What is UPJ obstruction?
The ureteropelvic junction is located where the pelvis of the kidney meets the ureter (the tube that drains urine into the bladder). The term ureteropelvic junction (UPJ) obstruction describes a blockage to this area. The obstruction impedes the flow of urine down to the bladder, causing the urine to back up in the kidney and dilate it (hydronephrosis).
Unilateral UPJ obstruction is the most common prenatally detected obstructive disease, often picked up on maternal ultrasounds during pregnancy. Each year, the Division of Urology treats nearly 150 children who have a UPJ obstruction.