Duplex kidneys, ureteroceles and ectopic ureters

AK Taghizadeh
Consultant Paediatric Urologist
Evelina Children’s Hospital
London SE1 7EH

 

 

 

 

Introduction

Duplex kidneys are a relatively common abnormality.  Duplex kidneys may be associated with ureterocele, ectopic ureter insertion or vesicoureteric reflux (VUR).  This chapter will discuss the terminology, incidence, embryology and pathophysiology of duplex kidneys. The management of reflux into duplex kidneys, ectopic ureters and ureteroceles will then be discussed.

Single system ectopic ureters and single system ureteroceles are distinct entities from those seen in duplex kidneys.  For convenience discussion of the management of these conditions will be included in this chapter.

Terminology

The terminology surrounding duplex kidneys has been conflicting.  A standardized terminology was drawn up in 1984 by the American Academy of Pediatrics (AAP), and this has been widely adopted (1):
A duplex kidney has two separate pelvicalyceal systems.
A duplex or duplicated system describes a renal unit in which the kidney has two pelvicalyceal systems.  It may include a kidney with single or bifid ureters or two ureters that drain separately into the bladder.
A bifid system has two pelvicalyceal systems that join at the pelviureteric junction or two ureters (bifid ureters) joining before entering the bladder.  This represents a partial duplication.
Double Ureters are independent ureters that drain separately into the urinary or genital tract, and are seen in complete duplication.
Complete Duplication occurs when there are double ureters draining separately.
The upper (or lower) pole ureter is the ureter that drains the upper (or lower) pole of a duplex kidney.
An ectopic ureter is one that drains to an abnormal site.  The term is often applied to a caudal ectopic ureter, which is one where the orifice lies at the proximal lip of the bladder neck or beyond.
An intravesical ureterocele is one that lies entirely within the bladder.  It may also occur with a single system.
An ectopic ureterocele is one where some portion of the ureterocele is situated permanently at the bladder neck or in the urethra.

Incidence

The incidence of duplex kidneys in post-mortem series is between 0.5-1.25% (2-4).

Duplex kidneys were identified in 1.8% of intravenous urograms performed in 5196 patients.  In 69 (73%) of these patients the duplex kidney was considered to be an incidental finding (5). In this group, 30% of the duplex systems were complete duplex systems.  The incidence of duplex kidneys is similar for left and right sides. Duplex kidneys are seen approximately twice as frequently in females as males (4;5).  Duplex kidneys are bilateral in approximately one fifth.

The number of antenatally detected cases is lower than the incidence observed in autopsy or radiology series.  In a series of 19,750 women having antenatal scans, 13 foetus were identified with what was later confirmed as duplex kidney yielding an incidence of 0.6% (6), which the authors thought was an overestimate due to tertiary referral of complex kidneys.  In 6,292 pregnant women scanned by 28 weeks a 0.04% incidence of duplex kidney was identified (7).

There appears to be a strong genetic predisposition.  In those with duplex kidneys, up to 30% have relatives with compete duplex kidneys and two thirds with bifid systems, suggesting autosomal dominant inheritance with variable expression and incomplete penetrance (8-10).

Embryology

The kidney is formed when the ureteric bud, arising from the mesonephric duct, meets the metanephros, and by a process of reciprocal induction brings about the formation of the kidney.  The distal part of the ureteric bud eventually incorporates into the bladder to from the trigone.  At the cranial end branching of the ureteric bud gives rise to the ureter, renal pelvis, calyces and collecting ducts.  Premature branching of the ureteric bud results in an incomplete duplex with ureters that meet before the bladder, or a bifid renal pelvis.  If more than one bud develops and migrates to the metanephros a duplex kidney with two separate ureters forms.  Initially the more cranial ureteric bud connects to the upper pole.  However as the ureteric bud incorporates into the bladder, the upper pole ureteric bud rotates and migrates more caudally than the lower pole ureteric bud.  This results in the upper pole ureter having an opening that is more caudal than the lower pole ureter: an observation initially made by Weigert (11) and then independently by Meyer (12).  This is the Meyer Weigert Law.

The origin of the ureteric bud on the mesonephric duct is important for how well the kidney develops.  A bud that originates from the “normal” zone of the mesonephric duct will strike the metanephros correctly and result in good renal development.  However if the bud origin deviates from the normal zone, either too cranially or too caudally, it does not meet the metanephros properly and a poorly-formed, dysplastic renal segment results (13).  Thus the more abnormally sited a ureteric orifice the greater the likelihood that the associated kidney pole of the duplex kidney will be abnormal and poorly functioning.

