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CHAPTER32
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Vesico-ureteric Reflux (VUR)
CASE 1
Melanie is a 5-year-old girl who presents with a history of
recurrent urinary tract infection.
Q
1.1 Which further investigations should be performed?
1.2 What are the pros and cons of the micturating
Q
cystourethrogram?
Q
1.3 Are there any alternatives to the micturating
cystourethrogram?
Vesico-ureteric reflux (VUR) – the retrograde passage
of urine from the bladder up the ureter – is the most
common abnormality detected in children with a UTI.
It is found in up to a third of all children presenting
with a UTI and in greater than 50% of those less than
1 year old. Frequent and complete micturition protects against UTI by flushing the urinary tract and
removing any bacteria. Children with reflux do not
empty completely and are therefore at risk of UTI.
Furthermore, reflux allows transfer of bacteria from
the bladder to the kidney, with the risk of developing
pyelonephritis and renal scarring.
Incidence
Micturating cystourethrogram (MCUG) demonstrates
VUR in 1–2% of healthy children, although it is an
active and intermittent phenomenon and may be
missed in 15% of studies [Table32.1]. VUR is five
times more common in girls than boys and is up to
50times more common in siblings of children with
reflux.
CASE 2
A 1-year-old child with severe right-sided VUR and recurrent
urinary tract infection (UTI) is found to have reux nephropathy
with defects in the upper and lower poles of the right kidney.
Q 2.1 Is reux nephropathy congenital or acquired?
2.2 If the recurrent urinary tract infections are kept under
Q
control, will further renal damage occur?
Q
2.3 What are the indications for corrective surgery?
Pathogenesis
VUR may be a primary, congenital anomaly or secondary
to abnormal bladder function, which may itself be congenital or acquired.
Primary VUR is due to a failure of the one-way valve
at the vesico-ureteric junction. The normal ureter runs
inside the bladder muscle and under the epithelium for
some distance before opening into the bladder cavity.
This part of the ureter, known as the submucosal tunnel
or intramural ureter, is compressed against the muscular
bladder wall by the increased intravesical pressure
associated with bladder filling or micturition. If the submucosal tunnel length is too short, then the ureter may
not be adequately compressed to prevent reflux. It is the
increasing length of this submucosal ureter with growth
that is responsible for spontaneous resolution of low
grades of VUR with age.
Secondary VUR describes reflux due to impaired
bladder outflow. This impairment to outflow with a
subsequent increase in intravesical pressure may result
from physical or functional impediments to bladder
emptying. Congenital anatomical causes of secondary
Jones’ Clinical Paediatric Surgery, Seventh Edition. Edited by John M. Hutson, Michael O’Brien, Spencer W. Beasley,
Warwick J. Teague and Sebastian K. King.
© 2015 John Wiley & Sons, Ltd. Published 2015 by John Wiley & Sons, Ltd.
197
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Table 32.1 International Reflux Study Committee definitions
of grades of VUR, percentage incidence of each grade together
with likelihood of spontaneous resolution
Grade Definition Percentage
incidence
I Reflux into ureter only 7 83
II Non-dilating reflux to the
level of renal calyces
III Mild to moderate calyceal
dilatation with minimal
blunting of calyces
IV Moderate dilatation with
loss of forniceal angles
but preservation
of papillary impressions
V Gross dilatation and
tortuosity
Spontaneous
resolution
53 60
32 46
6 9
2 0
VUR include posterior urethral valve and neuropathic
bladder in patients with spina bifida. VUR may develop
secondary to voiding dysfunction seen in older girls or
in patients with dysfunctional elimination syndrome, hence
the association of VUR and constipation.
Consequences
The detection of reflux per se is of little significance;
rather, it is the consequences of its presence that matter.
It used to be thought that there was a clear association
between VUR, UTI and renal scarring, but in recent years,
the margins have become blurred (see Chapter 31 –
UTI). We now know that renal dysplasia can exist prior
to any infection, that sterile reflux does not produce
scars and that pyelonephritis can cause scarring in the
absence of reflux. In children found to have VUR after a
UTI, static isotope renography (e.g. DMSA scan) reveals
photopenic areas
in 25–40%. Some of these scars will not be due to infection but rather represent congenital renal dysplasia.
