Urinary flow patterns in first year of life

Purpose: We studied the natural development of urinary flow and lower urinary tract function in healthy male infants.

Materials and methods: Custom-made ultrasound flow probes connected to a flowmeter were mounted on the penis in 20 infants who previously had been assessed in the immediate postnatal period. Median subject age was 10.7 months (range 9.2 to 19.8). Flow data were sampled to a personal computer and flow curves were assessed regarding configuration, maximum flow rate and voided volume. Results were analyzed statistically and were compared to those obtained in the neonatal period. Comparison of uroflow parameters was assessed by using analysis of variance, while contingency coefficients and Wilcoxon test were used for comparisons involving nominal and paired data, respectively. A p value of less than 0.05 was considered statistically significant.

Results: A total of 19 infants had evaluable data, of whom 15 also had evaluable data from the original neonatal study. Flow curve pattern was bell shaped in 32% of patients, interrupted in 46%, staccato in 15%, tower in 3% and spike-dome in 3%. Dyscoordinated patterns accounted for 46% of all flows, a significant increase compared to the neonatal period, in which only 34% of flows were considered dyscoordinated (p <0.01). While voided volume increased significantly with age, maximum flow rate remained more or less stable.

Conclusions: Contrary to conventional wisdom, infants continue to exhibit urinary flow dyscoordination to an even greater extent than in the neonatal period. Therefore, the anticipated normalization of urinary flow is most likely to occur after the first year of life.