General Patterns

Abnormalities of ureteral development including ectopic ureters and ureteroceles represent a large component of clinical urology and continue to challenge clinical management, despite their wide recognition and well-defined surgical strategies. The wide spectrum of involvement and the variable patterns of presentation underlie the clinical challenge and require a thorough understanding of both normal and abnormal embryology of the lower urinary tract. This chapter presents the embryology, clinical manifestations, pathology, evaluation, and management strategies for ectopic ureters and ureteroceles, as well as other less common ureteral anomalies of formation. Obstructive ureteral pathologies including ureteropelvic junction (UPJ) obstruction and ureterovesical junction obstruction are reviewed in Chapter 120.

Although ectopic ureter and ureterocele are typically presented as distinct entities, they apparently share many common features and may well have the same underlying developmental mechanisms with slight variations that induce the obvious differences in their appearances. In many ways, they may be approached in a similar manner, with slight variation in management due to their particular differences. It is also apparent that clinical cases may represent manifestations that lie between the two entities, suggesting a continuum of embryologic maldevelopment.

Ectopic Ureter

By definition, an ectopic ureter is any ureter, single or duplex, that does not enter the trigonal area of the bladder (Glassberg et al, 1984). In a duplex system this is inevitably the upper pole ureter, presumably due to its budding from the mesonephric duct later than the lower pole ureteral bud. If it is simply near the bladder neck, it is not technically ectopic, which requires entry at the level of the bladder neck or distal. In females the ectopic ureter may enter anywhere from the bladder neck to the perineum and into the vagina, uterus, and even rectum (Weight et al, 2006). It may be associated with a cyst of Gartner duct, the remnant of the wolffian duct from which the ureter buds, and may include cystic dilation of the duct. The duct typically runs parallel to the vagina (the müllerian structure) and with rupture of the cystic ductal structure, communication with the vagina is established (Weiss et al, 1984; Rosenfeld and Lis, 1993). This is the basis for incontinence, the frequent presentation of an ectopic ureter in females. In males the ectopic ureter always enters the urogenital system above the external sphincter or pelvic floor and usually into the wolffian structures including vas deferens, seminal vesicles, or ejaculatory duct. These may be associated with cystic dilation, presumably due to continued urine production. Males do not present with incontinence but with infection and pain of the affected organs (testicles and epididymis).

Single-system ectopic ureters may present in a similar fashion but may also be associated with an apparently absent kidney. This usually reflects an inability to identify the kidney on typical imaging and has led to the use of computed tomography (CT) imaging with contrast to detect small poorly functioning renal units associated with an ectopic ureter (Borer et al, 1998). Either single or duplex systems with an ectopic ureter may present with severe hydronephrosis reflecting distal obstruction. This may have impaired normal renal development to the point that the affected segment is nonfunctional, which needs to be clinically assessed.

A rare entity of bilateral single-system ectopic ureters occurs and may be associated with a hypoplastic bladder and bilateral renal abnormalities, typically dysplasia (Noseworthy and Persky, 1982; Johnin et al, 2007). Some of these children may be considered to have bladder agenesis due to the absence of a recognizable bladder structure, presumably due to the absence of bladder filling and emptying in utero (Weight et al, 2006).

Ureterocele

Ureteroceles may be seen to represent a version of the ectopic ureter with a cystic dilation of the distal aspect of the ureter that is located either within the bladder or spanning the bladder neck and urethra. Studies in mouse models suggest that ureteroceles may reflect defective ureteral maturation, the process by which the developing ureteric bud detaches from the mesonephric duct and moves to the bladder (see later) (Mendelsohn, 2009). As with the ectopic ureter, ureteroceles may be associated with a single or duplex system and in duplex systems they are associated with the upper pole. Ureteroceles can extend into the urethra but do not form entirely within the urethra, nor do they attach to the wolffian ductal structures.

Several classification systems exist for ureteroceles, but the most useful one for clinical practice separates intravesical from extravesical ureteroceles. The intravesical ureterocele is entirely within the bladder and above the bladder neck. This would include a “simple” ureterocele that may be seen in the adult with minimal dilation and mild to no upper tract dilatation. This term, however, should be discouraged and the term single intravesical ureterocele used instead (Glassberg et al, 1984). An ectopic ureterocele includes those “in which some portion of the ureterocele is situated permanently at the bladder neck or urethra” (Glassberg et al, 1984). The orifice may be in the bladder, at the bladder neck, or in the urethra. This should be distinguished from an intravesical ureterocele that prolapses into the urethra with voiding.