Fifteen to thirty percent of infants born with antenatally
suspected VUR (based on ultrasonographic findings) will
have isotope evidence of renal dysplasia antenatally,
usually in the form of a global reduction in renal size.By
contrast, infective renal scarring tends to result in focal
areas of renal damage, usually at the poles of the kidney
where the renal papillae are most susceptible to reflux.
Some patients with renal scarring, regardless of the aeti-
ology, will develop hypertension. Raised blood pressure has
suggestive of inflammation or scarring
been found in about 15% of patients with VUR, UTI and
dysmorphic kidneys. Reflux nephropathy is responsible for
paediatric end-stage renal failure in about 22% of patients.
Presentation
Urinary tract infection
VUR is found in 30–50% of children presenting with a
symptomatic UTI (see Chapter31 – UTI).
Antenatal diagnosis
There is no accepted ultrasonographic definition ofantenatal hydronephrosis (ANH), but we would investigate all
infants in whom the anterior–posterior (AP) diameter of
the renal pelvis is 5
mm or more. VUR is detected postnatally in 10% of all neonates with ANH and is more likely
when the AP diameter isless than 15 mm; more severe
ANH tends to be associated with anatomical obstruction.
Postnatal confirmation of ANH is undertaken with an
ultrasound scan within the first week of life (and again at
6 weeks of age). If hydronephrosis is confirmed, then an
MCUGs is done to look for VUR (as well as to exclude
urethral obstruction caused by posterior urethral valve).
Interestingly, 25% of babies with normal postnatal ultrasound scans have reflux on MCUG, but mostly, this is of
no consequence.
The diagnosis of reflux on an MCUGs at this early
stage, before the development of UTI, enables
administration of prophylactic antibiotics, which, it is
hoped, by preventing reflux of infected urine will limit
renal scarring. There is some evidence that long-term
prophylactic antibiotics prevent recurrent UTIs but no
evidence that renal scarring is reduced. So, while it is
uncertain whether prophylactic antibiotics will reduce
the long-term risks of scarring, hypertension and renal
failure, the benefits of UTI reduction in infants are worthwhile, especially as these children are often hospitalised.
Family history
VUR has been found in a quarter to a half of siblings of
children with VUR. Given the current debate regarding
the significance of VUR, investigation of asymptomatic
siblings is even more controversial. There is some
evidence that a normal renal ultrasound scan obviates
Chapter32: Vesico-ureteric Reflux (VUR) 199
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further testing. VUR, if present, is likely to be low grade,
and in these patients, the benefit of prophylactic antibiotics has not been proven.
Diagnosis
There are no clinical symptoms or signs specific to VUR;
it can be diagnosed only by special investigations.
Lower tract studies
The MCUGs or MCUs is the gold-standard test for the
diagnosis of VUR [Fig.32.1]. The bladder is catheterised
and filled with x-ray contrast, and the child is then screened
while voiding. Although invasive and uncomfortable, as
well as documenting the presence of reflux, MCUGs
allows the severity of VUR to be graded [Table32.1] –
which has implications for prognosis and potential
spontaneous resolution – and provides detailed anatomical information about the bladder and urethra. Because
of the discomfort associated with urethral catheterisation and the risk of causing a UTI, MCUGs should not be
requested in every patient. Some factors to consider
when deciding on whom to order an MCUGs include:
1 Age: Urethral catheterisation is easier and the diagnosis
more important in infants less than 12 months of age.
2 Recurrent UTI: A child with recurrent UTIs proven on
urine culture should have an MCUGs to check for VUR
or other associated anomalies. The zeal with which an
MCUGs is sought will depend on the age of the child as
VUR is probably less significant in older children in
terms of further management.
3 First UTI: A child who has one documented UTI
should have an MCUGs if the child (a) is under 12
months of age; (b) has clinical or sonographic evidence of pyelonephritis; (c) has abnormalities, for
example, hydronephrosis, scarring, duplex on ultrasonography; and (d) there is a strong family history of
urinary tract abnormalities (controversial).
