to determine the effect of urethral catheterization on Qmax and other voiding parameters during PFS compared to the free flow produced during UF. METHODS: We retrospectively reviewed the charts of 63 consecutive children who underwent UF and PFS at our center in the same setting between 2019 and 2022. The patients first undergo a UF with full bladder, then PFS after insertion of a urethral catheter. We excluded patients who were known or investigated for urethral pathologies (n=6), who were on clean intermittent catheterization (CIC) (n=2) and those with major comorbidities (n=2). The indication for UF/PFS were LUTS, recurrent UTIs, incontinence or as part of neurosurgical pre-operative evaluation. Data was collected from the UF and the PFS and compared using paired t-test. Age and gender-specific nomograms for Qmax versus voided volume nomograms were available for 40 children ≤14 years old. RESULTS: Median age at the time of the study was 7 years old (IQR 5-11). Twenty-one (39.6%) patients were male and 32 (60.4%) patients were female. Of the 53 patients, three boys and four girls (n=7; 13.2%) were unable to void with the catheter in place during PFS but able to void its removal. The Qmax during PFS was 5 mL/s slower than the Qmax recorded on the UF without catheter, representing a decrease of 29% (12.3 vs 17.3 mL/s; p<0.0001). The impact of urethral catheter during PFS was more significant in males vs females (Qmax decreased by 7.7 vs 3.3 mL/s, or 45 vs 19%). Patients required on average 28.8 more seconds to achieve maximal flow during PFS compared to UF (p=0.0206). There was no statistically significant difference between the residual volumes when comparing PFS (done by CIC) to UF (done by ultrasound) (30 vs 25 mL, p=0.5774). When using age and gender-specific nomograms for Qmax versus volume voided, we noted that 14/40 (35%) fell from > 10th percentile in UF values to < 5th percentile with the PFS values. CONCLUSIONS: We conclude that Qmax is reduced by 29% in children due to the presence of a urethral catheter during PFS. Males, with an anatomically longer urethra, were particularly affected, with a mean decrease of 7.7 mL/s (45%, p=0.0113). Moreover, 13% of children undergoing PFS could not void at all secondary to the presence of the catheter. When using PFS parameters alone, a clinician may attribute abnormally low flow values to 35% of children assessed. Therefore, we suggest that abnormally low flow parameters on PFS be interpreted cautiously.
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