Further descriptive subdivision of ureterocele types has been published, particularly by Stephens (Stephens, 1971; Stephens et al, 1996). These include cecoureterocele, stenotic, sphincteric, sphinctero-stenotic, blind, and nonobstructed ureteroceles (Figs. 121-1 and 121-2). From a clinical perspective, the most important subgroup to recognize is the cecoureteroceles. In these cases the orifice of the affected ureter is within the bladder, but the cavity of the ureterocele extends beyond the bladder neck into the urethra. These may not be readily identified preoperatively (Smith and Parrott, 1994) and their complexity may create surgical challenges, particularly with endoscopic incision (see later).

Figure 121–1 The orifice of a stenotic ectopic ureterocele may be located at the tip or at the superior or inferior surface of the ureterocele.

Figure 121–2 A, Sphincterostenotic ectopic ureterocele. B, Cecoureterocele lumen extends distal to the orifice as a long tongue beneath the ureteral submucosa. The orifice communicates with the lumen of the bladder and is large and incompetent.

An unusual but diagnostically challenging ureterocele variant is the so-called “nonobstructive” ureterocele with duplication (Bauer and Retik, 1978) or “ureterocele disproportion” (Share and Lebowitz, 1989). These are associated with a duplex kidney, but the affected upper pole is nondilated and typically dysplastic to such a degree that it is not readily detected on most imaging and the affected ureter is not dilated beyond the bladder. A typical-appearing ureterocele is seen in the bladder, but the ipsilateral kidney appears normal.

There is some association of ureterocele type with outcomes of various therapeutic measures, but these have not proven to be as predictable as initially reported. Churchill and colleagues (1992) proposed a classification system on the basis of the impact of the ureterocele on the upper urinary tract including all renal units. This functional system separates those in which the upper pole only is in jeopardy, from those in which an entire ipsilateral kidney is threatened, to those in which the contralateral system is also at risk due to reflux or bladder outlet obstruction. The latter group comprised 26% of the reported cases.

Embryology and Etiology

The specific mechanisms responsible for ectopic ureters and ureteroceles remain undefined, but our emerging understanding of normal and abnormal ureterotrigonal development, along with new investigational tools, are likely to provide valuable insights (Mendelsohn, 2009). Although these molecular mechanisms will be of scientific importance, they will also permit potential separation between variants of these conditions that are likely to have therapeutic relevance, as well as perhaps ultimately permitting early detection (i.e., in utero) and intervention. The latter is a distant but not implausible horizon. At present experts remain uncertain as to fundamental mechanisms and yet need to know which ureteroceles and ectopic ureters may be associated with bladder neck and trigonal maldevelopment sufficient to cause incontinence. These children will require more aggressive therapy to achieve continence. Early identification may permit earlier and more effective surgical therapies.

Clinical Relevance

Understanding the potential relationships of the abnormal ureter associated with ectopia or a ureterocele, which is based on aberrations in normal development of the wolffian and müllerian ducts, ureteral bud, urogenital sinus (UGS), and bladder, can facilitate clinical interpretation of these conditions. Knowledge of the sites of ectopic insertion may be useful in planning imaging and in surgical correction. Recognition of the possible effects of abnormal ureteral development on bladder and urethral development is essential in determining reconstructive strategies, and an awareness of the possible coexistence of ureteral and müllerian abnormalities is important.

Ureteral-Trigonal-Renal Development

The pathogenesis of ureteral ectopia with or without a ureterocele rests in ureterotrigonal and renal development. This involves the common nephric duct (CND), ureteral budding, ureterometanephric interactions, and bladder and trigone development. Ectopic ureters can arise due to abnormal timing or location of the primary ureteral budding from the mesonephric ducts, or abnormalities at the stage of ureter. That temporospatial location will determine both the character of the ureter incorporated into the emerging bladder, as well as the development of the trigone and kidney. Ureter maturation occurs after the ureteric bud sprouts from the mesonephric duct when the posterior nephric duct segment (the common nephric duct, CND) expands and is absorbed into the bladder where the CND undergoes apoptosis. At this point, ureteral cells merge with bladder epithelia and undergo a second wave of apoptosis, generating a new ureteral orifice, which is now in the bladder neck. Growth and expansion of the bladder moves the ureteral orifice, which is now inserted in the bladder epithelium, farther away from the mesonephric duct to the final position. Of course, these elements can all be affected with both ureteral ectopia and ureterocele.