If the patient is due for an examination under anaesthetic
(e.g. cystoscopy) anyway, then a catheter can be inserted
under GA and the MCUGs carried out later the same day.
If clinician or parental concerns relate to the use of
radiation to the gonadal region, then a direct isotope
cystogram can be performed. This test also involves
urethral catheterisation and bladder instillation with a
radioisotope. This test will allow for a longer period of
assessment, making the detection of VUR more likely,
but does not enable accurate classification.
The indirect isotope cystogram avoids the need for
urethral catheterisation by extending the dynamic
renogram using either DTPA or MAG-3 isotope, which
having passed through the kidneys accumulates in the
bladder and may indicate the presence of VUR by showing a second increase in radioactivity with the renal
region of interest.
Figure 32.1 Bilateral Grade 1 VUR shown on MCUG. The
contrast in the lower ureters is arrowed. There is a high
chance that reflux of this grade will resolve spontaneously.
Upper tract studies
The performance of investigations to examine the upper
tracts is less controversial. Routine renal ultrasonography
is a well-tolerated, non-toxic, inexpensive investigation
that can be repeated periodically to assess renal growth
and scar progression.
Isotope renography, though more invasive, provides a
more accurate assessment of the presence of renal scars,
differential renal function and indirectly VUR.
Timing of investigations
Ultrasonography can be performed at any stage, potentially detecting pyelonephritis early or scars late in the
clinical course of infection. The MCUG, if undertaken, is
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usually delayed until the UTI has resolved, as VUR may be
more likely to cause a UTI. The MCUGs is usually carried
out prior to discharge. If the isotope study is carried out
during the acute episodes, it may detect photopenic areas
suggestive of either pyelonephritis or scars. Approximately
50% of these photopenic areas will disappear within
2months. For long-term prognosis, it is the presence of
permanent scars that is significant, and hence, the isotope
is best delayed for at least 2–6 months after UTI.
Natural history
There is a strong tendency for primary VUR to resolve
spontaneously in the preschool years, with the normal
growth of the bladder muscle offering better support to
the intravesical ureter. Nearly all cases of mild VUR
without ureteric dilatation (Grades I and II) [Table32.1]
resolve spontaneously. More severe cases of VUR with
dilatation of the ureter (Grades III, IV and V) [Fig.32.2]
have a lower rate of spontaneous resolution and may
require surgical correction. As well as grade of reflux,
the probability of spontaneous resolution is influenced
by laterality and age of the patient at diagnosis. As the
spontaneous resolution of reflux is associated with
bladder growth, reflux presenting in older patients is
less likely to resolve. Similarly, reflux is less likely to
resolve in patients with bilateral, as opposed to unilateral, reflux.
Management
Medical management
The initial management of VUR is always medical, which
aims to prevent symptomatic pyelonephritis and renal
scarring, while awaiting spontaneous resolution. Medical
management is based on preventing or minimising UTIs
on the premise that reflux of infected urine is harmful.
This is achieved by ensuring a normal fluid intake and
regular toileting, proper perineal hygiene – more important in girls, elimination of constipation if present and
administration of low-dose prophylactic antibiotics. The
optimum dose schedule and duration of treatment have
not been established. Most clinicians will start newly
diagnosed infants with VUR on low-dose continuous
antibiotic (trimethoprim or nitrofurantoin) administered
at night (as it is usually at this time that urine dwells in
the bladder for long), stopping either when the child is
toilet-trained or has been without a proven UTI for 12
months. Some clinicians would question the need for
prophylactic antibiotics at all.
The critical factor in medical management is vigilance
and prompt appropriate treatment of UTIs as they
occur. This requires close medical supervision and
well-informed, motivated parents with ready access to
medical attention to prevent pyelonephritis leading to
renal scarring and potential long-term damage.
Figure 32.2 MCUGs showing gross right-sided VUR (arrow) up
both ureters in a duplex system. There is no reflux on the left.
Surgical management
Where medical management has been a failure, as
evidenced by recurrent breakthrough UTIs, surgical
intervention may be appropriate. Structural anomalies
such as para-ureteric diverticulae, ureteric duplication
and ureterocele may make spontaneous resolution of
VUR less likely but do not negate the potential benefit
of a trial of medical therapy. Secondary VUR such as
that seen in association with a neuropathic bladder or
Chapter32: Vesico-ureteric Reflux (VUR) 201
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posterior urethral valve is best managed by treating the
underlying condition rather than surgical reimplantation of the ureters.
