What Is a Fetus With Hydronephrosis?

Written by darci pauser
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What Is a Fetus With Hydronephrosis?
Sonogram technicians diagnose fetal hydronephrosis while the baby is still in the mother's womb. (pregnant belly button image by davidcrehner from Fotolia.com)

"Nephros" translates from the Greek to "kidney," and "hydro" translates to "water". As the name suggests, a foetus still in the mother's womb suffering from hydronephrosis experiences a blockage of urinary liquid in the kidney. Ultrasound technicians detect fetal hydronephrosis more commonly than any other sonogram abnormality, according to Children's Memorial Hospital. Fetal hydronephrosis is not fatal, but may lead to a loss of kidney function in extreme cases.


Fetal hydronephrosis forms when the renal pelvis of the kidney overfills with urinary fluids. The renal pelvis acts as a way-station for urinary fluid until the fluid travels down the ureter tube into the bladder. When the renal pelvis is slightly larger than usual, the physicians refer to the condition as fetal pelviectasis or fetal pyelectasis. Physicians diagnose more extreme bulging of the renal pelvis as fetal hydronephrosis.

Symptoms and Diagnosis

Fetal hydronephrosis exhibits no obvious outward symptoms to the mother carrying the foetus. Rather, the mother's ultrasound technician detects the condition prior to the baby's birth, after 14 to 20 weeks of gestation. After birth, physicians may perform further diagnostic tests, including x-rays, post-natal sonography and magnetic resonance imaging (MRI).


According to Cornell Urology, ureteropelvic junction obstruction most commonly causes fetal hydronephrosis. The ureteropelvic junction exists at the meeting of the renal pelvis and ureter tube. When this junction is obstructed, urinary fluid cannot drain effectively into the bladder. Other possible causes include vesicoureteral reflux (when urinary fluid backwashes into the kidney) and posterior urethral valves.


According to Cornell Urology, 1.4 per cent of fetal ultrasounds in the United States reveal fetal hydronephrosis. Half of babies exhibiting fetal hydronephrosis while in the womb no longer have the condition after birth.


Usually, doctors choose to wait until after birth before administering any treatment options. However, in severe fetal hydronephrosis, doctors may perform intrauterine surgery to drain the foetus' kidney. In mild cases, or those that are not severe while the baby is in the womb, doctors perform surgery that empties the kidney and repairs blockage or urethral valves after the baby is born.

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