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82 Vesicoureteral Reux
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KEY POINTS
●
VUR is an important cause of morbidity in children because of its role in
urinary tract infection, pyelonephritis
and renal scarring and its association
with renal dysplasia.
●
Reux nephropathy may result from
congenital or acquired renal damage or a combination of both mechanisms.
●
VUR is strongly associated with
bladder and bowel dysfunction.
Management of these conditions is an
essential adjunct to management of the
VUR itself.
●
e role of dierent imaging techniques for the diagnosis of VUR
remains controversial.
●
Continuous antibiotic prophylaxis
signicantly reduces the incidence of
symptomatic UTIs in children with
VUR but carries a higher risk of inducing antibiotic resistant bacteria.
●
Endoscopic correction and ureteroneocystostomy are eective ways of
correcting VUR but may not always
prevent the occurrence of further UTIs.
FURTHER READING
Holmdahl G, Brandstrom P, Lackgren G, Sillen
U, Stokland E, Jodal U, et al. The Swedish
reux trial in children: II. Vesicoureteral reux
outcome. J Urol. 2010;184(1):280–285.
Peters CA, Skoog SJ, Arant BS, Jr., Copp HL,
Elder JS, Hudson RG, et al. Summary of the
AUA guideline on management of primary
vesicoureteral reux in children. J Urol.
2010;184(3):1134 –1144.
Rivur Trial Investigators, Hoberman A,
Greeneld SP, Mattoo TK, Keren R, Mathews
R, et al. Antimicrobial prophylaxis for
children with vesicoureteral reux. N Engl J
Med. 2014;370(25):2367–2376.
Routh JC, Bogaert GA, Kaefer M, Manzoni
G, Park JM, Retik AB, et al. Vesicoureteral
reux: current trends in diagnosis, screening,
and treatment. Eur Urol. 2012;61(4):773–782.
Shaikh N, Hoberman A, Keren R, Gotman N,
Docimo SG, Mathews R, et al. Recurrent
urinary tract infections in children with
bladder and bowel dysfunction. Pediatrics.
2016;137(1).
Skoog SJ, Peters CA, Arant BS, Jr., Copp
HL, Elder JS, Hudson RG, et al. Pediatric
Vesicoureteral Reux Guidelines Panel
summary report: clinical practice guidelines for screening siblings of children
with vesicoureteral reux and neonates/
infants with prenatal hydronephrosis. J Urol.
2010;184(3):1145 –1151.
Wang HH, Gbadegesin RA, Foreman JW,
Nagaraj SK, Wigfall DR, Wiener JS, et al.
Efcacy of antibiotic prophylaxis in children with vesicoureteral reux: systematic review and meta-analysis. J Urol.
2015;193(3):963–969.
Upper Tract Obstruction
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KIM A R HUTTON and DAVID F M THOMAS
Topics covered
7
Acute and chronic upper tract obstruction
Diagnosis
Ultrasound
Isotope renography
INTRODUCTION
Upper urinary tract obstruction is an extremely
important condition in children because it endangers renal function, poses a risk of potentially
serious urosepsis and can cause distressing symptomatology. A high proportion of cases of possible upper tract obstruction are now identied
prenatally following the discovery of fetal hydronephrosis or hydroureteronephrosis on maternal
antenatal ultrasound scans. A substantial part of
paediatric urological practice is now concerned
with distinguishing between those infants who
have signicant obstruction demanding surgical
intervention and those who can be safely managed
conservatively.
e management of upper tract obstruction has been hindered by the indiscriminate
use of terms such as ‘idiopathic hydronephrosis’
and ‘pelviureteric junction (PUJ) obstruction’
or ‘vesicoureteric junction (VUJ) obstruction’
Other imaging and diagnostic modalities
Pelviureteric junction obstruction
Vesicoureteric junction obstruction
and ‘primary megaureter’ which are oen used
interchangeably. e use of other poorly dened
terms such as ‘physiological hydronephrosis’ and
‘transient hydronephrosis’ further add to the
confusion.
