Urinary Flow Patterns in Premature Males

The voiding pattern in healthy pre- and term infants and toddlers: a literature review

Toilet training in Western culture starts between 18 and 24 months. At this age, a child is assumed to have procured the competences needed for bladder control. Since the knowledge of reference values of a normal micturition serves as a guide to diagnose urologic pathology, the aim of this systematic review is to obtain a more comprehensive picture of normal voiding pattern in healthy infants, who have not yet reached bladder control. The systematic literature search was performed in two databases. This systematic review was conducted by the preferred reporting items for systematic reviews and meta-analyses (PRISMA statement). Twenty-one studies were selected that demonstrate factors associated with voiding pattern. Diuresis, interrupted voiding, post-void residual urine and voiding frequency are parameters decreasing with age. Bladder capacity, the lowest volume triggering micturition, flow rate, voiding volume and the level of awake voiding expand with age.

CONCLUSION

When evaluating the voiding pattern in infants, the normal evaluation of micturition parameters in healthy normal developing infants must be taken into consideration.

WHAT IS KNOWN

• Different voiding parameters in healthy infants who are not yet toilet trained are reported. • Voiding was believed to be induced by a constant bladder volume, while nowadays, it is detected that infants possess a functional spino-pontospinal voiding pathway.

WHAT IS NEW

• Arousal was detected in less than 60 % of all preterm micturitions, while it was present in more than 90 % of the micturitions of healthy "term" infants. • Voided volume, bladder capacity, and flow rate tend to increase with age. In contrast, voiding frequency, post-void residual urine, and interrupted voiding diminishes with an increasing age.

Free voiding patterns in preterm and full-term newborn infants are different between males and females

AIM

The neonatal period is critical in bladder development, encompassing the transition from foetal bladder contractions to voluntary infant urination. The aim of this study was to investigate different voiding parameters between male and female newborn infants.

METHODS

We studied 102 healthy, single birth newborn infants - 54 preterm and 48 full-term - without lower urinary tract diseases, hospitalised in the neonatal intensive care unit from March 2011 to March 2012. Free voiding was observed from 9 a.m. to 9 p.m., and the free voiding parameters and fluid intake were recorded and compared between male and female newborn infants using the Student's t-test and chi-square test.

RESULTS

Male preterm newborns demonstrated larger mean postvoid residual volumes and lower bladder emptying rates than female preterm newborns (p < 0.05), and male full-term newborns had lower bladder emptying rates than female full-term newborns (p < 0.05). The bladder emptying rates of newborns defecating simultaneously with voiding were not statistically different between males and females of the same gestational age (p > 0.05).

CONCLUSION

Male newborns were more likely to have larger postvoid residual volumes than females, and defecating simultaneously with voiding may promote bladder emptying in male newborns.

Urinary flow patterns in infants with distal hypospadias

OBJECTIVE

To investigate preoperative urinary flow patterns in hypospadic infants and compare them to those from normal infant boys.

PATIENTS AND METHODS

Twenty-one boys (median age 14.0, range 12.8-21.6 months) referred for distal hypospadias surgery were compared to 19 healthy boys (median age 12.0, 9.2-19.8 months). In both groups a 14-mm transit-time ultrasound flow probe mounted around the base of the penis continuously registered uroflow.

RESULTS

Median maximum flow rate (Q(max)) was significantly lower in hypospadics (2.4 vs 4.4 ml/s, P < 0.01) while there was no difference in the voided volume per micturition (19.0 vs 21.0 ml, P 0.33). Flow curve pattern analysis revealed plateau-shaped curves in 31% of hypospadics compared to none in normal infant boys. Interestingly, dyscoordinated flow curves (interrupted, staccato, spike-dome) were less common in the hypospadics (36% vs 64%, P < 0.01). Meatal size did not correlate to Q(max) (rho = 0.26, P = 0.26).

CONCLUSIONS

Infants with hypospadias void with a lower Q(max) and a lesser degree of dyscoordination as compared to normal infant boys. It can be speculated that decreased urethral compliance may contribute to the lower Q(max) and may act as a silencer for dyscoordination.