**5. Our observation on Doppler waveform of the ureteric jet**

In our institution, we have studied the pattern and physical properties of the ureteric jet in the normal population. The characteristics of ureteric jet are studied under specific physio‐ logical conditions such as pregnancy, pharmacological effect under general anaesthesia and after structural ureteric modification following renal transplantation. The characteristics of jet are also assessed under different pathological conditions such as: children with VUR and UTI, children with nocturnal enuresis and children with neurogenic bladder.

### **5.1. Physical properties of ureteric jet in normal population**

This part of study is based on a normal population of 1,341 subjects with age ranging from 15 days to 82 years old (Leung et al., 2002a).

### *5.1.1. General properties of jet*

**Figure 9.** Multispike pattern (arrows) of the ureteric jet.

120 Recent Advances in the Field of Urinary Tract Infections

the jet.

**Figure 10.** Changing of angle in the ureteric jet: from vertical at the beginning (a) to slightly inclined at the end (b) of

In our institution, we have studied the pattern and physical properties of the ureteric jet in the normal population. The characteristics of ureteric jet are studied under specific physio‐ logical conditions such as pregnancy, pharmacological effect under general anaesthesia and after structural ureteric modification following renal transplantation. The characteristics of jet are also assessed under different pathological conditions such as: children with VUR and

This part of study is based on a normal population of 1,341 subjects with age ranging from

**5. Our observation on Doppler waveform of the ureteric jet**

UTI, children with nocturnal enuresis and children with neurogenic bladder.

**5.1. Physical properties of ureteric jet in normal population**

15 days to 82 years old (Leung et al., 2002a).

In the normal population, four common patterns can be identified: monophasic, biphasic, triphasic and polyphasic (Table 1). The square and continuous patterns occur under force di‐ eresis, which contributes only 1.5% of cases in the normal population. With increasing age from infancy, the proportion of monophasic waveform decreases while the more complex patterns prevail.


**Table 1.** Incidence of the four patterns in different age groups of the normal population.

In the normal population, there is strikingly larger number of monophasic patterns in chil‐ dren (22%) than in adult (1.9%) (Table 2).


**Table 2.** Incidence of monophasic jet in children and adult.

For the mean velocity, it is 34.03 cm/s for the monophasic jet and 61.82 cm/s for the complex pattern in children. While in adult, the mean velocity of the monophasic jet is 57.65 cm/s and 78.89 cm/s for the complex pattern.

For the mean jet duration, it is 1.17 s for children with monophasic pattern and 5.26 s for the complex pattern. In adults, the mean jet duration is 1.91 s for monophasic jet and 6.9 s for complex pattern.

For the mean initial slope, it is 211.82 cm/s2 for monophasic jet and 293.32 cm/s2 for the com‐ plex pattern in children. While in adults, the mean initial slope of the monophasic jet is 195.54 cm/s2 and 271.21 cm/s2 for the complex pattern.

women (1.9%). However, the incidence drops to again and becomes comparable to the nonpregnant women (1.6% vs. 1.9%) after 3-month postpartum (Leung & Metreweli, 2002a).

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123

In the above study, we conclude that pregnancy does modify the ureteric jet pattern. One possible explanation is that the VUJ reverts to the simpler mechanism to produce the mono‐ phasic pattern by the myogenic component when the mature neural component fails or is inactivated to produce complex jet pattern. Therefore the complex ureteric jet is subject to an on-off switch. If it is switched off then the ureter reverts back to a monophasic jet. The above observation leads to the hypothesis about a myogenic origin related to the monophasic

Another study has been set to investigate for any effect of the anaesthesia drug on functional sphincteric action of the VUJ. If so, this will be reflected by changes in the Doppler wave‐ form of the ureteric jet after application of anaesthesia. We have studied a total of 16 chil‐ dren while they underwent surgery under general anaesthesia. Before anaesthesia, 14 of them showed a complex pattern and two showed a monophasic pattern. However, after an‐

This observation confirms that the change in the ureteric jet from a complex to a monophasic waveform is brought by the effect of the drugs acting on the functional sphincteric action of the VUJ. This observation again supports the hypothesis of a functional active sphincter and supports the dual components of the VUJ sphincter. In this scenario, the neural component of the VUJ is inactivated by the anaesthesia, leaving only the myogenic component to func‐

Ureteric peristalsis in the transplanted ureter should be the same as that in the normal sub‐ ject. The traditional concept about VUJ competence is mechanical in origin, so that during re-implantation of the donor ureter into the native bladder, the structure or function of the native VUJ is destroyed and the equivalent of a mechanical flap valve is "re-created" (Pa‐ quin, 1959; Politano et al., 1958). However, no one has studied whether the surgical VUJ be‐ haves in a similar manner as a native VUJ. In our institution, we have assessed for any change in the ureteric jet after ureteric transplantation for renal transplantation, so as to