It is important to recognise that ‘hydronephrosis’ is not a pathological entity in its own right but
simply a descriptive term denoting dilatation of
the renal pelvis and calyces. Unfortunately, the
term hydronephrosis is oen used synonymously
with PUJ obstruction. When this is accompanied
by dilatation of the ureter the term ‘hydroureteronephrosis’ is used.
ere are essentially four potential causes of
upper tract dilatation:
●
Urinary tract obstruction
●
Vesicoureteric reux (VUR)
●
Developmental anomalies of the upper uri-
nary tract
●
Pathologically high rates of urine production
(‘ow uropathy’)
83
84 Upper Tract Obstruction
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In an attempt to achieve uniformity in the assessment of upper tract dilatation and obstruction
a new classication was proposed following a
multidisciplinary consensus conference held in
the United States in 2014.
This classification (which is applicable to
pre- and post-natal assessment) uses the following criteria to evaluate the severity and
clinical significance of upper urinary tract
dilatation:
1. Anterior-posterior renal pelvic diameter;
2. Calyceal dilatation;
3. Renal parenchymal thickness;
4. Renal parenchymal appearance;
5. Bladder abnormalities;
6. Ureteral abnormalities.
e ndings of preliminary studies appear to
validate the predictive value of this classication
when applied to the clinical management of prenatally detected hydronephrosis. However, further studies are required to establish whether it
oers any signicant advantages over previously
used scoring systems.
WHAT IS OBSTRUCTION AND
HOW IS IT DIAGNOSED?
ere is no universally accepted denition of
obstruction nor is there a single investigation
which is capable of providing an unequivocal
diagnosis of obstruction in a dilated upper urinary tract. One widely used denition states
that obstruction is any impairment to urine ow
which, if le untreated will lead to progressive
deterioration of function. However, this is not a
very useful denition in clinical practice because
it implies that the clinician should wait for evidence that the obstruction has caused renal damage before taking steps to prevent it. In clinical
practice, decision-making is therefore guided by
a combination of clinical factors and the evidence
of imaging studies.
Acute Obstruction
e pathophysiology of acute obstruction has
been studied in experimental animal models.
In the rst few hours, a sharp rise in intrarenal
pressure is accompanied by a marked reduction in blood ow in the renal cortex. Some
equilibration occurs aer 24 hours but without
prompt relief of the obstruction, rapid damage to
the nephrons supervenes, with loss of approximately 50% of functioning nephrons aer 6 days
and irreversible loss of the entire function of the
obstructed kidney within 6 weeks. However,
acute obstruction is relatively rare in children.
Possible causes include: impaction of a urinary
calculus at the PUJ, acute PUJ obstruction or
VUJ obstruction or early postoperative obstruction following a pyeloplasty or ureteric reimplantation which has not been protected by stenting.
Chronic Obstruction
is is encountered far more commonly in children but the pathophysiology is less well understood because of the diculty in creating reliable
experimental models.
Historically, it was far easier to justify a decision to intervene surgically because the majority of children with upper tract obstruction
presented clinically with symptoms such as pain
or urinary infection. Following the widespread
introduction of antenatal ultrasound it became
apparent, however, that the presence of mild to
moderate upper tract dilatation is more prevalent
in healthy, asymptomatic infants than was previously recognised. Indeed, some degree of dilatation of the fetal urinary tract is present in 1-2%
of pregnancies. Even when obstruction has been
demonstrated by the relevant investigations, the
natural history is oen characterised by progressive improvement and spontaneous resolution.
e challenge is therefore to try to distinguish
those infants in whom the dilatation/obstruction
is destined to remain stable or resolve without
aecting renal function from those with clinically
signicant obstruction which is likely to lead to
loss of function unless intervention is undertaken
to relieve it.
