Ureteropelvic junction

The ureteropelvic junction (UPJ, also uretero-pelvic junction or ureteral pelvic junction) is the junction between the ureter and the renal pelvis of the kidney.

During the embryologic development of the kidney, this is the last part of the ureter to become patent.

Failure of this segment of ureter to become patent during development is the most frequent cause of bilateral hydronephrosis, particularly in male neonates. Pyeloplasty, which involves excision of the stenotic section and creation of a new junction, is the most common and effective treatment for this problem.