Diagnostic ultrasound ( PDFDrive )

CHAPTER 52 The Pediatric Urinary Tract and Adrenal Glands 1785
lower renal pole to the ectopic upper renal pole (Fig. 52.14,
Video 52.1). he ureter of the ectopic kidney crosses the midline
to insert normally within the bladder. Crossed renal ectopia is
more frequent in boys than girls (male-to-female ratio is 1.4 : 1),
and is two to three times more common on the right side than
on the let. 27 As with other renal anomalies, crossed ectopia can
be an incidental inding but is also associated with other congenital
anomalies. 28
Rarer patterns include crossed unfused ectopia and solitary
or unfused bilateral crossed ectopy. Another pattern of combined
ectopy and fusion of two pelvic kidneys is variably referred to
as a “pancake” or “cake” kidney, depending on the extent of
fusion and the resultant appearance. hese more complex
abnormalities can be isolated or associated with other congenital
conditions.
CAUSES OF HYDRONEPHROSIS
Dilation of the renal collecting system—hydronephrosis—is a
fairly common problem in the pediatric patient. It is frequently,
but not always, associated with obstruction, and ultrasound is
FIG. 52.13 Horseshoe Kidney. Transverse supine image depicts
fusion of the medially rotated lower poles of the right and left kidneys
(K) by a parenchymal band (arrow) extending anterior to the spine (S).
particularly sensitive for its detection. Investigation of a child
with suspected hydronephrosis usually begins with sonography
to evaluate the anatomy of the kidneys, ureters, and bladder. 29
he degree of functional obstruction is evaluated by diuretic
renography. 30 If the obstruction is mild, the patient is followed
because the obstruction and dilation oten resolve as the patient
grows older. 31,32
Congenital hydronephrosis is almost always initially detected
on fetal sonography and the infant referred for evaluation ater
birth. Fetal hydronephrosis may be due to obstruction, VUR,
or a physiologic variant without obstruction. 33 Small amounts
of luid may be detected in the normal renal pelvis. However,
dilation of the renal calyces is abnormal and suggests signiicant
pathology. To make a more precise diagnosis and to estimate
severity, information regarding renal length, parenchymal thickness
and echogenicity, degree of pelvicalyceal and ureteral dilation,
bladder wall thickness, and volume should be obtained with
sonography. 31 Voiding cystourethrography (VCUG) and nuclear
scintigraphy using technetium 99m ( 99m Tc) mercaptoacetyltriglycine
(MAG3) with furosemide (diuretic renography) are oten
performed for complete evaluation. 30,34
Signiicant variation currently exists in the clinical management
of infants and children with prenatally diagnosed urinary
tract dilation (UTD) that is related to a lack of evidence-based
information correlating the severity of prenatal dilation to
postnatal urologic abnormalities. To address the perceived
need for a uniied classiication system with a widely accepted
terminology for the diagnosis and management of prenatal
and postnatal UTD, a UTD classiication system was devised
in 2014 during a consensus meeting of eight medical societies
concerned with the prenatal and postnatal diagnosis and
management of UTD. 35,36 his grading system is correlated with
the risk of postnatal uropathies and is based on six sonographic
features: (1) anterior-posterior renal pelvic diameter (APRPD), (2)
calyceal dilation with distinction between central and peripheral
calyceal dilation postnatally, (3) renal parenchymal thickness,
(4) renal parenchymal appearance, (5) bladder abnormalities,
and (6) ureteral abnormalities. For prenatal studies, the seventh
A
B
FIG. 52.14 Crossed Renal Ectopia. (A) Longitudinal and (B) transverse images of the right lank reveal fusion of the lower pole of the orthotopic
right kidney (R) to the upper pole of the ectopic left kidney (L). The left kidney is medially rotated. See also Video 52.1.