chapter 127 Non-Neuropathic Dysfunction of the Lower Urinary Tract in Children

Our increasing understanding and recognition of non-neuropathic lower urinary tract dysfunction as a cause of various urologic disorders in childhood has had a profound influence on our management strategies over the past decade. What was known as primary or idiopathic, such as primary vesicoureteral reflux (VUR) or primary nocturnal enuresis, is often associated with underlying bladder dysfunctions evident on urodynamics and resolves with successful correction of the bladder physiology (Koff and Murtagh, 1983; Homsy et al, 1985; Watanabe et al, 1994; Yeung et al, 1998, 1999). Conversely, failure of recognition and treatment of the associated problem can result in persistence or even further deterioration.

The understanding of the spectrum of dysfunction of the bladder and even of normal bladder physiology in infants and young children is complex. Not only are the dynamics and functional disturbances of the lower urinary tract different from those in adults, but the evolution in normal bladder-sphincteric function during growth and maturation in children poses continuous changes (Yeung, 1995; Yeung et al, 1995; Sillen et al, 1996; Holmdahl, 1997). More confusingly, one type of bladder dysfunction may often progress with time and evolve imperceptibly into another, without a sharp distinction between the different stages. This is further confounded by a lack of age- and sex-specific normal reference values for various urodynamic parameters, especially for the very young age groups (Yeung et al, 1995).

Recent advances and development in the use of urodynamic techniques specially designed for infants and young children have allowed more accurate assessment of bladder function and provided much better understanding of bladder pathophysiology. This has allowed for better recognition of functional disorders, as well as to provide a scientific basis for their therapy (Hjalmas, 1988; Perez et al, 1992; Bauer, 1997; Nevéus et al, 2007). In view of the important association of bladder dysfunctions with various common urologic disorders, urologists should be acquainted with the spectrum of dysfunction and the techniques to facilitate proper diagnosis and treatment.

Normal Bladder Function in Infants and Children

Anatomy of Bladder

The bladder is a unique organ of the human body in that it not only carries a dual function of both storage and emptying of urine but also has a complex innervation of voluntary and involuntary control of function. Understanding of the functional anatomy of the lower urinary tract stems from extensive postmortem studies carried out over decades (Gosling et al, 1981; Gosling, 1985; DeLancey, 1988; de Groat, 1993; Zvara et al, 1994).

The bladder is an abdominal organ, and when full it can be readily palpable in infants and young children due to a shallow pelvis (Wiegel, 1990). The bladder wall consists of three layers: mucosa, detrusor, and adventitia. The detrusor consists of a meshwork of smooth muscle fibers arranged into a single functioning unit with an ability to elicit nearly maximum active tension over a wide range of length. This allows the bladder to fill with urine from the upper tract at low pressures (compliance) (Mattiasson, 1994). The ability of the bladder to store urine (reservoir function) is determined by the concomitant activity of the detrusor muscle and the bladder outlet (consisting of the bladder neck, proximal urethra, and striated muscle of the pelvic floor) (de Groat, 1993).

The bladder sphincter (external and internal) plays a major role in urinary continence by closure of the bladder neck and proximal urethra. The anatomy of the external urinary sphincter consists of a cylindrical structure, which is accentuated anteriorly and thinned out or actually absent posteriorly, thus giving a characteristic horseshoe or omega shape on cross section. It has an inner layer of smooth muscle and an outer layer of striated muscle, extending from the apex of the prostate to invest the length of the membranous urethra in males. In the females this is less well developed and extends from the bladder neck to the midurethra. The internal sphincter, however, has not been well delineated anatomically. It has generally been accepted that it consists of smooth muscle fibers continuing from the bladder base and trigone, which traverse inferiorly through the bladder neck to extend toward the proximal urethra. Its existence has been better delineated on radiologic and urethral pressure measurement studies. During micturition, the bladder base, bladder neck, and proximal urethra can be shown to contract simultaneously as a unit, producing a funneling effect that opens up the bladder outlet with initiation of voiding.

Little, too, is known about the natural course of development or maturation of the structure and function of the sphincter mechanism. Literature suggests that immature detrusor-sphincter coordination, manifested as detrusor hypercontractility and interrupted voiding, commonly occurs in the first 1 to 2 years of life, causing some degree of functional bladder outflow obstruction (Sillen et al, 1992; Yeung et al, 1998). In a postmortem study of the ontogeny of the external urinary sphincter in human fetuses, infants, and young children, Kokoua and Homsy found significant age-related differences in the histologic structure of the sphincter as compared with that in adults. Striated muscle fibers of the sphincter first appeared at around 20 weeks of gestation and then became arranged in a concentric pattern as a closed ring, fused posteriorly to form a tail-like structure that was directed to the perineal body. Posterior splitting of the striated sphincter, starting first caudally and progressively in a cephalad manner, then occurred during the first year of life, coinciding in parallel with gradual resorption of the “tail,” to eventually giving way to a mature omega-shaped structure (Kokoua et al, 1992). As a complete closed ring of striated sphincteric muscle was present up to 1 year of age in more than 40% of cases, it may well be conjectured that this could be related to the high intravesical pressures and interrupted voiding that are commonly observed during urodynamic studies in infants (Sillen et al, 1992; Yeung et al, 1995, 1998).

Innervation of Bladder

Activation, coordination, and integration of various parts of the bladder-sphincteric complex involve both the central somatic and autonomic nervous systems through three sets of peripheral nerves: sacral parasympathetic (pelvic nerve), thoracolumbar sympathetic (hypogastric nerves and sympathetic chain), and sacral somatic nerves (primarily the pudendal nerve) (Fig. 127–1) (deGroat, 1993; Mattiasson, 1994).

Figure 127–1 Diagram to illustrate the innervation of the bladder-sphincter complex.

(From Yeung CK, Barker GM, Läckgren G. Pathophysiology of bladder dysfunction. In: Gearhart JP, Rink RC, Mouriquand PDE, editors. Pediatric urology. 2nd ed. Philadelphia: Elsevier Saunders; 2010. p. 353–65.)

Parasympathetic nerve fibers run in the pelvic nerve (S₂-S₄) to supply the pelvic and vesical plexuses before entering the bladder. Parasympathetic ganglia are found within these plexuses and in the bladder wall. Sympathetic nerves arise from segments T₁₀-L₂ of the spinal cord and go to the inferior mesenteric ganglion through the sympathetic trunk. From the inferior mesenteric ganglion the nerve fibers pass to the pelvic plexus and bladder through the hypogastric nerves. There is also sympathetic innervation originating from T_10-L₂ supplying the detrusor and urethral sphincter (Bradley et al, 1974). The somatic nervous system (pudendal nerve) supplies the periurethral pelvic floor musculature (Mattiasson, 1994). The sensory and motor nerves carried by all three nerves innervate both the bladder and urethral sphincter. They originate from parasympathetic ganglia located in the second, third, and fourth segments of the sacral spinal cord (Bradley et al, 1974). Within the spinal cord, information from bladder afferents is integrated with that from other viscera and somatic sources and projected to the brainstem centers that coordinate the micturition cycle (Harrison and Abrams, 1994).

