Urine Blockage in Newborns
urinary tract consists of
- two kidneys, which filter waste materials and excess water from the blood
- two ureters, which carry urine from the kidneys to the bladder
- the bladder, where urine is stored until it is released
- the urethra, where urine flows out
of the body
We rely on our kidneys and urinary system to keep fluids and natural
chemicals in our bodies balanced. While a baby is developing in the mother's
womb, much of that balancing is handled by the mother's placenta. The baby's
kidneys begin to produce urine at about 10 to 12 weeks after conception, but the
mother's placenta continues to do most of the work until the last few weeks of
the pregnancy. Wastes and excess fluid are removed from the baby's body through
the umbilical cord. The baby's urine is released into the amniotic sac and
becomes part of the amniotic fluid. This fluid plays a role in the baby's lung
Sometimes, a birth defect in the urinary tract will block the flow of urine
in an unborn baby. As a result, urine backs up and causes the ureters and
kidneys to swell. Swelling in the kidneys is called hydronephrosis. Swelling in
the ureters is called hydroureter.
Swelling in the kidney is called hydronephrosis. Swelling in the ureter is called hydroureter.
Hydronephrosis is the most common problem found during ultrasound examination
of babies in the womb. The swelling may be barely detectable or very noticeable.
The results of hydronephrosis may be mild or severe, but the long-term outcome
for the child's health cannot always be judged by the severity of swelling.
Urine blockage may damage the developing kidneys and reduce their ability to
filter. The blockage may also raise the risk that the child will develop a
urinary tract infection (UTI). Recurring UTIs can lead to more permanent kidney
damage. In the most severe cases of urine blockage, the amniotic sac is so
reduced that the lack of fluid threatens the baby's lung development.
Types of Defects in the Urinary Tract
Hydronephrosis can result from many
types of defects in the urinary tract. Doctors use specific terms to describe
the type and location of the blockage.
- Vesicoureteral reflux (VUR). The openings where the ureters empty urine into
the bladder should work like valves to keep urine from backing up into the
ureters. Sometimes the valve doesn't work properly and urine flows back into the
kidneys. The urine may flow only a short way back into the ureters, or it may go
all the way back to the kidneys, causing the ureters and kidneys to swell. VUR
may occur in only one ureter or in both. Kidneys with severe reflux may not
develop normally, and after birth kidneys with reflux may be at risk for damage
Ureteropelvic junction (UPJ) is the point where the ureter joins the kidney.
- Ureteropelvic junction (UPJ) obstruction. The point where the ureter joins
the kidney is called the ureteropelvic junction. If urine is blocked here, only
the kidney swells. The ureter remains at a normal size. UPJ obstruction usually
only occurs in one kidney.
- Bladder outlet obstruction (BOO). BOO describes any blockage in the urethra
or at the opening of the bladder. The obstruction may occur in boys or girls.
The most common form of BOO seen in newborns and during prenatal ultrasound
examinations is posterior urethral valves (PUV). BOO caused by PUV occurs only
- Posterior urethral valves (PUV). In boys, sometimes an abnormal fold of
tissue in the urethra keeps urine from flowing freely out of the bladder. This
defect may cause swelling in the entire urinary tract, including the urethra,
bladder, ureters, and kidneys.
- Ureterocele. If the end of the ureter does not develop normally, it can
bulge, creating what is called a ureterocele. The ureterocele may obstruct part
of the kidney or the bladder.
Ureterocele. The inset shows a cross-section of the ureter bulging into the
interior of the bladder.
- Nerve disease. Urination requires coordinated nerve signals between the
bladder, spinal cord, and brain. Spina bifida and other birth defects that
affect the spinal cord may interrupt nerve signals and lead to urine retention
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Urine Blockage in Newborns - Diagnosis
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Urine Blockage in Newborns - Treatment
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Urine Blockage in Newborns - Syndromes
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