The cranial ureteric bud, which meets the upper moiety of the duplex, will migrate more caudally.  Ultimately its position will be more medial and caudal than a normally situated ureteric orifice.  This can result in a ureter that may insert into the urogenital canal or mesonephric duct structures.  In boys, this would include the bladder, the prostatic urethra or the structures derived from the mesonephric duct: ejaculatory duct, seminal vesicle, vas deferens, epididymis.  These structures all lie above the external urethral sphincter, and so will not cause incontinence.  In girls, the ureter may insert into urogenital canal structures: bladder, urethra or distal vagina.  The mesonephric duct regresses in girls leaving epoöphoron, paraoöphoron or Gartner’s cyst.  Insertion of the ureteric bud into these structures may result in rupture through into adjacent paramesonphric duct structures resulting in ureteric insertion into the Fallopian tube, uterus or upper vagina.  In girls therefore, an ectopic ureter can result in continuous urinary incontinence.

A ureterocele is a ballooning of the terminal ureter as it enters the bladder.  The embryology of ureteroceles is not as neatly explained and there are several theories.  Persistence of a thin membrane of opposing urogenital and ureteric epithelium at the insertion of the ureter into the bladder may provide an explanation for obstructive ureteroceles (14).  This does not explain the existence of ureteroceles with large or non-obstructed openings.  Perhaps independently of obstruction, there may be an abnormality of collagen or muscle in the wall of the ureterocele (15;16).  Another possibility is late arrival or the ureteric bud into the bladder allowing the ampullary origin of the ureteric bud to over-expand even before it has reached the bladder (17).

The development of a caecoureterocele requires a more complex explanation.  It is possible that the distal ureter is affected by growth stimuli of adjacent structures.  Stimulation of growth of the ureteric bud causes enlargement of the distal ureter and its opening.  Further expansion of the ureter is brought about by the stimulus that causes bladder enlargement. Finally, a tongue of this part of the ureter is carried distally by the caudal migration of the Műllerian bulbs (18).

Pathophysiology

At first appearance the subject of duplex kidneys appears complex and daunting.  However most of the clinical problems relate to the way the ureters insert into the bladder.  It is worth repeating that the ureter from the upper pole of a duplex kidney will have a more distal/ medial insertion into the bladder than the ureter from the lower pole.  The ureter from the lower pole can either have a normal insertion or it can be associated with vesicoureteral reflux (VUR). The ureter from the upper pole can have a normal insertion, insert ectopically, or it may be associated with an ureterocele.  Reflux, ectopic ureters and ureteroceles will be discussed in more detail below. 

Although the lower pole ureter is most commonly affected by reflux, it can sometimes be affected by obstruction.  This may occur as a result of compression from a abnormal dilated upper pole ureter (18).  Duplex kidneys are susceptible to other pathologies; for example, pelviureteric junction obstruction can affect the lower pole in up to 2% (19).

The parenchyma of a duplex kidney is not distributed equally between the two poles (Figure 1).

  In an IVU series, normal kidneys were observed to have a mean of 9.4 calyces whilst duplex kidneys had 11.3 calyces; the upper pole having 3.7 calyces and the lower pole 7.6 calyces (5).  In general, the upper pole thus contributes about a third to the overall mass of renal parenchyma.

Vesicoureteric reflux in duplex kidneys

In general, the lower pole ureter of a complete duplex inserts more laterally into the bladder and will have a shorter and less oblique intramural course through the bladder wall than a normal ureter.  This makes it more prone to reflux.

Reflux is a common finding in those with duplex kidneys.  In one retrospective series of 24 patients with duplex kidneys who had a micturating cystogram, 15 (36%) were identified as having reflux (5).  In a series of children under the age of six years presenting with UTI, 23 of 35 (66%) with complete duplex systems had VUR, grade III-V in 19 (54%).  In the same series, 106 of 406 (26%) children with simplex kidney systems had VUR, 48% grade III-V (20).  Even incomplete duplex systems seem to be associated with an increased incidence of VUR, with 17 of 36 (47%) systems affected eight with grade III-V reflux.  In another study of girls presenting with UTI, 25 of 36 (69%) with complete duplex systems were found to have reflux (21): in 72% reflux was to the lower pole only, to upper and lower poles in 20%, and 8% of reflux was to the upper pole only.  In 18 partial duplex kidneys VUR occurred in four (22%).  These figures are similar to a 76% incidence of reflux in complete renal duplication detected by Fehrenbaker in a series of children presenting with UTI (22). 

Lower pole VUR in duplex kidneys most commonly presents with UTI, with only a minority presenting on antenatal scans (23).  If the lower moiety kidney is dysplastic or scarred, hypertension is another way the lower pole reflux may come to urological attention.  Pain is an unusual presentation and other causes of loin pain should be looked for.

Investigation by ultrasound may show a dilated lower pole or dilated ureter (see Figure 2). 