There are a number of surgical strategies that may be
employed in patients with VUR. Circumcision may be
appropriate in boys with VUR, especially if the UTI is
due to Proteus mirabilis, a known preputial commensal.
A nephro-ureterectomy may be appropriate if the reflux
is into a non-functioning dysplastic kidney. In the very
young/small infant, a temporary vesicostomy – permitting the bladder to drain at low pressure onto the
abdominal wall, decompressing the upper tracts and
minimising reflux – may be appropriate. However, the
primary aim of surgical therapy for VUR is to prevent
reflux, and this can be achieved either endoscopically or
surgically with ureteric reimplantation.
Endoscopic treatment (STING or HIT)
Endoscopic injection with synthetic polysaccharide is
gaining increasing acceptance worldwide, with published success rates of 75% following a single injection,
85% following two injections and 95% following three
injections. Endoscopic therapy offers a number of
advantages over open surgery in that it is a day-case
procedure, it can be easily repeated and it does not
make surgery – for those patients in whom it fails – more
difficult. Disadvantages are lingering doubts about its
long-term safety and efficacy and some concerns about
overtreatment in patients who may have resolved spontaneously anyway (i.e. Grades I and II VUR).
Ureteric reimplantation
For many years, this was the mainstay of surgical
management of VUR. This is because the reported success
rates for reflux resolution were in excess of 95%. There
are a number of differing surgical approaches that traditionally have involved detaching the ureter from the
bladder and creating a new submucosal tunnel and neoureterovesicostomy largely from within the bladder.
More recently, it has been shown that minimally invasive
ureteric reimplantation can be done with pneumovesicum (bladder filled with CO
), although the merits of this
2
new approach have yet to be demonstrated.
KEY POINTS
• VUR is associated with abnormal development of the kidney
(dysplasia) and secondary scars of pyelonephritis.
• VUR is common in fetuses and babies, as the bladder (and
ureteric valve) is small: resolution is common with growth.
• VUR may be diagnosed antenatally, but postnatal MCUGs
isneeded for conrmation.
Further reading
McQuiston LT, Caldamone AA (2012). Renal Infection,
Abscess, Vesicoureteral Reflux, Urinary Lithiasis and
RenalVein Thrombosis. In: Coran AF, Adzick NS, Krummel
TM, Laberge T-M, Shamberger RC, Caldamone AA (eds)
Pediatric Surgery, 7th Edn, Elsevier Saunders, Philadelphia,
pp.1427–1440.
CHAPTER33
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Urinary Tract Dilatation
CASE 1
Antenatal ultrasonography at 18 weeks shows bilateral
hydronephrosis in the fetus, which is still present in the third
trimester, when oligohydramnios develops.
Q 1.1 What is the natural history of antenatal hydronephrosis?
Q 1.2
What conditions cause antenatal hydronephrosis?
What treatment is required at birth?
Q 1.3
Hydronephrosis is defined as an abnormal dilatation of
the kidney, specifically the renal pelvis, and sometimes
referred to as pelviectasis. More severe cases have an
associated dilatation of the calyces (caliectasis) and,
possibly, also the ureter (hydroureter). The presence
of hydronephrosis implies a degree of partial outflow obstruction (which may still be present or have
resolved), but can also be found associated with retrograde flow of urine or vesico-ureteric reflux (VUR).
Differentiating those patients with hydronephrosis
secondary to a persisting and potentially harmful partial
obstruction from those in whom the dilatation probably
represents the sequelae of an obstruction that is now
resolving or has resolved presents an interesting clinical
challenge. Having determined the level of the likely
obstruction, we must then ascertain the potential for
renal injury or loss of function.
Hydronephrosis is diagnosed by ultrasonography. A
normal kidney will not have any dilatation of its collecting system, and therefore, any dilatation is defined as
hydronephrosis. The Society of Fetal Urology has proposed a grading system for hydronephrosis, but most
units adopt descriptive documentation of the maximum
anteroposterior renal pelvis diameter in a transverse
plane at the level of the renal hilum, often referred to as
CASE 2
An 18-month-old male infant presents with fever and dysuria.