Radiological investigation of upper tract obstruction / Isotope Renography 85
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RADIOLOGICAL INVESTIGATION
OF UPPER TRACT OBSTRUCTION
With the rare exception of acute obstruction
by an impacted calculus, upper tract obstruction always gives rise to dilatation. However, the
presence of dilatation does not always signify
obstruction. Non-obstructive causes of dilatation include; VUR, developmental anomalies
such as primary non-obstructive mega ureter and residual dilatation which may persist
despite relief of obstruction in a previously
obstructed system. Pathologically high urine
ow, for example in diabetes insipidus, is a rare
cause of dilatation.
Ultrasound
e diagnostic pathway usually starts with the
ultrasound nding of dilatation (Figure 7.1).
e most valuable measurement derived from
an ultrasound scan is the anteroposterior (AP)
diameter of the renal pelvis at the renal hilum.
In the neonate, this gure should not normally
exceed 6 mm. However a diameter of 10 mm
is usually taken as the upper limit of normal.
Signicant obstruction posing an active threat to
renal function is most unlikely to be present if the
AP diameter is less than 15 mm. Conversely, an
Figure 7.1 Postnatal ultrasound conrming
antenatal ultrasound appearances of grossly
hydronephrotic right kidney with marked dilatation
of renal pelvis and calyces with thinned cortex.
AP diameter greater than 50 mm is almost invariably associated with impaired function, either at
the time of initial assessment or during the course
of follow up.
Additional parameters which may increase
the sensitivity of ultrasound for the diagnosis of
obstruction include calyceal dilatation (central
or peripheral), thickness and ultrasound appearances of the renal parenchymal thickness and
abnormal appearances of the ureters or bladder.
e use of Doppler ultrasound has been described
for the measurement of renal resistive index and
assessment of jets of urine emerging from the
ureteric orices. However, this has not proved
suciently sensitive to be of diagnostic value in a
routine clinical practice.
e presence of ureteric dilatation is always an
abnormal ultrasound nding because a ureter of
normal calibre cannot be visualised on ultrasound.
Isotope Renography
e central role played by isotope renography
in the diagnosis of upper tract obstruction is
considered in detail in Chapter 3. In summary,
dimercaptoacetyltriglycine (MAG3) labelled with
metastable 99-Technetium (
radiopharmaceutical agent of choice.
In addition to quantifying dierential function, dynamic renography provides serial gamma
camera images of the kidneys and urinary tract
and generates a graphic display of the uptake and
clearance of the isotope from the kidneys over
time. e use of dimercaptosuccinic acid (
DMSA) is largely conned to assessing low levels
of dierential function when deciding between
pyeloplasty and nephrectomy.
Diuresis renography provides a means of
distinguishing between obstructed and nonobstructed dilatation.
e characteristics of the uptake and drainage
curves, oen referred to as the O’Reilly curves,
fall into ve well-recognised patterns (Fi gu re 7.2):
●
Type 1. Normal uptake with prompt washout
●
Type 2. Rising uptake curve; no response to
diuretic (obstruction)
99m
Tc) is currently the
99m
Tc
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Type 1 and type 3a curves are normal and nonobstructed. However, interpreting the clinical
signicance of type 2, type 3b and type 4 curves
in children can oen be more problematic.
Magnetic Resonance Imaging
Dynamic contrast-enhanced magnetic resonance
imaging (MRI) can combine the anatomical
information yielded by ultrasound with much
of the functional information provided by renal
scintigraphy. It has the advantage of providing anatomical and functional information in a
single study without exposure to ionising radiation. e main drawback is the requirement for
general anaesthesia or sedation in infants and
younger children – although a ‘feed and wrap’
technique can be used in small infants.
e anatomical detail provided by dynamic
contrast-enhanced MRI is excellent (Fi g u r e 7.3).
In many centres dynamic contrast-enhanced
MRI is replacing ultrasound and isotope as a ‘one
Figure 7.2 Patterns of isotope renogram curves,
as classied by O’Reilly and associates.