In infants, a micturating cystogram gives accurate information about the anatomy of the reflux.  A Dimercaptosuccinic acid (DMSA) radionucleotide scan provides information about the function of the affected pole, and information about focal scarring (see Figure 3).

   The natural history of VUR in duplex kidneys is one of spontaneous resolution in a large proportion.  Rates of spontaneous resolution of VUR of 58% have been observed in those treated non-surgically (24). Spontaneous resolution of VUR in complete duplex kidneys is comparable to single kidneys (26), with 85% resolution of grade I-II and 36% resolution for grade III (25). However a more recent study found that when higher grades of reflux are included in the comparison the rate of spontaneous resolution is not as good (23).  Only 7% of grade III VUR in duplex kidneys resolved, and none of the higher grades of VUR resolved over a mean follow-up of three and a half years.

The anatomy of the insertion of a refluxing lower pole ureter will make surgery more difficult.  Therefore when formulating a management plan for a patient with a duplex kidney, it is especially important to be clear about the goal of treatment before embarking on a surgical plan.  It is not appropriate to treat reflux in a duplex kidney simply because it is there.  Indications for surgery for VUR in duplex kidneys are similar to those for reflux into single systems: failure of medical therapy to control pyrexial infections, or to prevent new scars.

A robust treatment of a refluxing duplex ureter is to re-implant it.  Doing this necessitates that the lower pole and upper pole ureters are mobilized together in their common sheath and re-implanted together (27).  A range of common-sheath intravesical re-implantations techniques in a series of 48 duplex renal units produced a 96% success rate in curing reflux (28).  More recently there has been interest in extravesical detrusorrhaphy, which has the benefit of avoiding cystostomy.  Success rates of 98% have been reported in a series of 51 units (29), or 95% in at series of 65 units (30).  The procedure carries a risk of urinary retention, with 5% of children requiring a further two weeks of an indwelling urinary catheter and one patient requiring 6 weeks of intermittent catheterization (30).

Recently, there has been a interest in performing ureteric re-implants laparoscopically or more accurately vesicoscopically (31;32).  Two series demonstrate that it is technically possible to perform the procedure in duplex kidneys.  However, at the time of writing, the long-term success of vesicoscopic ureteric re-implantation in patients with duplex kidneys has yet to be reported.

Uretero-ureterostomy is an alternative treatment.  The diseased donor ureter is disconnected and anastomosed to the recipient ureter lying alongside.  In the treatment of VUR, the advantages of this procedure are that there is no need to open the bladder, nor to perform ureteric tapering if the ureter is very dilated. Uretero-ureterostomy was originally described by Buchtel (33).  The indications for uretero-ureterostomy extend beyond lower pole reflux to include treatment of ureters that are ectopic, associated with an ureterocele or have upper pole reflux.  Published success rates are impressive (34-39).  Potential complications include obstruction at the site of the anastomosis, yo-yo reflux through the anastomosis, or reflux into the retained ureteric stump.  There has been renewed interest in the technique with the application of laparoscopic techniques either to make a distal ureteric anastomosis (40), or a more proximal anastomosis (41).

Endoscopic injection therapy to treat reflux is now widespread for single system kidneys.  Initial concern about applying this method to ureters, with a significant co-existing anatomical abnormality such as a duplex ureter, seemed to be borne out by an early meta-analysis giving injection therapy a 50% success rate for duplex kidneys compared to 73% in single system kidneys.  However a more recent review, which included a greater number of studies looking at duplex kidneys, gave injection therapy a much better account (42).  This meta-analysis of injection treatment for reflux gave a success rate of 64% for duplex kidneys and 68% for single system kidneys, with no statistically significant difference between the two groups.

Where the lower pole of the duplex kidney is beyond salvage, its removal by hemi-nephrectomy is advocated (43;44).  Removal of the lower pole can be slightly more difficult than an upper pole hemi-nephrectomy as the lower pole nests into the upper pole and so is trickier to separate.  It can be difficult to access the most distal ureter from the approach required to perform a lower pole hemi-nephrectomy, so that a second incision may be required to completely remove the lower pole ureter.  Fortunately reflux into the ureteric stump is not often a problem and a subsequent stump ureterectomy is required in less than 5% (45;46).  A drop in differential function of the remaining renal moiety of about 6% following hemi-nephrectomy has been reported (47).  It is not certain whether this represent a true drop or is the effect of the way regions of interest are drawn on renograms. 

Hemi-nephrectomy is increasingly performed laparoscopically or retroperitonoscopically.  These procedures are challenging, although outcomes equivalent to open surgery are reported (48-51). Urinary cysts and loss of function of the remaining moiety are complications that have been described with an incidence as high as 9% (49).

