Children's Hospital Colorado


What is hydronephrosis?

Hydronephrosis is the dilation or stretching of the kidneys that occurs when there is an obstruction or partial blockage to the flow of urine at some point along the urinary tract. Normally, urine flows from the kidneys through the ureters and into the bladder. If there is a blockage that prevents the urine from draining properly, urine can back up in the kidneys and hydronephrosis occurs.

What causes hydronephrosis?

Some children are born with hydronephrosis, while others can develop it as a result of a kidney stone or injury to the urinary tract. There are many different kinds of urinary tract obstructions that can lead to hydronephrosis. The most common type is at the junction where the ureter joins the kidney, called the ureteropelvic junction. This blockage is caused by an abnormal narrowing of the ureter at this location. The next most common site of narrowing is where the ureter meets the bladder, called the ureterovesical junction.

Some conditions commonly associated with blockage of the kidneys include:

Hydronephrosis cannot be prevented, but it may be prevented from worsening depending on the degree of the condition.

Who gets hydronephrosis?

Hydronephrosis is more common in males than in females. It can run in families.