Development of Normal Bladder Function and Micturition Control

Urodynamic studies on normal infant bladders have shown that bladder function in young children is different from that in adults. During the first 2 to 3 years of life there is progressive development from an initially indiscriminate infantile voiding pattern to a more socially conscious and voluntary or adult type of micturition. This is achieved through an active learning process whereby the child acquires the ability to voluntarily inhibit or initiate voiding at socially convenient times. This natural evolution of bladder control entails an intact nervous system and depends on at least three main events occurring in parallel: (1) a progressive increase in bladder functional storage capacity; (2) maturation of voluntary control over the urethral striated muscle sphincter; and, perhaps most importantly, (3) development of direct volitional control over the bladder-sphincteric unit so that the child can voluntarily initiate or inhibit the micturition reflex. This process can also be influenced by an awareness of the accepted social norms in families during toilet training (Yeung et al, 2010).

Change in Bladder Functional Parameters

Voiding Frequency

During the third trimester of pregnancy, the fetus is voiding at the rate of approximately 30 times every 24 hours (Goellner et al, 1981). However, immediately after birth, this drops dramatically for the first few days of life, only to increase again after the first week to reach a peak by weeks 2 to 4 to an average of once per hour. Subsequently this rate declines again to about 10 to 15 times per day between 6 and 12 months and to about 8 to 10 times per day by 2 to 3 years (Goellner et al, 1981; Yeung, 1995; Holmdahl et al, 1996). This reduction in voiding frequency observed during the first few years of life appears to be related mainly to an increase in bladder capacity in parallel to body growth, which is proportionately greater than simultaneous increase in urine volume production (Yeates, 1973; Koff, 1997). By the age of 12, the voiding pattern is similar to that in an adult and usually comprises 4 to 6 voids per day (Fig. 127–2).

Figure 127–2 Changes in voided volume and micturition frequency from neonates to early infancy.

Bladder Capacity, Voided Volume, and Emptying Efficiency

The increase in bladder capacity with the growth of the child is a crucial step in the development of bladder function and urinary continence. An adequate reservoir function for urine storage is necessary to meet the increased rate of urine production and decreased voiding frequency in the growing child.

Several studies have shown that functional bladder capacity at a certain age can be accurately estimated and expressed as a function of age with no difference in sex. For young infants it can be expressed as:

For older children, one of the most widely accepted formulas is the Koff formula:

In parallel to the increase in bladder capacity, the mean voided volume of each micturition increases with age. Of note, urodynamic studies have shown that a significant proportion of infants with incomplete maturation of detrusor-sphincter coordination before the age of 1 are still able to achieve satisfactory bladder emptying (>80% efficacy) (Yeung, 1995; Yeung et al, 1995, 1998; Holmdahl et al, 1996; Bachelard et al, 1999; Sillen et al, 2000).

Detrusor Pressure at Voiding

Studies on detrusor pressures at voiding in normal infants are limited due to (1) the technical difficulties involved in performing urodynamic studies in young infants and (2) an ethical consideration in justifying doing so. From the data in a natural filling cystometric study of infants with normal lower urinary tracts (as indicated by a normal micturating cystourethrogram) and who had undergone either dismembered pyeloplasty for pelviureteric junction obstruction or nephrectomy for dysplastic kidney, the authors have documented significantly higher maximum detrusor pressures with micturition (Pdetmax) than in normal adults. It was also noted that male infants voided with significantly higher pressures than females (mean Pdetmax: 118 versus 75 cm H₂0 respectively, P < .03) (Yeung et al, 1995a, 1995b, 1998). Similar findings were reported in healthy, asymptomatic infant siblings of children with VUR (Bachelard et al, 1999).

Studies have also shown that these high detrusor pressures noted during micturition were mainly observed only during the first year of life and decreased progressively with age. Furthermore, an interrupted or “staccato” type of urinary stream was noted in more than half of the patients (Yeung et al, 1995a, 1995b, 1998). This was demonstrated by fluctuations of the detrusor pressure when it reached maximum during voiding and resumption of urinary stream in conjunction with a sharp fall in the detrusor pressure. The high detrusor pressures during voiding are thought to represent variations among individual infants in the maturation process of detrusor and sphincter coordination during the first 1 to 2 years of life (Yeung et al, 1995, 1998; Holmdahl et al, 1996; Bachelard et al, 1999; Sillen et al, 2000).

The authors have further confirmed this finding using video cystometry under fluoroscopy combined with natural fill urodynamics and perineal electromyography (EMG) in infants with a history of urinary tract infections (UTIs). Periods of increase in perineal or sphincteric EMG activities were noted during voiding and associated with a sudden cessation of urinary flow with a simultaneous isometric rise or high peak of detrusor pressure. In contrast, resumption of urinary flow was associated with relaxation of the external urinary sphincter and a paradoxical drop in detrusor pressure. Also, the detrusor pressure associated with the initiation of urinary flow was usually significantly lower than the maximal detrusor pressure during micturition (Pdetmax) and that the Pdetmax was significantly higher than those recorded in normal adults (Fig. 127–3).

Figure 127–3 Interrupted voiding pattern due to detrusor-sphincter discoordination as revealed by urodynamic study with simultaneous perineal electromyographic (EMG) monitoring and videocystourethrography. Arrows with letters in top graph correspond to urethrograms at bottom. A, Urinary flow started. B, Premature sphincteric contraction and urethral closure as evidenced by the urethrogram and increase in sphincteric EMG activities, leading to a sharp spike of detrusor pressure (isometric increase) associated with a paradoxical abrupt cessation of urinary flow. C, Urinary flow resumed in parallel with sphincter relaxation. D, Repeated sphincteric contraction leading to another sharp increase in detrusor pressure and paradoxical interruption of urinary flow. P abd, abdominal pressure; Pdet, detrusor pressure; Pves, intravesical pressure.

Evolution of Normal Micturition Control

Traditionally, it has been assumed that micturition in newborns and young infants occurs automatically with a full bladder by a simple spinal cord reflex, with little or no mediation by the higher neural centers, and that with progressive maturation, voluntary inhibition of the bladder emptying reflex is achieved by adulthood. A delay in the normal maturation of bladder control was attributed to certain conditions such as primary nocturnal enuresis and hence the traditional belief that all enuretics would get better with age (Nash, 1949). However, more recent studies have indicated that this is an oversimplification of what actually occurs. Even in full-term fetuses and newborns, it has been shown that micturition is modulated by higher centers. Ohel and colleagues (1995) showed that intrauterine micturition almost exclusively occurs while the fetus is awake rather than randomly distributed over various behavioral (sleep/arousal) states. Furthermore, it has been observed that micturition in a full-term fetus can be elicited by vibroacoustic stimulation, all of which indicates that the micturition reflex is probably under higher neural control even at near gestational term (Zimmer et al, 1993). Further extensive modulation occurs during the postnatal period.