Ectopic ureters in duplex kidneys

Ectopic ureters are a relatively uncommon problem relating to duplex kidneys.  In one series of children whose duplex kidneys were detected after presentation with UTI only one out of 35 (3%) was found to have had an ectopic ureter (20).

The problems caused by ectopic ureters relate to the way they insert into the genitourinary tract.  In girls, ectopic ureters that drain below the level of the sphincter will result in continuous urinary incontinence.  In boys, low ectopic insertion will result in the ureter draining into a mesonephric duct structure: ejaculatory duct, seminal vesicle, vas deferens or epididymis.  Drainage into these structures may result in recurrent epididymo-orchitis.  Ectopic insertion of ureters outside the bladder may result in impaired drainage, is associated with dilation and urinary tract infection.

Identifying the presence of an ectopic ureter associated with a duplex kidney can be difficult.  This relates to the original embryology of the ectopic ureter and the position of origin of the ureteric bud giving rise to the ectopic ureter.  The further the origin of the ectopic ureter bud from the normal zone, the greater the likelihood of impaired function and dysplasia of the related renal moeity (13).  In practice, this means that the upper pole of a duplex kidney with an ectopic ureter may be very small and poorly functioning.  Its small size makes it difficult to identify on morphological imaging, whilst its poor function means that when functional imaging is performed there is minimal uptake of tracer or contrast (52).  Finding the opening to an ectopic ureter at cystoscopy or vaginoscopy may be difficult.  It is therefore easy to understand the origin of the term “cryptic duplex” in relation to ectopic ureters.  Identification of a duplex kidney with an ectopic ureter requires a high index of suspicion from the outset (52;53).

Clinical examination of a girl with an ectopic ureter may identify continuous dripping of urine from the introitus.  There may be perineal irritation from continuous leaking.  It is sometimes possible to identify continuous leaking by asking the girl to sit directly on the paper towel covering an examination couch.  After a few minutes the leaking will be confirmed by an area of wetness on the paper. 

Renal ultrasound and antenatal scanning may provide a clue about the presence of an ectopic ureter if there is dilation of the ectopic ureter or its upper pole kidney.

In the past, intravenous urograms helped diagnose ectopic ureters.  The upper pole does not effectively excrete contrast during the study, so its presence is alluded to by the absence of the upper pole calyces.  A pelvicalyceal pattern described as the “drooping lily” is seen, with the ureter, pelvis and lower pole calyces opacifying (Figure1).  Further clues are provided by a smaller number of calyces than expected and the abnormal axis of the visualised pelvicalyceal system. Today, intravenous urograms are now so rarely performed in children that the skills required to identify these subtle changes are probably not adequately practiced in most radiology departments.

CT scanning with contrast has been suggested as a possible investigation to successfully identify duplex kidneys with ectopic ureters (55). Magnetic resonance imaging (MRI) is probably a more useful test where a suspected upper pole of a potential duplex kidney has been hard to identify.  It can pick up 10% more duplex kidneys than ultrasound (56-58).  Even so, careful image acquisition and interpretation are required to maximize sensitivity.  Allowing a delay for the upper pole to take up contrast may enhance the sensitivity of the MRI scan.

A reflection of how difficult it can be to identify ectopic ureters is the number of tests that have been suggested to help secure the diagnosis.  Intravenous administration of indigo carmine (59) or bladder instillation of methylene blue have been suggested as methods to identify ectopic ureters by differential staining of urine from the ectopic and normal urinary tracts.  Careful targeted cystoscopy and vaginoscopy may locate an ectopic ureteric opening, but identification can be difficult and the opening easily missed (52).

Ectopic ureters inserting into the urinary tract are frequently associated with reflux observed on micturating cystogram.  A ureter placed above the sphincter will demonstrate the reflux during filling; a ureter placed below the sphincter will demonstrate reflux during voiding (54).

Treatment of a symptomatic ectopic ureter requires surgery.  The upper pole kidney associated with an ectopic ureter is usually poorly functioning and so is appropriately treated by upper pole hemi-nephrectomy (60;61).  Retaining the distal ureteric stump carries a less than 10%  chance of re-operation for distal ureteric removal, whilst reducing the morbidity from a complete ureterectomy (62;63).  Laparoscopic methods have been applied to hemi-nephrectomy (48;49;51;64).  As with lower pole hemi-nephrectomy the laparoscopic procedure is challenging, with risks of retroperitoneal fluid collection, loss of renal tissue and hypertension.

Where upper pole function is preserved, an alternative to hemi-nephrectomy is ureteric re-implantation.  In this case, both ureters from the duplex kidney should be re-implanted together.  Re-implantation, however, can be avoided by draining the upper pole into the lower pole system either with an uretero-ureterostomy or a uretero-pyelostomy (65). Today, laparoscopy has progressed to such reconstruction, and both laparoscopic uretero-ureterostomy and uretero-pyelostomy are described (41;66).

