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142 Urinary Tract Calculi
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Underlying Urological Conditions
Predisposing urological abnormalities can be
identied in approximately 20–30% of children
with urinary calculi. However, since the majority
of children with urinary tract abnormalities do
not develop urolithiasis it seems likely that additional factors, notably a concomitant metabolic
abnormality are implicated in the small minority
of who do develop stones.
Stone formation is a rare complication of
pelvic-ureteric junction (PUJ) obstruction and
when it does occur the stones are characteristically small and multiple. Although vesicoureteral
reux (VUR) is present in 14% of cases it may be
a secondary phenomenon following the passage
of uretric calculi rather than being implicated as
a primary cause of urinary tract infection (UTI).
Neuropathic bladder dysfunction carries an
increased risk of stone formation due to incomplete bladder emptying and UTIs.
e use of intestinal segments for bladder
reconstruction (enterocystoplasty) is accompanied by a 20–40% risk of bladder stones. is
is due to factors which include; urinary stasis,
intestinal mucus in the urine acting as a nidus
for crystalline deposition and chronic low-grade
bacteriuria. e risk can be reduced by the use
of regular bladder washouts to promote eective
clearance of urinary mucus.
failure to thrive. e isolation of Proteus from a
child’s urine should always prompt investigation
for possible stone disease.
Haematuria
Macroscopic or microscopic haematuria is a common feature of calculi, but there is only a poor
correlation between its severity and the extent
and distribution of stones within the urinary
tract. e absence of haematuria on microscopy
or reagent strip testing does not exclude the possible presence of stones.
Passage of Stone Material Per Urethra
Occasionally stones come to light when a fragment or some soer matrix material is passed
per urethra. Rarely, a urethral stone can cause
acute urinary obstruction. In infants the presence
of unusual material and streaks of blood in the
nappy may be incorrectly ascribed to balanitis.
Pain
Acute renal colic of the pattern and severity
encountered in adults is not a prominent feature
of the symptomology in children. When pain
does occur, it is oen a poorly localised symptom
in a fractious, unwell child.
CLINICAL PRESENTATION
Age
Stones may develop from 1 to 2 months of age
onwards, with the incidence being higher under
5 years of age – reecting the relative importance
of infective stones (predominantly in boys) in this
age group.
Urinary Infection
Although stones typically present in older children with recognisable symptoms the clinical picture in infants may be deceptively non-specic,
consisting of vague ill health, low-grade fever and
Abdominal Mass
Xanthogranulomatous pyelonephritis presents
with general ill health, which may be accompanied by a palpable abdominal mass – a clinical
picture resembling Wilms’ tumour.
Incidental Finding
e presence of stones may occasionally come
to light as an entirely incidental nding.
Alternatively, they may be identied unexpectedly in a child without urinary symptoms who
is being investigated for other symptoms caused
by unsuspected stone disease. Stones may also be
detected on sibling screening and in our experience a third of cystinuria patients are diagnosed
in this way.
Diagnosis / Initial Screening for Calculi 143
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Figure 11.1 Ultrasound appearances of renal calculi with posterior acoustic shadowing (left image)
and corresponding ‘twinkle artefact’ (right image).
DIAGNOSIS
Initial Screening for Calculi
Ultrasound
Ultrasound is the primary diagnostic modality in
children because of the quality of the imaging and
because it does not entail exposure to radiation.
Stones are seen as discrete echogenic foci which cast
a posterior acoustic shadow (Fig ures 11.1 & 11.2). A
‘twinkle artefact’ is seen with colour Doppler ultrasound due to multi-reecting rough surface of the
Figure 11.2 Ultrasound scan demonstrating a
distal ureteric calculus with associated proximal
ureteric dilatation and posterior shadowing.
stone. Ultrasound has high sensitivity and specicity for the visualisation of renal stones (61–93% and
95–100%, respectively) but these gures are much
lower for the detection of ureteral stones.
Acute upper tract obstruction caused by the
impaction of a stone may only be associated with
a misleadingly mild degree of hydronephrosis,
with an anterior-posterior diameter of <15mm.
Abdominal X-ray (AXR)
e sensitivity of an abdominal X-ray for detecting radio-opaque urinary stones is only 50% and
it is not routinely used for urolithiasis screening.