The ureteric jets from 55 renal transplant patients have been compared with 817 healthy sub‐ jects. The Doppler waveform of transplant ureters is distinctly different from those of healthy adult ureters. Only two patterns can be identified in transplanted ureters: more commonly a short monophasic waveform (66.1% vs. 2.6% in the health ureters), and less commonly a longer multiphase pattern but does not resemble the patterns of the healthy

In conclusion, the ureteric jet patterns associated with transplant ureters are very differ‐ ent from those ureters with an intact VUJ, but resemble the pattern expected from simple

waveform and a neurogenic origin related to the complex waveform.

aesthesia, all of them showed a monophasic waveform (Leung et al., 2003).

tion, hence producing the monophasic jet pattern.

demonstrate the effect of structural change at VUJ.

*5.2.3. Structural modification effect*

ureter (Leung & Metreweli, 2002b).

*5.2.2. Pharmacological effect*

The direction of flow of the jet can be directed anteriorly, anteromedially (with or without crossing of the jets), or in amore vertical direction or perpendicular to the bladder base.

### *5.1.2. Different effects on ureteric jet*

The laterality differences, effect of age, gender and bladder filling status on the pattern of ureteric jet have been investigated.

In general, there is no significant difference in waveform pattern, initial slope, velocity and duration of ureteric jet between the right and left sides in both children and adults.

For the effect of age, children have a higher incidence of monophasic jet. This immature pat‐ tern occurs constantly in the first 6 months of life and becomes mature at the age of 4.54 years. There is no significant gender difference for the mean age of VUJ maturity in children (Leung et al., 2007a). Adults have higher jet velocity and longer duration of jet than children for both the monophasic and complex patterns. However, the initial slope of the jet shows no significant difference between children and adults.

For the gender effect, in children, there is no significant difference in velocity, duration, ini‐ tial slope or number of peaks within a single jet between boys and girls. In adults, male sub‐ jects have a higher incidence of polyphasic waveform than females involving both right and left side. Male subjects also have a higher velocity and longer duration of the jet than female on both sides.

Finally, as for the effect of bladder filling status on the jet, 42.2% of subjects show no change in the number of peaks within a single jet waveform, 28.9% show a decrease and 26.5% show an increase, and 2.4% has square and continuous jet when the bladder becomes very full (Leung et al., 2002a). In all subjects, the initial slope, velocity and duration of the jet are not affected by different stages of bladder filling. In conclusion, the stage of bladder filling should have little effect to determine whether a subject has an immature or complex pattern.

### **5.2. Characteristic of the jet in different physiological conditions**

### *5.2.1. Physiological effect*

Hormonal changes of pregnancy are thought to cause smooth muscle relaxation (Hundley et al., 1942; Kumar, 1962). In our institution, we sought to investigate whether this hormonal effect on the smooth muscle exists within the maternal urinary tract, if the hypothesis of a functional active sphincteric mechanism at the VUJ is sound. A longitudinal study has been used to illustrate this physiological change. A total of 107 pregnant women have performed Doppler study of the ureteric jet at 20, 32 weeks' gestation, and 3 months postpartum. The incidence of monophasic jet (immature jet) is significantly higher at 20 weeks' gestation (18.7%), and even higher at 32 weeks' gestation (41.1%) when compared with non-pregnant women (1.9%). However, the incidence drops to again and becomes comparable to the nonpregnant women (1.6% vs. 1.9%) after 3-month postpartum (Leung & Metreweli, 2002a).

In the above study, we conclude that pregnancy does modify the ureteric jet pattern. One possible explanation is that the VUJ reverts to the simpler mechanism to produce the mono‐ phasic pattern by the myogenic component when the mature neural component fails or is inactivated to produce complex jet pattern. Therefore the complex ureteric jet is subject to an on-off switch. If it is switched off then the ureter reverts back to a monophasic jet. The above observation leads to the hypothesis about a myogenic origin related to the monophasic waveform and a neurogenic origin related to the complex waveform.

### *5.2.2. Pharmacological effect*

For the mean initial slope, it is 211.82 cm/s2 for monophasic jet and 293.32 cm/s2 for the com‐ plex pattern in children. While in adults, the mean initial slope of the monophasic jet is

The direction of flow of the jet can be directed anteriorly, anteromedially (with or without crossing of the jets), or in amore vertical direction or perpendicular to the bladder base.

