Ureteropelvic Junction (UPJ) Obstruction

What happens under normal conditions?

Kidneys produce urine by filtering the blood and removing wastes, salts and water. The urine must then drain from the kidney through an internal collecting system.

That system ends in a funnel-shaped structure called the renal pelvis. From there, it flows into a natural tube called the ureter.

Each kidney must have at least one functional ureter (some have two) to carry the urine from the kidney to the bladder.

  • What is ureteropelvic junction obstruction?


    The most common cause of a child’s urinary tract blockage is an obstruction at the point where the ureter joins the renal pelvis. This area is known as the ureteropelvic junction (UPJ).

    Obstructions like these happen to roughly one in 1,500 children.

  • How is it detected?


    • Obstructions will develop in a forming kidney before a child is born. We can usually spot them on prenatal ultrasound screenings.

    • In UPJ obstruction, the kidney produces urine at a higher rate than what can be drained into the ureter. This causes urine to accumulate within the kidney. This is called hydronephrosis.

    • Hydronephrosis can easily be seen on ultrasound. That’s how our doctors can predict the presence of UPJ obstruction before the baby is born.

  • What are the symptoms?


    Ultrasounds allow doctors to identify most UPJ obstructions long before birth. However, if this screening doesn’t catch it, symptoms can include:

    • Abdominal mass

    • Urinary tract infection

    • Fever

    • Flank pain, especially with increased fluid intake

    • Stones

    • Bloody urine

    • Pain, with or without an infection

    • Because some UPJ obstructions are irregular in nature, urine may drain normally at one time and be completely blocked at others. This will produce sporadic pain.

  • How is ureteropelvic junction diagnosed?


    Ultrasound helps, but it can’t diagnose a UPJ obstruction on its own. So we will perform a functional test on your child, which allows us to measure how well the kidney can produce and drain urine. The classic version of this examination is called the intravenous pyelogram (IVP). Here’s how it works:

    • A dye is injected into the blood stream, and the kidneys remove that dye from the blood. The dye passes into the urine and eventually out of the bladder.

    • The dye is visible with X-rays throughout the process, allowing our doctors to see the shape of the kidney, renal pelvis and ureter.

    While this test continues to be helpful, there’s a more useful examination for children called the furosemides renal scan. This test is similar to the intravenous pyelogram, except that a we use a special (and completely safe) radioactive material, rather than the X-ray dye.

    By following the material with a special camera, this test can give more accurate information about kidney function and drainage.

  • How is UPJ treated?


    Before considering treatment, remember that poor drainage through the UPJ in infants and young children less than 18 months of age may be temporary. This subject remains controversial, and many experts hold different opinions.

    However, here’s what we do know: Many infants with good kidney function and poor drainage will have a dramatic improvement of drainage over the first few months of life, while some will not improve and others will get worse.

    For this reason, patients in this age range who suffer from hydronephrosis (fluid-filled enlargement of the kidney) are watched with repeat CT scans and ultrasounds. If there is no improvement within the first 18 months of life, we’ll establish a diagnosis of UPJ obstruction. From there, the condition requires surgical treatment.

  • Treatment: Minimally Invasive Surgery


    Newer treatment of UPJ obstruction involves minimally invasive surgery. There are two options:

    Option 1: We perform a laparoscopic pyeloplasty by placing several instruments through the abdominal wall.


    • Less pain and nausea, especially in older children and adults.


    • Could potentially cause scarring or adhesions within the abdomen.

    • Surgeons cannot use techniques that are as delicate in a laparoscopic as in an open procedure. The clear advantages of laparoscopic surgery are less pain and nausea especially in older children and adults.

    Option 2: We insert a wire through the ureter, then use it to cut the tight and narrow UPJ from the inside. A special ureteral drain is left in place for several weeks and then removed.


    • The UPJ heals in a more open manner in most patients.

    • Less pain and nausea than open surgery.


    • The treatment may need to be repeated.

    • Success rates are clearly less than those of open surgery.

  • Treatment: Pyeloplasty


    With pyeloplasty, our doctors perform an open operation to remove the ureteropelvic junction. We then reattach the ureter to the pelvis of the kidney. This creates a much wider junction between the two.

    Usually, the surgery’s incision is just below the ribs, and just behind a line that would pass from the patient's arm to their leg on the affected side. The incision is typically two to three inches long.

    Hospitalization after surgery depends on your child’s age.

    There are a variety of drainage tubes we use to promote healing. Their use depends on the surgeon's preference.

    What are the advantages?

    • A pyeloplasty allows rapid and easy drainage of urine produced by the kidney.

    • It relieves symptoms and the risk of infection.

    • The procedure only takes a few hours.

    • It has a success rate in excess of 95 percent with one operation.

    • The incision is usually just below the ribs and just behind a line that would pass from the patient's arm to their leg on the affected side. The incision is usually two to three inches long.