Unenhanced ultra-low dose spiral
computed tomography (CT)
CT is considered the gold standard imaging
modality for urolithiasis. In the paediatric age
range it is generally reserved for indeterminate
cases following ultrasonography or where exact
details regarding the stone are necessary for surgical decision-making. With the ultra-low dose
Stone Protocol sequences, the radiation exposure has been reduced to <3mSv whilst maintaining sensitivity for urolithiasis at over 96%
(Figu re 11. 3). With dual-energy CT-imaging, the
stone density (in Hounseld units) can be calculated to further aid surgical planning.
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Figure 11.3 Low dose CT image demonstrating
complex left staghorn calculus.
Evaluation Prior to Treatment
of Proven Stone Disease
DMSA
Dierential function in the aected kidney(s)
should be documented on a
cinic acid (DMSA) scan before intervention and
re-evaluated aer treatment. is can be combined with a low-dose unenhanced CT scan of
the urinary tract which is co-registered with the
DMSA tomographic images (DMSA SPECT-CT)
to provide the additional assessment of the renal
parenchymal function adjacent to renal stones
(Figu re 11.4).
Figure 11.4 DMSA SPECT-CT demonstrating
left staghorn calculus and small stones on the
right with good functioning surrounding renal
parenchyma.
99m
Tc dimercaptosuc-
Intravenous urography
Intravenous urography (IVU) can provide additional anatomical information (e.g. on calyceal
anatomy) but an ultra low-dose CT scan is usually sucient to provide the information needed
when planning percutaneous nephrolithotomy.
Additional investigations
DYNAMIC RENOGRAPHY
Dynamic renography, e.g. (
triglycine (MAG3), is undertaken if obstruction
is suspected. However, it is not possible to make
a reliable diagnosis of PUJ obstruction when a
stone is present in the renal pelvis. e presence
of underlying obstruction can only be reliably
diagnosed aer complete removal of the stone.
MICTURATING CYSTOGRAPHY
Micturating cystography (MCUG) is not performed routinely. Even when VUR is demonstrated it may be a transient phenomenon
(secondary to infection and the passage of stone
material to the bladder) which resolves once
the infection has been treated and stone clearance has been achieved. If indicated (e.g. to
exclude posterior urethral valves or other pathology) cystoscopy can be performed at the time of
an interventional procedure for the stone(s).
METABOLIC INVESTIGATIONS
If stone fragments are obtained, crystallographic
evaluation with infra-red spectroscopy may aid
the diagnosis of an underlying metabolic disorder. However, metabolic screening by urinary
biochemistry analysis must also be undertaken
routinely because underlying metabolic disorders
may not always be reected in the chemical composition of the stones. e presence of urinary
infection and/or abnormalities of the urinary
tract abnormality does not exclude the possibility of co-existing metabolic disorder and every
child with stone disease, regardless of the perceived aetiology, should therefore undergo metabolic screening aer the eradication of infection
and ideally at least 6 weeks aer stone clearance
(Table 11.1).
99m
Tc)mercaptoacetyl-
Management / Treatment Modalities 145
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Table 11.1 Metabolic screening protocol
Plasma levels of urea, electrolytes, creatinine,
calcium, phosphate, magnesium, uric acid
Early morning urine sample (pH to exclude
renal tubular acidosis)
‘Spot’, i.e. untimed, urine sample 2–5 ml:
– Ratio of calcium, oxalate, cystine, citrate
and urate to creatinine
–Urine microscopy and culture
24-hour urine collection:
– Calcium, cystine, creatinine clearance, total
urinary volume
– A separate 24-hour collection is required
for oxalate analysis as the sample is
acidied during collection
METABOLIC SCREENING
Stone screening can be reliably undertaken on a
random ‘spot’ sample of 2–5 ml of urine, although
an early morning specimen may be preferable for
some studies. Twenty-four hour urine collections
may be indicated depending on the clinical presentation, a positive family history for stones,
stone analysis and results from the urinary ‘spot’
samples. Urine biochemistry analysis is used to
monitor the eect of preventative measures where
a metabolic cause has been identied.
Treatment Modalities
Less invasive techniques have become increasingly applicable for use in children and have
consequently reduced the requirement for open
surgery in this age group.
Guidelines based on the published literature
can be briey summarised as follows:
●
ESWL is the treatment of choice for renal
calculi <20 mm in size.
●
PCNL is the treatment of choice for renal
calculi >20 mm in size.
●
Ureteroscopy and lithotripsy with the
holmium laser is the treatment of choice for
ureteric calculi.
