The Study On Voiding Pattern Of Newborns

Background and ObjectiveVoiding is the process that after the formation in the kidneys, urine is temporarily stored in the bladder by ureter, then excreted by transurethral. Urination is a complex reflex activity controlled by the central nervous system. The expansion of the bladder increases the bladder wall tension, the inflated feeling of the stretch receptors in the bladder wall is produced, which lead to voiding. The greater the traction tension, the stronger the inflated feeling.Neonates and infants void at varying bladder volumes during infancy and this is contrary to the belief that the voiding reflex is a simple spinal reflex elicited by a constant bladder volume. This has been shown in free voiding studies of both pre-term15and full-term infants13in whom bladder volume initiating voiding varies from30%to100%of functional bladder capacity. The reason for this variation is unknown, but the bladder volume initiating micturition is higher after a period of sleep.Increase of bladder capacity is not linear to age or weight during the first years of life. There are two periods when the increase is accelerated. The first is during the first months of life. In free voiding studies of pre-term infants in gestation week32, median bladder capacity was12ml and in similar studies of full-term babies3months of age median capacity was52ml. The capacity is almost unchanged at1and 2years of age (67and68ml, respectively). At3years of age, on the other hand, the median capacity is123ml, meaning a doubling during the third year of life. The first step in increase of bladder capacity is thus around birth and is a fourfold increase, which should be compared with the increase in body weight, which is only three-fold. The second step is at the age of toilet-training when gaining control over voidings. The main stimulant for this second increase in bladder capacity can be suggested to be due to the fact that the child starts to get dry at night, which means higher overnight bladder volumes. Indications for such a connection are the finding that high overnight bladder volumes have been shown to be responsible for development of high bladder capacity in patients with VUR and also in boys with posterior urethral valves. Overnight bladder volume has also been shown to be the determinant for functional bladder capacity in healthy children after potty-training. The relationship between free voiding and cystometric capacity changes during the first years of life. In the neonatal period, cystometric capacity is lower as compared to free voiding capacity, whereas after the infant year the opposite is seen. This can be partly attributed to the fact that older children postpone voiding at cystometry due to fear of voiding with a catheter in the bladder and of the unfamiliar situation of the assessment. This fear cannot be expected in the neonatal child and voiding is thus not postponed for this reason. Another possible explanation for the low cystometric capacity in the neonatal period might be the overactivity suggested by Bachelard et al, shown as an ease to induce detrusor contractions prematurely in catheter investigations. Even if development of bladder capacity during the first years of life is not linear, we suggest that a linear formula is used for calculation of expected bladder capacity for age as a simple rule of thumb. We have chosen to use:Expected bladder capacity (ml)=30+(age in years X30) since this linear increase in capacity is very similar to the nonlinear increase in capacity as described by Jansson et all investigating children longitudinally from birth to age3years in free voiding studies.The infant’s voiding is also characterized by a physiological form of detrusor-sphincter dyscoordination, which has been shown in free voiding studies as interrupted voidings and increase in post-void residual urine. This phenomenon has also been observed in urodynamic studies as an intermittent increase in the electromyographic (EMG) activity of the pelvic floor during voiding, concomitant with fluctuations in voiding detrusor pressure. A longitudinal study of free voidings from birth to age3years revealed that the suggested dyscoordination disappears successively, and is not seen after potty-training age. Another important observation in the study by Jansson et all is the increase in post-void residual urine during the first couple of years of life. The reason for the incomplete emptying in infancy is probably the physiological form of dyscoordination discussed above, with