Introduction When the bolus of urine being transmitted through the ureter reaches the terminal portion, it is ejected forcefully into the bladder through the vesicoureteric junction (VUJ). This creates a jet of urine that can be seen within the urinary bladder during cystoscopy and grey-scale ultrasonography (US). Ureteric jets are also occasionally visible during intravenous urography (IVU) and voiding cystourethrography (VCU). 1 2 3 n 4 n 5 n 6 n 7 n 8 Discussion Basic ureteric jet patterns on Doppler US 9 2 10 11 1 Fig. 1 a b c d e f  11 Occasional modification features of the ureteric jet Some interesting features have been observed in the jet patterns of some normal subjects. These features include (a) the presence of breaks, (b) a multispike pattern, and (c) change of angle of the jet between the beginning and the end. The number of cases with the above features is too small for statistical analysis; however, we sought to describe them in detail for completeness of the whole spectrum of ureteric jet patterns. These features also provide indirect supportive evidence for the hypothesis of functional sphincteric action at the VUJ and are discussed further in the final section. Breaks 2 P Fig. 2 Break within a ureteric jet  Multispike pattern 3 Fig. 3 A multispike pattern of a ureteric jet  Change in angle of the jet 4 Fig. 4 a b  Ureteric jet pattern and physical properties of jets in normal subjects General properties Direction of flow 1 12 2 9 13 16 Mean jet velocity 1 2 9 17 18 2 18 19 Table 1 Mean values of jet parameters in children and adults with the monophasic pattern   Right side Left side Children Adults P Children Adults P Number of ureteric jets 83 18  80 18  −2 211.82 195.54 0.60 256.55 281.10 0.87 −1 34.03 57.65 <0.01 38.66 63.93 <0.01 Duration (s) 1.17 1.91 <0.01 1.17 1.90 <0.01 Table 2 Mean values of jet parameters in children and adults with the complex pattern   Right side Left side Children Adults P Children Adults P Number of ureteric jets 293 910  296 892  −2 293.32 271.21 0.09 264.48 309.13 0.13 −1 61.82 79.89 <0.01 61.97 73.83 <0.01 Duration (s) 5.26 6.92 <0.01 5.15 7.03 <0.01 Mean jet duration 1 2 2 16 18 20 9 18 Laterality difference in ureteric jets 18 P 3 P 4 Table 3 Waveform patterns in children and adults in relation to sex (total of 2,629 ureteric jets in 1,341 subjects)   Children Adults Female Male Female Male Right Left Right Left Right Left Right Left Number of ureteric jets 166 164 211 215 567 560 373 373 Pattern Monophasic 28 (16.9%) 19 (11.6%) 55 (26.1%) 61 (28.4%) 14 (2.5%) 12 (2.1%) 4 (1.1%) 6 (1.6%) Biphasic 54 (32.5%) 53 (32.3%) 59 (28.0%) 63 (30.2%) 219 (38.6%) 224 (40%) 110 (29.5%) 89 (23.9%) Triphasic 54 (32.5%) 53 (32.3%) 57 (27.0%) 54 (25.1%) 207 (36.5%) 183 (32.7%) 134 (35.9%) 122 (32.7%) Polyphasic 29 (17.5%) 37 (22.6%) 40 (19.0%) 34 (15.8%) 120 (21.2%) 126 (22.5%) 120 (32.2%) 148 (39.7%) Square 1 (0.6%) 1 (0.6%) 0 (0%) 0 (0%) 5 (0.9%) 13 (2.3%) 2 (0.5%) 1 (0.3%) Continuous 0 (0%) 1 (0.6%) 0 (0%) 1 (0.5%) 2 (0.4%) 2 (0.4%) 3 (0.8%) 7 (1.9%) Table 4 Mean values of jet parameters in children and adults in relation to sex   Children Adults Female Male Female Male Right Left Right Left Right Left Right Left Number of ureteric jets 165 162 211 214 560 545 368 365 −2 290.73 261.06 264.22 264.31 268.12 274.72 271.93 234.07 −1 56.31 57.02 55.72 57.60 69.94 68.84 94.01 80.82 Duration (s) 4.64 4.56 4.21 4.20 6.37 6.43 7.52 7.69 Effect of age on ureteric jets 11 P 5 4 P Z 21 P t P t 18 P t 1 2 Effect of gender on ureteric jets P 3 P t P t 4 P t 4 5 Table 5 Incidence of monophasic jet in children and adults (total of 2,629 ureteric jets in 1,341 subjects). Note that the total number of ureteric jets is less than double the number of subjects as jets in some subjects could not be satisfactorily demonstrated on both sides by Doppler US   Right side Left side Children Adults P Children Adults P Number of ureteric jets 377 940  379 933  Monophasic pattern 83 (22%) 18 (1.9%) 0.01 80 (21.1%) 18 (1.9%) 0.01 Effect of bladder filling status on ureteric jets 11 P t 6 Table 6 Mean values of jet parameters in 102 subjects under different stages of bladder filling. Only the jet on the right side is shown for comparison as there was no significant difference between the two sides Jet parameter Bladder status P Not full Maximally full −2 245.27 209.44 0.39 −1 62.81 58.30 0.37 Duration (s) 6.24 6.23 0.81 Characteristics of ureteric jet under specific physiological conditions Pregnancy (physiological) 6 General anaesthesia (pharmacological) 7 Ureteric transplantation following renal transplantation 8 Ureteric jet characteristics in paediatric conditions Literature review 22 23 24 25 25 24 25 17 24 17 26 9 27 In two recent studies carried out by our group, we found a high correlation between the immature monophasic jet pattern in children with specific urinary disease entities. The details are discussed in the following sections. Children with VUR and UTI 4 Children with nocturnal enuresis 5 Taking all the observations together, we postulate a hypothesis concerning the mode of action of the VUJ as illustrated in the last section. Hypothesis of an active sphincter at the VUJ 28 29 30 32 33 11 11 We hypothesize that dual components are present regarding the mode of action in the active functional sphincter. The first component is the “myogenic” (primary or “immature”) and the second component is “neural” (secondary or “mature”). The distal ureteric muscle and possibly part of the detrusor muscle may contribute to the functional sphincteric action at the VUJ. 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 neural component in response to the distal intraureteric pressure. The mode of the functional sphincteric action of the VUJ and the subsequent ureteric jet waveform vary depending upon whether or not the neural component is active. In normal adults and in children reaching a certain age of maturity, the neural component modulates the myogenic component and complex patterns can thus be seen. When the neural component is absent, for example in a small immature child, under general anaesthesia or in certain pathological conditions, only the myogenic component is functioning, and thus the jet pattern reverses to the monophasic pattern. 8 Although the neural component governing the ureteric jet pattern is either present (resulting in a complex pattern) or absent (resulting in a monophasic pattern), the characteristics (initial slope, velocity, and duration) of the monophasic and complex pattern within the same age group remain distinct. Although there is a trend for a longer duration and higher peak velocity of the ureteric jet with increasing age, this could be explained by a larger bolus of urine in each jet in adults than in smaller children. 6 7 34 4 4 5 The hypothesis of dual components in the sphincteric action of the VUJ might also help explain some of the jet phenomena that we have described previously. The multispike pattern in the ureteric jet resulting from pulsations transmitted from adjacent arteries could probably be explained by premature relaxation of the VUJ that precedes the ureteric jet proper so that the transmitted arterial pulse becomes dominant. Premature relaxation of the VUJ is also likely to be governed by the neural mechanism seen in forced diuresis. The modification involving breaks in the jet is predominantly observed when the bladder is maximally full. Under these circumstances the intravesical pressure would be very high, which might impose a countering effect on the pressure wave of the ureteric jet emitted from the VUJ. Breaks might therefore appear within the jet waveform when the jet velocity drops significantly to zero flow on entering the bladder. In summary, based on all the above observations, we postulate that the human VUJ can act as a functional sphincter with two possible components: (1) a myogenic component which has a simple “open and close” action that gives rise to the monophasic jet pattern, and (2) a neural component that modulates the monophasic waveform into a more complex pattern. Further anatomical study to determine the exact nature of the sphincteric muscle governing VUJ function is warranted. The major implication of this overview of ureteric jet patterns is a change of concept for the human VUJ. Rather than being a passive valve, the VUJ functions as an active sphincter. This might lead to a novel approach to the management of VUR, UTI and enuresis in children which could replace traditional treatment. Conclusion This review has provided a comprehensive understanding of the physiological pattern of ureteric jets and contributes to our knowledge of the pathophysiology of urinary dysfunction in disease entities such as UTI, VUR and primary enuresis. The application of this technique in future studies might lead to novel approaches to the monitoring and prognosis of these conditions and more evidence-based treatment of related diseases.