Ureterocele

Describing ureteroceles as obstructive does not give an adequate account of the differences in how they behave.  The AAP classification of ureteroceles (1), which distinguishes intravesical and ectopic ureteroceles, has the advantage of being simple and is widely used.  Another classification regularly encountered in the literature was developed by Stephens et al (18).  This classification is described below and includes differences in the way that ureteroceles act:

Stenotic

This is the most common type of ureterocele.  The ureterocele lies within the bladder. Its orifice lies within the trigone and is obstructive. It corresponds to an intravesical ureterocele.

Sphincteric

In this form of ureterocele, a rather dilated ureter courses through the submucosa of the bladder, and adopts a more normal calibre as it travels into the urethra. It has an opening at the level of the sphincter.  Its orifice is not narrow, but drainage from the ureterocele is impaired by contraction of the sphincter. The associated ureterocele can be very large.

Sphincterostenotic

Here the ureterocele has an orifice that is at the level of the sphincter.  Its narrow orifice further impedes its drainage so that the ureterocele remains inflated and obstructs the bladder outlet.

Blind

This form of ureterocele extends under the trigone and into the bladder outlet. No opening is identifiable.  The dilated ureterocele can cause severe bladder outlet obstruction.

Non-obstructive

This type of ureterocele lies entirely within the bladder, and has a large opening which does not impede drainage of the ureterocele.

Caecoureterocele

This form of ureterocele extends submucosally into the urethra.  The orifice of the ureterocele lies more proximally either in the urethra or the bladder.  A “tongue” of submucosal ureterocele lies caudal to the opening.  If its opening is small, filling of the ureterocele may obstruct the bladder outlet.  If the ureterocele has a large opening (either naturally or iatrogenically) the tongue of the caecoureterocele will fill by reflux during voiding and may obstruct the urethra.

In a series of 60 ureteroceles: 40% were stenotic, one third sphincteric, 6% sphincterostenotic, 5% blind, 5% non-obstructive, and 5% a caecoureterocele (18).

Presentation

The incidence of ureterocele at post-mortem is 1 in 500-4,000 (67;68).  In patients who are identified as having duplex kidneys, 5-20% will be found to have ureteroceles (20;21).  The majority of ureteroceles used to present with urinary tract infection.  With improvement in antenatal scanning half to three quarters are detected antenatally (69-72).

It is common for ureteroceles to obstruct the upper pole of the affect kidney from which they have arisen (73).  It is possible for further obstruction to occur.  The lower pole ureter may be obstructed by the dilated upper pole ureter.  A ureterocele that obstructs the bladder outlet will affect the contralateral kidney as well.

Co-existing vesicoureteric reflux is common, affecting the ipsilateral lower pole in half, and the contralateral kidney in a quarter (74). Abnormal bladder function is common in children with ureterocele.  More than half will have abnormally large bladders, and residual volumes are common (75).  Stones have been observed in a large proportion of adult patients presenting with ureterocele (76).

Investigation

Investigation of a ureterocele is aimed at confirming its presence, describing its structure (intravesical or ectopic) and identifying coexisting pathology (e.g. VUR, lower pole and bladder outlet obstruction).

The ureterocele and its associated dilated ureter and upper pole are usually identified on ultrasound (see Figure 4).

  Care should be taken that a dilated distal ureter adjacent to a bladder is not mistaken for a ureterocele.  A ureterocele that is collapsed may be missed at the time of ultrasound scanning.  A careful ultrasound can give useful information about the extent of the ureterocele and the thickness of its posterior wall.

Micturating cystogram is an invaluable investigation in the patient with a ureterocele (see Figure 5).

  It identifies its size, and the relationship of the fundus and base of the ureterocele to the bladder neck and urethra, indicating possible bladder outlet obstruction. Additional baseline information about VUR is obtained.  Care should be taken that an everted ureterocele is not miss-identified as a paraureteric diverticulum (77). 

A Dimercaptosuccinic acid (DMSA) radionucleotide scan is useful to confirm poor function in the upper pole and also provides a baseline prior to surgery.

A combination of ultrasound and micturating cystogram can often distinguish intravesical from ectopic ureteroceles.  However this is not always possible, and cystoscopy may be required to make the distinction in up to a quarter (78).  When performing cystoscopy care must be taken not to obliterate the ureterocele; ideally the patient should be well hydrated, and irrigation flow kept to a minimum.

