Hydronephrosis in newborns is enlargement, or dilation, of the renal pelvis—the basin in the central part of the kidney where urine collects. Hydronephrosis can occur in one or both kidneys. This condition is often diagnosed before birth during a prenatal ultrasound.

Where does hydronephrosis occur?

Hydronephrosis is the swelling of a kidney due to a build-up of urine. It happens when urine cannot drain out from the kidney to the bladder from a blockage or obstruction. Hydronephrosis can occur in one or both kidneys. The main function of the urinary tract is to remove wastes and fluid from the body.

What is the main cause of hydronephrosis?

Hydronephrosis is usually caused by a blockage in the urinary tract or something disrupting the normal workings of the urinary tract. The urinary tract is made up of the kidneys, the bladder, the ureters (the tubes that run from the kidney to the bladder) and the urethra (the tube that carries urine out of the body).