Urine culture shows an infection and an ultrasound scan shows
hydronephrosis and hydroureter (bilateral).
Q 2.1 What causes hydroureter?
Q 2.2
What investigations are needed for UTI?
the RPD or renal APD. By consistently measuring the
renal pelvis at this point, it standardises repeated observations to look for trends towards progression or regression and also to compare with the published literature
for prediction of outcome. A precise APD threshold
above investigation should be pursued cannot be found,
but most surgeons would investigate a patient with an
APD greater than 5
mm.
Clinical presentation
Prior to the advent of routine antenatal screening,
patients with urinary tract dilatation typically presented with pain or urinary tract infections (UTIs). Pain
is the most common presenting feature in the older
child and may be accompanied by infection or haematuria, especially after minor trauma [Table33.1]. A distinguishing clinical feature is lateralisation of the pain
to the loin and accompanying nausea or vomiting.
Symptoms are exacerbated by a fluid load and sometimes by position. Intermittent loin pain precipitated by
a fluid load (known as a Dietl’s crisis) is caused by
stretching the renal capsule with a sudden onset of
hydronephrosis.
Jones’ Clinical Paediatric Surgery, Seventh Edition. Edited by John M. Hutson, Michael O’Brien, Spencer W. Beasley,
Warwick J. Teague and Sebastian K. King.
© 2015 John Wiley & Sons, Ltd. Published 2015 by John Wiley & Sons, Ltd.
202
Chapter33: Urinary Tract Dilatation 203
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Table 33.1 Clinical presentation of urinary tract obstruction
Child Infant/neonate
Pain Antenatal hydronephrosis on ultrasound
Infection Incidental finding
Haematuria Infection
Loin Mass Loin Mass
Incidental finding Haematuria
Pain
Nowadays, most neonates and infants with hydronephrosis are detected by antenatal ultrasonography. For
that small proportion not detected antenatally, hydronephrosis in the neonate may manifest as a UTI or as a palpable abdominal mass. Presentation as a loin mass is
unusual except in a neonate, in whom 50% of all abdominal masses are renal in origin. The most common renal
abnormality detected on antenatal screening is hydronephrosis picked up at the 18–20 weeks of gestation scan.
When defined as an APD greater than 5
mm, antenatal
hydronephrosis was detected in 100 of 18,766 antenatal
ultrasound scans or 0.59% of pregnancies. However, in
approximately half of these patients, the postnatal ultrasound will be normal. The likelihood of significant
pathology increases with increasing size of antenatal
hydronephrosis, such that if the antenatal APD was greater
than 20 mm, then the majority would require surgery or
long-term follow-up; of those with an APD of 10–15
mm,
half will have a significant abnormality, and of those with
APD less than 10
mm, only 3% have an abnormality.
Another mode of presentation is where renal investigations are performed for suspected abnormalities in
children with known multiple anomalies.
Investigations
The investigation for suspected or proven urinary tract
dilatation aims to:
1 Demonstrate and document the nature and degree of
dilatation
2 Assess renal function (on both sides)
3 Define the abnormal anatomy
Physical examination
Physical examination is aimed at detecting an abdominal mass (suggestive of obstruction or a large multicystic dysplastic kidney) or a palpable bladder.
Ultrasonography
Ultrasonography is the first investigation performed
forsuspected obstruction and will not only demonstrate
any abnormal anatomy but also may determine the
likely cause. However, an ultrasound scan will not prove
that a dilated system is obstructed, nor will it demonstrate function in the dilated system. Given its non-toxic
nature, efforts are continually being made to extend its
role to hopefully replace other tests, hence the use of
Doppler ultrasound and resistive indices for obstruction
and scarring and contrast-enhanced ultrasound to demonstrate VUR (see Chapter32).