The laterality differences, effect of age, gender and bladder filling status on the pattern of

In general, there is no significant difference in waveform pattern, initial slope, velocity and

For the effect of age, children have a higher incidence of monophasic jet. This immature pat‐ tern occurs constantly in the first 6 months of life and becomes mature at the age of 4.54 years. There is no significant gender difference for the mean age of VUJ maturity in children (Leung et al., 2007a). Adults have higher jet velocity and longer duration of jet than children for both the monophasic and complex patterns. However, the initial slope of the jet shows

For the gender effect, in children, there is no significant difference in velocity, duration, ini‐ tial slope or number of peaks within a single jet between boys and girls. In adults, male sub‐ jects have a higher incidence of polyphasic waveform than females involving both right and left side. Male subjects also have a higher velocity and longer duration of the jet than female

Finally, as for the effect of bladder filling status on the jet, 42.2% of subjects show no change in the number of peaks within a single jet waveform, 28.9% show a decrease and 26.5% show an increase, and 2.4% has square and continuous jet when the bladder becomes very full (Leung et al., 2002a). In all subjects, the initial slope, velocity and duration of the jet are not affected by different stages of bladder filling. In conclusion, the stage of bladder filling should have little effect to determine whether a subject has an immature or complex pattern.

Hormonal changes of pregnancy are thought to cause smooth muscle relaxation (Hundley et al., 1942; Kumar, 1962). In our institution, we sought to investigate whether this hormonal effect on the smooth muscle exists within the maternal urinary tract, if the hypothesis of a functional active sphincteric mechanism at the VUJ is sound. A longitudinal study has been used to illustrate this physiological change. A total of 107 pregnant women have performed Doppler study of the ureteric jet at 20, 32 weeks' gestation, and 3 months postpartum. The incidence of monophasic jet (immature jet) is significantly higher at 20 weeks' gestation (18.7%), and even higher at 32 weeks' gestation (41.1%) when compared with non-pregnant

duration of ureteric jet between the right and left sides in both children and adults.

for the complex pattern.

195.54 cm/s2

on both sides.

*5.2.1. Physiological effect*

and 271.21 cm/s2

122 Recent Advances in the Field of Urinary Tract Infections

*5.1.2. Different effects on ureteric jet*

ureteric jet have been investigated.

no significant difference between children and adults.

**5.2. Characteristic of the jet in different physiological conditions**

Another study has been set to investigate for any effect of the anaesthesia drug on functional sphincteric action of the VUJ. If so, this will be reflected by changes in the Doppler wave‐ form of the ureteric jet after application of anaesthesia. We have studied a total of 16 chil‐ dren while they underwent surgery under general anaesthesia. Before anaesthesia, 14 of them showed a complex pattern and two showed a monophasic pattern. However, after an‐ aesthesia, all of them showed a monophasic waveform (Leung et al., 2003).

This observation confirms that the change in the ureteric jet from a complex to a monophasic waveform is brought by the effect of the drugs acting on the functional sphincteric action of the VUJ. This observation again supports the hypothesis of a functional active sphincter and supports the dual components of the VUJ sphincter. In this scenario, the neural component of the VUJ is inactivated by the anaesthesia, leaving only the myogenic component to func‐ tion, hence producing the monophasic jet pattern.

### *5.2.3. Structural modification effect*

Ureteric peristalsis in the transplanted ureter should be the same as that in the normal sub‐ ject. The traditional concept about VUJ competence is mechanical in origin, so that during re-implantation of the donor ureter into the native bladder, the structure or function of the native VUJ is destroyed and the equivalent of a mechanical flap valve is "re-created" (Pa‐ quin, 1959; Politano et al., 1958). However, no one has studied whether the surgical VUJ be‐ haves in a similar manner as a native VUJ. In our institution, we have assessed for any change in the ureteric jet after ureteric transplantation for renal transplantation, so as to demonstrate the effect of structural change at VUJ.

The ureteric jets from 55 renal transplant patients have been compared with 817 healthy sub‐ jects. The Doppler waveform of transplant ureters is distinctly different from those of healthy adult ureters. Only two patterns can be identified in transplanted ureters: more commonly a short monophasic waveform (66.1% vs. 2.6% in the health ureters), and less commonly a longer multiphase pattern but does not resemble the patterns of the healthy ureter (Leung & Metreweli, 2002b).