Treatment

Given the complexity and variation in the anatomy of ureteroceles, it is perhaps not surprising that there is no clear consensus on the management of ureteroceles.  The goals of treatment can be conflicting:  the aim of minimising damage from obstruction of the upper tract and the bladder, the desire to offer single or minimal treatments, the goal of avoiding iatrogenic problems such as new reflux or bladder outlet obstruction, and the desire to effect definite anatomical correction.  Thus there are several possible treatment approaches that can be offered to a patient with a ureterocele, with distinct recommendations made for intravesical and ectopic ureteroceles. Broadly, the treatment options range between conservative treatment, ureterocele puncture, upper pole hemi-nephrectomy and ureterocele excision with bladder neck repair and re-implantation.

Conservative treatment

Expectant management of antenatally detected ureteroceles may be a successful treatment avoiding potentially difficult surgery and its complications.  Leaving dysplastic renal tissue in situ may not pose an increased risk of hypertension (79). The main concern over expectant management of ureteroceles is the predisposition of an obstructed hydronephrotic kidney to infection.

Non-surgical treatment of ureteroceles was suggested by Rickwood et al (80).  They reported on the outcome of ureterocele treatment, and observed that a subgroup treated expectantly did very well.  This was subsequently elaborated on.  Patients with ureterocele with poorly functioning upper poles, and reflux of less than grade IV (making up 27% of their patients with ureterocele) did not develop infection or require surgery over a median follow up of 8 years, often with an improvement in hydronephrosis, or collapse of the ureterocele (81).

In a different series, 13 patients were selected for conservative treatment on the basis of non-obstruction on their mercapto-acetyl-triglycine (MAG3) scan and grade III or less VUR and followed for a median of four years (72). Only four required operation for break through infection or increasing dilation.  In those who were managed non-surgically, all VUR resolved.

Successful conservative treatment was also reported by Direnna and Leonard (82).  A select minority of their patients (with no lower pole or bladder neck obstruction, less than grade IV reflux, and upper poles that drained if they were functioning) had no infection and required no surgery after a median follow-up of five years.  In four patients the hydronephrosis improved and in one the ureterocele collapsed. Reflux improved or resolved in three out of four with lower pole reflux.

This approach can be successfully applied to ureteroceles associated with a multicystic dysplastic kidney (83), with only one UTI in a group of those being treated expectantly.

Sauvage et al, initially took a different stance (84). However, on assessing their outcomes from surgery for ureterocele, they were disappointed by their own operative results. They suggested that a period of careful observation might be useful in stratifying which patients actually require surgery and in which surgery can be altogether avoided.

Upper pole hemi-nephrectomy

This treatment strategy is sometimes referred to as a “simple treatment”. The upper pole of the kidney associated with a significant ureterocele usually has minimal function.  Removing the upper pole by hemi-nephrectomy will remove an obstructed system predisposed to urinary tract infection.  Removal, combined with suction of the distal ureter at the time of operation will also bring about collapse and decompression of the ureterocele.  Co-existing reflux to the lower pole is then expected to resolve in the majority (85).  However, Husmann et al found reflux was not solved by hemi-nephrectomy; 15% of those without  pre-existing reflux developed reflux, and reflux continued after hemi-nephrectomy in 84% of those with pre-existing reflux (86).

A significant advantage of hemi-nephrectomy is that difficult surgery at the bladder neck and distal ureter is avoided and re-operation is evaded in 85% (87;88).  Incontinence following hemi-nephrectomy has been reported in 6% (89).  Bladder dysfunction is probably an inherent problem associated with ureterocele and not related to hemi-nephrectomy.  Nevertheless, there is a concern that the simple approach may be associated with UTI, diverticula and even bladder outlet obstruction (90).

One group reports a success rate of 80% for the simple approach (70).  This is slightly worse than the re-operation rate for bladder neck reconstruction in the same study. However, the authors noted that reconstruction was associated with more severe complications. They therefore recommend the simple approach for the majority of patients in the absence of high grade reflux.

A further modification is to perform upper pole hemi-nephrectomy laparoscopically (91;92).  This is a technically difficult procedure even for an experienced laparoscopic surgeon.  Conversion to open is required in upto 12.5%, perirenal collections are seen in a fifth, and it is not yet clear if the re-operation rate is comparable to open hemi-nephrectomy.

Ureterocele puncture/endoscopic treatment

Endoscopic treatment of ureteroceles by puncture is a potentially very attractive solution.  Puncturing the ureterocele using cystoscopy is an operation with much lower perioperative morbidity than the alternatives of upper pole nephrectomy or bladder neck reconstruction.  It can almost be performed as day-case surgery.  An individual puncture carries only a 10-20% chance of repeat puncture being required (69;93;94).  It may even be possible that some upper pole function may be recovered.

Recovery of upper pole function following ureterocele puncture is often cited as a reason for performing ureterocele puncture (95).  One series of neonatal ureterocele puncture managed to produce a mean upper pole function of 8% (96).  However recovered function is likely to be limited if underlying poor function is because of dysplasia rather than obstruction (80;97-99), and histology studies often indicate dysplasia rather than inflammation to be the main feature in the upper pole.