Classical understanding of uretero-trigonal development has indicated that the trigone originates from the mesodermal CND, as does the ureter, and is distinct from the endodermal origin of the bladder. According to this model, the CND expands, moving the ureter away from the mesonephric duct, and is incorporated into the primitive bladder, repositioning the ureter orifice at the bladder neck (Wesson, 1920; Tanagho and Pugh, 1963; Woodburne, 1965). Normal regulation of ureter remodeling permits fusion of the ureter and the UGS, as well as separation of the ureter and the wolffian duct (Mendelsohn, 2009; Tanaka et al, 2010).

However, the observation that the CND degenerates during ureter maturation suggests that it may not give rise to the trigone as previously thought (Batourina et al, 2002, 2005; Viana et al, 2007; Chi et al, 2009; Mendelsohn, 2009; Uetani et al, 2009; Tanaka et al, 2010). Consistent with this, lineage studies and tissue recombination studies in mice suggest that the trigone is formed by bladder mesoderm/muscle and muscle surrounding the intravesical ureter. One possibility is that intersection between ureteral fibers and bladder muscle give the trigonal region its distinct morphology.

A revised model of ureteral bud–trigonal maturation based on these studies requires coordinate expansion and subsequent apoptosis of the CND between the developing ureter and wolffian duct. Expansion of the CND permits correct alignment of the ureter with the UGS and may be seen to determine the position of the attachment of the ureter to the bladder and trigone. In contrast to the classic model, however, in which the CND forms the trigone, the revised model includes regression of the CND in the normal animal through apoptosis (Batourina et al, 2002, 2005; Viana et al, 2007; Chi et al, 2009) (Fig. 121–3).

Figure 121–3 Top: schematic showing a revised model of ureter maturation. Bottom: images of Hoxb7-Gfp expressing embryos showing different stages of urinary tract morphogenesis. In the lower urinary tract, the Hoxb7-Gfp transgene is localized in the ureter, mesonephric (wolffian) duct, and common nephric duct (CND) (Srinivas et al, 1999). A, Whole mount urogenital tract from an E9 Hoxb7-Gfp embryo counterstained with E-cadherin to reveal the mesonephric duct (green) inserting into the primitive bladder (red). B, A whole mount urogenital tract from an E11 Hoxb7-Gfp embryo counterstained with E-cadherin (red). The CND lies below the primary ureteric bud branch, which at this stage has invaded the kidney blastema (not visible). C, Whole mount urogenital tract from an E12 Hoxb7-Gfp embryo (green) stained with cytokeratin (red). Apoptosis of the CND has brought the caudal-most ureter into close contact with the bladder, where it aligns, setting the position of the future ureteral orifice. D, A vibratome section from an E13 Hoxb7-Gfp urogenital tract stained with E-cadherin (red). Cells from the most distal ureter epithelium have now merged with the bladder epithelium, where they will undergo apoptosis, creating a new ureteral bud connection. E, A whole mount urogenital tract from an E13.5 Hoxb7-Gfp embryo stained with Laminin to reveal the basement membrane of the bladder epithelium (red). The ureter orifice is now inserted in the epithelium and is separated from the mesonephric duct by a short distance. F, Expansion and elongation of the bladder has moved the ureter orifice farther away from the mesonephric (wolffian) duct. Ugs, urogenital sinus.

The revised model of ureteral maturation provides possible mechanisms for ureteral ectopia and ureterocele formation. Abnormal apoptosis may maintain the connection between the ureter and the wolffian duct and prevent incorporation of the ureter and the UGS. This defect would produce a ureter attached to the wolffian remnants in girls (Gartner duct) or to the vas deferens or ejaculatory system in boys. Abnormal timing of ureteral budding may be one cause of this dysregulated apoptosis and would explain the occurrence of these defects with duplicated systems, particularly the upper pole (later budding) ureter. A lesser defect, either by timing or completeness of the defect, might explain the ectopic ureter to the urethra distal to the bladder neck in girls. Specific defects in the signaling molecules, as seen in knockout mouse models, may produce isolated defects, but by disruption of the normal sequence both temporally and spatially, could produce a range of downstream abnormalities. Similar phenotypes may be caused by multiple mechanisms, with more subtle variation among individuals. This may explain some of the variation seen in both ectopic ureters and ureteroceles.