interruption of the urine stream before the bladder is empty. However, with the acquisition of continence the residual volume decreased in this group of healthy children and the ability to empty the bladder was complete at the age of3.Bladder function during infancy has previously been regarded as automatic, with voiding induced by a constant volume in the bladder and without cerebral influence. During the last decade it has been shown convincingly that the brain is already involved in the voiding reflex from birth. This is best illustrated by the finding that in the majority of cases newborn babies wake up or show signs of arousal before voiding. This means that the reflex pathway connection to the cerebral cortex is anatomically already developed in this age group; however, voiding is neither conscious nor voluntary-the infant is only disturbed by the signal. Both maturation and probably training are needed for the voidings to be conscious and voluntary.How to diagnose the bladder dysfunction in newborns is challenging, not only due to the practical difficult in manipulation of the newborns, but also the normal value of voiding pattern in newborns is still unclear. This study was included by3parts:Part Ⅰ:A study on voiding pattern of term and preterm newborns;Part Ⅱ:The change of voiding pattern of newborns with the development of age;Part Ⅲ:The effects of voiding pattern of newborns. Part Ⅰ:A study on voiding pattern of term and preterm newbornsMaterals and MethodsA total of26hospitalized newborn aged3to7days at The First Affiliated Hospital of Zhengzhou University from Mar to May2010were included in this study. Twelve of them were term newborns (38.3±1.1weeks of gestation) with weight (3.1±0.4) kg, another14preterm newborns (32.5±1.6weeks of gestation) with weight (1.7±0.4) kg. The voiding volumes, post-void residual volumes, state of consciousness at voiding, voiding time, voiding frequency per12hours, and meanwhile, the quantity of intake milk, liquid within the same time schedule for12hours from9AM to9PM were recorded. The liquid intake was given according to standards protocol. The diaper weight difference before and after voiding was defined as voiding volumes. The post-void residual volumes was determined by ultrasound.ResultsComparing term with preterm newborns, voiding volumes and consciousness voiding rate was significant higher [(19.8±10.9) ml vs (11.1±7.5) ml and (43.5±26.8)%vs (24.7±19.1)%,(P<0.05), respectively], whereas post-void residual volumes and voiding frequency were significant lower [(1.55±1.01) ml vs (1.82±0.88) ml,(P<0.05) and (7.2±1.9) times vs (9.6±2.5) times per12hours,(P<0.05), respectively]. Part Ⅱ:The change of voiding pattern of newborns with the development of ageMaterals and Methods1. Healthy newborns (11males and10females) during the first28days of their life at the First Affiliated Hospital of Zhengzhou University were included in the study. Of the newborns10were full term (38.5±1.3gestational weeks, range37to40; weighing3.2±0.4kg at birth) and11were preterm (32.7±1.6gestational weeks, range29to36; weighing1.8±0.5kg at birth). None of the newborns had any signs of urinary tract symptoms.2. All newborns were observed for12h by well trained urologists according to International Children’s Continence Society (ICCS) standards. The subjects were observed from9a.m. to9p.m. at day1,4,7,14and28.3. Student’s t-test was used for statistical analysis and p<0.05was considered significantly.Results1. Altogether778voids were recorded. Four newborns did not void during their first4hours observation and their first voiding occurred at the5th or6th hour after birth. Voiding frequency, voiding volume and post residual volume varied between newborns, with a high standard deviation.2. Comparing fullterm to preterm at the same day age after birth, voiding frequency was lower at day14(P<0.01) and day28(P<0.05), and voiding volume was higher at day4(P<0.01), day7(P<0.05), day14(P<0.05) and day28(P<0.01), and post residual volume was higher at day4(P<0.05) and day28(P<0.05).3. In preterm group, voiding frequency increased significantly at day4compared to day1, at day7compared to day4(p<0.01), and decreased at day28compared to day14(p<0.01). voiding volume increased significantly only once in the preterm, from day14to day28(p<0.05). In fullterm group, voiding frequency increased significantly at day7compared to day4(p<0.01). voiding volume increased significantly twice in fullterm, from day1to day4and from day14to day28(p<0.01). Post-void residual volumes was increased from day1to day4, but