●
Type 3a. Initially rising curve, which falls
rapidly in response to diuretic (non-obstructive dilatation)
●
Type 3b. Initially rising curve, which neither
falls promptly nor continues to rise (equivocal)
●
Type 4. ere is a secondary peak suggesting
obstruction precipitated by high urinary ow
rates – the so-called Homsy’s sign. Similar
ndings can be observed in patients with high
grade VUR and no obstruction
Figure 7.3 Contrast-enhanced MR scan demon-
strating bilateral obstruction.
Radiological investigation of upper tract obstruction / Integrated Approach to Diagnostic Imaging 87
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the United Kingdom but may still play a limited
role – for example in identifying rare cases with
obstruction at more than one level in the ureter.
Antegrade Pyelography
This contrast study, which is performed via
ultrasound guided puncture of the kidney
can be valuable for demonstrating obstruction distal to the PUJ and in cases of suspected
recurrent PUJ obstruction following previous
Figure 7.4 CT scan showing a horseshoe kidney
with bilateral hydronephrosis due to bilateral
PUJ obstruction. The isthmus can be seen
crossing the abdominal aorta.
pyeloplasty.
Integrated Approach
to Diagnostic Imaging
stop shop’ imaging modality for the assessment
of upper tract obstruction in children.
Computerised Tomography
Although not suitable for the routine assessment of upper tract obstruction in children, noncontrast and contrast-enhanced computerised
tomography (CT) may be indicated in children
presenting with obstruction due to calculi. CT
may also be helpful delineating complex anatomy
and aberrant renal vasculature – for example,
horseshoe kidney (Fig ure 7.4). However, MRI has
largely superseded CT in such cases.
Intravenous Urography
Intravenous urography (IVU), once the standard
investigation for suspected upper tract obstruction, is now rarely used in children because the
relevant functional and anatomical information
can provided more accurately by other imaging
modalities.
Retrograde Pyelography
is investigation entails cystoscopic catheterisation of the ipsilateral ureteric orice and injection
of X ray contrast to outline the upper urinary
tract from below. It is not routinely performed
prior to pyeloplasty by paediatric urologists in
e aims of imaging are as follows:
●
To determine whether the dilatation is genu-
inely due to obstruction.
●
To establish the precise level of obstruction
●
To measure dierential renal function
●
To assess the potential for recovery in poorly
functioning kidneys
●
To manage complications arising from infec-
tion in an obstructed system
Isotope renography is the principal investigation used to conrm or refute the diagnosis of
obstruction but other imaging modalities may
be needed to exclude reux and non-obstructive
dilatation. Renal ultrasound will usually provide
adequate information on the level of obstruction.
When this is unclear MRI is the investigation of
choice, supplemented by antegrade or retrograde
pyelography in dicult cases.
Dierential renal function can usually be reliably assessed by MAG3 renography or dynamic
contrast-enhanced MRI. However, in poorly
functioning kidneys
99m
Tc DMSA isotope scintigraphy provides more accurate information and
serves as a more reliable predictor of potential
recovery of function. When percutaneous nephrostomy (PCN) has been performed to drain an
infected/obstructed kidney, measurement of differential function (usually with
99m
Tc DMSA)
should ideally be delayed until aer 3–4 weeks of
drainage.
88 Upper Tract Obstruction
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PELVIURETERIC JUNCTION
OBSTRUCTION
PUJ obstruction is characterised by impairment
of urine transport across the pelviureteric junction leading to elevated renal pelvic pressures,
dilatation of the proximal collecting system
and the potential for nephron loss. It is a heterogeneous condition with a number of dierent
causes and considerable variability in severity,
clinical features, presentation and natural history. Estimates derived from antenatal screening place the incidence of PUJ obstruction in the
range 1:750–1:1000. However, PUJ obstruction
can also occur de novo as an acquired condition
in older children.
e male to female ratio is approximately equal
and the le kidney is more commonly aected
than the right, by a ratio of approximately 2:1.