In conclusion, the ureteric jet patterns associated with transplant ureters are very differ‐ ent from those ureters with an intact VUJ, but resemble the pattern expected from simple efflux of urine secondary to ureteric peristalsis. On the other hand, this jet pattern of transplanted ureter also has little resemblance to the normal monophasic pattern because the latter requires some functional sphincteric type activity, referred as myogenic compo‐ nent in the dual component theory that we have described earlier. Furthermore the more complicated transplant jet bears no resemblance to the normal complex category. This can be explained by the loss of the proposed neural component. Inherent ureteric muscular peristalsis has been shown to be preserved in transplanted ureter, which is likely to be the vis-a-tergo producing the jet. In conclusion, there is a loss of functional active sphinc‐ ter mechanism of the VUJ in the transplanted ureter as a result of the operative proce‐ dure. This observation again supports the hypothesis that VUJ is a functional active sphincter.

*5.3.2. Children with nocturnal enuresis*

opment of primary enuresis.

*5.3.3. Children with neurogenic bladder*

of monophasic jet in patients with neurogenic bladder.

is present in children with nocturnal enuresis.

In our institution, a study has been set to investigate whether immature ureteric jet pattern

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125

We have studied 511 children presenting with primary nocturnal enuresis. There was a higher incidence (19%) of immature waveform observed in children with nocturnal enuresis as compared with normal children within the same age range (7.4%) (Leung et al 2006). This study suggests that there is a lower level of maturity in the VUJ in enuretic children. Anoth‐ er interesting finding is that the immature jet is more commonly seen in enuretic children with markedly thickened bladder wall and multiple urodynamic abnormalities. This obser‐ vation suggests that monophasic waveform is associated with abnormalities of the detrusor muscle as well as an increase in detrusor pressure. All these parameters might be indicators of immaturity of the VUJ-detrusor complex, which predispose affected children to the devel‐

As discussed previously, VUJ has a nervous component with hitherto unknown functions. Patients with inactivated neural component within the VUJ due to drug effects or surgery have a higher incidence of monophasic jet pattern. It is well known that patients with neuro‐ genic bladder have high incidence of secondary VUR while VUR is associated with mono‐ phasic ureteric jet. In our institution, we sought to investigate whether there is a prevalence

In a study of 27 children with neurogenic bladder, the frequency of monphasic jet is much higher in neurogenic bladder group (40.7%) when compared with normal population within the same age range (7%). Despite the small number of subjects, the observation again sup‐ ports the theory of functional active sphincteric mechanism of VUJ. In this scenario, mono‐

In summary, combining the anatomical and histochemical data, as well as the observations from Doppler ultrasound studies of ureteric jets, a functional sphincter with dual mode ac‐ tion at the VUJ is proposed. This sphincter is not a passive valve. On top of the monophasic ureteric peristaltic wave within the ureters as demonstrated by M-mode, a more complex pattern is observed in the ureteric jet emanating from VUJ demonstrated by Doppler wave‐ form. The reason for the change in waveform pattern of the ultimate ureteric jet is due to

In brief, six patterns of ureteric jet and three uncommon variations are identified. They are classified as the monophasic, mature complex (bi, tri and polyphasic) and diuretic pattern. In the normal population, a higher incidence of the monophasic pattern is seen in immature neonate and in children under four years old. The monophasic pattern occurs constantly in

phasic pattern prevails when the neural component within the VUJ is deactivated.

**6. Dual mode of action of the functional sphincter at the VUJ**

modification of jet by an active sphincter mechanism at the VUJ.

### **5.3. Characteristic of the ureteric jet in different pathological condition**

Characteristic of Doppler waveform of the ureteric jet in different pathological groups have also been investigated, as illustrated below.

### *5.3.1. Children with VUR and UTI*

We have previously shown that young children have a much simpler monophasic immature pattern. A study has been carried out to study whether there is any correlation between the presence of such immature pattern with UTI and VUR.

We have studied 98 children with UTI and VUR and compared with 241 healthy children. The incidence of monophasic jet (immature pattern) is 29% in healthy children overall, but varies greatly according to age. The immature pattern is universal in the first 6 months of life, but drops significantly to below 15% in late childhood. This immature pattern is more commonly seen in children with UTI (37.5%) and VUR (90.5%) than in healthy controls of the same age (Leung et al., 2002b).

An immature pattern of ureteric jet is seen predominantly in three groups of subjects: (1) ne‐ onatal and infant group, (2) children with UTI and (3) children with VUR,. However in older children between 2-14 years of age, there is a higher tendency of persist immature pattern in both UTI and VUR groups. The persistence of immature jet pattern suggests that develop‐ mental immaturity might be a feature of children with UTI and VUR.

As immature ureteric jet pattern is associated with immaturity of ureteric function during infancy, a similar pattern observed in UTI / VUR groups lead to a hypothesis that this devel‐ opmental immaturity of VUJ might be a contributing/ predisposing factor to urinary infec‐ tion and the reflux problem in children.

