Atoosa Adibi MD. Isfahan University Of Medical scienses
Slide 3
Ultrasound (US) is the most widely used and primary imaging
modality for the urinary tract in children. magnetic resonance (MR)
imaging as second step, particularly in pediatric patients. an
advanced pediatric radiology unit : most routine uroradiologic
examinations can be performed with US and MR imaging
Slide 4
exception is: following an US, additional diagnostic imaging
for urolithiasis is needed in the case of severe
polytrauma,including blunt abdominal trauma. computed tomography
(CT)
Slide 5
MR IMAGING OF THE URINARY TRACT
Slide 6
Indications: congenital anomalies,mainly pelvicaliectasis
and/or ureterectasis, renal and bladder tumors. Infections and
vascular anomalies of the urinary tract
Slide 7
precontrast, postcontrast, and dynamic postcontrast studies.
The precontrast sequences are optimal for depicting the
urine-filled pelvicalyceal system and ureter and provide exquisite
morphologic detail. After administering intravenous (IV) contrast,
performing dynamic sequences is a better choice for the kidneys, as
it provides the information of a non dynamic contrast study in
addition to functional information with depiction of the arterial,
venous, nephrographic, and urographic phases. The postcontrast
dynamic study can be conducted as MR angiography (MRA).
Procedure Preparation:Hydration with IV fluid administration
starting a half hour before the scan A bladder catheter is placed.(
A distended bladder may have a negative effect on the excretion of
urine) The urine bag is placed below the level of the scanner table
Furosemide (Lasix) is administered IV at a dose of 1 mg/kg (maximum
20 mg), 10 minutes before the procedure.
Slide 10
It is best to place the patient in the prone position if we are
evaluating the contrast excretion into the pelvicaliceal system.
Gadolinium-DTPA (Magnevist), has higher (1.208) specific gravity
than urine (1.002 1.030) and settles in the dependent
position.
Slide 11
a sagittal T2 sequence An axial T2 with fat saturation A 3D T2
with fat saturation The T1 fa tsaturated +post contrast
Slide 12
axial plane in T2 with fat saturation The sagittal T1sequence
with fat saturation
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Procedural and scan modifications 1. Ectopic ureter: the
precontrast series may suffice to depict the morphologic findings
and the postcontrast part needs to be added only if functional
evaluations of the kidneys are requested
Slide 16
2. Cyst versus diverticulum: Calyceal diverticulum fills with
contrast in a retrograde manner later than the calyces or renal
pelvis. The delay(sometimes needs to be 1 hour or longer)
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CT OF THE URINARY TRACT: URO-CT
Slide 20
the main attractions for using uro-CT in pediatrics are
availability, fast speed, less frequent/no need for sedation, and
lesser cost. CT may be used as a confirmatory secondary modality,
as in the case of CT for urolithiasis.
Slide 21
try to find alternative modalities,completely avoiding
potential radiation exposure. uro-CT needs to be considered as a
secondary option if US and/or MR imaging are inadequate,
unavailable,or cannot be performed and the clinical suspicion
warrants further imaging clarification.
Slide 22
Slide 23
It is important to note that in blunt abdominal trauma in
children, renal lesions are more frequent. than in adults because
of a nonossified thoracic cage, thin abdominal wall, and paucity of
perirenal fat. try not to overdo CT, even in the setting of
pediatric trauma
Slide 24
Procedure preceded at least by US A multiphase study has rarely
any place in pediatric uro-CT
Slide 25
arterial phase: a bolus triggering, or a delay of 8 to 20
seconds Nephrographic phase: delay of 70 to 100 seconds the
excretory phase: delay can be 5 to 15 minutes. Additional CT
angiography and/or urography are not routinely performed. For renal
trauma, mostly a nephrographic phase acquisition will suffice.