Studies on normal neonates using ambulatory bladder monitoring techniques in conjunction with polysomnographic recordings have shown that even in newborns, micturition does not occur during sleep (Yeung et al, 1995). During sleep the bladder is normally quiescent and stable with lack of facilitation of detrusor contractions, whereas during wakefulness marked detrusor overactivity is observed. Clear electroencephalographic (EEG) evidence of cortical arousal or actual awakening occurs in response to bladder distension, and sleeping infants are noted to wake up before bladder activity returns and voiding occurs. However, this arousal period may often be transient with the infant crying or moving for a brief period, micturating, and then going back to sleep without being noticed to have awakened. This wakening response to bladder distension probably involves more complicated neural pathways and higher centers than has been appreciated up until now (Fig. 127–4).

Figure 127–4 Incidence of micturition during different sleep states, according to age group.

These results also correlate with recent animal studies showing a sophisticated integration of preexisting central and peripheral neural pathway in micturition control at birth with remodulation occurring in the early postnatal period (Maggi et al, 1986; Thor et al, 1989). Extensive studies using experimental animals by de Groat and colleagues (1993, 1998) have indicated that early postnatal maturation of bladder function probably occurs at different levels: (1) changes in the properties of detrusor muscle; (2) developmental modifications in the peripheral innervation of the bladder; and (3) alterations in central synaptic circuitry and neuroplasticity in the parasympathetic reflex pathways to the bladder (Sugaya and de Groat, 1994; Araki and de Groat, 1997; Sugaya et al, 1997). Recordings of spontaneous activity in bladder smooth muscle in neonatal rats showed much larger amplitude and more synchronous rhythmic contractions compared with those observed in adult rats (Sugaya and de Groat, 1994). This suggests that there is a progressive reduction in intercellular communication between detrusor smooth muscle cells, resulting in less spontaneous activities and hence more efficient urine storage, during early postnatal development. In addition, peripheral and central neural mechanisms also change extensively during this period. In cats (and some other species) micturition during the newborn period is dependent on an exteroreceptive somatovesical reflex triggered when the mother licks the perineum of the kittens (de Groat et al, 1993, 1998; Araki and de Groat, 1997). This somatovesical reflex, processed in the sacral spinal cord, disappears in older animals but may reappear after spinal cord injury. Further neuroanatomic studies have indicated that spinal bladder reflexes are mediated via interneurons located immediately adjacent to, and synapsing with, the sacral preganglionic neurons (Sugaya et al, 1997). This interneuron–preganglionic neuron synaptic transmission is efficient immediately after birth but is abruptly downregulated during the third postnatal week when the mature supraspinal micturition reflexes start to appear (Araki and de Groat, 1997). Transection of the spinal cord prevents this downregulation, indicating that the higher neural centers play an important role in this synaptic remodeling, which contributes to postnatal development of micturition reflexes.

During the second or third year of life there is progressive development toward a socially conscious continence and a more voluntary or adult type of micturition control. The child becomes more aware of the sensation of bladder distension and the urge to urinate, as well as the social norm and embarrassment associated with urinary incontinence. Through an active learning process, the child acquires the ability to voluntarily inhibit and delay voiding until a socially convenient time and then actively initiate urination even when the bladder is not very full and allow it to proceed to completion. This natural evolution of micturition control mechanisms depends on an intact neural pathway and awareness of social norms, as well as multiple factors including the gradual increase in functional bladder capacity, maturation of detrusor-sphincter coordination, and progressive development of voluntary control over the whole bladder-sphincteric-perineal complex. The final steps are usually achieved at around the age of 3 to 4 years, when most children have developed the adult pattern of urinary control and will be dry both day and night. The child has learned to inhibit a micturition reflex, postpone voiding, and voluntarily initiate micturition at socially acceptable and convenient times and places. This development of continence and voluntary micturition is also dependent on behavioral learning and can be influenced by toilet training, which in turns depends on the cognitive perception of the maturing urinary tract. It is understandable therefore that this series of complex events is highly susceptible to the development of various types of dysfunctions.

Neurologic control of normal micturition occurs at different levels of the central nervous system (CNS), from the spinal cord with the “sacral micturition center,” to the brainstem with the “pontine micturition center,” the cerebellum, basal ganglia, limbic system, thalamus and hypothalamus, and cerebral cortex (Blaivas, 1982; McLorie and Husman, 1987; de Groat, 1993; Fernandes et al, 1994). It should be noted that the bladder is unique among other visceral organs in that its function is under the control of both the somatic and the autonomic nervous system. Besides acetylcholine and norepinephrine, various other neurotransmitters including prostaglandin substance P, opioid peptides, vasoactive intestinal peptide, and neuropeptide Y are involved during bladder stimulation (Fernandes et al, 1994). Simple manipulation of adrenergic and cholinergic receptors may only partially abolish the effect of neural stimulation, which explains why pharmacologic blockage of the classic neurotransmitters (acetylcholine and norepinephrine) alone may fail to elicit the expected full clinical response.

Transitory Detrusor-Sphincter Discoordination in Infancy

Studies have shown that in making the transition from an infantile to an adult pattern of micturition control, all children may transiently display some degree of abnormal bladder-sphincteric function (Koff, 1997). For instance, it has been clearly shown that a significant proportion of normal infants exhibit prominent detrusor-sphincter discoordination and interrupted voiding during the first 1 to 2 years of life. This is manifested by a discoordinated and interrupted urine flow, which may even be brought to a complete stop for 1 to 2 minutes before restarting, producing a pattern of repeated small voidings in quick succession (Yeung et al, 1995a, 1995b, 1998). Urodynamic findings show association with high voiding pressures and interruption of flow but no impairment of overall bladder emptying. However, this type of dysfunction resolved with a period of successful toilet training and was only transitory or intermittent and did not persist. One must therefore be cautious in the assessment of young children with apparent voiding dysfunctions and resist the temptation to overinterpret intermittent or transient symptoms as pathologic and hence overinvestigate. However, if voiding dysfunctions are persistent well beyond the period of toilet training, especially if associated with urinary complications like recurrent urosepsis, then the possibility of underlying anatomic and neurologic causes must be considered and duly evaluated.

Key Points: Normal Bladder Function and Development in Infants and Children

• The bladder has dual function (storing and emptying) and dual innervation (central somatic and autonomic nervous systems).

• Evidence indicates that micturition is modulated by higher neural centers even in full-term fetuses and newborns and that micturition almost always occurs during wakefulness.

• In the transition from an infantile to adult bladder, detrusor-sphincteric discoordination may be a normal transient phenomenon that resolves after toilet training.

