A view on the anatomy of the ureterovesical junction

The 5:1 rule overestimates the needed tunnel length during ureteral reimplantation

AIMS

Paquin asserts that in order for ureterovesical junctions (UVJs) to prevent reflux, the ureteral tunnel length-to-diameter ratio needs to be 5:1. We hypothesize that the surgical implementation of this observation results in an overestimation of the needed length-to-diameter ratio to prevent vesicoureteral reflux.

METHODS

With finite elements, we model the urine storage phase of the bladder under nonlinear conditions. In the reference state, the bladder is assumed to be a sphere with an oblique straight elliptical hole as the UVJ. Broad parametric studies on different length-to-diameter ratios are performed as the bladder volume increases from 10% to 110% capacity.

RESULTS

The capability of the UVJ to prevent reflux during storage depends on its length-to-diameter ratio. UVJs with larger length-to-diameter ratios lengthen and narrow as the bladder volume increases, causing the closure of the UVJ and rise in its flow resistance. Our model shows that the UVJ length-to-diameter ratio decreases as the bladder volume increases. The 5:1 ratio implemented at 80% capacity-approximate volume or bladder wall stretch during ureteroneocystostomy (UNC)-corresponds to 7:1 at the reference state-used by Paquin. The 5:1 ratio implemented at the reference state corresponds to 3:1 at 80% capacity.

CONCLUSIONS

Our modeling results are consistent with Paquin's original observation on the significance of the UVJ length-to-diameter ratio in preventing reflux. They, however, indicate that the surgical implementation of this rule during UNC results in an overestimation of the requisite tunnel length-to-diameter ratio to prevent reflux. They also suggest that the UVJ closure is due to the bladder wall deformation rather than the pressure.

Morphological study of the ureterovesical junction in children

Morphological and morphometric assessment of the elements of the ureterovesical junction in children was performed in the present study in different age groups ranging from 24 weeks of gestation to 16 years old. We tried to answer the question whether, in human ontogenesis, there is a period of anatomical predisposition to primary vesicoureteral reflux. The study included 210 urinary bladders with juxtavesical parts of the ureters that had been obtained from routine autopsies. As a result of the study, we showed that provided the pregnancy is uncomplicated there is no inherited susceptibility that would account for reducing or disturbing the development of ureterovesical junction elements. Based on the analysis of our results concerning the anatomy and morphological changes taking place in the elements of the ureterovesical junction in different age groups, one could put forward a hypothesis that anatomical predisposition to primary vesicoureteral reflux occurs in age group II, i.e. between 28 and 37 weeks of gestation. The parameters that define interrelations between elements of the ureterovesical junction and that are considered essential for normal functioning of antireflux mechanism were still observed in age group VI in our study. This suggests that these relations are not unambiguous in children with normally structured and functionally competent vesicoureteral junction.

Evaluation of the ureteral jet in dogs by using color Doppler ultrasonography

Ureteral jets are the result of a forceful ejection of urine from the vesicoureteral junction into the urinary bladder. By using color Doppler ultrasonography (US), we aimed to identify distinct ureteral jets in dogs, provide insight into ureteral obstruction, and facilitate study of urodynamics and vesicoureteric sphincter function via pulsed Doppler US. Color Doppler US was applied to detect urinary flow from the right ureteral orifices in eight healthy beagles. Under anesthesia, 0.9% saline (2.5 mL/kg/h) and furosemide (0.5 mg/kg) were administered intravenously to assist in detection of distinct ureteral jets and examine their frequency, velocity, duration, and waveform. In all dogs, ureteral jets were visualized under diuresis and anesthesia within 2 to 5 min (mean 3.57 ± 0.90 min) of the furosemide injection. Mean frequency, peak velocity, and duration of right ureteral jets in seven dogs in whom six ureteral jet waveform patterns were identified were 9.86 ± 3.09 jets/min, 34.07 ± 10.02 cm/sec, and 2.82 ± 1.08 sec, respectively. During the 10 min period starting 10 min after the initial jet appeared, only three waveforms were identified. Color Doppler US of ureteral jets may aid in assessing vesicoureteric sphincter function and ureteral abnormalities, such as ureteral obstruction, in dogs.