PUJ obstruction is associated with an
increased incidence of other urinary tract anomalies such as:
●
Multicystic dysplastic kidney (MCDK)
●
Horseshoe kidney
●
Ectopic kidney
●
Duplex collecting systems (usually the lower
moiety is aected)
Aetiology of PUJ Obstruction
Although the ndings on diagnostic imaging,
notably MRI, oen provide a guide to the likely
aetiology it is not usually until the time of operation that this can be established with certainty.
e causes of PUJ obstruction can be classied
as follows:
Intrinsic obstruction (Figure 7.5a)
Typically, this comprises a short stenotic segment at the PUJ. However, in some cases, this
may extend distally to involve a more extensive
segment of proximal ureter. Although physical
obstruction appears to play the most important
role in children, functional obstruction due to an
‘adynamic segment’ is very occasionally implicated as the likely cause. A number of histological
abnormalities of smooth muscle and collagen have
been reported and innervation abnormalities with
reduced neural density and abnormalities of the
interstitial cells of Cajal have also been described.
Extrinsic obstruction
Aberrant ‘crossing’ lower pole vessels are found
in more than 30% of older children and adults
undergoing pyeloplasty.
Figure 7.5 Aetiology of PUJ obstruction. (a) Intrinsic stenosis. Obstruction due to narrowing of
a segment of ureter which is usually localised to the region of the pelviureteric junction but may
extend over a length of several centimetres. (b) Ureteric folds. Tortuous segment of proximal
ureter giving rise to varying degrees of obstruction. Straightening of this segment with growth may
explain the spontaneous resolution of obstruction observed in a proportion of prenatally detected
cases. (c) Extrinsic obstruction by crossing lower pole vessels.
Pelviureteric junction obstruction / Variants of PUJ Obstruction 89
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In some cases, the presence of these vessels
appears to be simply incidental to an intrinsic PUJ
obstruction. However, in many cases, particularly
older children presenting with intermittent loin
pain, it is clear from the operative ndings that
the aberrant vessels are directly responsible for
external compression and obstruction at the level
of the pelviureteric junction. In suitably selected
cases laparoscopic transposition of the lower pole
vessels can successfully relieve the obstruction
without the requirement for any surgical procedure on the pelviureteric junction itself.
In infants with prenatally detected PUJ
obstruction, however, lower pole vessels account
for less than 5% of cases requiring pyeloplasty.
In some cases the PUJ itself is normal in
calibre but the proximal ureter is tortuous and
obstructed by the presence of kinks and folds
(Fi gure 7. 5b). Overlying bands and adhesions may
also be present. is variant of PUJ obstruction
may have the potential to resolve spontaneously
as the proximal ureter straightens with growth.
Intraluminal obstruction
A urinary tract stone which originated within the
kidney may become impacted at the PUJ to cause
acute or acute -on- chronic obstruction. Other
causes include: broepithelial polyps arising from
the renal pelvis (Fig ure 7.6 ), and mycelial balls
resulting from fungal urinary tract infection –
typically with Candida albicans (Figure 7.7).
High insertion of the pelviureteric
junction
In cases where the PUJ is found to be high on
the anterior wall of the dilated renal pelvis this is
generally regarded as being a secondary phenomenon (upwards displacement of the PUJ due to
progressive dilatation of the pelvis) – rather than
the primary cause of obstruction.
Variants of PUJ Obstruction
Horseshoe kidney
e majorit y of horseshoe kidneys remain asymptomatic and do not cause urological problems.
Figure 7.6 PUJ broepithelial polyps. Operative
ndings at open surgery in an 11-year-old boy
presenting with loin pain. Preoperative imaging
with ultrasound and isotope renography had
shown hydronephrosis with obstruction at the
PUJ. The intraluminal polyps, which resembled
‘a bunch of grapes’, were an unexpected nding on opening the ‘bulky’ upper ureter/PUJ
region. Resection of all polyps together with
an Anderson-Hynes dismembered pyeloplasty
successfully relieved his symptoms and the
obstruction. (Reprinted from paediatrics and
child health, volume 18, edition 6, Kim A R
Hutton and Ram Shrestha, surgical management
of renal tract problems, page 260, Copyright
2008, with permission from Elsevier.)
