Diagnostic ultrasound ( PDFDrive )

1788 PART V Pediatric Sonography
is typically used to clarify whether the dilation is caused by
obstruction.
An obstructed ureter can result from many causes. Ectopic
insertion of a ureter can cause obstruction either with or without
a ureterocele and may result in dilation of the more proximal
collecting system and ureter, typically manifesting with ureteral
duplication. he ureter can also be obstructed by an intraluminal
abnormality, such as a stone, blood clot, or fungus ball. Increased
peristalsis in the ureter proximal to the obstruction may be
detected with real-time sonography. Doppler sonography may
show a diminished or abnormal ureteral jet on the side of
obstruction. 18,40,41 he ureter can also be obstructed anywhere
along its course by extrinsic compression from a mass, such
as a lymphoma or abscess. he exact site of obstruction may
be diicult to visualize by ultrasound because of overlying
bowel gas.
Bladder Outlet Obstruction
Bilateral hydronephrosis is frequently caused by obstruction at
the level of the bladder or bladder outlet. Congenital obstruction
due to posterior urethral valves (PUVs) results in an irregular,
thick-walled bladder. PUV can occasionally be diagnosed by
ultrasound, with demonstration of a dilated posterior urethra.
Transperineal contrast-enhanced ultrasound (CEUS) diagnosis
of PUV has also been described 42,43 (Fig. 52.19). However,
VCUG should be performed for optimal visualization of
the valves.
Patients with spinal dysraphism and hyperrelexive detrusor
muscle activity will have a functional obstruction due to a
neurogenic bladder that produces high bladder pressure during
voiding. hese patients may develop a thick-walled, trabeculated
bladder 44 (Fig. 52.20, Video 52.2, Video 52.3, Video 52.4).
Congenital anomalies of the spine should be sought with radiographs
and spinal ultrasound in neonates, if not obvious
clinically.
A pelvic mass that obstructs the bladder outlet, such as
rhabdomyosarcoma, or less commonly, a ibroepithelial polyp,
can also be associated with bilateral hydronephrosis and
hydroureter. 45
Vesicoureteral Relux
Dilation of the renal collecting system is not always caused by
obstruction, and other abnormalities, such as VUR, should be
considered. In a child with hydronephrosis detected by ultrasound,
the bladder size and contractility and the urethra should be
further evaluated with VCUG. In addition, VUR can be diagnosed
and may be the cause of the UTD.
Contrast-enhanced voiding urosonography is a safe, nonionizing,
radiation-free alternative to the luoroscopic VCUG that
is used by experienced investigators in some centers throughout
the world for the management of VUR. Its sensitivity is comparable
to or greater than that of VCUG or radionuclide cystography
in the diagnosis of VUR. 46 Published studies reporting use of
this technique in the United States to date have been limited. 47,48
Contrast-enhanced voiding urosonography is performed ater
bladder catheterization and intravesical infusion of normal saline
containing the ultrasound contrast agent. Sequential imaging of
the bladder, kidneys, and urethra is performed during bladder
illing and voiding. Ultrasound contrast-speciic settings are used
to image the microbubbles. Digital ultrasound still images as
well as image clips are used for documentation purposes (see
Fig. 52.20). he severity of VUR can be graded using a scale
similar to the International Grading System used for conventional
VCUG. 49 Patients with relux are oten treated endoscopically
with a submucosal, subureteric injection of a bulking agent.
Follow-up sonography of the bladder will depict the implants,
which over time may undergo changes in size and shape as well
as calciication 50,51 (Fig. 52.21). Paltiel and colleagues 52 showed
that nonvisualization of the implant or a multilobed contour is
associated with persistent relux.
Prune-Belly Syndrome
Prune-belly syndrome, also known as Eagle-Barrett syndrome,
is a rare congenital disorder that occurs almost exclusively in
males and is thought to result from urethral obstruction early
in development. Abnormalities include absence or deiciency of
the abdominal musculature; large, hypotonic, dilated and tortuous
ureters; a large bladder; a patent urachus bilateral cryptorchidism;
and a dilated prostatic urethra. here are decreased muscular
ibers throughout the urinary tract and prostate, resulting in
dilation and hypoperistalsis. Renal dysplasia and hydronephrosis
can occur to varying degrees. Associated malformations of the
cardiopulmonary, gastrointestinal, and skeletal systems are
common. 53
Megacystis-Microcolon-Malrotation–
Intestinal Hypoperistalsis Syndrome
Megacystis-microcolon-malrotation–intestinal hypoperistalsis
syndrome (MMIHS), a rare syndrome, is an inherited, autosomal
recessive disorder that falls on the spectrum of chronic intestinal
pseudo-obstructive disorders, which includes chronic adynamic
ileus, hypoganglionosis, Hirschsprung disease, intestinal
neuronal dysplasia, and total colonic aganglionosis. It is more
common in girls than boys. Presentation is usually in the neonatal
period, although the diagnosis can also be suspected on prenatal
sonography. 54 Typical clinical features include abdominal distention,
hypoactive or absent bowel sounds, and an inability to void
spontaneously. A markedly dilated, nonobstructed bladder, a
microcolon, and decreased or absent intestinal peristalsis are
characteristic indings. Other frequent abnormalities include
hydroureteronephrosis, VUR, intestinal malrotation, and a
shortened bowel. Although the exact etiology has not yet been
elucidated, smooth muscle myopathic changes have been demonstrated
at pathology. Marked abnormality of the detrusor
muscle of the bladder results in voiding dysfunction. 55 Most
patients with MMIHS eventually succumb to sepsis, malnutrition,
or multiorgan failure. Recurrent UTIs result from the need for
chronic bladder catheterization. Intestinal function is resistant
to surgical intervention. Children who survive beyond the
neonatal period require long-term total parenteral nutrition
(TPN), which eventually results in TPN-associated chronic liver
disease. Transplantation is currently the only successful management
option for those patients who cannot tolerate TPN. he