was decreased at day4to day7, and increased again at day14to day28significantly (p<0.05).4. Percentage of intermittent voiding occurred in70%preterms, but only40%in full terms. Bladder empty percentage was higher in full terms at day28(56%vs.40%), but awake voiding percentage was no more than30%in the preterms, being60%in full terms at day28after birth.Part Ⅲ:The effects of voiding pattern of newborns The effects of age and weight on voiding patternMaterals and Methods1. One hundred and two healthy, single birth newborns (54preterm and48full term) without low urinary tract pathological diseases, hospitalized in NICU from Mar.2010to Mar.2011were recruited in this study. Twelve hours (9:00am～9:00pm) observation of free voiding was performed. The voiding interval time, voiding volumes, post-void residual volumes, bladder capacity, voiding times, state of consciousness at voiding and the number of defecate simultaneously at voiding as well as fluid intake were recorded and analyzed retrospectively.2. A total of33newborns were included in this study. The newborns aged7～28days old, without low urinary tract pathological diseases, single birth,were divided into two groups,15cases of low weight newborns (birth weight1.88±0.32kg, gestational age33.6±1.5weeks, aged15±8.3days old),18cases of normal weight newborns (birth weight3.24±0.43kg, gestational age34.2±1.5weeks, aged11.8±2.2days old). Each group undertook12hours (9:00am～21:00pm) free voiding observation, recording voiding time, the voiding volume, post-voiding residual urine(PVR) by ultrasound, awake or sleep when voiding.Results1. The total number of voiding and defecate simultaneously at voiding of the preterm neonates was318and40respectively. VIT and BC between male and female preterm newborns had no statistical significance, whereas, the mean PRV of the male was larger ((1.9±0.9) mL vs.(0.9±0.8) mL) and the bladder emptying rate was lower (8.3%vs.44.1%) than those of the female newborns (P<0.05). If reject the effect of BER, the difference of PRV between the two genders ((2.1±0.5) mL vs.(1.8±0.6) mL) do not have statistical significance any more. The total number of voiding and DSV of the term neonates was350and43respectively. The BER of the female term neonates was higher than that of the male term neonates (43.0%vs.15.3%; P<0.05). BC and the mean PRV between the two genders of term newborns have no statistical significance. Comparing with the female neonates of the same gestational age, the difference of BER of the male neonates do not have statistical significance any more when defecated simultaneously at voiding (preterm41.7%vs.25.0%; term36.4%vs.28.1%,P>0.05).2. The frequency, voiding volume, PVR, voidng empty percentage and awake percentage in two groups are7.1±2.2times vs7.7±2.4times,21.1±11ml vs13.1±6.2ml,1.52±1.33ml vs1.86±1.08ml,34.6%vs14.8%,40.9%vs18.3%, respectively. There were significantly difference of voiding volume in two groups (T=2.5010, P<0.05)The effects of disorders on voiding patternMaterals and Methods1. A total of40hospitalized newborns aged4to21days were included in this study. Twenty-one of them were preterm newborns with HIE, another19preterm newborns without HIE. The voided volume, post void residual volume, consciousness at voiding, voiding time, voiding frequency as well as the quantity of intake milk and liquid within4hours from8AM to12AM were recorded. The liquid intake was same in both groups according to standard protocol. The diaper weight difference before and after voiding was defined as voided volume. The post void residual volume was determined by ultrasound. The state of consciousness at voiding was monitored by electroencephalography.2. Fifty-two newborns with the gestational ages ranged from37to42weeks were observed by4-hour observation, of whom,18were newborns with mild to moderate hyperbilirubinemia, blood total bilirubin level (Tbil) ranging from221μmol/l to342μmol/l, and15with severe hyperbilirubinemia, Tbi1>342μmol/l. Nineteen ones with normal bilirubin level, Tbi1<221μmol/l. The voiding frequency, voiding volume, post-voided residual volume, and percentage of awake voiding of every infant were recorded from8AM to12AM. A total of328voidings were observed in this study.3. A total of67newborns,34cases with mild asphyxiation and33cases normal, without low urinary tract pathological diseases, single birth, hospitalized in NICU at the First Teaching Hospital of Zhengzhou University from March to May2010were included in this study. They were divided into4groups as16cases of asphyxiation with normal weight (ANW),18cases of asphyxiation with low weight (ALW),18cases of no asphyxiation with normal weight (NANW) and15cases of no asphyxiation with low weight (NANW). Voiding time, voiding volume, post-voided residual volume by ultrasound, empty voiding percentage and awake or sleep when voiding were recorded in12h observation (9Am-9Pm).Results1. Voided volume and rate of consciousness at voiding was significant lower in newborns with HIE compared with the control group [(10.8±6.5) ml,(16.3±17.1)%vs.