Hydronephrosis

Hydronephrosis (upper urinary tract dilation) is a condition where something keeps pee (urine) from flowing from your kidney to your bladder. When that happens, one or both of your kidneys swell.

It can be sudden or chronic, partial or complete, one-sided or bilateral (both sides). If only one kidney is affected, the condition is called unilateral hydronephrosis. If both kidneys are affected, it’s called bilateral hydronephrosis. It can also vary in severity from mild swelling to severe swelling.

Hydronephrosis may lead to loss of kidney function or kidney failure. However, prompt treatment reduces the risk of long-term complications.

How your urinary tract works

The main job of your urinary tract is to remove waste and fluid from your body. Your urinary tract consists of the following:

• Two kidneys. Kidneys clean toxins and waste out of your blood.
• Two ureters. Ureters are ducts that carry pee from your kidney to your bladder.
• A bladder. Your bladder is an organ that stores your pee.
• A urethra. Your urethra is a tube that lets pee leave your body.

Often, a blockage or obstruction between your kidney and ureter is the cause of hydronephrosis.

How common is hydronephrosis?

Hydronephrosis can occur in people of all ages. It occurs in about 1 in 100 adults at some point in their life.

In infants, it’s often due to an obstruction (blockage) that happens during fetal development (antenatal hydronephrosis). This occurs in up to 1% of all pregnancies. It usually resolves on its own before birth.