Previous studies have been that majority of children with VUR do not have an anatomically defined congenital anomaly at the VUJ, (Dixon et al., 1998a), however, a functionally imma‐ ture or transitory phase of developmental immaturity of VUJ might be present and predis‐ pose the affected children to VUR and UTI.

### *5.3.2. Children with nocturnal enuresis*

efflux of urine secondary to ureteric peristalsis. On the other hand, this jet pattern of transplanted ureter also has little resemblance to the normal monophasic pattern because the latter requires some functional sphincteric type activity, referred as myogenic compo‐ nent in the dual component theory that we have described earlier. Furthermore the more complicated transplant jet bears no resemblance to the normal complex category. This can be explained by the loss of the proposed neural component. Inherent ureteric muscular peristalsis has been shown to be preserved in transplanted ureter, which is likely to be the vis-a-tergo producing the jet. In conclusion, there is a loss of functional active sphinc‐ ter mechanism of the VUJ in the transplanted ureter as a result of the operative proce‐ dure. This observation again supports the hypothesis that VUJ is a functional active

Characteristic of Doppler waveform of the ureteric jet in different pathological groups have

We have previously shown that young children have a much simpler monophasic immature pattern. A study has been carried out to study whether there is any correlation between the

We have studied 98 children with UTI and VUR and compared with 241 healthy children. The incidence of monophasic jet (immature pattern) is 29% in healthy children overall, but varies greatly according to age. The immature pattern is universal in the first 6 months of life, but drops significantly to below 15% in late childhood. This immature pattern is more commonly seen in children with UTI (37.5%) and VUR (90.5%) than in healthy controls of

An immature pattern of ureteric jet is seen predominantly in three groups of subjects: (1) ne‐ onatal and infant group, (2) children with UTI and (3) children with VUR,. However in older children between 2-14 years of age, there is a higher tendency of persist immature pattern in both UTI and VUR groups. The persistence of immature jet pattern suggests that develop‐

As immature ureteric jet pattern is associated with immaturity of ureteric function during infancy, a similar pattern observed in UTI / VUR groups lead to a hypothesis that this devel‐ opmental immaturity of VUJ might be a contributing/ predisposing factor to urinary infec‐

Previous studies have been that majority of children with VUR do not have an anatomically defined congenital anomaly at the VUJ, (Dixon et al., 1998a), however, a functionally imma‐ ture or transitory phase of developmental immaturity of VUJ might be present and predis‐

mental immaturity might be a feature of children with UTI and VUR.

**5.3. Characteristic of the ureteric jet in different pathological condition**

also been investigated, as illustrated below.

124 Recent Advances in the Field of Urinary Tract Infections

presence of such immature pattern with UTI and VUR.

*5.3.1. Children with VUR and UTI*

the same age (Leung et al., 2002b).

tion and the reflux problem in children.

pose the affected children to VUR and UTI.

sphincter.

In our institution, a study has been set to investigate whether immature ureteric jet pattern is present in children with nocturnal enuresis.

We have studied 511 children presenting with primary nocturnal enuresis. There was a higher incidence (19%) of immature waveform observed in children with nocturnal enuresis as compared with normal children within the same age range (7.4%) (Leung et al 2006). This study suggests that there is a lower level of maturity in the VUJ in enuretic children. Anoth‐ er interesting finding is that the immature jet is more commonly seen in enuretic children with markedly thickened bladder wall and multiple urodynamic abnormalities. This obser‐ vation suggests that monophasic waveform is associated with abnormalities of the detrusor muscle as well as an increase in detrusor pressure. All these parameters might be indicators of immaturity of the VUJ-detrusor complex, which predispose affected children to the devel‐ opment of primary enuresis.

### *5.3.3. Children with neurogenic bladder*

As discussed previously, VUJ has a nervous component with hitherto unknown functions. Patients with inactivated neural component within the VUJ due to drug effects or surgery have a higher incidence of monophasic jet pattern. It is well known that patients with neuro‐ genic bladder have high incidence of secondary VUR while VUR is associated with mono‐ phasic ureteric jet. In our institution, we sought to investigate whether there is a prevalence of monophasic jet in patients with neurogenic bladder.

In a study of 27 children with neurogenic bladder, the frequency of monphasic jet is much higher in neurogenic bladder group (40.7%) when compared with normal population within the same age range (7%). Despite the small number of subjects, the observation again sup‐ ports the theory of functional active sphincteric mechanism of VUJ. In this scenario, mono‐ phasic pattern prevails when the neural component within the VUJ is deactivated.