The main criticism of ureterocele puncture as a treatment modality is the need for further surgery, despite adequate decompression.  In a meta-analysis of 912 patients undergoing endoscopic treatment of their ureteroceles 47% went on to have further surgery (100).  The chance of re-operation is higher when the ureterocele is ectopic compared to intravesical (relative risk 2.78), in a duplex system compared to a single system (relative risk 1.41) or if there is pre-existing reflux (relative risk 1.56).  With extended and longer term follow-up the re-operation rate can climb to 71% (69;101).

The most common indication for re-operation is VUR.  This can affect half the patients having a ureterocele puncture (94;95) and commonly affects the upper pole in about a third (102).  Ureterocele puncture can result in resolution of some pre-existing VUR (103).  Treatment of VUR following ureterocele puncture has usually been by reconstruction.  However, the minimally invasive approach of ureterocele puncture has been extended by some groups to the treatment of VUR, with success rates of 60-70% reported for cystoscopic injection therapy (103-105).

Antenatal diagnosis of ureteroceles opens the possibility of antenatal intervention for ureteroceles.  Puncture of ureterocele may be considered in utero where there are features of bladder outlet obstruction, for example where there is oligo- or anhydramnios.  There are case reports of successful foetal intervention (106-110), but results of larger case series and longer follow-up are awaited.

Puncture should not be regarded as a universal treatment for ureterocele but should have a defined role.  For the child presenting with an acute infection it can provide emergency relief of obstruction (70;86).  Puncture has a high success rate for intravesical ureteroceles, and for these puncture can be offered as a definitive treatment (100;111-114).  For ectopic ureteroceles, a high rate of re-operation should be expected.  Here, ureterocele puncture should be viewed as part of a staged procedure: either making subsequent reconstructive surgery easier (69;115), or enabling VUR to be controlled cystoscopically (103-105).

Bladder neck reconstruction

The intent of bladder neck reconstruction in the management of ureterocele is correcting the anatomical abnormalities that are encountered with ureteroceles.  It may include all or part of the following:  excision of the ureterocele, repairing the weakness of the bladder neck and bladder wall, re-implantation of the associated ureters, and hemi-nephrectomy of a poorly functioning upper pole.  Marsupialisation of the ureterocele, rather than its complete excision, may be performed to avoid difficult dissection in the urethra (116).  The benefit of reconstruction is that the functional problems associated with the ureterocele can all be corrected: VUR, sphincter weakness, and bladder outlet obstruction from the ureterocele, primarily or iatrogenically created (90). 

Reconstruction may be offered as either the primary or secondary treatment.  Reconstruction surgery is difficult, especially when performed on a young infant.  In early life the risk of UTI is a particular concern, and so ureterocele puncture may be performed to control this early risk.  Reconstruction can then be performed at an age when reconstruction surgery is easier. Alternatively reconstruction has been performed as a primary procedure with good effect.  Excellent results were reported in a group of 16 patients undergoing primary repair with a mean follow up of more than five years (115). In a series of 40 patients with ectopic ureterocele reported by De Jong et al (78), all underwent upper pole hemi-nephrectomy, ureterocele excision, bladder neck reconstruction, re-implantation and even colposuspension at a single operation.  All children became clinically continent, although many children had a tendency to void infrequently, five requiring biofeedback because of bladder-sphincter dysfunction, three requiring temporary intermittent catheterization.  The same group reported longer term follow up of similar patients (117). After a median follow-up of 9 years, 31% of patients who were treated with primary bladder surgery required re-operation. Re-operation was performed endoscopically in all, either for reflux or obstructive voiding.  Incontinence was seen in 7%, and 20% had dysfunctional voiding requiring bio-feedback. 

A more sanguine view of reconstruction is provided by others.  One series reported a success rate of 83% for primary reconstruction, but the authors warned of the possibility of major complications for this difficult surgery (70).  In another a series of girls undergoing reconstruction for bilateral ureterocele, 70% had significant post-operative residuals and a fifth needed to perform intermittent catheterization (118).  Another group reported a 20% incidence of UTI following reconstruction, and a 13% incidence of bladder dysfunction (119).

Uretero-ureterostomy

Connecting the drainage of the upper pole ureter to the lower pole is another technique that can be applied to children with ureterocele.  Anastomozing one ureter to the other less diseased ureter is relatively simple and may avoid problems of ureterocele excision and bladder neck reconstruction (38;120;121).  This is a procedure which carries less morbidity than hemi-nephrectomy or reconstruction.  A 91% success rate for the treatment of ureteroceles has been reported, with a patent anastomosis, and without reflux or obstruction (38).  Another series reported success after two year follow up in eight children with ureterocele but no reflux (121).  

