Hydronephrosis (pronounced high-dro-nef-row-sis) is a radiology term for swelling or fluid in the kidney. Hydronephrosis is not a disease, but can be a radiographic sign of other kidney or bladder problems or developmental issues. Similar terms for less severe kidney swelling which are used interchangeably are pyelectasis or pelviectasis.
Hydronephrosis is usually determined on imaging studies such as renal ultrasounds, CT scan or MRIs. Regular X-rays can show the outlines of an enlarged kidney, but hydronephrosis is not typically diagnosed on this type of film.
Much of the hydronephrosis seen in children is diagnosed prior to birth during a prenatal ultrasound of the fetus which checks the organs and development of the baby before birth. This would be called prenatal or congenital hydronephrosis. The majority of these dilated kidneys will improve to a more normal size some time after birth, although this process may take a couple of years.
Acquired hydronephrosisis due to some event or disease process that happens after birth, like a kidney stone blocking flow of urine or some kind of external mass compressing the urine tube.
Most hydronephrosis in children is first diagnosed with a renal ultrasound. Other tests used may include one or more of the following: voiding cystogram, nuclear medicine renal scan, MRI or CT scan. Depending on the severity of hydronephrosis and its cause, additional follow up studies are usually necessary over time to track the improvement or worsening of the kidney swelling.
Most children with prenatal hydronephrosis have no symptoms and experience no pain, although there can be abdominal pain, nausea or vomiting in some children who have severe hydronephrosis. When the hydronephrosis occurs later on and is acute, it is usually accompanied with these symptoms as it represents a sudden obstruction of urine flow and stretching of the kidney.
Sometimes there is swelling of the kidney and the ureter, or urine tube to the bladder, when both the kidney and the ureter are dilated. This is known as hydroureteronephrosis. This can be seen with different kinds of ureteral issues or bladder outlet obstruction where the bladder is not emptying normally. Depending on the etiology of this issue, there can be decreased drainage of the urine on the involved side and increased risk of urine infection.
If the hydronephrosis is not symptomatic and is improving, then surgical intervention may not be needed.
Surgery can become necessary if the disease associated with the congenital hydronephrosis worsens or the child develops an acute cause of hydronephrosis.