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

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

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 the first six months of life. There is a significant drop in the incidence of monophasic pattern by the age of four. The complex waveforms prevail in older children and normal adults. There are two components in the dual mode action of such functional sphincter. They are the "myogenic" (primary or immature) component and the "neurogenic" (secondary or ma‐ ture) component. We postulate that the monophasic jet pattern is the result of contraction caused by the myogenic component of the VUJ, while the complex pattern is the result of modulation of the myogenic component of the jet by the neurogenic component in response to the distal intrauretetic pressure (Fig 11). The mode of the functional sphincteric action of the VUJ and the subsequent ureteric jet waveform vary depending upon whether or not the neurogenic component is active.

effect temporarily inactivates the neurogenic component. Once the hormonal effect is lost, the neural component is activated again. In the anaesthetized (GA) children, the drug ef‐ fect also temporarily inactivated the neurogenic component. In patients undergoing renal transplantation, the normal VUJ mechanism in the transplant ureter is altered or com‐ pletely lost as a result of the operative procedure, thus a totally different ureteric jet pat‐

Functional Anatomy of the Vesicoureteric Junction: Implication on the Management of VUR/ UTI

http://dx.doi.org/10.5772/52168

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**Figure 12.** Diagram showing the inactivation of the neurogenic component under different physiological and patho‐

Under pathological conditions, there is strong correlation between the presence of VUR and the immature monophasic waveform. This suggests that the more mature complex jet pat‐ tern is associated with a more efficient anti-reflux mechanism than the simple immature pat‐ tern. The immature jet pattern may represent a temporary developmental immaturity of the VUJ, which predisposes children to the risk of VUR. Monophasic jet is also found in children with nocturnal enuresis associated with detrusor immaturity. A higher incidence of mono‐ phasic waveform is also found in children with neurogenic bladder, consistent with loss of the neural component. This might also explain why there is a higher incidence of VUR and UTI in children with neurogenic bladder when the anti-reflux mechanism is lost at the VUJ

The concept of dual mode action (myogenic and neurogenic component) of a functional ac‐

tive sphincter at human VUJ has the following implications:

**1.** Human VUJ function takes time to mature.

tern is observed (Fig 12).

logical conditions

(Fig 12).

**7. Conclusion**

**Figure 11.** Diagram showing the dual mode of action of the VUJ in the normal population

The presence of the less frequently observed modifications of the ureteric jet pattern is also contributed to the dual mode action of VUJ. The multispike pattern appears to be a prema‐ ture relaxation of the VUJ that precedes the ureteric jet proper. It is related to the relaxation mechanism found in forced diuresis. Forced diuresis is probably caused by permanent re‐ laxation of the VUJ functional sphincter allowing free flow of urine modified by ureteric peristalsis. These modifications are under the control of neural mechanism. The breaks mod‐ ification is found under condition of maximum bladder filling hence increased intravesical pressure. This is probably a result of the pressure wave of the ureteric jet generating appa‐ rently lower velocities and intervening with zero flows.

Whenever the neurogenic component is switched off, only the myogenic component oper‐ ates and thus results in a reversion to the monophasic pattern of the ureteric jet. The above holds true under three physiological conditions. During pregnancy, the hormonal effect temporarily inactivates the neurogenic component. Once the hormonal effect is lost, the neural component is activated again. In the anaesthetized (GA) children, the drug ef‐ fect also temporarily inactivated the neurogenic component. In patients undergoing renal transplantation, the normal VUJ mechanism in the transplant ureter is altered or com‐ pletely lost as a result of the operative procedure, thus a totally different ureteric jet pat‐ tern is observed (Fig 12).

**Figure 12.** Diagram showing the inactivation of the neurogenic component under different physiological and patho‐ logical conditions

Under pathological conditions, there is strong correlation between the presence of VUR and the immature monophasic waveform. This suggests that the more mature complex jet pat‐ tern is associated with a more efficient anti-reflux mechanism than the simple immature pat‐ tern. The immature jet pattern may represent a temporary developmental immaturity of the VUJ, which predisposes children to the risk of VUR. Monophasic jet is also found in children with nocturnal enuresis associated with detrusor immaturity. A higher incidence of mono‐ phasic waveform is also found in children with neurogenic bladder, consistent with loss of the neural component. This might also explain why there is a higher incidence of VUR and UTI in children with neurogenic bladder when the anti-reflux mechanism is lost at the VUJ (Fig 12).