The sheath of Waldeyer is not a specific anatomical trait of the ureterovesical junction

The function of the ureterovesical junction depends upon a peculiar structure, the adventitial fibromuscular sheath of Waldeyer, which coats the distal end of the ureter. The origin of the smooth muscle of Waldeyer's sheath (WS) is disputed. Evidence points more likely to an ureteral one. In this regard we hypothesized the WS is not specific to the distal ureter but is rather a common trait. We therefore aimed at exploring whether or not the proximal ureter is provided with a similar adventitial fibromuscular coat. We performed an immunohistochemical study on human samples of proximal ureter resulted after nephrectomies in ten patients. We applied myoid immunohistochemical markers: α-smooth muscle actin (α-SMA), desmin, and heavy chain of smooth muscle myosin (SMM) which labeled additional adventitial smooth muscle bundles, a discontinuous inner circular one applied on the muscular coat, and outer longitudinal cords specifically located on one side of the ureter, as is the case for WS. Moreover, the lamina propria myoid deep layer showed isolated smooth muscle fibers and spindle-shaped stromal cells with telocyte morphology. Our results support the idea that WS may not be a specific structure of the distal ureter, instead being just a common anatomical characteristic of the ureter.

Vesicoureteral reflux and the extracellular matrix connection

Primary vesicoureteral reflux (VUR) is a common pediatric condition due to a developmental defect in the ureterovesical junction. The prevalence of VUR among individuals with connective tissue disorders, as well as the importance of the ureter and bladder wall musculature for the anti-reflux mechanism, suggest that defects in the extracellular matrix (ECM) within the ureterovesical junction may result in VUR. This review will discuss the function of the smooth muscle and its supporting ECM microenvironment with respect to VUR, and explore the association of VUR with mutations in ECM-related genes.

Doppler waveforms of the ureteric jet: an overview and implications for the presence of a functional sphincter at the vesicoureteric junction

This paper is a comprehensive review of the Doppler waveform appearance of ureteric jets. Six jet waveform patterns have been identified: monophasic, biphasic, triphasic, polyphasic, square and continuous. Details of the physical properties of jet patterns and their changes under various physiological conditions are illustrated. The immature monophasic ureteric jet pattern is common in infancy and early childhood up to around 4 years of age. This pattern is also noted to have a high incidence in older children with urinary tract infection/vesicoureteric reflux, nocturnal enuresis and in other special physiological conditions such as in children undergoing general anaesthesia, in women during pregnancy, and in patients who have had ureteric transplantation. A hypothesis of dual myogenic and neurogenic components is proposed to explain the mode of action of the vesicoureteric junction (VUJ). The implication of this hypothesis is that it alters the scientific basis of the understanding of the VUJ. Furthermore, the application of colour Doppler US to ureteric jets may provide a non-invasive technique to study the physiology or pathophysiology of the VUJ in humans. This might shed light on new novel approaches to the monitoring and treatment of diseases related to VUJ function.

An anatomical study of the buccinator muscle fibres that extend to the terminal portion of the parotid duct, and their functional roles in salivary secretion

Until now there has been no definitive anatomical study describing the area where the parotid duct enters the buccinator muscle. In this study, we performed anatomical and histological examinations to investigate the relationship between the parotid duct and the buccinator muscle. Thirty specimens (including the buccinator and the terminal portion of the parotid duct) were obtained from embalmed Korean cadavers. Dissection was performed on 22 of these specimens, and the remaining eight specimens were prepared for histological examination and stained with haematoxylin-eosin or Gomori trichrome. In all specimens, small, distinct muscle fibres originating from the buccinator muscle extended to and inserted into the terminal portion of the parotid duct. The topography of these fibres varied, and we classified them into three categories according to where they originated. Type I buccinator muscle fibres, which inserted into the terminal portion of the parotid duct, originated simultaneously from the anterior and posterior aspects of the duct (ten cases, 45.5%). Type II fibres originated from the anterior aspect of the duct and inserted into the anterior side of the duct (seven cases, 31.8%). Type III fibres originated from the posterior aspect of the parotid duct and ran anteriorly toward the duct (five cases, 22.7%). These results were confirmed in the histological examination of all eight specimens. Based on these findings, we have proposed a tentative description of the physiological role of the buccinator muscle fibres in salivary secretion and in the formation of the sialoliths.