The expansion of the CND that permits normal alignment of the developing ureter appears to be in response to contact with the UGS (Batourina et al, 2005) and must be coordinated with later apoptosis of the CND, as well as being regulated by local factors and CND cellular responsivity. Impaired expansion may produce ectopia due to delayed or limited movement of the ureter relative to the UGS, whereas unregulated expansion may prevent normal communication of the ureter with the UGS and perhaps be the initiation of terminal ureteral expansion as seen in ureteroceles. Tanagho (1976) postulated that ureteroceles resulted from the distal ureter being inappropriately exposed to the factors inducing expansion of the UGS and bladder. Nearly all growth during development is the result of balanced stimulatory and inhibitory factors, regulated by temporal and spatial gradients, proximity, and cofactors that are, in turn, regulated by similar mechanisms. Altered timing and coregulation of these systems are likely the basis of altered development.

The classic explanation of ureterocele formation is that of Chwalle (1927), postulating that distal ureteral expansion is produced by failure of rupture of a distal membrane at the ureteral orifice (Chwalle membrane). Obstruction is unlikely to be a major and certainly not the only factor producing ureteral dilation, as seen with ureteroceles. Ureteroceles with large orifices and no apparent obstruction are well recognized clinically. Ectopic ureters with insertion into the bladder neck are dilated but do not have the disproportionate distal dilation characteristic of the ureterocele. Obstruction plays some role in ureterocele pathophysiology, however, as is evident in the frequent occurrence of decompression with ureterocele puncture. Whether this is determined by the degree of muscularization of the ureterocele is undefined. Recent studies support the idea that degeneration of Chwalle membrane is important for generating a patent connection between the ureter orifice and the bladder. These studies suggest that Chwalle membrane, which has been thought to form from the UGS, may in fact be derived from luminal cells in the ureter that undergo apoptosis at a relatively late stage, before the onset of renal function, which may be important for generating a patent connection between the distal ureter and bladder.

Relationship with Embryonic Ductal Structures

The embryologic relationships of the developing ureter and the metanephric (wolffian) and müllerian ducts are important to understand the possible sites of ectopic ureteral insertion. Because the ureteral bud derives from the wolffian duct, the ectopic ureter will not insert directly into the müllerian structures (i.e., vagina, cervix, uterus) but will be associated with them through the remnant of the wolffian duct, Gartner duct, that runs alongside the mature müllerian structures. Communication into these structures is likely due to rupture of Gartner duct or of a cyst of Gartner duct into the vagina (see later).

The possible sites of ectopic ureteral insertion are shown in Figure 121–4, including the common locations that are associated with normal wolffian duct development; however, more aberrant locations have been reported. It is unclear what the embryologic mechanisms of these locations, including rectum, might be, but they probably reflect more diffusely deranged overall development. Given that the wolffian duct in the male is never associated with any structures below the pelvic floor and sphincter, males do not present with urinary incontinence, as is seen in females. Abnormal bladder function is recognized in children with ureteroceles and is characterized by larger than normal bladders with inadequate emptying (Abrahamsson et al, 1998). This is potentially consistent with not only the obstructive effect the ureterocele can have on the bladder outlet, but also abnormal bladder and trigone development.

Figure 121–4 Sites of ectopic ureteral orifices in the male and female.

Patterns Associated with Duplication

As the developing ureteral buds incorporate into the developing UGS, the lowest bud, associated with the lower pole of the kidney, is incorporated first and migrates more laterally. The upper pole ureter is later to be incorporated and thereby is closer to the bladder neck. The Weigert-Meyer rule (Fig. 121–5) (see also Chapter 111) describes the inverse relationship of the duplex ureteral orifices, in which the ectopic ureter or ureterocele associated with the upper pole is caudal to the lower pole ureteral orifice. The association of the upper pole ureter and renal segment with the abnormally developed distal ureter further supports the principle that ectopic ureters and ureteroceles result from aberrant temporo-spatial signaling as the CND merges with the UGS.