Medical expulsive therapy (MET)
is can be considered for the treatment of an
uncomplicated ureteral stone <10 mm if the
child’s clinical condition is stable. Medical expulsive therapy using alpha-adrenergic antagonists to
relax the ureteric smooth muscle has been shown
to increase stone expulsion rates in children
without causing signicant adverse side eects.
Tamsulosin and doxazosin are the most commonly used agents. Close follow-up is essential to
conrm stone-clearance and assess the possible
need to move on to other treatment modalities.
MANAGEMENT
Children who present acutely with complications
should be urgently referred to a paediatric stone
unit. Following initial resuscitation, the priority
is decompression of the obstructed urinary system. is may be achieved by percutaneous nephrostomy or by retrograde insertion of a JJ stent if
this is feasible and the child’s condition is stable.
Denitive stone surgery should be deferred until
the patient has recovered from the acute episode.
e aims of treatment are to achieve complete
stone clearance whilst minimising renal tissue
damage and complications. Some patients may
need a planned, staged approach with a combination of interventions at dierent intervals to
achieve complete stone clearance.
External shockwave lithotripsy (ESWL)
Shockwaves, generated either by piezoelectric
energy or by an electromagnetic generator, are
transmitted to the patient via a silicon-membrane
covered cushion containing a uid or water lm
(Figu re 11. 5). Using in-line ultrasound or X-ray
linked to the shockwave generator, this energy is
focused on the renal stone(s). Unlike adults, children frequently require general anaesthesia or
heavy sedation to ensure they maintain a suitable
position throughout the duration of the treatment session.
ESWL is valuable for the treatment of renal
stones <2 cm and stones in the upper ureter. e
reported success rates range from 49% to 95%.
It is less eective for the treatment of very dense
stones (>1000 HU) such as those composed of
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Figure 11.5 Child being treated under general anaesthesia by a current generation Piezolith litho-
tripter. Stone localisation and imaging during the treatment is achieved by a combination of in-line
ultrasound and, if necessary, X-ray C-arm.
cystine or calcium-phosphate, although this is
not an absolute contraindication. ESWL also has
a role for ‘mopping up’ residual fragments following PCNL. JJ stents are not routinely placed for
ESWL. If the child already has a stent in situ it is
removed at the end of the ESWL session under
the same general anaesthetic to facilitate the passage of fragments.
Complications
Steinstrasse (the presence of a column of stone
fragments in the ureter) occurs in 8% of cases –
with the risk being higher in smaller children with
large stones. It can be managed by retrograde
insertion of a JJ stent, although ureteroscopy may
be required for stone clearance.
Children who are thought to be at greater risk of
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developing steinstrasse are monitored aer ESWL
with an early ultrasound scan and planned review.
Dermal bruising is common and haematuria
occurs in up to 40% of patients. Initial concerns
regarding risks of impaired renal growth, renal
scarring or hypertension have not materialised
and the published data have demonstrated that
ESWL is a safe treatment modality in children.
Percutaneous nephrolithotomy
(PCNL)
PCNL is typically used for large staghorn calculi,
renal stones unsuitable for ESWL or stones persisting following previous intervention. Stonefree rates of up to 98% have been reported and
PCNL has largely replaced open surgery for the
treatment of large stones in children.
e procedure starts with a cystoscopy and
retrograde contrast studies to delineate the ipsilateral renal and ureteric anatomy. en, with
the patient prone, percutaneous needle puncture into the selected calyx is performed under
ultrasonographic or uoroscopic guidance. Serial
dilators are passed over a guidewire to widen
the tract suciently to permit the introduction
of an endoscope into the renal collecting system
(Figu re 11.6). Under direct vision, the stone is
Management / Complications 147
Figure 11.7 Endoscopic view with the nephro-
scope. Stone fragment removed with a grasper
under direct vision after disintegration with a
pneumatic probe.
either removed or is disintegrated with an ultrasonic or pneumatic probe (Figure 11.7). e kidney is drained post operatively by a nephrostomy
tube or internal JJ-stent.
e “standard” PCNL tract corresponds to
24–30Fr but miniaturised PCNL systems are now
available, such as the SuperMini PCNL with tract
size of 14F. However, reduced tract size usually
comes at the expense of speed of stone clearance.
e stone(s) are disintegrated with Holmium
YAG laser and removed via active suction along
the tract.
Figure 11.6 PCNL – percutaneous sheath, neph-
roscope and lithoclast.