The ureteric jet doppler waveform as an indicator of vesicoureteric sphincter function in adults and children. An observational study

The nature of the action of the vesicoureteric junction (VUJ) in humans is still controversial. We were interested in the reasons why the jet consists of several peaks. We hypothesised that the modification of the jet into a variable number of peaks is the result of an active sphincter mechanism at the VUJ. A total of 1,010 subjects of all ages and both genders were recruited into this study. The Doppler waveform of the jet was recorded bilaterally. We could identify six basic patterns of ureteric jet according to the number of peaks: monophasic, biphasic, triphasic, polyphasic (four or more peaks), square and continuous. By analysing the duration, maximum peak velocity and initial slope of the first four patterns, a mechanism of action of an active VUJ sphincter could be postulated. Furthermore, the basic patterns could be assigned to three modes of ureteric actions: the square and continuous are only seen during diuretic stress; the biphasic, triphasic and polyphasic patterns are variations of the adult physiological steady-state mode, and the monophasic is distinctly different and represents the immature mode.

Immature ureteric jet doppler patterns and urinary tract infection and vesicoureteric reflux in children

The Doppler waveform of the ureteric jet is the result of modification of ureteric peristalsis by an active sphincteric mechanism of the vesicoureteric junction (VUJ). The monophasic pattern is associated with immaturity. This study set out to see the correlation between this immature pattern with urinary tract infection (UTI) and vesicoureteric reflux (VUR) in children. Ureteric jets of 241 healthy children and 98 children with UTI were studied. The monophasic pattern was found in 29% of healthy children overall, but varied greatly according to age. The monophasic pattern was virtually universal in the first 6 months of life, dropping to below 15% in late childhood. This immature pattern was more commonly seen in the UTI (73.5%) and VUR (90.5%) groups than in the healthy controls. The difference was statistically significant (p = 0.0005 for both). The persistence of this immature pattern was highly associated with UTI and VUR.

Localization of nitric oxide synthase and haemoxygenase, and functional effects of nitric oxide and carbon monoxide in the pig and human intravesical ureter

The distribution of nitric oxide synthase (NOS)-immunoreactive (IR) and haemoxygenase (HO)-IR nerves was investigated in the pig and human intravesical ureter (IVU). NOS activity was measured by monitoring the conversion of [3H]-arginine to [3H]-citrulline. Effects of NO and resulting changes in cyclic nucleotide concentrations were assessed in vitro. The effects of carbon monoxide (CO) on IVU motility was also tested. Immunohistochemistry revealed an abundant overall innervation of the IVU and numerous NOS-IR nerves. Nerve trunks were also found expressing immunoreactivity for HO-1, one of the enzymes synthetising CO. Similar profiles of nerve structures expressing immunoreactivities for NOS and tyrosine-hydroxylase (TH), as well as NOS and vasoactive intestinal peptide (VIP) were demonstrated. In the pig IVU, measurement of NOS activity revealed a moderate calcium-dependent catalytic activity, NO and the NO-donor SIN-1 reduced in a concentration-dependent manner serotonin-induced contractions of pig and human IVU, and the spontaneous contractions of pig IVU. In pig IVU strips precontracted with the thromboxane analogue U-46619, tetrodotoxin-sensitive relaxations were abolished by the NOS inhibitor NG-nitro-L-arginine. CO exerted no significant effect on spontaneous or induced contractions in the pig and human IVU. In precontracted strips of the pig and human IVU exposed to SIN-1 or NO, significant increases of cyclic GMP levels were measured in comparison to control preparations. The results suggest that the L-arginine/NO/cyclic GMP pathway may play a role in the regulation of the valve function in the uretero-vesical junction (UVJ). A role for CO in the UVJ has yet to be established.

The structure and autonomic innervation of the vesico-ureteric junction in cases of primary ureteric reflux

OBJECTIVE

To determine the histological structure and autonomic innervation of the vesico-ureteric junction (VUJ) in cases of primary ureteric reflux, to compare the results with those reported previously for non-refluxing VUJs and thus determine possible structural anomalies which could be responsible for vesico-ureteric reflux (VUR).

MATERIALS AND METHODS

Nineteen specimens of VUJs with reflux were obtained from four males and 10 females undergoing ureteric reimplantation. Serial frozen sections were cut and stained either with Masson's trichrome or immunostained for protein gene product (PGP 9.5), a general nerve marker, dopamine beta hydroxylase (D beta H), a marker for noradrenergic nerves, or neuropeptide Y (NPY).