• The natural evolution of micturition control involves the gradual increase in functional bladder capacity, maturation of detrusor-sphincter coordination, and progressive development of voluntary control over the whole bladder-sphincteric-perineal complex.

Epidemiology and Classification of Non-Neuropathic Bladder-Sphincter Dysfunction in Children

Epidemiology and Prevalence

Non-neuropathic bladder-sphincter dysfunction in children is probably more common than what meets the eye, but many times it only presents to us when UTI, VUR, or urinary incontinence is manifested. It has been reported that 15% of 6-year-old children suffer this condition (Hoebeke, 2002).

Categorization of Non-Neuropathic Bladder-Sphincter Dysfunction in Children

Various conditions have been described under the category of non-neuropathic bladder-sphincter dysfunction, but it must be emphasized that these conditions should not be viewed rigidly as separate and distinct entities but rather as transitional phases of a complex sequence of events. For instance, a girl with dysfunctional voiding may start with having detrusor instability associated with sphincter and pelvic floor overactivity, then gradually evolve to develop fractionated voiding with increasing postmicturition residues, and finally develop bladder decompensation and the “lazy bladder” syndrome (van Gool et al, 1992). It must also be emphasized that use of the term “non-neuropathic” is based purely on the fact that no obvious and identifiable neurologic lesions can be identified. However, conditions like the urofacial syndrome complex (Ochoa syndrome) and the Hinman syndrome behave almost identically to the typical neuropathic bladder-sphincter dysfunctions. It is indeed conceivable that they do have an organic underlying neurologic cause, although the exact neuroanatomic lesion has not yet been identified. Hence the distinction between neuropathic and non-neuropathic bladder dysfunctions may not be as clear as traditionally thought.

In adults, lower urinary tract function has been well understood and standardization of terminology has been established by a committee working under the International Continence Society (ICS) since the early 1970s (Bates et al, 1976a, 1976b, 1979). In contrast, neural control over the bladder-sphincter unit in children is age dependent and is much more variable and complex. Definitions of normal versus abnormal lower urinary tract function have therefore been far less standardized. Various classifications for bladder dysfunctions in children have been described over the past few decades (Bellinger, 1996; Lapides, 1970; Wein, 1998). To avoid confusion, the classification proposed by the International Children’s Continence Society in 2007, with a standardized set of terminology and definitions for different lower urinary tract dysfunctions, was adopted (Nevéus et al, 2007).

During the Filling (Storage) Phase

Detrusor Activity

Normal bladder volume increases during filling without a significant rise in detrusor pressure or involuntary phasic contractions despite provocation.

Overactive bladder is characterized by phasic involuntary detrusor contractions, which may occur either spontaneously or on provocation. The exact pathogenesis for detrusor overactivity has not been resolved. Various underlying causes have been proposed: (1) failure of maturation of CNS control mechanisms; (2) low detrusor levels of inhibitory vasoactive intestinal peptide; (3) abnormal enkephalin-mediated inhibitory neurotransmission; (4) denervation hypersensitivity; and (5) alterations in the properties of the detrusor myocytes (Wein and Barrett, 1992; Harrison and Abrams, 1994; Brading, 1997). Detrusor overactivity was frequently found in children with both diurnal and nocturnal enuresis (Bauer et al, 1980; Nevéus et al, 2007). However, the precise relationship between detrusor overactivity contraction exhibited on a cystometrogram and different types of urinary incontinence is still debated (Nevéus et al, 2007). Children with an unstable bladder typically present with a sudden urge to void that can be only be partially suppressed. Often a girl with an unstable bladder will squat down on the heel of one foot, demonstrating the pathognomonic sign of Vincent curtsy.

Detrusor overactivity may also be qualified when possible according to cause into neurogenic detrusor overactivity (formerly called detrusor hyperreflexia) when there is objective evidence of a relevant neurologic disorder.

Bladder Sensation

This can be normal, increased (hypersensitive), reduced (diminished), or absent (no sensation).

Bladder Capacity

This can be normal, high, or low.

Compliance

This can be normal, high, or low. During normal bladder filling, little or no pressure change occurs but there are no standardized reference ranges for compliance in children.

Urethral Function

Normal positive urethral closure pressure is maintained during filling, even in the presence of increased abdominal pressure (guarding reflex), but it decreases immediately before micturition to allow flow.

Incompetent leakage of urine occurs in the absence of detrusor contraction despite urethral closure.

During the Voiding (Emptying) Phase

Dysfunctional Elimination Syndrome

The association of constipation with urologic pathologies has been described in the literature since the 1950s, but it was only over the past decade that clinicians have paid more attention to this relationship and recognized its existence with the term dysfunctional elimination syndrome (DES). This term is used to reflect the broad spectrum of functional disturbances that may affect the urinary tract, including that of functional bowel disturbances, and can be classified as follows:

• Functional disorder of filling: overactive bladder, overdistension of bladder or insensate bladder, which may be associated with fecal impaction or rectal distension with infrequent call to stool.

• Functional disorder of emptying: over-recruitment of pelvic floor activity during voiding, causing interrupted and/or incomplete emptying also associated with defecation difficulties due to nonrelaxation of pubo-rectalis, pain on defecation, or even anismus (Bower et al, 2005).

Koff and colleagues (1998) showed that the pattern of DES significantly influenced clinical outcome of ureteric reimplantation surgery for VUR in children. Children with constipation had the highest likelihood of developing a breakthrough UTI and thus required surgery. DES also had an adverse effect on the rate of spontaneous reflux resolution, with children requiring an average of 1.6 years longer to outgrow reflux than children without DES. For those requiring surgery, both the results and postoperative complications seemed to be negatively influenced by DES. Postoperative UTIs developed in 78% of children with DES. All children who had persistent reflux, recurrent reflux after 2 years, and contralateral reflux after unilateral reimplantation had DES.

Loening-Baucke (1997) looked at resolution of urinary incontinence and UTIs in children after treatment of their constipation. This study showed that after successful treatment of constipation, 89% of those with daytime incontinence and 63% with nighttime incontinence became dry. None of the children who had UTI had recurrence after treatment of constipation.

It therefore seems from these data that management of the underlying dysfunction should be given priority in the treatment protocol of children with conditions such as VUR, incontinence, and UTI because successful management may significantly improve outcome. Thus more attention should be paid to evaluate for the presence of functional bowel disturbances even in cases of urologic pathologies.

