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Pediatric Hydronephrosis

Hydronephrosis means that the kidneys are abnormally dilated or overfilled with urine. There are several causes, many of which do not cause any harm to the kidneys, but in some cases hydronephrosis can be associated with poorly functioning kidneys. Hydronephrosis can affect one (unilateral) or both (bilateral) kidneys, and it resolves on its own in about half of all cases.

Hydronephrosis can be caused by blockage at some part of the urinary tract or by reflux of urine (abnormal backflow of urine from the bladder). It can also be due to the abnormal development or formation of the kidney in the absence of obstruction or reflux. There are few genetic causes of hydronephrosis and it can occur with other conditions in the baby.
There are three major categories of hydronephrosis:
- Vesicoureteral reflux is when urine does not properly flow from the kidneys to the bladder, but instead abnormally backs up in the ureter (the tube connecting the kidneys to the bladder).
- Blockage/obstruction occurring in four possible places:
  - Where the kidney meets the ureter (ureteropelvic junction – UPJ)
  - Where the ureter meets the bladder (ureterovesical junction – UVJ)
  - Within the urethra (the tube that carries urine from the bladder out of the body, occurring only in males) (posterior urethral valves – PUV)
  - Incorrect attachment of the ureter to the bladder (ectopic ureter or ureterocele)
- Idiopathic hydronephrosis that has no obvious cause and usually resolves on its own before or after birth
Newborns and infants with hydronephrosis usually show few or no symptoms at all. Older children who have moderate to severe cases may experience:
- Pain in the side or abdomen
- Blood in the urine
Older children may be more likely to get urinary tract infections, in which symptoms include:
- Persistent feeling of needing to urinate
- Pain in the lower abdomen during urination
- Cloudy or bloody urine
- Back or side pain
- Fever
- Vomiting
Your physician can usually detect hydronephrosis through a routine prenatal ultrasound during the second trimester. If so, your physician may refer you to our Prenatal Pediatrics Institute for a high-resolution (level II) ultrasound and MRI scans to evaluate your baby’s condition.
The Prenatal Pediatrics Institute at Children’s National Hospital may recommend further testing after your baby is born. This testing may include:
- X-ray of the bladder to check for vesicoureteral reflux
- Diagnostic imaging of the kidneys to assess function and proper urine drainage
Read more about the high-risk prenatal care services at the Prenatal Pediatrics Institute of Children’s National.
There are four main options for treatment, depending on the severity of hydronephrosis in your baby:
- Close observation for mild or moderate cases, including ultrasounds before and after birth
- Antibiotics after your baby is born to prevent infection, in select cases where infection may be more likely to occur
- Surgery to repair any urinary tract blockage, in more severe cases
- Prenatal surgery to place a drainage tube in your baby’s bladder, in the most severe cases
The urologists and surgeons at our Prenatal Pediatrics Institute have extensive experience in the management of hydronephrosis. We develop plans that ensure continuity of care from the early stages of pregnancy, after birth, and across childhood.

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Coronavirus Update:What patients and families need to know

Pediatric Hydronephrosis

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Nephrology

Neonatology

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