Fetal hydronephrosis
Fetal hydronephrosis is the swelling of the kidney when too much urine
collects in the pelvis (or basin) of the kidney. This occurs because there is a
blockage of the normally free flow of urine, most commonly in the ureter (the
tube that connects the kidney to the bladder), and the urine is not allowed to
drain into the bladder. This blockage causes a pressure buildup which causes the
kidney to enlarge. The severity of fetal hydronephrosis depends on how large the
kidney has ballooned and the extent of the blockage. If not corrected, it can
cause the kidney to lose its ability to make urine. True hydronephrosis is,
therefore, a major concern.
The symptoms of fetal hydronephrosis
There are no outward symptoms to the pregnant mother that her fetus
has hydronephrosis. Once the baby is born, the pediatrician may be able
to feel a swelling in the region of the kidney (under the angle of the ribs in
the back or deep in the mid-abdomen), but many times the newborn examination is
normal. Decreased urine flow after birth, swelling that occurs later in the
kidney area or urinary infection are other possible symptoms of this
problem.
What causes it?
Fetal hydronephrosis is caused by an obstruction to what should be a free
flow of urine out of the kidney. An example of this is kinking of the ureter. It
may also be caused by an abnormal backwashing of urine from the bladder back
into the kidney. An example of this is vesicoureteral reflux or "reflux."
Diagnosis of the condition
Hydronephrosis is diagnosed prenatally
(before birth) using ultrasound
(sonogram) examination. After the baby is born, ultrasound or other tests may be
necessary to determine the cause and severity of the hydronephrosis. Tests may
include intravenous pyelogram (IVP), voiding cystourethrogram (VCU), renal scan, or magnetic resonance
imaging (MRI).
The treatment of fetal hydronephrosis and its long-term
outlook
Treatment of fetal hydronephrosis is usually postponed until after
delivery. Only in the most severe cases (in which the loss of kidney
function is expected if left untreated to delivery) is intrauterine surgery
attempted during the pregnancy. In these most severe cases, an attempt is made
to place a drain through the baby's back into the kidney to allow passage of
urine and relief of the pressure in the kidney. This is done with endoscopic
instruments inserted through mother's abdomen into the uterus (womb) itself.
Because of the risks of preterm labor, infection, injury to baby or mother, and
poor outcome, this procedure is reserved for the most severe
cases.
Less severe cases are treated after
delivery, and the kidney usually recovers well and there are no long-term problems. Treatment
involves surgery, either major or minor, to correct whatever is causing the
blockage of urine or to repair the valves of the ureter to prevent backflow of
urine from the bladder.