Hydronephrosis is when one or both kidneys swell with backed up urine. This swelling can lead to kidney infection or kidney damage.

Hydronephrosis is not a condition but a symptom of another condition.

Urinary Tract System
si55551330_urinary tract child.jpg
Copyright © Nucleus Medical Media, Inc.

Hydronephrosis is caused by urinary tract problems that makes it difficult for urine to leave the kidneys. Urine may be slowed or blocked by:

  • An obstruction, bulge, or narrowing in the tube that carries urine from the kidney to the bladder
  • In boys, flaps of tissue obstructing the tube that carries urine out of the body or narrowing of the tip of the penis

Other conditions that may cause problems with urine flow include:

  • The backwards flow of urine from the bladder into the kidneys
  • Problems with the tube that carries urine to the bladder or in the way that it connects

Occasionally it is from an abnormal kidney

In most cases, the child is born with one of these conditions that affect the urinary tract. For some, the condition develops later on.

Sometimes the cause of hydronephrosis is not known.