Micturating cystourethrogram (MCUG)
An MCUG is essential in the investigation of children
with dilated upper tracts, to exclude associated reflux,
but also to exclude distal obstruction, for example, posterior urethral valve in boys. The fervour with which one
pursues an MCUG will depend on the individual scenario; for instance, all newborn male infants with small
thick-walled bladders and bilateral hydro-ureteronephrosis must have an MCUG. By contrast, a 7-year-old
asymptomatic female sibling of a patient with VUR who
is found to have mild unilateral hydronephrosis may not
have her clinical management altered by the result of an
MCUG and hence could be justifiably spared the trauma.
Renal isotope scan
Nuclear medicine or renal isotope scintigraphy may be
useful in ascertaining differential renal function and
even implied absolute renal function. Renal isotope
scans are either static (DMSA), for demonstrating absolute renal parenchyma detection of scars, or dynamic
(DTPA or MAG3). Dynamic isotope renography provides both differential renal function and evidence
about obstruction or reflux. The interpretation of MAG3
or DTPA excretion curves is prone to significant error
and should be left to experts.
A MAG3 scan can be used in the first few months
of life when renal function is low (and DTPA scan is
ineffective).
Intravenous pyelogram
Intravenous pyelography is used rarely today for
thedemonstration of function, but is still an excellent
investigation where it is essential to demonstrate the
anatomy, particularly in duplex systems where both
moieties are functioning.
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Retrograde and antegrade pyelography
Both techniques are employed to demonstrate anatomy
or obstruction when this is essential to the management
of the patient.
MR urography
MR urography is increasingly being employed as a nontoxic investigation for the determination of differential
renal function as well as anatomical information.
PET
PET scanning, especially when combined with CT or
MR, provides an excellent opportunity to locate the elusive upper pole of a duplex kidney in a young girl with
urinary incontinence.
Pitfalls of investigations
The immaturity of the neonatal kidney presents difficulties in interpretation of functional tests in the first
month of life. As the concentrating ability and total
renal function is low in the neonate, it is likely that
functional studies will give misleading results. For this
reason, it is best to defer any functional study for at least
6 weeks post-term, although a MAG3 scan can be used
at this time. Isotope renography is further prone to
errors caused by the level of patient hydration and the
regions of interest drawn by the radiographer.
(a)
Aetiologic factors
Pelvi-ureteric junction (PUJ) obstruction
PUJ obstruction affects approximately 1 in 2000 children, is more common in boys and on the left side, but
may be bilateral in 20–25%. Partial obstruction of the
PUJ is caused by intrinsic stenosis (75%), congenital
kinking or a lower pole vessel crossing the ureter as it
joins the renal pelvis (20%). If the obstruction is intermittent, there is good preservation of renal function in
the early stages [Fig. 33.1]. Infection and progressive
obstruction lead to loss of renal function, unless severe
blockage is relieved surgically. Occasionally, if progressive deterioration has been identified prenatally, early
intervention is necessary after birth. However, less
severe degrees of hydronephrosis in the newborn often
resolve spontaneously. In a large series of babies with
antenatal hydronephrosis, babies with postnatal APD
less than 12mmrarely required surgery, those with APD
(b)
Figure 33.1 Postnatal ultrasonography examination in an
infant with antenatal hydronephrosis, showing (a) PUJ
obstruction (arrow) with pelvi-calyceal dilatation, but good
preservation of renal parenchyma; (b) nuclear renal scan
(DTPA) showing holdup at the PUJ at 45 min.
greater than 50mm all required surgery and 25% of
those with APD of 12–50 mm required surgery because
of progressively increasing hydronephrosis or loss of
function on repeated isotope renography.
Chapter33: Urinary Tract Dilatation 205
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Vesico-ureteric obstruction
Any degree of ureteric dilatation seen on ultrasonography is abnormal as the ureter is a conduit for urine
and not a storage vessel. A dilated ureter or megaure-
mm) may be due to obstruction, reflux or a
ter (>7
combination of both. Obstruction is usually secondary
to a stenosis, or valve in the lower ureter [Fig.33.2].
Mild cases may resolve spontaneously, leaving a persistently dilated ureter that is no longer obstructed. A
ureterocele is a cystic dilatation of the intravesical
ureter, which may be associated with a duplex kidney
and usually requires endoscopic surgery to relieve the
obstruction and improve drainage. More severe cases
of ureteric obstruction may require surgical correction
in the form of a ureteric reimplantation.
