Pyelectasis is a common condition that develops during pregnancy.  It affects about 1 out of ever 40 fetuses.  Pyelectasis causes one or both of the kidneys to swell.  This swelling is caused by a buildup of urine in the fetus’ kidney. 

The actual cause is unknown, but there are two conditions that can cause pyelectasis.  Ureteropelvic junction obstruction which causes a blockage preventing urine to pass through the ureter into the bladder.  Vesicoureteral reflux is when there is abnormal flow of urine from the bladder to the kidney. 

It can also be caused by immaturity of the fetus, an extra ureter, or multicystic kidney which is a birth defect that causes the kidneys to fail. 

Pyelectasis is three times more common in boy babies than it is in female babies.  



There usually are no signs or symptoms related to pyelectasis.  It is normally detected at the 20 week ultrasound.  The ultrasound may show that the kidney is more enlarged than it should be.  During the ultrasound your doctor will be looking for how large the kidney is, the appearance of the kidney, how many kidneys are affected, overall growth of the baby, gender of the baby, the amniotic fluid index, size of the bladder, and how well your baby empties its bladder.  After this finding, you may be subject to additional monitoring. 

Most doctors will want you to have an ultrasound every four weeks until the condition resolves itself.  Most of the time pyelectasis resolves on its own. The fluid usually resolves by the third trimester. 

Sometimes after birth a pediatric urologist may want to examine the baby just to make sure everything is functioning normally.  There is no way to prevent pyelectasis. 



There are some complications that can stem from pyelectasis.  Pyelectasis can lead to hydronephrosis.  Hydronephrosis is when the urine drains from the kidneys too slowly.  This condition may result in your baby needing surgery after birth.  Only about 15% of babies that have hydronephrosis will require surgery.  Pyeloplasty is a procedure done to help remove the blockage between the kidney and the ureter.  Babies with hydronephrosis may be prescribed antibiotics after birth to help stop a UTI from occurring. 

Low amniotic fluid can also happen as a result of pyelectasis.  Amniotic fluid is made up partly of the baby’s urine, so when the baby is not producing enough urine the amount of amniotic fluid may be lower than normal.  Lung development can also be compromised.  The baby practices breathing in the amniotic fluid to help make their lungs stronger.  If the levels of amniotic fluid are low, it stops the baby from being able to strengthen their lungs.  This can cause the lungs to be underdeveloped.  



Ninety percent of cases go away on their own.  Having pyelectasis does not mean your baby will have an affected kidney function long term.  Sometimes though the kidneys may be damaged from swelling or blockage.  Children who develop hydronephrosis and need surgery will need to be watched overtime to make sure their kidney function stays healthy.  

Sometimes when diagnosed at the 20 week ultrasound, pyelectasis can be an indicator of Down Syndrome.  But it doesn’t always mean that your child will have Down Syndrome.  Your doctor will be able to run a few tests to see if there is another condition that is causing your baby’s pyelectasis. 



One or two kidneys can be affected by pyelectasis.  It is a common condition that can affect your baby.  After diagnosis, having follow up ultrasounds can be important to make sure no other complications arise.  The most harmful one is low amniotic fluid.  Babies with pyelectasis are usually born healthy and need no further intervention to have healthy kidney function for the rest of their lives.  




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