Uretero-ureterostomy may be combined with ureteric re-implantation of the less dilated ureter with good outcome (39).

One of the advantages of uretero-ureterostomy is that it can be performed through a small incision.  However, even this morbidity may be reduced by performing the operation laparoscopically (40;41).

In conclusion, no single procedure provides a universal treatment for all ureteroceles.  A few generalisations may be made: ureterocele puncture is appropriate for emergency decompression of acutely infected systems and for intravesical ureteroceles; upper pole hemi-nephrectomy carries a good success rate where there is no associated reflux.  Even so, the treatment for ureteroceles should be tailored to the individual patient.

Single system ureterocele

A fifth of all ureteroceles occur in single systems, as opposed to duplex systems (122;123).  Single system ureteroceles are most commonly intravesical and the associated kidneys often have reasonable function.  The majority of single system ureteroceles presenting in childhood are detected antenatally (124).

Investigation should begin with a renal ultrasound.  Hydronephrosis may be absent in up to two thirds (125).  They can often be small and missed. Vesicoureteric reflux into the ureterocele is not seen (124;125).  MAG3 scanning is useful to quantify function in the affected kidneys, and to provide information about drainage of the affected system.

If there is no obstruction or reflux of the affected kidney then non-surgical treatment is appropriate (82) and good outcomes should be expected from conservative treatment  If the ureterocele impairs the drainage of an affected kidney then surgery is indicated. Transurethral puncture or incision of the ureterocele is much more likely to be successful in simplex system ureteroceles than in duplex kidneys.  Re-operation rates for ureteroceles in single systems are low, with rates of 0-25% quoted (95;112;113;126).

Single system ectopic ureter

About one fifth of ectopic ureters are associated with single system kidneys (127).  Some report that they are more common in boys (128-130), others that there is a female preponderance in India and Japan (131;132), and yet others found an equal distribution in boys and girls (133).

Single system ectopic ureters are frequently associated with other congenital problems, including anorectal, oesophageal and renal tract anomalies (128;129;133).  About half of those with single system ectopic ureters present during investigation of other anomalies, the remainder with either incontinence or infection. 

Renal dysplasia is common.  However, unlike duplex ectopic ureters, single system ectopic ureters are associated with kidneys with reasonable function.  For example, in one series of single system ectopic ureters, three-quarters of the kidneys were worth preserving (132).  Another series found that five out of twelve kidneys associated with single ectopic ureters were dysplastic, and two out of the twelve kidneys were absent (134).

Diagnosis of single system ectopic ureters can prove difficult.  On micturating cystogram, reflux can be demonstrated in only half (128). Initial cystoscopy can fail to identify the ectopic ureter in two-thirds (134).

Bilateral ectopic ureter

Bilateral ectopic ureters are a rare and distinct malformation affecting girls (133). Neither ureter drains into the bladder which is small with a poorly developed sphincter.  It is possible that during development the abnormal origin of both ureteric bud results in poor mesenchymal induction of the urogenital structures.  This results in failure of normal development of the bladder and the bladder neck.  Both the sphincter and reservoir functions of the bladder are severely effected (135;136).  Thus although the child may present with incontinence, ureteric re-implantation will fail to correct the incontinence (137).  One review of the literature back to 1937 found that despite surgery only 20% became continent (138).

Achieving continence requires ureteric re-implantation, improvement of bladder storage and improvement in bladder outlet resistance.  Ureteric re-implantation is difficult because of the small bladder size.  Creation of a window between a distal ureter and the bladder may, by allowing bladder cycling, allow reasonable bladder capacity to develop and possibly avoid the need for bladder outlet procedures and augmentation (119;139) .  Bladder capacity may be improved with enterocystoplasty.  A variety of bladder outlet procedures have been described in this context: Young-

Dees-Leadbetter bladder neck reconstruction (140), Kropp procedure, pubovaginal sling (136), bladder neck closure (141), and artificial urinary sphincter (142;143).

Legend to Figures

Figure 1: Intravenous urogram of an uncomplicated right duplex kidney.

Note that the majority of the calyces belong to the lower pole.  In a situation where the upper pole is non-functioning and dilated, one can imagine that the lower pole calyces are displaced inferiorly and laterally giving the appearance of a “drooping lily”.

Figure 2: Ultrasound showing a dilated lower pole of a duplex kidney

Figure 3: DMSA scan showing a poorly function lower pole of a left duplex kidney

Figure 4: Ultrasound scan showing a ureterocele in the bladder

Note that in this case the urine in the bladder is more echogenic than that in the ureterocele, implying poor bladder emptying.

Figure 5: Micturating cystogram showing an ectopic ureterocele

Note the ureterocele extending into the urethra and the associated reflux into the dilated lower pole ureter.

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