Figure 121–5 The Weigert-Meyer rule is depicted. The upper pole ureter and the lower pole ureter rotate on their long axes to yield an upper pole orifice (b) that is medial and caudal to the lower pole orifice (a).

Imaging

Incidental

When significant hydronephrosis is present with either an ectopic ureter or ureterocele, an incidental diagnosis will occasionally be made. In some cases, however, this may result from a search for an explanation of general abdominal pain that was not considered to be due to a renal cause. It is also possible that the dilated ureter may not be recognized as such, and cases of presumed ovarian cysts that were actually markedly dilated ureters have been seen (Fig. 121–6).

Figure 121–6 Magnetic resonance urogram of 15-year-old girl with intermittent abdominal pain attributed to ovarian cysts but, in fact, caused by an ectopic ureter. The association with the upper pole of the left kidney and the insertion just below the bladder neck are evident on this image.

Infection

Infection remains a significant reason for clinical presentation of both ectopic ureters and ureteroceles, and these may be at any age and have a highly variable pattern.

Incontinence

Pain

Pain is uncommonly associated with either an ectopic ureter or ureterocele. The exceptions are acute infection, as well as episodic obstruction of the ectopic ureter or bladder pain due to an obstructing ureterocele. Occasional cases of intermittent drainage of an ectopic ureter in older children have been experienced and are characterized by abdominal pain followed by perineal drainage of urine or purulent material. It is presumed that this reflects accumulation of urine in a system that is obstructed at the level of the orifice with subsequent drainage and relief of symptoms. One such case was attributed to an ovarian cyst, supported by the finding of a large cystic structure in the pelvis, which was in fact a dilated ureter.

Prolapse

Ureterocele prolapse is an unusual but distinctive presenting sign that may still confuse the clinician. These are usually smooth, congested, mucosa-covered intralabial masses, and the child may be experiencing difficulty voiding. The mass protrudes from the urethra, distinct from the vagina, and is not circumferential as a urethral prolapse will be (Fig. 121–7). It is not lobulated as a sarcoma botryoides appears. An US of the bladder will usually confirm the diagnosis, and kidney images will further support this.

Figure 121–7 A prolapsed ureterocele presented as an interlabial mass in a 3-week-old girl.

Evaluation

Management of ectopic ureter or ureterocele is based on a thorough assessment of the affected anatomy and the functional implications of the condition. This may usually be obtained readily but in some cases will require more involved imaging such as magnetic resonance (MR) urography.

Anatomic Assessment

Physical Examination

With both ectopic ureter and ureterocele, physical findings may facilitate diagnosis. The prolapsed ureterocele is diagnostic and dramatic but unusual. Further study of the anatomy is necessary. It is unusual to be able to detect an ectopic perineal ureteral orifice in a child, but this will provide much information as to the character of the situation and best treatment (Fig. 121–8). A search for the perineal orifice in a child with continuous wetting or a known leaking ectopic ureter is worthwhile. Rarely, the dilated Gartner duct cyst may be detected on careful perineal examination (Fig. 121–9). These orifices or cystic structures may then be imaged by injection of contrast. Continuous dripping or pooling of urine may be seen in the introitus of females. Visualizing the actual orifice in the introitus is difficult due to the many mucosal folds. However, absence of dripping of urine does not exclude the diagnosis of ectopic ureter. The ectopic ureter may be connected to renal tissue so dysplastic that it rarely produces urine.

Figure 121–8 Perineal ectopic ureteral orifice (bottom arrow) cannulated with an angiocatheter, situated between the urethral orifice (top arrow) and the vagina, just to the left of midline.

Figure 121–9 A, Gartner duct cyst (bottom right arrow) in newborn with a left multicystic dysplastic kidney. B, Injection of the cyst communicated with the ureter and dysplastic kidney.

The dilated upper pole of either an ectopic ureter or ureterocele may be palpable in the relaxed infant, but this is difficult in the older child.

