Ureteropelvic Junction (UPJ) obstruction occurs when the area that connects the kidneys (renal pelvis) to the ureters (tubes that carry urine from the kidney to the bladder) is blocked. As a result, urine cannot flow to the bladder properly. This condition is more common in infants and young children, but it does occur in adult patients, as well.

UPJ obstruction may be severe, minimal, or intermittent. It can be related to a congenital condition (occurring at the time of birth) that causes narrowing of the ureter as it forms in fetal development, or the result of kidney stones, a tumor, scarring from previous surgery, or other disorders that can cause inflammation of the upper urinary tract.


  • Sudden pain on the side of the abdomen, especially after drinking large quantities of liquids.
  • Pressure in the pelvis region (lower abdomen) due to the enlargement of the kidneys. This pressure is due to the build up of urine in the kidneys (hydronephrosis), which can’t drain to the bladder due to the blockage. If hydronephrosis continues for too long loss of kidney function may result.
  • Blood in the urine (hematuria)
  • High blood pressure (hypertension)
  • Frequent urinary tract infections (UTIs).