RESULTS

Longitudinally orientated muscle bundles of narrow diameter accompanied the ureter to its termination at the ureteric orifice. Where they merged with those of the superficial trigone. In some specimens, an additional muscle component was identified, situated on the outer aspect of the ureteric muscle coat, consisting of an incomplete layer of distinctive muscle whose constituent cells formed an interlacing mesh-work. Occasionally, specimens included detrusor muscle which consisted of relatively large diameter compact bundles separated from the ureter by a connective tissue sheath. D beta H- and NPY-immunoreactive (-IR) nerves were numerous among the ureteric muscle bundles. Many NPY-IR nerves occurred within the detrusor muscle while D beta H-IR nerves were mainly perivascular. When present, the outer muscle component was richly innervated by both D beta H- and NPY-IR nerves. PGP immunoreactivity varied among regions in the same section, PGP-IR nerves frequently being less numerous than those containing D beta H or NPY.

CONCLUSION

These results indicate that the morphology of the VUJ in cases of VUR is indistinguishable from the normal VUJ described previously. Furthermore, the density and distribution of D beta H- and NPY-IR nerves is identical to that in controls. However, the antigenicity of PGP in the reflux specimens appears to be masked in some regions by an unknown factor.

Functional anatomy of the human ureterovesical junction

BACKGROUND

The valve function of the ureterovesical-junction (UVJ) is responsible for protection of the low pressure upper urinary tract from the refluxing of urine from the bladder. Controversy about the microanatomy of the human ureterovesical-junction persists.

METHODS

Ten (3 male and 7 female) fresh cadaveric bladders (mean age 70 years old) were studied. The bladders were fixed within 24 hours postmortem, frozen, and serially sectioned. Acetyl- and butyryl- (nonspecific) cholinesterase activity were visualised as described by Karnovsky and Roots. The three-dimensional distribution of the different muscle groups participating in the formation of the UVJ was reconstructed.

RESULTS

Three different muscle groups were identified: (1) the detrusor muscle and the deep trigone were mainly acetylcholinesterase-positive, (2) the inner and outer layer of the ureteric muscle were butyrylcholinesterase-positive and merged into a single longitudinal layer at the level of the UVJ and form the superficial trigone distally to the ureteric orifices, and (3) the muscularis mucosae is a discontinuous butyrylcholinesterase-positive layer in the bladder that is absent from the trigone. No evidence of any muscular connection was found between the ureter and bladder musculature.

CONCLUSIONS

The anatomy of the UVJ as observed by us suggests the following model of the ureteric peristalsis. The urine bolus arrives in the ureteric lumen at the UVJ level. The ureter can only shorten its length, slides freely in its tunnel, and discharges the urine bolus in the bladder cavity. Ureteric constriction due to the peristalsis and thickening of the contracted portion of the ureter prevents the upstream leakage. Distal spreading of the ureteric "peristalsis" in the superficial trigone increases the submucosal ureteric length and prevents reflux.

The functional anatomy of the ureterovesical junction

OBJECTIVE

To obtain a new insight into the anti-reflux mechanism of the ureterovesical junction by studying the topographical anatomy of the juxta- and intravesical ureter and its relationship to the surrounding bladder musculature.

MATERIALS AND METHODS

Fresh pig bladders were fixed, frozen and serially sectioned. Enzyme histochemistry was performed to demonstrate tissue acetyl- and butyryl- (non-specific) cholinesterase. Smooth muscle cells were identified by immunohistochemistry using a monoclonal anti-alpha actin smooth muscle antibody. Three-dimensional computer reconstructions of the different muscle groups of the bladder and ureterovesical junction were generated.

RESULTS

On the basis of expression patterns of the cholinesterase isozymes, five different groups of muscles were identified: the detrusor, the muscularis mucosae of the bladder, the muscle layer of the intravesical ureter and the separate inner and outer muscular layers of the pelvic ureter.

CONCLUSION

No separate ureteric sheath was identified. There appeared to be few or no (muscular) connections between the ureter and the bladder musculature. The muscle layer of the ureter ended beneath the mucosa of the bladder, without extension into the trigone. The submucosal section of the ureter was very short, although its length was thought to be of importance in the anti-reflux mechanism. Examination using enzyme histochemistry demonstrated a muscularis mucosae in the bladder which was absent from the trigone.