Slide 26
splitting the contrast bolus and injecting at 2 different time
points can produce both nephrographic and urographic phases
simultaneously on one scan
Slide 27
Diagnostic Utility In trauma cases, a meticulously conducted
abdominal US and Doppler study is adequate to exclude major renal
injury in children. In the follow-up of traumatic renal findings,
US is also the imaging modality of choice
Slide 28
uroCT and urolithiasis Suspected stone of the urinary tract
when an US with color Doppler does not depict a stone, but
secondary signs are present, or an US is inconclusive/ negative,
and high clinical suspicion remains
Slide 29
a well-hydrated patient is optimal. The patient is placed in
prone position to be able to differentiate an impacted stone at the
ureterovesical junction from that of a mobile bladder calculus
Slide 30
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Assessment: Diagnostic Utility: difference in usefulness
between the 2 tests may not be clinically significant.
Slide 33
CT ANGIOGRAPHY Indications: Renovascular hypertension traumatic
renovascular injury other less common renovascular disorders
Slide 34
For optimal power injection of the contrast, a suitable size of
peripheral IV catheter is necessary (neonate, 24 G; infant, 22/24
G; >1 year, 20/22 G ). The IV access is first tested with saline
at the same flow rate planned for contrast injection.
Slide 35
The scan extends from the supraceliac aorta to the upper
external iliac arteries Alternatively, a split-bolus technique may
be used, injecting one third to one-half of the contrast volume
beforehand and the other two- thirds to one-half for an arterial
phase scan. This allows a combination of an arterial and a
urographic phase in one single acquisition.
Slide 36
Assessment In renovascular hypertension, the focus is on
morphologic changes of the renal arteries (stenoses,aneurysms,
beadings) and secondary signs (poststenotic dilatation, collateral
formation, focal parenchymal perfusion defects, asymmetric
nephrogram, parenchymal scarring)
Slide 37
a 3-year-old patient with hypertension and neurofibromatosis
type I demonstrates a short-segment high-grade stenosis
Slide 38
CT CYSTOGRAPHY Active contrast filling of the urinary bladder,
to detect extraluminal contrast, which is an indicator of rupture.
Direct CT cystography entails retrograde filling of the bladder and
indirect CT cystography passive antegrade filling of the bladder
after IV contrast administration.
Slide 39
Slide 40
Indications Bladder trauma with or without known pelvic
fracture and hematuria workup for suspected delayed spontaneous
rupture of augmented bladder
Slide 41
Procedure For direct CT cystography before bladder
catheterization: exclude urethral injury An age appropriate Foley
catheter is placed; the balloon is not inflated. A precontrast scan
is performed from the diaphragm to the ischial tuberosity. A drip
infusion is prepared with diluted (10%) water-soluble contrast (eg,
50 mL in 450 mL 0.9% NaCl solution). The bladder is filled until
the patient starts to void or the maximal bladder capacity ([age 1,
2] 30, mL) is reached. Wait for about 5 minutes and rescan the
abdomen and pelvis. If no contrast extravasation is visualized, it
may be necessary to perform further delayed scan of just the
pelvis
Slide 42
Indirect CT cystography is performed after IV contrast
administration and antegrade filling, particularly in the setting
of polytrauma. This includes occlusion of the Foley catheter, if
present, when the patient arrives in the CT suite and a delay of 5
to 10 minutes after the IV contrast administration before
rescanning the abdomen and pelvis. However,the indirect cystography
is much less reliable in the diagnosis of bladder rupture.
Slide 43
Slide 44
KEY POINTS: Ultrasound is the primary imaging modality for the
pediatric urinary tract. Magnetic resonance (MR) imaging needs to
be the second imaging option after ultrasound in children.
