INTRODUCTION AND ANTENATAL
Blockages of the renal/urinary tract
can be physical, where there is a narrowing or obstruction
to the flow of urine, or functional, where the tubes
are open (patent) but are not working properly to
propel the urine along.
Obstruction of the pelvi-ureteric
junction (PUJ)
PUJ obstruction is functional stenosis
at the junction between the renal pelvis and ureter
and is the most common cause of hydronephrosis. PUJ
occurs sporadically and is usually functional, where
the PUJ is patent, rather than due to a physical
obstruction but may be due to ureteral valves.
Most cases of PUJ obstruction are
unilateral (80%), the prognosis is good, and most
cases can be managed conservatively. In cases of
bilateral PUJ obstruction, the degree of obstruction
may vary between sides. In severe cases, the kidney
may dilate to form an abdominal cyst. This cyst can
obstruct the intestine and lungs causing polyhydramnios.
On ultrasound examination hydronephrosis is present but the ureters and bladder
are not dilated and the volume of amniotic fluid is normal. Dilated renal pelves
are seen with or without calyceal dilatation. Serial scans should be performed
to monitor any pelvicalyceal dilatation and amniotic volume.
Ureterocele
Ureterocele is the congenital cystic
dilation of the terminal ureter. Ureterocele may
be simple (functional) or ectopic. In cases of simple
ureterocele, the ureteric orifice in the bladder
wall is normally situated but the VUJ is obstructed
and the ureter dilated at the orifice.
Ectopic ureterocele is a more complex anomaly often associated with ectopic
ureters and ureteral duplications. The cystic part of the intramural segment
of the ureter bulges around the bladder wall and the ureter extremity is ectopic,
often situated at the bladder neck or urethra.
Obstruction of the urinary flow by
a ureterocele is usually accompanied by dilatation
ureter and hydronephrosis. Surgical removal is possible.
Obstruction of the uretero-vesicle
junction (UVJ)
Anomalies of the uretero-vesicle junction
are the second most common cause of hydronephrosis.
Distal obstruction of the ureter is usually functional
but less frequently may be due to ureteral atresia
or stricture. On ultrasound a normal ureter cannot
be seen, so any ureter seen is dilated. UVJ obstruction
usually causes a mild degree of hydronephrosis and
hydroureter, the bladder is normal in size and not
hypertrophic. Unlike cases of megaureter where the
ureter is straight, obstruction of the UVJ can make
the ureter serpiginous (snake-like). The prognosis
of an isolated anomaly is usually good.
Primary vesicoureteral reflux (VUR)
Vesicoureteral reflux is the retrograde
flow of urine up the ureter from bladder to kidney.
Distal obstruction of the ureter is usually functional.
Primary VUR can occur due to a shortening of a narrow
segment (intramural segment) of the ureter when passing
though the bladder wall, reducing the ratio of the
length and diameter of this section, causing a failure
in the transmission of the normal peristaltic waves.
On ultrasound, this anomaly should
be suspected when intermittent dilatation of upper
urinary tract is seen. It frequently results in mild
hydronephrosis and mild dilatation of pelvis and
ureter, liquor volume may be unaffected.
Twenty percent of cases are familial
in origin, and VUJ is a common finding in children
with urinary tract infection. Many cases resolve
spontaneously in childhood although long-term outcomes
depend on the extent of renal growth failure and
reflux nephropathy (scarring).
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POSTNATAL
Complete obstruction early in fetal
life causes renal hypoplasia and dysplasia. Intermittent
obstruction may allow normal renal development. Obstruction
in later pregnancy will result in hydronephrosis
and the severity of renal impairment depends on the
degree and duration of obstruction.
It is important to delay postnatal
assessment until 48 hours as mild to moderate hydronephrosis
may be present in the first day of life due to dehydration.
Postnatal renal function assessed by serial isotope
imaging, or pyeloplasty.
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WEST MIDLANDS DATA
Information to follow
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