(14.1±7.1) ml,(57.1±21.0)%,(P<0.05), respectively], whereas post void residual volume and voiding frequency were significant higher [(1.6±1.0) ml,(4.0±1.1) times vs.(1.2±0.9) ml,(3.2±0.9) times per4hours,(P<0.05), respectively].2. The voiding frequency and post-void residual volume [(3.28±1.18) times, (1.82±0.53) ml] of severe hyperbilirubinemia is higher than NB[(2.71±0.84) times,(1.26±0.83) ml] and mild to moderate hyperbilirubinemia [(2.75±0.81) times,(1.41±0.72) ml],(P<0.05). The voided volume of severe hyperbilirubinemia (23.05±8.34) ml is lower than normal bilirubin (27.75±7.29)ml and mild to moderate hyperbilirubinemia (26.88±5.59)ml,(P<0.05).There is no difference of percentage of awake voiding among3groups.3. All newborns voided totally533times. The voiding frequency in ANW is higher than NANW (P<0.05), but the voiding volume and post-voided residual volume are no significant difference (P>0.05). The voiding frequency, volume and post-voided residual volume in ALW and NALW are no significant difference (P>0.05).The voiding frequency and volume in ANW is higher than ALW (P<0.05), but post-voided residual volume is no significant difference (P>0.05). The voiding volume in NANW is higher than NALW (P<0.05), but the voiding frequency and post-voided residual volume are no significant difference (P>0.05). Voiding empty and awake percentage are higher in ANW and NANW, but no difference; voiding empty and awake percentage in LNW and NALW are no difference.The effects of humidity/temporature on voiding patternMaterals and MethodsSix dry diapers were placed into seven levels of humidity, between55%and85%inclusive, in an incubator set at37℃. Hourly weight increments were recorded. The study was repeated with5ml of normal saline added to the center part of diaper to mimic prior urine output.ResultsDry diapers increased in weight for each humidity level after1h (p<0.001). This was significantly greater at higher humidity (75%). The maximum increase was an average of (2.34±0.12)g at85%humidity after6hrs. When5mL of0.9%saline had been added, the diaper weight changes depended on environmental relative humidity. At≥80%humidity, the diapers continued to gain weight; at70%or75%humidity, they did not change weight.Conclusions1. Both term and preterm newborns have shown a high post void residual volume indicating the incomplete voiding pattern exists in newborns. The difference of voiding patterns between term and preterm newborns evidenced the different stages of bladder function development, more maturation of bladder function in term than those of preterm newborns.2. Voiding pattern in the preterm has shown many differences from those of fullterms in the very beginning of life. Frequent interrupted and incomplete voiding pattern in the preterm newborns indicated a disrupted coordination of the detrusor-sphincter and a delayed maturation of the neural maturation center.3. Compared to female, male newborns are more likely to have post-void residual volumes.4. Voiding volume, emptying and awake percentage are lower in low birth weight newborns comparing to normal weight newborns. The bladder function and the degree of the brain involved in urination are lower in low birth weight newborns.5. The differences in voiding pattern supported the concept that the higher centers of the central nervous system were involved in the control of voiding, HIE had a significant effect on voiding pattern of preterm newborn.6. There is a significant change of voiding pattern in newborn with severe hyperbilirubinemia indicating the severe hyperbilirubinemia has an effect on the nerve micturition center.7. Mild asphyxiation induced more voiding frequencies for more fluid intake in NANW,the lower weight,the lighter;but it had little influence on voiding volume, PVR, empty voiding percentage and awake voiding percentage.8. The humidity/temporature may have effect on the voiding pattern of newborns. This study demonstrates the need for caution when interpreting this measure, and we discuss some possible clinical approaches to ameliorate this difficulty.