UP junction obstruction

Alternative names
Ureteropelvic junction obstruction; UPJ obstruction; Obstruction of the ureteropelvic junction

Ureteropelvic junction (UPJ) obstruction involves a blockage in the area where a ureter, one of the tubes that carries urine from the kidney to the bladder, attaches to the part of the kidney known as the renal pelvis.

Causes, incidence, and risk factors

UPJ obstruction is generally a congenital (present from before birth) condition caused by narrowing of the connection between the ureter and the renal pelvis, which is part of the kidney. This blockage causes urine to build up in the renal pelvis, damaging the kidney.

UPJ obstruction is the most frequently diagnosed cause of urinary obstruction in children. It is now commonly diagnosed during prenatal ultrasound studies that show a dilated renal pelvis or a condition called hydronephrosis.

When recognized before the baby is born, UPJ obstruction may require surgical correction in the first few days after birth. Less severe cases may not require surgery until later in life, and some cases do not require surgery at all.

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 UPJ obstruction.


  • Back or flank pain  
  • Urinary tract infection with fever  
  • Bloody urine (hematuria)  
  • Lump in the abdomen (abdominal mass)

Signs and tests
Maternal pregnancy ultrasound may show hydronephrosis in the fetus.

Tests after birth may include:

  • Creatinine clearance  
  • BUN  
  • Electrolytes  
  • IVP  
  • Nuclear scan of kidneys  
  • Voiding cystourethrogram


Surgical correction of the obstruction allows urine to flow normally. Open surgery is usually performed in infants, although adults may be treated with less-invasive procedures:

  • Percutaneous technique - the obstruction is corrected via a small incision in the side.  
  • Endoscopic technique - the obstruction is cleared via a small instrument inserted through the urethra.

These procedures involve much smaller incisions than traditional open surgery.

A tube called a stent may be placed to drain urine from the kidney until the patient heals. A nephrostomy tube, which is placed in the patient’s side to drain urine, may also be required for a short time after the surgery.

Expectations (prognosis)

Rapid decompression of the kidney immediately following birth may substantially improve kidney function in an infant with UPJ obstruction diagnosed before the child is born. Early recognition and repair may also preserve future kidney function.

Most patients do well with no long-term consequences, although a small number of patients will require dialysis at some point in their lives as a result of this problem.


Permanent loss of kidney function (kidney failure) is a possible complication of UPJ obstruction.

Calling your health care provider

Call your health care provider if your infant has bloody urine, fever, a lump in the abdomen or if the baby seems to have back pain or pain in the flanks (the area towards the sides of the body between the ribs and the pelvis).

Johns Hopkins patient information

Last revised: December 7, 2012
by Mamikon Bozoyan, M.D.

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