Complications
Bleeding requiring transfusion occurs in <10%
of cases. Infective/febrile complications occur in
up to 15% of cases – highlighting the importance
of appropriate peri-operative antibiotic cover.
Persistent urinary leakage, hydrothorax, injury
to lung/liver/spleen and pelvicalyceal scarring are
uncommon but recognised complications.
Ureterorenoscopy (Ureteroscopy)
(URS)
Ureteric stones and renal stones in favourable anatomical positions can be treated using
semirigid ureteroscopes (4.5/6.5 6.8/8.5 F) or by
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exible ureteroscopy (Figure 11.8a, b). Under
direct vision, the stones are fragmented by laser.
Small stone fragments can be cleared with an
endoscopic basket and sent for stone analysis.
e remainder can be further fragmented to dust
which passes spontaneously. However, passive
dilatation of the VUJ/PUJ by a period of indwelling ureteral stenting may sometimes be necessary
to enable the ureteroscope to be negotiated into
the ureter and kidney.
A stone-free rate of 90% has been reported
in children. Complications occurring in 10%
of cases include UTI, haematuria and intraoperative complications such as ureteral
perforation or tear. Ureteral strictures are
uncommon but it is important that care is taken
to minimise trauma to the ureter and VUJ during instrumentation.
Minimally invasive cystolithotomy
Endoscopic treatment is now feasible for the
majority of bladder stones. Access can be achieved
per urethra, via a Mitrofano channel or via a
direct percutaneous channel – percutaneous
cystolithotomy (PCCL). e stone is fragmented
using a lithoclast or laser and fragments can be
extracted directly (Figure 11.9a, b). e PCCL
route avoids urethral trauma and permits the
use of a larger access sheath to deal with larger
bladder stones and reduce operative time. Open
surgery (cystolithotomy) remains the preferred
option for very large stones or if there are a large
number of stones of signicant size.
Urethra
Urethral calculi are rare in children. ey may
result from impaction of a calculus (or postESWL fragments) during its passage through the
urethra, or the formation of a stone within an
anatomical abnormality of the urethra such as
the remnant of a rectourethral stula following
surgery for an anorectal anomaly.
Urethral calculi can be removed or crushed
using rigid endoscopic biopsy forceps. Meatotomy
may be required to release a stone impacted
within the fossa navicularis.
Figure 11.8 (a) Ureteroscopy and laser litho-
tripsy (left). (b) Ureteroscopic view (right)
demonstrating ureteric stone partially laser
fragmented. Note the clear laser bre in the
7 o’clock position and the two guide wires
running in 2 o’clock position that aid passage
of the ureteroscope. The smaller telescopes
limit the optics which reduces the image
quality.
Follow-up / Recurrence 149
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Figure 11.9 (a) Endoscopic fragmentation of bladder calculus by lithoclast (left). (b) PCCL access
into bladder with a nephroscope passed via a clear access sheath.
Laparoscopy
A poorly functioning kidney which has been damaged by stone disease or xanthogranulomatous
pyelonephritis can be removed laparoscopically.
However, laparoscopic nephrectomy in such cases
should only be undertaken by an experienced laparoscopic surgeon because of the extensive perirenal inammatory adhesions and risk of damage to
adjacent organs.
Open pyelolithotomy
Although, largely superseded by ESWL and
endoscopic techniques, open surgery still plays a
limited role – for example in urolithiasis in congenitally obstructed systems or children with
severe skeletal abnormalities which may preclude
endoscopic intervention.
Following exposure and mobilisation of the
kidney, isolated stones within the collecting system can usually be removed with stone forceps
via an incision in the renal pelvis (Figure 11.10).
e bulk of a staghorn calculus can also be
removed by this approach, but the subsequent
removal of fragments impacted in the calyces can
be dicult and may require later intervention
with ESWL to achieve complete stone clearance.
Complications include haemorrhage, particularly aer multiple nephrotomies, retained
or displaced stone fragments, prolonged urinary
Figure 11.10 Pyelolithotomy. Open removal of a
calculus from the renal pelvis.
leakage and parenchymal damage resulting in
loss of renal function.
FOLLOW-UP
Recurrence
Stone disease in children is associated with a
signicant risk of recurrence – with a 20% incidence of further stone formation within 10 years.
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is risk can be reduced by appropriate follow
up and management – ideally in a joint urologynephrology clinic.
