An obstruction that forms at the area where the ureter attaches to the kidney pelvis.

Alternative Names

Ureteropelvic junction obstruction; U-P junction obstruction; Obstruction of the ureteropelvic junction

Causes, incidence, and risk factors

Ureteropelvic junction (UPJ) obstruction is generally a congenital condition caused by narrowing (stenosis) that occurs at the junction of the ureter (muscular tube from the kidney to the bladder) and the pelvis of the kidney (the pelvis is the triangular collecting structure of the kidney). This blockage causes urine to collect in the pelvis of the kidney under pressure. The constant increased pressure causes damage to the kidney and loss of kidney structure. UPJ obstruction is the most frequently diagnosed cause of urinary obstruction in children. UPJ obstruction is now commonly diagnosed during prenatal ultrasound studies that show a dilated renal pelvis or " hydronephrosis ." This condition, when recognized, is surgically corrected in the first few days after birth. Experimental decompression of the kidney has been tried with the fetus still in the uterus. UPJ obstruction may be recognized after birth when an abdominal mass is found on examination, or if the infant develops a urinary tract infection associated with fever . Back pain and blood in the urine may also be signs of obstruction.

Signs and tests

Maternal pregnancy ultrasound may show hydronephrosis in the fetus. Tests on the infant may include:

Treatment

Expectations (prognosis)

Early recognition of UPJ obstruction preserves kidney function. Rapid decompression of the kidney immediately following birth can improve kidney function substantially.

Complications

Calling your health care provider

Call your health care provider if your infant has bloody urine , fever , a lump in the abdomen , or acts as if it is having back pain or pain in the flanks (the area towards the sides of the body between the ribs and the pelvis).

Prevention

There is no known prevention for this condition.