Ultrasound

The US image will usually provide the anatomic diagnosis and permit inference of functional assessment. The typical findings are as with the prenatal imaging of a dilated upper pole with ureteral dilation or a dilated single system (see Fig. 121–9). The character of the renal parenchyma will be more readily seen postnatally, and if it appears healthy, the true need for functional upper tract imaging can be questioned. Depending on the chosen treatment algorithm, it may be argued that this is unnecessary because it will not change treatment. The difference between functioning upper poles and those with little to no function are usually apparent (Figs. 121-10 and 121-11).

Figure 121–10 Ultrasound image of dilated upper pole (UP) associated with a ureterocele, demonstrating limited renal parenchyma (same patient as Fig. 121–30). LP, lower pole.

Figure 121–11 Ultrasound demonstrating dilated upper pole (UP) and lower pole (LP) associated with a ureterocele. The upper pole has evident renal parenchyma. The lower pole is dilated due to compression of the dilated upper pole ureter on the lower pole system, creating a partial obstruction.

No characteristics permit differentiation between a dilated ectopic ureter and ureterocele above the bladder. The bladder images therefore become critically important because management is different.

Bladder views should be diagnostic to differentiate ureterocele from ectopic ureter (Fig. 121–12). The ureterocele is characterized by a thin-walled, cystic dilation within the bladder and not extending beyond its walls. The laterality of the ureterocele is usually apparent but may appear midline if large. A lobulated ureterocele may appear as two structures, but careful examination should show communication. It is difficult to visualize extension of a cecoureterocele into the bladder neck, so nonvisualization is not diagnostic.

Figure 121–12 Ultrasound image of an intravesical ureterocele at the bladder level.

Several US patterns may produce confusion in diagnosis. A large ureterocele may completely fill a bladder with no urine in the bladder itself. A full bladder with an effaced ureterocele may be mistakenly considered an ectopic ureter. Observation of the bladder over time will usually avoid these errors. A ureterocele may also evert and has been seen outside the bladder and mistakenly diagnosed as a diverticulum. A dilated ectopic ureter may produce an impression on the bladder and appear as a ureterocele (the previously noted “pseudoureterocele”) as noted in fetal diagnosis, but the wall will be clearly bilaminar and much thicker than typically seen with a ureterocele. Further, the lumen of the ectopic ureter will extend well outside the bladder walls (Fig. 121–13).

Figure 121–13 A, Ultrasound image of bladder in a child with an ectopic ureter extending into the bladder. The wall of the ureter is thicker than a ureterocele, and the lumen of the ureter extends well outside the bladder lumen, indicating that this is an ectopic ureter rather than a ureterocele. B, Voiding cystourethrogram of a large ectopic ureter pushing inward on the back of the bladder and appearing as a filling defect in the bladder (pseudoureterocele).

(B, Courtesy of Dr. Jeanne Chow, Assistant Professor of Radiology, Harvard Medical School and Children’s Hospital Boston.)

Magnetic Resonance Imaging

MR urography can provide the most detailed images of an affected urinary tract as a whole along with functional information yet is rarely useful to provide more data than may be obtained with less expensive methods not requiring sedation. Eventually, however, MR imaging (MRI) is likely to become the modality of choice. At present the value of MRI rests with cases in which other imaging cannot define complex anatomy. This may occur with massive dilation in which the existence of duplication may be uncertain or in which anatomic relationships are significantly distorted (Fig. 121–14). Not all ectopic ureters are massively dilated, and the MR can also be helpful in identifying a small, dysplastic upper pole and its ectopic ureter that was unrecognized on US. If this type of anatomic delineation is necessary, MR offers the addition of functional information that is an equally important aspect of evaluation. The ability to integrate detailed anatomic assessment of MR with functional assessment can be useful in the detection of the occult ectopic ureter causing incontinence with minimal function (Fig. 121–15).

Figure 121–14 Use of magnetic resonance imaging to define the complex anatomy of a child with an ectopic ureter associated with a right dysplastic, cystic kidney (arrow) draining into an obstructed hemi-vagina and producing urinary dilation of the right hemi-uterus. Initial therapy constituted creating a distal window between the two vaginae. Subsequently she underwent right nephrectomy.

Figure 121–15 Magnetic resonance urography demonstrating the presence of an occult upper pole associated with an ectopic ureter producing incontinence. The left upper pole ureter is marked by the arrow at the level of the lower pole pelvis.