e commonest complication is obstruction –
which may be caused by the deviated course of
the proximal ureter over the renal isthmus or,
more commonly, by extrinsic compression by
aberrant vasculature. On rare occasions a constellation of renal pathology can be encountered
in the same patient – such as a horseshoe kidney,
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Figure 7.7 Renal fungal balls causing PUJ
obstruction. A neonate born prematurely
at 27 weeks gestation suddenly became
completely anuric during the course of his
intensive care treatment. A renal ultrasound
showed marked bilateral hydronephrosis and
echogenic material obstructing both PUJs.
The patient required bilateral PCN insertion. In this right nephrostogram study a
fungal ball can be seen obstructing the PUJ.
The fungal balls and candida infection were
successfully treated with the patient making
a full recovery. (Reprinted from Paediatric
Surgery International, Volume 20, Edition 10,
R. Babu and K A R Hutton, Renal fungal balls
and pelvi-ureteric junction obstruction in a
very low birth weight infant: treatment with
streptokinase, page 805, Copyright 2004, with
permission from Springer Nature.)
renal duplication, and lower pole PUJ obstruction
(Figure 7.8).
Retrocaval ureter
is rare anomaly, which more commonly
aects the right ureter, originates from abnormal development of the posterior cardinal veins,
the precursors of the inferior vena cava. Further
investigation by MRI is indicated if this diagnosis
is suggested by the ultrasound ndings. A laparoscopic or robotic-assisted approach to treatment
is preferable to open surgery.
Reux in association with PUJ
obstruction
Severe tortuosity and kinking of the proximal
ureter associated with high grade VUR (e.g.
grades IV and V) can sometimes give rise to xed
obstruction to the drainage of urine from the kidney. e diagnosis is conrmed by performing
MAG3 renography with a catheter in the bladder
to ensure that isotope does not reux back to the
kidney to interfere with interpretation of the ndings. Antegrade pyelography may also be diagnostic. Depending on clinical factors the management
options include conservative management, pyeloplasty (possibly combined with ureteric reimplantation), and ureteric reimplantation alone. It has
been argued that pyeloplasty and ureteric reimplantation should not be performed simultaneously for fear of compromising the blood supply
to the ureter. However, this appears to be a largely
theoretical risk and in practice the two procedures
can be safely combined if necessary.
Although primary ureteric reimplantation can
be expected to correct the reux it oen fails to
alleviate the secondary obstruction – thus necessitating a subsequent pyeloplasty.
Natural History of PUJ Obstruction
is is very variable, ranging from complete resolution to rapidly increasing obstruction causing
deterioration in renal function. In a substantial
proportion of cases the obstruction, whilst persisting, nevertheless remains stable for many years,
with little or no impact on renal function. e later
Presentation 91
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Figure 7.8 Bilateral renal duplication within a horseshoe kidney with left lower pole PUJ obstruction.
This 5-year-old girl was referred with increasing left loin pain following conservative management of
a prenatally detected uropathy. (a) Contrast CT image showing both upper poles. (b) Image showing the functioning right lower pole, ‘chunky’ isthmus and grossly hydronephrotic, non-functioning
left lower pole. A left lower pole heminephrectomy with division of isthmus tissue overlying the
aorta resulted in complete relief of her symptoms.
onset of PUJ obstruction in a previously normal
kidney may be associated with aberrant lower pole
vessels rather than intrinsic stenosis (Figure 7. 9).
PRESENTATION
Prenatal detection: PUJ obstruction is the
most common clinically signicant uropathy
detected during pregnancy. However, mild to
moderate degrees of PUJ obstruction may not
be present or may not yet have given rise to
detectable dilatation at the time when routine
fetal anomaly scans are performed in the second
trimester. Such cases either remain undetected
or are only detected if additional scans are performed later in pregnancy. e severity of dilatation (AP diameter of the renal pelvis) is a more
accurate predictor of functional impairment
than the gestational age at which dilatation was
rst detected.
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