VUR
VUR may present with a UTI and hydro-uretero-nephrosis on ultrasonography or may be found in 9% of neonates with antenatal hydronephrosis (see Chapter 32).
Secondary PUJ obstruction due to increasing ureteric
tortuosity and kinking may occur.
Posterior urethral obstruction
Posterior urethral valve affects 1 in 8000 newborns
and accounts for less than 1% of antenatally diagnosed hydronephrosis. In males, epithelial folds
running down from the verumontanum in the posterior urethra form a membrane or valve that impedes
the flow of urine with back pressure on the bladder,
ureters and kidneys. When the obstruction is severe,
intrauterine renal failure occurs with fetal death in
utero or death soon after birth from Potter syndrome.
Less severe obstruction allows the fetus to survive,
but if the problem is not detected early, septic complications from UTI and metabolic abnormalities caused
by renal failure soon occur. The majority of boys
are detected or suspected on antenatal ultrasound.
The postnatal features include a thick-walled, palpable bladder and a poor urinary stream in a newborn
male infant. The diagnosis is confirmed on MCUG
[Fig.33.3]. Fetal intervention is often considered, but
is seldom appropriate, and if it has any role, it is probably beneficial to lung development in severe oligohydramnios rather than to preserving or improving
renal function. Up to a third of boys with a posterior
urethral valve will develop renal insufficiency or endstage renal failure.
Figure 33.2 Right vesico-ureteric junction obstruction. Note
the dilated ureter right down to the bladder.
Figure 33.3 Posterior urethral valve (membrane) seen on a
lateral view of the urethra on MCUG (arrow). Note reflux into
a megaureter, massive dilatation of the posterior urethra and a
urethral catheter.
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Figure 33.4 Duplex kidney with dilated upper moiety (arrow)
on ultrasonography.
Neurogenic (neuropathic) bladder
Neurogenic bladder causes hydronephrosis in a number
of ways. Patients may have a functional bladder neck
obstruction from sphincter dysfunction, with upper
tract dilatation secondary to high intravesical pressure.
Many patients with neurogenic bladder have VUR
secondary to the neuropathy, which further exacerbates
the upper tract dilatation.
Double ureters and kidneys
(duplexsystem)
Congenital duplex kidneys may develop hydronephrosis of either part of the duplex system. The upper
moiety is usually the more abnormal [Fig.33.4], and
the dilatation is caused by dysplasia or distal obstruction (from ureterocele) [Fig.33.5], or an ectopic position of the ureteric orifice (e.g. in the bladder neck).
Ectopic ureteric insertion is often associated with dysplasia in a very poorly functioning upper renal moiety.
Dilatation of the more normal lower moiety may be
caused by PUJ obstruction or may be associated with
high-grade VUR.
Stones (urolithiasis)
Rarely in children, a renal or ureteric calculus may cause
an acute obstruction, resulting in hydronephrosis.
Figure 33.5 Ultrasonography of bladder showing ureterocele
(arrow) in the same patient shown in Figure33.4.
Management of obstructive lesions
It is best to divide the investigation and management of
hydronephrosis into two age groups: those presenting in
the neonatal period and those presenting later.
Antenatal hydronephrosis
Not all hydronephroses on antenatal examination turn
out to be significant. In fact, approximately half do not
have any abnormality detected on postnatal investigation and are labelled as having had transient hydronephrosis. However, when hydronephrosis is detected
antenatally, it is important to follow it throughout pregnancy. If other urinary tract abnormalities are detected
on scanning, this would suggest that the hydronephrosis
is pathological. Increasing hydronephrosis with oligohydramnios is also pathological, suggestive of low urine
output with a posterior urethral valve. The more severe
the hydronephrosis, the more likely there will be a pathological cause: most cases with antenatal APD less than
mm will either be normal or have VUR, whereas PUJ
10
obstruction is more likely if APD is greater than 15 mm.
Despite lack of good randomised evidence of benefit,
most urologists/nephrologists commence all neonates
with antenatally diagnosed hydronephrosis on prophylactic antibiotics from birth while awaiting full
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