Functional MR urography (fMRU) provides comprehensive morphologic
and functional information. Computed tomography (CT) is the imaging
choice in children only in the following circumstances: (1)
inadequate ultrasound for urolithiasis, and (2) blunt abdominal
trauma in the setting of polytrauma. The choice of CT over MR for
uroradiologic imaging is mainly for ancillary reasons:
availability, fast speed, no sedation, and low cost. In children,
CT angiography (CTA) of the urinary tract is primarily performed
for evaluation of therenal arteries for suspected stenosis. Direct
CT cystography may be necessary for evaluation of bladder
rupture.
Slide 45
Slide 46
Diagnostic examination of the child with urolithiasis or
nephrocalcinosis
Slide 47
Stones of all composition, with the exception of drugs (e.g.
indinavir) and matrix (protein), have distinguishing
characteristics of echogenicity and shadowing on ultrasonography.
Ultrasonography has the additional advantages of wide availability,
avoidance of ionizing radiation, ready detection of hydronephrosis,
and ability to define some aspects of the anatomy of the urinary
tract.
Slide 48
stones as small as only 1.52 mm in diameter can be visualized
on ultrasonography (US), the success of this imaging method clearly
depends on inter-observer and intra- observer variability and
skills.
Slide 49
For the detecting and monitoring of
nephrocalcinosis,high-resolution ultrasonography is the optimal
imaging method.Nephrocalcinosis is classified according to the
anatomic area involved.
Slide 50
Some pitfalls in the renal ultrasonography of neonates, and
especially preterm infants, have to be noted: TammHorsfall protein
(THP) deposits within the renal calyces may look like
nephrocalcinosis. THP deposition,however, disappears within 12
weeks, and follow-up will show completely normal kidneys.
Slide 51
the echogenicity of the renal cortex in neonates is
physiologically increased, hence detection of cortical
nephrocalcinosis can be difficult and may become evident only some
weeks later when a rim of cortical calcification becomes
visible.
Slide 52
Normal, still hyperechoic kidney of a preterm infant
Slide 53
TammHorsfall kidney
Slide 54
medullary nephrocalcinosis (NC) grade 1
Slide 55
medullary NC grade II (mild increase of echogenicity at whole
pyramid)
Slide 56
medullary NC grade III (more severe hyperechogenicity of entire
pyramid);
Slide 57
Diffuse corticomedullary NC
Slide 58
Slide 59
vesicoureteral reflux in children Imaging studies are the basis
of diagnosis and management of VUR. The standard imaging tests
include renal and bladder ultrasonography and voiding
cystourethrography (VCUG).
Slide 60
Indications for imaging studies are as follows: Imaging after
the first UTI is indicated in all children younger than 5 years,
children of any age with febrile UTI, and boys of any age with UTI
Children with prenatally identified hydronephrosis should be
evaluated postnatally; however, ultrasonography performed during
the first 3 days of life may have a high rate of false- negative
results because of relative dehydration during the neonatal
period
Slide 61
Although the traditional approach in children with UTI has been
evaluation for VUR with VCUG or radionuclide cystography (RNC),
some authorities now advocate that children with a history of
febrile UTI undergo a dimercaptosuccinic acid (DMSA) renal scan, to
assess for evidence of kidney involvement, kidney scarring, or
both; if DMSA scan findings are positive, VCUG is recommended.
Slide 62
One approach is to perform RNC as the initial screening test in
girls and then to perform standard VCUG when VUR is observed. Other
clinicians use VCUG for the initial diagnosis and use RNC for
follow-up studies.
Slide 63
VCUG is the criterion standard in diagnosis of VUR, providing
precise anatomic detail and allows grading of the reflux. The
International Classification System for VUR is as follows [3] :
Grade I - Reflux into nondilated ureter Grade II - Reflux into
renal pelvis and calyces without dilation Grade III - Reflux with
mild to moderate dilation and minimal blunting of fornices Grade IV
- Reflux with moderate ureteral tortuosity and dilation of pelvis
and calyces Grade V - Reflux with gross dilation of ureter, pelvis,
and calyces, loss of papillary impressions, and ureteral
tortuosity
Slide 64
In general, VCUG should be performed after the child has fully
recovered from the UTI. However, some children demonstrate reflux
only during an episode of cystitis.
