Hydronephrosis is a condition in which the kidney swells and becomes filled with urine in the part of the kidney called the collecting system.

Hydronephrosis can be detected in the fetus during pregnancy, or at any point after birth. Sometimes hydronephrosis can be serious if undetected and untreated but generally it requires no specific treatment except for ultrasound testing and following it on serial ultrasounds.

Causes of Prenatal Hydronephrosis

Normally, kidneys produce urine that is routed through the ureters to the bladder. If some abnormal development occurs along this path, the flow of urine from the kidney can be partially blocked. This causes the kidney to retain fluid and swell.

This abnormal development may include ureters that are too narrow where they join the kidney or bladder. There may also be a blockage in the ureter or a faulty valve where the ureter enters the bladder. Occasionally, during development of the urinary system, two ureters may be found to drain one kidney. If one of them is blocked, it can lead to hydronephrosis of the part of the kidney that is drained by that ureter.


Symptoms of Hydronephrosis

  • Prenatal hydronephrosis, of course, cannot be diagnosed through direct observation of the patient. The doctor must look for signs of the condition on an ultrasound obtained during pregnancy on the mother. An enlarged kidney and any associated abnormalities of the ureters sometimes can be seen in this way.
  • After birth, an infant may show fever, nausea, and general failure to thrive. An infection may produce pain in the back over the kidney.

Treatment of Hydronephrosis

Treatment of prenatal hydronephrosis usually involves a watch-and-wait strategy. Otherwise, treatment consists of keeping an eye on how the kidney is growing and whether its function is impaired.

Once the infant is born, hydronephrosis generally corrects itself. The fluid drains, the kidney returns to normal size, and it functions normally. Some degrees of hydronephrosis require more laboratory tests and x-ray tests and timing for this depends on the degree of hydronephrosis, if both kidneys are affected with hydronephrosis, and if there is concern about blockage of the bladder or kidneys.

A doctor will usually continue to monitor a child that has had hydronephrosis to be sure the condition does not recur. This is done with periodic ultrasounds.