Bladder-Sphincter Dysfunction during Bladder Filling

Overactive Bladder, Urge Syndrome, and Urge Incontinence

Overactive bladder (OAB) is the most common term currently used in clinical medicine to describe a complex of lower urinary tract symptoms (LUTS). Traditionally, the infant bladder has been described as unstable (replaced with OAB now) or uninhibited, but recent studies using prolonged natural filling bladder monitoring techniques have shown that to the contrary, the bladder is normally quiescent and stable even in newborns (Yeung et al, 1995). Clinically, the condition of OAB is best exhibited by urge syndrome with or without urge incontinence. The syndrome, characterized by frequent attacks of sudden and imperative sensations of urge, due to detrusor overactivity during the filling phase, is more prevalent in girls. This burning sensation or urge to void occurs even with small bladder capacities. The unstable contractions are often counteracted by voluntary contraction of the pelvic floor muscles in an attempt to externally compress the urethra (hold maneuvers) exhibited as squatting (Vincent curtsy sign) in many cases (Vincent, 1966; van Gool and de Jonge, 1989). However, despite this move, urge incontinence can still occur with frequent urine leakage onto the underpants. Urge incontinence usually consists of small quantities of urine loss and occurs most often in the afternoon or when the child is preoccupied in play or other activities and is not alert enough to contract the pelvic floor in response to the urge sensation. Children with urge syndrome have small bladder capacities for age and often choose to drink extremely little in order to escape from the social embarrassment of frequent imperative urges to go to the toilet and from urinary incontinence, but otherwise they have complete relaxation of the pelvic floor musculature in most instances. In addition, habitual voluntary pelvic floor contraction to counteract every urge to void may often lead to inappropriate postponement of defecation, constipation, and fecal soiling (Vincent, 1966; O’Regan et al, 1986). This should not be confused with encopresis in children with behavioral problems.

Functional Urinary Incontinence

This can be defined as the involuntary loss of urine due to a failure of control of the bladder-sphincteric unit, which is frequent enough to constitute a social or hygienic problem, and in the absence of underlying anatomic causes (Nevéus et al, 2007). Apart from urge incontinence that is associated with detrusor overactivity and urge syndrome as described earlier, other forms of functional urinary incontinence exist as a result of failure of the bladder storage and/or sphincteric control mechanisms. Stress incontinence represents the involuntary leakage of urine occurring at times when the intravesical pressure exceeds the bladder outlet or urethral resistance, in the absence of measurable detrusor contraction. Unlike in adults and particularly in elderly women, true stress incontinence is extremely uncommon in neurologically normal children and is in general not associated with any demonstrable urodynamic abnormalities. It should therefore be differentiated from urge incontinence and detrusor overactivity. Insufficient bladder outlet or urethral resistance is usually not a main factor. Because the amount of urine leakage in most patients is usually small, the incontinence may at times be only scarcely discernible. It is possible therefore that the actual incidence of this condition may be underestimated.

Giggle Incontinence

Giggle incontinence is usually seen in girls and is characterized by involuntary and typically unpredictable wetting during giggling or laughter. In contrast to stress incontinence, it produces a much larger volume of urine leakage, often amounting to complete bladder emptying. Similar to stress incontinence, however, cystometry may be completely normal or occasionally demonstrate some detrusor overactivity. Treatment is notoriously difficult, but sometimes a course of anticholinergic drugs may help to ameliorate the symptoms.

Bladder-Sphincter Dysfunction during Bladder Emptying

Dysfunctional Voiding

Dysfunctional voiding is characterized by incomplete relaxation or overactivity of the pelvic floor muscles during micturition. It can manifest in different patterns depending on the degree of functional outflow obstruction caused, as well as the status of the detrusor activity. As outlined earlier, the underlying bladder-sphincter dysfunction may evolve progressively and change with time through a transitional phase of a complex sequence of events of bladder functional development.

Staccato and Fractionated Voiding

In staccato voiding the urinary stream is often delayed after the onset of detrusor contraction and is typically interrupted, resulting in a few small squirts of urine passed in quick succession. The interrupted voiding is caused by periodic bursts of pelvic floor muscle activities during micturition, resulting in the characteristic abrupt elevation or spikes of voiding pressures, coinciding with paradoxical cessation of urinary flow. The flow time is usually prolonged and bladder emptying is often incomplete, resulting in increased postmicturition residues and hence a predisposition to UTIs.

Fractionated voiding is characterized by infrequent and incomplete emptying secondary to detrusor inactivity. Micturition occurs in several small, discontinuous fractions due to poor and unsustained detrusor contractions, leaving significant postvoid residual urine volumes. Abdominal straining is usually evident as an effort to improve bladder emptying. However, this is often paradoxically counteracted by a reflex increase in activities of the pelvic floor muscles that is triggered by an increase in intravesical pressure. The bladder capacity is usually large for age and may gradually increase as the condition further progresses. Overflow incontinence may ultimately develop.

Infrequent Voiding and Underactive Bladder Syndrome (“Lazy Bladder”)

These two conditions are described together because they represent a spectrum of disease that more commonly occurs in girls. The old entity “lazy bladder” is now replaced by the term underactive bladder. At one end of the spectrum, the underactive bladder is generally regarded as the end point of long-standing dysfunctional voiding culminating in a fully decompensated system. As a result of the chronic functional bladder outflow obstruction, there is a gradual deterioration in detrusor contractility and emptying efficiency. Postmicturition residual urine and bladder capacity progressively increase, eventually developing into a large, floppy bladder with inefficient emptying. The child uses abdominal straining as the main driving force for bladder emptying, and detrusor contractions are small and unsustained with low pressures, at times being completely undetectable using conventional cystometry. Because urge sensation is either absent or diminished, voiding is infrequent and occasionally the child may not void for 8 to 10 hours or even longer if engaged in activities. The typical presentation of a child with infrequent voiding syndrome is where the mother always complains that the child never voids unless told to do so. The resultant large volume of postmicturition residual urines predispose to recurrent UTIs, which often constitute the primary complaint bringing the child to the pediatric urologist. Overflow incontinence is usually evident, which may be further associated with constipation and/or fecal soiling. Urodynamic studies typically reveal a large-capacity bladder with high compliance on filling. Detrusor contractions are noticeably absent, and voiding is associated with increased abdominal pressures, resulting in a fractionated flow pattern. Electromyography often shows increased activity in the pelvic floor muscle with each abdominal strain.

