Pelvi-Ureteric junction (PUJ) obstruction

(or Uretero-Pelvic junction or UPJ obstruction) is a blockage or obstruction between the pelvis of the kidney and the ureter.

The renal pelvis is the hollow part of the kidney that collects the urine. It is connected to the ureter at a point called the Ureto-Pelvic junction. The ureter carries the urine down to the bladder.

When a junction between the pelvis and the ureter is blocked, it causes the pelvis to balloon out. This is called a Hydronephrosis