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Ureteropelvic Junction Obstruction

What is an Ureteropelvic Junction Obstruction?

A ureteropelvic junction obstruction (UPJO) is a congenital narrowing or obstruction where the ureter meets the kidney. This develops prenatally as the kidney forms. Studies confirm that it is more common in males and on the left side. Both kidneys may be involved though.

This narrowing prevents normal draining of urine from the kidney. This causes hydronephrosis (kidney swelling). With pre-natal ultrasounds, hydronephrosis is often diagnosed as early as 15 weeks of fetal development. Early detection allows for evaluation and treatment soon after birth.

Signs and Symptoms

Symptoms of the UPJO may be an abdominal mass (felt on a routine exam by the primary care provider) or a urinary tract infection with fever, belly pain or back (flank) pain. The flank pain may be present even more so with increased fluid intake. Symptoms of a UPJO may not occur until the obstruction has progressed. High grade obstruction of the kidney can lead to kidney damage and loss of kidney function. Sometimes they are found after an injury to the back or abdomen occurs and imaging shows a swollen kidney.


UPJO can be diagnosed with different imaging methods. The method depends upon the age of the baby or child. Common radiology tests include renal / bladder ultrasound and Lasix renal scan.

  1. If a prenatal ultrasound shows hydronephrosis, a renal / bladder ultrasound will be done in the first few days after birth. A renal / bladder ultrasound will show kidney size and the degree of swelling. This will be repeated later.
  2. A VCUG (voiding cystourethrogram) will often be done at the same time as the renal ultrasound or soon after. This test will show if there is backflow of urine from the bladder up the ureter and maybe to the kidney. This is called vesicoureteral reflux.
  3. A Lasix renal scan is a nuclear medicine study that is done to look at how much blockage is in the kidney. With this test, a dye is injected into the child's vein along with Lasix, a diuretic. The drainage of the dye from the kidney is then "timed." Drainage times from both kidneys show the amount of blockage. They also show how much work each kidney is doing.

Your child's urologist will study the test results to see if the kidney is blocked. Sometimes, follow-up testing is needed to make this decision. There are times when the swollen kidney improves on its own and no surgery is needed. Your doctor will talk to you about this.

Surgery for UPJO is recommended in many cases to protect kidney function. Surgery right after birth is most often not necessary. This is often done after the age of 4 weeks. Close monitoring and testing will be done by your Urologist.

Pyeloplasty is the surgical repair of the kidney to drain and decompress the swollen kidney. During the surgery, the narrowed segment is removed. The ureter is then re-connected to the kidney. Your child may have a temporary drainage tube in the kidney. The surgery usually takes three to 3½ hours. Your child will stay in the hospital for one to three days.

Follow-up testing will include a renal ultrasound one to three months after the surgery. Your child will stay on a low dose of antibiotic, taken by mouth, to help prevent urinary tract infections. Your doctor will decide when the medicine can be stopped.

Call Your Child's Doctor If:

  1. Temperature greater than 101 degrees
  2. Bleeding from the incision
  3. Bright, red blood in the urine
  4. Extreme irritability / pain not controlled with pain medicine
  5. Difficulty urinating
  6. Lack of drainage out of the kidney drainage tube

Last Updated 07/2021

Reviewed By Pramod Reddy, MD

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