Hinman Syndrome and Occult Neuropathic Bladder

Hinman, Allen, and Dorfman first coined the terms non-neurogenic neurogenic bladder or subclinical neurogenic bladder, and later Hinman syndrome to describe a presumably acquired form of bladder-sphincter dysfunction in children that was characterized by a combination of bladder decompensation with incontinence, poor emptying, and recurrent urinary infections (Dorfman et al, 1969; Hinman and Baumann, 1973; Allen, 1977; Hinman, 1986). Most children also have significant bowel dysfunction including encopresis, constipation, and fecal impaction. In British literature the condition is often referred to as “occult neuropathic bladder” after the article by D. Innes Williams and colleagues (1975). The condition has all the clinical and urodynamic features typical of neuropathic bladder dysfunction, but no neurologic pathology can be demonstrated. Hinman and Baumann initially hypothesized that the condition could be ascribed to acquired psychologically abnormal behavior with voluntary discoordination between the detrusor muscle and the pelvic floor–external urethral sphincter complex during voiding (Hinman and Baumann, 1973). This notion, however, has not received strong support from later studies, and controversies still exist as to whether a subtle or occult spinal pathology can occur to account for an isolated bladder neuropathy in a child who does not exhibit other somatic neurologic deficits and has normal magnetic resonance imaging of the spinal cord. Urodynamic studies often revealed marked sphincteric overactivity and abrupt contractions of the pelvic floor as the child attempted to control incontinence from uninhibited bladder contractions. In its severe form, the bladder-sphincter dysfunction can cause full-blown bladder decompensation with day-and-night wetting, large postmicturition residual urine volumes, recurrent urinary infections, and significant damage to the upper urinary tracts (Dorfman et al, 1969; Hinman and Baumann, 1973; Williams et al, 1975; Allen, 1977; Hinman, 1986, 1997; Jayanthi et al, 1997). Imaging studies often reveal profound changes in the upper urinary tracts, with about two thirds of the children developing hydroureteronephrosis and over half having VUR. Nearly every patient has a grossly trabeculated, large-capacity bladder with a considerable volume of postmicturition residual urine. Treatment should therefore entail measures to control infection and to restore normal bladder storage and emptying function. Due to the great similarities to neuropathic bladder dysfunction, the management strategy in these children generally follows similar principles for the former condition.

Another piece of indirect evidence that a subtle or occult neurologic lesion may account for some cases of “non-neurogenic neurogenic” bladder-sphincteric dysfunction is the Ochoa (urofacial) syndrome. Children with this syndrome exhibit all the classical features of dysfunctional voiding including urinary incontinence, recurrent UTI, constipation, reflux and upper tract damage, but in addition have a peculiar painful or apparently crying facial expression during smiling (Ochoa and Gorlin, 1987; Ochoa, 1992). The condition has an autosomal recessive inheritance and the gene has been located on chromosome 10. Urodynamic studies characteristically showed a sustained contraction of the external sphincter during voiding. The resulting severe bladder-sphincter dysfunction is often associated with a dismal outcome. Of the 66 children reported by Ochoa, 33% had renal functional impairment, 26% had hypertension, and 24% had end-stage renal failure. Five patients received renal transplantation and 17 were dead (Ochoa, 1992). Because the neural ganglia controlling the facial muscles are situated close to the pontine micturition center, it is tempting to speculate that a small, genetically predetermined, congenital neurologic lesion in this area may be responsible for both the peculiar facial expression and the bladder dysfunction. Further studies in this direction may help to resolve some of the continuing dilemma.

Postvoid Dribbling

Postvoid dribbling refers to involuntary leakage of urine immediately after voiding. Typically this refers to post–toilet-trained girls who dribble soon after standing up following a void and are otherwise normal with no other associated urinary symptoms. In these circumstances it may be a result of vesicovaginal reflux whereby urine is trapped in the vagina during voiding, and once the child stands the urine begins to dribble out. When in doubt, it can be confirmed by performing a micturating cystourethrogram. The condition is harmless and tends to resolve with age, but the child may also be taught to empty her vagina by simply voiding with her thighs apart and leaning forward after voiding before getting up.

Dysfunctional Elimination Syndrome, Constipation, and Bladder Dysfunction

It has long been recognized that children with dysfunctional voiding and recurrent urinary infections often have associated bowel dysfunction including constipation, fecal impaction, and encopresis. However, only recently has the term dysfunctional elimination syndrome been given to recognize the existence of this relationship. Studies have been performed to explain how constipation and chronic rectal dilatation may interfere with the normal function of the lower urinary tract, resulting in bladder dysfunction, reflux, and UTIs (Yazbeck et al, 1987; O’Regan et al, 1997). The close proximity of the rectum to the posterior wall of the bladder makes it possible that any gross distension of the rectum by impacted feces can result in mechanical compression of the bladder and bladder neck leading to urinary obstruction (Shopfner, 1968; O’Regan et al, 1997). In addition, it has been observed that large fecal impaction may induce significant detrusor instability and other bladder dysfunctions, which in turn will result in urge syndrome, UTI, and reflux (Shopfner, 1968; Yazbeck et al, 1987; O’Regan et al, 1997). O’Regan and colleagues have reported a high incidence of enuresis in children with urinary infection and constipation. It has been noted that in constipated enuretic children who had detrusor instability, treatment of concomitant constipation resulted in cessation or improvement of enuresis (O’Regan et al, 1985, 1986). Animal studies have also revealed an increased predisposition to bacteriuria in rats with surgically induced fecal retention (Breda et al, 1975). The evidence available so far therefore strongly suggests that there is an important relationship among constipation, detrusor instability, reflux, UTI, and enuresis. Proper attention to associated bowel dysfunction should therefore form an integral part of the overall management in children with bladder dysfunctions.

Relationship among Bladder-Sphincter Dysfunction, Vesicoureteral Reflux, and Recurrent Urinary Tract Infections

Impairment in the functions of the lower urinary tract often coexists with recurrent UTIs and VUR, without any identified neurologic or other causal pathology (Koff and Murtag, 1983; Griffiths and Scholtmeijer, 1987; Sillen et al, 1992; Chandra et al, 1996; Yeung et al, 1998). Incidence of higher intravesical pressure, detrusor overactivity, detrusor-sphincter dyssynergia, or incomplete voiding have been reported in a significant proportion of children with VUR and conversely, micturating cystourethrograms (MCUs) performed in children with bladder dysfunctions often find concomitant VUR. The most common abnormalities of the lower urinary tract found to coexist with VUR are predominantly detrusor overactivity and uncoordinated detrusor-sphincter function during micturition. These abnormalities may occur secondary to urinary infection or can be acquired during the period when voluntary control of micturition is being established. Although the bladder instability can occur in most children with VUR, it is unlikely to have its role in initiating VUR (Koff and Murtag, 1984). However, reflux from incompetence of the ureterovesical junction (UVJ) may be worsened by detrusor instability (Stephens, 1979). The urethral sphincteric dysfunction or discoordination is characterized urodynamically by obstruction during voiding due to involuntary constriction of the urinary sphincter and is believed to be the normal response of the individual to an uninhibited bladder contraction while attempting not to void (Scholtmeijer and Griffifths, 1990; Koff, 1992; Homsy, 1994; Scholtmeijer and Nijman, 1994). It is considered as the most serious dysfunction because it has been reported that patients with this dysfunction often have bilateral high-grade reflux and injured upper renal tracts (Griffiths and Scholtmeijer, 1987; Orellana et al, 2004). The discoordinated bladder also regularly decompensates, and a significant number of children with moderate or severe VUR were reported to have overdistended bladder with weak contractions and high capacity (Hjalmas et al, 1994; Koff et al, 2002; Garat Barredo et al, 2004).