Functional Assessment

Functional urinary assessment in association with an ectopic ureter or ureterocele is the foundation for both initial management and postoperative care. Both renal and bladder function are affected by the developmental abnormalities of abnormal ureteral formation and may ultimately require complex surgical interventions.

Renal Function

Nuclear Imaging

Radionuclide renal imaging remains the gold standard for renal functional assessment, and this is usually best provided by dimercaptosuccinic acid (DMSA) imaging. The function of the affected upper pole is the principal focus, but the health of the other renal moieties must be determined as well, particularly if there is lower pole reflux or hydronephrosis of any unit. Although there have been some attempts to define what the “normal” function of an upper pole associated with an ectopic ureter or ureterocele should be, there are no criteria to define this. The clinical impact comes with the decision to preserve the upper tract or not, yet there are no objective parameters to determine what level of functional contribution should be preserved. The functional assessment therefore offers the dichotomy of “some function” versus “no function,” and this may or may not determine clinical management (see later) (Figs. 121-16 and 121-17). In general, this is clear, but there will always be ambiguous cases. Preoperative assessment is further confused by the lack of ability to predict the effect of decompression.

Figure 121–16 Dimercaptosuccinic acid renal scan in a child with a left ureterocele demonstrating no function in the affected upper pole.

Figure 121–17 Dimercaptosuccinic acid renal scan in a child with a ureterocele with evidence of upper pole function after transurethral incision to decompress the ureterocele. The upper pole was separately assessed as contributing approximately 18% of total renal function.

The assessment of drainage function is rarely of practical utility in that a purely observational approach is only rarely entertained and usually not on the basis of functional parameters. There are no guidelines as to the level of obstructive effect that will cause a clinical problem, particularly infection, although this has been used as a selection tool for nonoperative management (Han et al, 2005).

Intravenous Pyelogram

In unusual situations the intravenous pyelogram (IVP) may offer adequate functional information with anatomic delineation without the complexities of MRI. Because the quantitative measure of upper pole function is rarely necessary with any precision, the IVP can offer an efficient means to complete the renal functional assessment (Fig. 121–18). The IVP may be of particular value in the ectopic ureter without ureteral or upper pole dilation.

Figure 121–18 Intravenous pyelogram image of a 10-year-old child with life-long wetting and evidence of ureteral duplication (black arrow—upper pole) with no hydronephrosis. The distal ureter (white arrow) can be seen passing by the bladder and bladder neck and inserting into the urethra near the perineum.

Bladder Function

Although the bladder is not usually the focus of clinical attention in the evaluation of the ectopic ureter or ureterocele, the potential for impaired bladder function cannot be ignored. This may be due to bladder outlet obstruction from a ureterocele or impaired continence due to inadequate bladder neck function with an ectopic ureter or ureterocele. In the extreme case of bilateral single-system ectopic ureters, bladder development may be severely impaired due to the absence of developmental bladder filling.

Reflux

The presence of reflux may determine initial treatment for some practitioners and is an important parameter in clinical management after initial decompression of the ureterocele. Lower pole reflux may be of any degree and can often be associated with a massively dilated ureter (Fig. 121–19). In the setting of an ectopic ureter, ipsilateral lower pole reflux is unlikely to resolve spontaneously and will determine definitive treatment options.

Figure 121–19 Voiding cystourethrogram image of child with a ureterocele appearing as a filling defect within the bladder and massive ipsilateral lower pole reflux.

Following endoscopic incision of a ureterocele, the presence of reflux either ipsilaterally or contralaterally will be critical in therapeutic decision making.

Ureterocele and Bladder Outlet

The appearance of the bladder base with filling and voiding demonstrated on VCUG will also be useful in therapeutic decisions because massive eversion indicates a weak trigonal floor that may be more likely to require surgical repair. Prolapse of a ureterocele into the urethra and demonstration of a cecoureterocele are important factors in planning and performing a TUI. These factors may be more predictive of the subsequent need for secondary surgery. The usual descriptive terms in the context of a ureterocele include effacement or flattening of the ureterocele with bladder filling; prolapse, which is movement of the ureterocele into the urethra; eversion; diverticulum-like protrusion of the bladder base and trigone with filling and voiding (Fig. 121–20); and intussusception, or protrusion of the ureterocele into its ureter (Fig. 121–21).

Figure 121–20

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