Slide 65
Radionuclide cystography Instillation of technetium-99m
pertechnetate into the bladder and observation with a gamma camera
is a highly sensitive test for VUR Advantages include substantially
lower radiation doses than with VCUG and the potential for
increased sensitivity because of the ability to conduct prolonged
periods of observation Disadvantages primarily consist of the poor
anatomic detail, especially of the male urethra Grade I reflux is
poorly detected by this study, because the distal ureters are
commonly obscured by the bladder Grading by nuclear cystography is
limited to mild, moderate, and severe grades.
Ultrasonography After the prenatal presumptive diagnosis UPJ
obstruction or other conditions causing hydronephrosis is made, the
neonate should undergo ultrasonographic evaluation, but the timing
is controversial. Transient neonatal dehydration occurs 48-36 hours
after birth, so follow-up ultrasonography of mild-to-moderate cases
of hydronephrosis should be performed after this period. In severe
cases, such as very large renal pelvis, bilateral hydronephrosis,
solitary kidney, or oligohydramnios, immediate evaluation within 48
hours must be performed; severe hydronephrosis in spite of the
oliguric status of the child can suggest the need
Slide 69
Postnatal evaluation consists of a urinary tract study to
determine whether the calyceal pelvic dilation with or without
renal cortical thinning is present. The most widely used grading
system of the severity of hydronephrosis on ultrasonography after
birth is SFU system, rather than the anteroposterior diameter of
the renal pelvis.
Slide 70
The SFU grading system for hydronephrosis is as follows [19] :
Grade 0 - No hydronephrosis, intact central renal complex seen on
ultrasonography Grade 1 - Only renal pelvis visualized, dilated
pelvis on ultrasonography, no caliectasis Grade 2 - Moderately
dilated renal pelvis and a few calyces Grade 3 - Hydronephrosis
with nearly all calyces seen, large renal pelvis without
parenchymal thinning Grade 4 - Severe dilatation of renal pelvis
and calyces with accompanying parenchymal atrophy or thinning
Slide 71
Voiding cystourethrogram (VCUG) Vesicoureteral reflux (VUR) has
been found in as many as 40% of affected children. The degree of
reflux is often low grade, not contributing to upper urinary tract
obstruction, and it is likely to spontaneously resolve. However,
UPJ obstruction may also be seen with severe VUR when the tortuous
dilated ureter develops a kink in the UPJ area, which is relatively
fixed to surrounding structures, and may cause secondary
obstruction.
Slide 72
Diuretic renography Diuretic renography is the most widely used
noninvasive technique to determine the severity and functional
significance of UPJ obstruction. Various protocols and techniques
have been developed, resulting in significant variability in the
interpretive criteria and results.
Slide 73
Doppler ultrasonography [ The development of Doppler
ultrasonography has become another useful diagnostic modality in
the assessment of kidneys with ureteropelvic junction (UPJ)
obstructions. With duplex Doppler ultrasonography, intrarenal
vasculature can be assessed to determine the resistive index.
Normal kidneys reliably demonstrate resistive indices less than
0.7, and obstructed kidneys show higher values. Administration of
diuretics can aggravate the preexisting obstruction, thereby aiding
the diagnosis by Doppler ultrasonography. It is especially reliable
in the preoperative diagnosis of aberrant-accessory blood vessels
associated with UPJ obstruction.
Slide 74
Intravenous pyelography (IVP) IVP has been used to evaluate UPJ
obstruction, but IVP may not provide adequate information to
determine the true obstruction, and it is especially difficult to
interpret in children. IVP provides information about the
obstruction and contralateral side and especially facilitates
operative planning; however, infant urograms are compromised by the
immature renal function, which impedes adequate visualization of
the collecting system. Bowel gas and underlying bony structures
also make interpretation of the urogram difficult.