Previous studies showed that infants with UTI and VUR have a high prevalence of high voiding detrusor pressure (Fig. 127–6) (Sillen et al, 1992, 1996; Yeung et al, 1998). Male refluxers are characterized by considerably higher maximum voiding pressures associated with detrusor overactivity, which may represent a more pronounced form of detrusor-sphincter dyssynergia, as compared with age-matched female refluxers and normal nonrefluxing infants. In contrast, in the majority of female refluxing infants no detrusor hypercontractility was noted and instead they often displayed a urodynamic pattern with normal voiding pressures and relatively large bladder capacity with or without emptying inefficiency and postmicturition residues. The finding of higher voiding detrusor pressure in male infants compared with female infants may be attributed to higher urethral resistance of the longer male urethra and smaller urethral meatus and anatomic difference in the configuration of external sphincter. Studies have also shown that high intravesical pressure significantly contributes to the development and severity of VUR. It was shown that infants with bilateral high-grade VUR had significantly higher voiding detrusor pressures and higher prevalence of detrusor overactivity than those with lower-grade or unilateral VUR (Chandra and Maddix, 2000).

Figure 127–6 Urodynamic patterns in infants with vesicoureteral reflux. A, Normal: a period of low-pressure detrusor contraction (co) preceded a more formal contraction associated with the onset of urinary flow (arrow). B, Immature: urinary flow (arrows) was interrupted during periods of sudden elevation of detrusor pressure. C, Unstable: frequent high-pressure unstable bladder contractions associated with occasional leakage of urine (arrows). D, Inadequate: unsustained low-pressure detrusor contractions associated with the passage of small dribbles of urine (arrows) and a large PVR. E, Dyssynergic: significant interruption of urinary flow (arrows) associated with spikes of increase in detrusor pressure. F, Obstructive: note frequent voiding (v) with high detrusor pressures, greater than 20 cm H₂O.

(From Yeung CK, Godley ML, Dhillon HK, et al. Urodynamic patterns in infants with normal lower urinary tracts or primary vesico-ureteric reflux. Br J Urol 1998;81:461–7.)

It has been further shown that the spontaneous resolution of VUR may be delayed in the presence of abnormal dynamics of the bladder (Godley et al, 2001; Sofia et al, 2004). Bladder dysfunction was shown to have a powerful relationship with the nonresolution of high-grade infant VUR. It is generally accepted that bladder dysfunction delays the spontaneous resolution of reflux in older children (Koff and Murtag, 1984; Taylor et al, 1982). Studies have also shown that there is a strong correlation between recurrent infections and nonresolution, which probably reflects the fact that most infections were seen in infants and children with bladder dysfunction. Therefore recurrent infections can be regarded as a marker of bladder dysfunction, indicating an investigation of bladder function (Sofia et al, 2004).

Moreover, successful treatment of the underlying bladder dysfunction resulted in marked increase in the rate of spontaneous resolution of reflux and significant reduction in recurrent UTIs. Therefore early detection and proper management of underlying lower urinary tract abnormalities are crucial in the treatment of VUR in infants and children. The first step in management in those children presenting postnatally with VUR or UTI should be a detailed evaluation of bladder function to choose an appropriate treatment modality and to prevent renal deterioration.

Why do children who have VUR have such a high incidence of bladder dysfunction? The correlation of this maturational lag in the bladder function and development of the CNS is the other untouched area of investigation. A similar association between gastroesophageal reflux and cerebral palsy is now well studied; understood and effective surgical treatment protocol has evolved over the past 2 decades.

Key Points: Epidemiology and Classification of Non-Neuropathic Bladder-Sphincter Dysfunction in Children

• Bladder dysfunctions during filling include overactive bladders, urge syndrome, functional urinary incontinence, and giggle incontinence.

• Bladder dysfunctions during emptying include dysfunctional voiding, staccato voiding, infrequent voiding, Hinman syndrome, Ochoa syndrome, and postvoid dribbling.

• It is now well recognized that dysfunctional voiding often has associated bowel dysfunction, and together this is known as the dysfunctional elimination syndrome.

• VUR may be secondary to underlying bladder dysfunction, particularly in girls. Treatment should aim at correcting the voiding dysfunction before contemplating surgery.

Evaluation of Non-Neuropathic Bladder-Sphincter Dysfunction

History

The majority of children with non-neuropathic bladder-sphincter dysfunction typically present after toilet training with symptoms of either nighttime or daytime urinary incontinence or both. Occasionally they can be recognized at an earlier age when the child presents for investigation of UTIs or VUR. In any case, it is important to obtain a detailed history from the child and guardian. This should include relevant questions to exclude neurologic and congenital abnormalities. Bowel dysfunction can coexist in the form of encopresis, constipation, and fecal impaction and should be noted during history-taking. The urinary history should focus on symptoms related to both the storage and evacuation of urine.

Voiding Diary

A voiding diary is used to record daily fluid intake and urine output at home under normal conditions. When properly filled in, it can be informative and give us clues to the underlying dysfunction. The number of voidings per day, the distribution of voids during the day, and each voided volume are recorded. It can also record any episodes of urgency and leakage. It is a useful tool to help identify those who may warrant further studies, as well as in follow-up of patients (Fig. 127–7).

Figure 127–7 Examples of voiding diary.

Physical Examination

Physical examination is usually normal in children with non-neuropathic bladder-sphincter dysfunction, but careful examination is required to exclude those who may require further neurologic evaluation. Occasionally, in an otherwise normal child, one may find a palpable bladder on abdominal examination in cases of decompensated bladders. Abnormalities of the lower spine should be sought specifically to exclude the possibility of an occult spinal dysraphism. Lesions such as an asymmetric gluteal fold, hairy patch, dermovascular malformation, or lipomatous abnormality of the sacral region should prompt further imaging evaluation. The external genitalia may be examined to exclude any obvious anatomic problems that can explain the urinary symptoms in question. Rectal examination may reveal fecal impaction or distended rectum in those with chronic constipation. In the absence of any positive findings on examination, further investigations may be warranted.

Laboratory Investigations

Laboratory investigations are generally not routinely required unless the child presents with complications such as UTIs. However, to complement a full workup, urinalysis may be performed to rule out bacteriuria and glucosuria. Serum and urine osmolality may be looked at in cases of nocturnal enuresis to assess renal concentrating ability.

Ultrasonography

Ultrasonography (USG) is often the first-line investigation in children with non-neuropathic bladder-sphincter dysfunction because it is a simple, readily available, and noninvasive tool that is able to provide information both on anatomic and functional problems when performed by experienced pediatric radiologists.

Ultrasonography has been increasingly used in the study of the pelvic floor musculature. In boys the external sphincter, puborectalis, and bulbocavernosus have been observed to contract during a hold maneuver on USG. In girls, lengthening of the urethra and movement of the bladder neck in the direction of the symphysis are seen. However, in patients with non-neuropathic bladder-sphincter dysfunction, approximately one third of the children were unable to elicit movement of the pelvic floor or had paradoxical movement. The clinical significance of this remains unclear, but when introduced to a program of urotherapy, marked improvement of symptoms was reported. Similarly, the USG had been employed in the study of bladder neck mobility. Studies have shown that in a proportion of girls with hyperlaxity of joints, coughing or straining would result in a wide opening of the bladder neck and urethra. In this group of girls, urotherapy would prove difficult and occasionally some would go on to require surgery to the bladder neck (deJong, 2005).