Infective calculi
e recurrence risk can be minimised by correcting any underlying predisposing anatomical
abnormality and by maintaining infection-free
urine with antibiotic prophylaxis for 12 months
following surgery. A circumcision can be considered in young boys with infective stones.
Metabolic calculi
Following the initial stone episode, the recurrence rate in children with underlying metabolic
disorders is around 40% within 5 years.
A high uid intake is essential for all groups
together with dietary modications dependent
on the metabolic abnormality. In addition, a
number of specic measures can be utilised as
outlined in Table 11.2 .
Residual fragments
Even in the absence of infection or urinary stasis, seemingly ‘insignicant’ residual stone fragments of less than 4mm have a 50% likelihood
of increasing in size (‘regrowing’) in structurally normal kidneys and up to 80% in abnormal
kidneys. Achieving complete stone clearance at
the time of initial intervention is therefore of the
upmost importance.
Table 11.2 Medications commonly used for
metabolic stone prevention
Thiazide diuretic Hypercalcuria
– despite diet
modication
Potassium citrate Hypercalcuria,
hyperoxaluria,
Cystinuria – only
with acidic urinary
pH
Tiopronin,
D-penicillamine
Pyridoxine Primary hyperoxaluria
Cystinuria
XANTHOGRANULOMATOUS
PYELONEPHRITIS
(FIGURE 11.11A, B)
is rare manifestation of stone disease is characterised by a destructive inammatory mass
which invades renal parenchyma. e presentation is with chronic sepsis: weight loss, anaemia,
elevated inammatory markers and the presence of a mass which may extend to involve adjacent viscera. Pain is usually dull and persistent.
e diagnosis is conrmed by a combination of
ultrasound, CT and DMSA, which reveals absent
or minimal function in the aected kidney.
Open nephrectomy is usually preferred because
of the dense perirenal inammatory adhesions
and risk of damage to adjacent organs. Postoperative monitoring of the remaining kidney
and aggressive treatment of any further UTIs
are essential.
KEY POINTS
●
Urinary calculi are becoming more
common in children. Urinary infection
is still an important aetiological factor
but the importance of predisposing
metabolic disorders is being increasingly recognised.
●
Every child who presents with calculi
should be thoroughly evaluated to identify any underlying metabolic disorder
or urological malformation – regardless
of presumed primary aetiology.
●
e initial priorities of management
consist of relieving obstruction, treating sepsis and achieving complete stone
clearance.
●
Urine biochemistry should be combined with stone analysis to diagnose
metabolic disorders.
●
Minimally invasive modalities such
as ESWL, PCNL and endoscopic
lithotripsy have now superseded open
techniques in the treatment of children’s stones.
Xanthogranulomatous pyelonephritis 151
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Fig ure 11.11 (a) CT scan (left): xanthogranulomatous pyelonephritis of the right kidney illustrat-
ing calculi embedded within a non-functioning inammatory renal mass. Normal left kidney.
(b) Histopathology specimen of an XPN kidney (right): the kidney has been split open along its
long axis.
●
Careful follow-up, with maintenance
of sterile urine and appropriate treatment of any metabolic disorder, is
essential to minimise the risk of stone
recurrence.
FURTHER READING
Bowen DK, Tasian GE. Paediatric stone disease.
Urol Clin N Am. 2018;539–550.
Issler N, Dufek S, Kleta R et al. Epidemiology
of paediatric renal stone disease: a 22-year
single centre experience in the UK. BMC
Nephrol. 2017; 18:136
Papageorgiou E, Smeulders N. Renal Calculi.
In: Davenport M, Geiger J. (eds), Operative
Paediatric Surgery, 8th Edition. Taylor &
Francis, [In Press].
Purkait B, Sinha RJ, Bansal A, Sokhal AK, Singh
K, Singh V. What is the fate of insignicant
residual fragment following percutaneous
nephrolithotomy in paediatric patients with
anomalous kidney? A comparison with normal kidney. Urolithiasis. 2018;46:285–290.
Rob S, Jones P, Pietropaolo A, Grifn S, Somani
BK. Ureteroscopy for stone disease in paediatric population is safe and effective in
medium-volume and high-volume centres:
evidence for a systematic review. Curr Urol
Rep. 2017;18:92.
Velázquez N, Zapata D, Wang HHS et al.
Medical expulsive therapy for paediatric
urolithiasis: systematic review and metaanalysis. J Ped Urol. 2015;11(6):321–327.
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