الفهرس 
Uretero-pelvic Junction Obstruction (UPJOOnly 14 pages are availabe for public view
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Abstract
Prior to the advent of maternal ultrasonography in the 1980s, children with significant congenital
hydronephrosis requiring surgery presented symptomatically with abdominal pain, urinary
infection, hypertension, hematuria, or failure to thrive 1. Prenatal diagnosis of urinary tract
dilation occurs in 1-2% of all pregnancies. Based on an estimated birth rate in the United States
of 4 million per year, approximately 40-80,000 children are diagnosed annually with this
condition. The prenatal sonographic identification of urinary tract dilation reflects a spectrum of
potential etiologies and uropathies 2.
Antenatal hydronephrosis may develop secondary to transient dilation of the collecting
system, upper/lower urinary tract obstructive uropathy, and organic non-obstructive processes
such as vesicoureteral reflux (VUR), megaureters, and prune-belly syndrome. The most common
causes are transient hydronephrosis, ureteropelvic junction obstruction (UPJO), and VUR. In
many cases, the etiology of urinary tract dilation is unable to be determined before birth and is
diagnosed postnatally with additional imaging including ultrasound and voiding
cystourethrogram 1.
The rationale of prenatal detection is to identify pathology prior to the development of
complications such as urinary tract infection (UTI), and renal dysfunction. In the majority of the
cases, the prenatal finding of urinary tract dilation is transient or physiologic and has no clinical
significance. In other cases, it represents obstructive conditions such as posterior urethral valves
that have significant morbidities and even mortalities. In many of the cases, the etiology of
urinary tract dilation is unable to be determined before birth and is diagnosed postnatally with
additional imaging including ultrasound and voiding cystourethrogram 3.
Clinical practice patterns vary considerably regarding recommendation for the follow-up
evaluation of fetuses and children who have been diagnosed with prenatal urinary tract dilation.
This stems from the challenge of predicting which children will have a clinically significant
uropathy and would benefit from postnatal imaging.
Evaluating every child with prenatal urinary tract dilation results in the expenditure of
significant healthcare resources and could cost over $90 million annually. This does not factor in
the cost associated with travel, time off from work for the parents, unnecessary parental anxiety,
childhood radiation, and antibiotic exposure. Alternatively, not evaluating any child with
prenatal urinary tract dilation could avoid these initial costs but might delay the diagnosis of significant uropathies such as PUV and consequently, incur higher long-term health and financial
costs3.
High-grade antenatal hydronephrosis usually requires extensive evaluation and strict
follow-up. This might necessitate the use of continuous antibiotic prophylaxis (CAP), further
evaluation, longer follow-up period, and possibly surgical intervention, depending on the
underlying etiology. On the other hand, low-grade hydronephrosis is usually benign in nature
and about 50% of fetuses and infants diagnosed with this entity might show complete resolution
on follow-up 4.
Infants with high-grade isolated hydronephrosis and preserved DRF may be safely
followed with serial diuretic renograms. Patients with SFU Grade 4 isolated hydronephrosis are
more likely to require surgery. Worsening drainage is a useful indicator for surgical intervention
which limits the number of pyeloplasties while preserving differential renal function 5. Recurrent
FUTI despite continuous antibiotic prophylaxis is the main indication for surgical intervention in
VUR and other megaureters 6-8.