What is hydronephrosis?

Your kidney filters blood to make urine. After urine is made, it goes into a funnel-shaped portion of the kidney called the collecting system. When this part of the kidney is enlarged and holding more urine than normal, the condition is called hydronephrosis. It is diagnosed by radiologic imaging studies such as ultrasounds or CT scans.

Hydronephrosis may be congenital (something a child is born with) or acute. It is sometimes caused by an obstruction (blockage) of the urinary tract, but it may also be due to a high-pressure bladder, over-filling of the bladder or vesicoureteral reflux — a condition in which urine flows backward from the bladder to the kidney. Some cases are idiopathic, which means that testing won’t reveal a cause.

Prenatal ultrasound screening is the most common way congenital hydronephrosis is diagnosed. Other cases can be diagnosed when imaging is done because a child has a urinary tract infection or symptoms like abdominal pain or back pain. Most children with congenital hydronephrosis don’t have any symptoms.

The severity of hydronephrosis can vary, but most cases are mild. Mild congenital hydronephrosis is generally not worrisome and often resolves on its own. A more severe congenital case increases your risk of urinary tract infection and loss of kidney function. When the cause is acute or sudden obstruction, such as from a kidney stone, the hydronephrosis can resolve once the obstruction is relieved.

Depending on the cause and severity of hydronephrosis, surgery may be recommended. Minimally invasive approaches, including robotic or endoscopic surgery, are usually an option. Robotic surgery involves the insertion of a camera and surgical instruments into the body through very small incisions. The instruments are then controlled by a surgeon seated at a console.

Most children with congenital hydronephrosis do not need surgery; instead, they are monitored with periodic ultrasounds. The frequency of ultrasounds depends on the severity of your diagnosis, generally ranging from every three to 24 months. Surgery may be recommended if the hydronephrosis is increasing over time or if you develop a urinary tract infection or other symptoms.

Dr. Mark Faasse and Dr. Monica Velasquez are pediatric urologists at Advocate Children’s Hospital.

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