More recently, the ultrasound has been used to measure bladder parameters used in calculating a “bladder volume and wall thickness index” (BVWI). This BVWI can be classified into normal, thick, or thin according to the measured parameters. Studies have shown that these classification corresponded closely to urodynamic findings of underlying bladder dysfunctions and can act as a reliable tool to guide for further invasive investigations (Yeung et al, 2004).

Other Imaging Studies

Radiologic examination of the spine may be necessary to rule out any neurogenic causes of bladder-sphincter dysfunction.

A micturating cystourethrogram may be performed in patients to rule out VUR. Information on the bladder emptying efficiency may be obtained, and the status of the urethra can be assessed to exclude any outflow obstruction.

Urodynamic Studies

Urodynamic studies are employed to describe the physiologic parameters involved in the bladder mechanics during filling and voiding.

Uroflowmetry

All urodynamics should be preceded by or combined with a uroflow study. When performing uroflowmetry, the child must experience normal desire to void for it to be representative and repeated recordings should be performed. Preferably, the voiding should be observed and correct sitting or standing position ascertained. In children, normal flow rates are different from adults and there is usually a poor correlation between maximal flow rate (Qmax) and outflow resistance as the detrusor is able to exert much stronger contractions to counteract any increased resistance. It is therefore important to study the pattern of the flow curve in addition to the flow rates in children. The precise shape of the flow curve is determined by detrusor contractility, the presence of any abdominal straining, and the bladder outlet. The normal pattern is that of a smooth bell shape. A tower-shaped curve produced by an explosive voiding contraction is seen in overactive bladders, and a low plateau-shaped curve is representative of an outlet obstruction. A staccato pattern is seen with sphincteric overactivity during voiding with peaks and troughs throughout voiding, and an interrupted flow is seen in acontractile or underactive bladders. When combined with cystometry and perineal EMG studies, further information on the different spectrum of functional bladder outflow obstructions can be analyzed (Nijman, 1997).

Conventional Fill Urodynamic Studies

This involves more sophisticated instruments and becomes more invasive to the patient, requiring a bladder catheter introduced transurethrally or suprapubically. The use of suprapubic catheterization has been suggested as a better alternative to transurethral catheterization. Although it may be considered more invasive, it is much more physiologic than to try to void with a catheter in the urethra, particularly in children. Not only is it obstructive to flow, but the trauma of placing the catheter just before the investigation may cause significant discomfort. For suprapubic catheterization, a 6-Fr double-lumen catheter is placed suprapubically under sedation and left in situ for 24 hours before commencement of the urodynamic study.

The suprapubic catheter is connected to a computer system and used to measure intravesical pressure. Another catheter is placed in the rectum to measure intra-abdominal pressure surrounding the bladder. By subtracting the latter from the intravesical pressure, one can calculate the detrusor pressure. Sphincteric activity can also be measured with simultaneous perineal EMG recordings. All the measured data are directly fed into a computer for analysis and display of graphical measurements. The urodynamic study looks at both the filling and voiding phases of the bladder. Bladder filling and storage are described according to bladder sensation, detrusor activity, bladder compliance, and bladder capacity. Pressure flow studies are carried out during the voiding phase.

Traditionally, the bladder is filled artificially with water/normal saline to speed up the procedure. The child is asked to indicate his or her desire to void (if old enough to do so) and then void into a specially designed seat with a uroflowmeter attached. The investigator observing the study should also make note of any events occurring during the study (e.g., any large movements of the patient, coughing, or in particular any urinary dribbling).

By combining cystometry with fluoroscopy, video-urodynamics can be performed with fluoroscopic images of the bladder, bladder neck, and urethra captured. Conventional fill urodynamics is performed in the usual manner with the child sitting in a specially designed chair with a uroflowmetry device in the fluoroscopy suite. Fluoroscopic images are taken during filling and voiding. This has the added advantage of being able to observe the shape of the bladder during filling and voiding, observing for signs of VUR, as well as the configuration of the urethra and pelvic floor.

Natural Fill Urodynamic Studies

More recently, studies have shown that the nonphysiologic filling of the bladder during conventional fill urodynamics, even at low filling rates, can lead to misrepresentations of true bladder activity during normal situations. Therefore natural fill urodynamic studies may be performed whereby the child is asked to drink to allow the bladder to fill up on its own rate. Urodynamic studies in children with urge syndrome usually reveal detrusor overactivity associated with a small bladder capacity but may occasionally be normal with incontinence only barely perceptible, particularly if conventional fill cystometry rather than natural filling cystometry is used. It appears that the artificial filling may inhibit the detrusor response and attenuate its maximum contractile potential, rendering detrusor instability much less pronounced and undetectable. Therefore natural fill cystometry is the preferred technique in children, or better still, the combined use of artificial and natural filling urodynamic studies is helpful to accurately delineate the underlying bladder dysfunction (Yeung et al, 1995).

Ambulatory Urodynamic Studies

The unfamiliar hospital and urodynamic laboratory environment, as well as the presence of a urodynamics investigator, can sometimes cause significant distress, particularly to young children. To overcome this, an ambulatory urodynamic study may be performed. This study is performed with ambulatory equipment strapped to the child and relies on infrared telemetry while the investigator sits behind a one-way mirror (Yeung, 1998).

The system consists of an ambulatory urodynamic recorder with a specially designed built-in extension board that converts digital pressure signals to a modulated infrared wave. Two external infrared leads are connected to the output and fixed to the clothing of the patient (Fig. 127–8). The optimal emission from the recorder has a 10-m range and completes the circuit of the infrared on-line link by cable to the computer. Direct line of sight from the transmitter to the receiver is unnecessary because the infrared signals reflect from the walls of the room before reaching the receiver. For active and uncooperative patients, more than one receiver connected in parallel with the power unit and computer can be used at the same time to enhance signal collection. The first receiver to receive valid signals transmits the data to the computer and inhibits the other receivers simultaneously (Fig. 127–9).

Figure 127–8 The ambulatory urodynamic recorder with the external infrared leads mounted in a plastic holder that can be attached to the patient.

(From Yeung CK. Continuous real-time ambulatory urodynamic monitoring in infants and young children using infrared telemetry. Br J Urol 1998:81;76–80.)

Figure 127–9 Schematic diagram to show the setup for continuous real-time ambulatory urodynamics using infrared telemetry.

(From Yeung CK. Continuous real-time ambulatory urodynamic monitoring in infants and young children using infrared telemetry. Br J Urol 1998:81;76–80.)