Ureteropelvic Junction (UPJ) Obstruction

What are ureteropelvic junction (UPJ) obstructions?

In a normal urinary system, urine flows from the kidney through the ureter and into the bladder. In children with a ureteropelvic junction (UPJ) obstruction, there is a blockage between the ureter and the kidney that can slow or block the flow of urine. In severe cases, the urine is unable to drain from the kidney, and can stretch the organ and cause permanent damage.

  • A UPJ obstruction occurs when a blockage between your child’s kidney and ureter impedes the flow of urine.
  • UPJ obstructions are not very common, occurring in approximately 1 out of every 1,500 babies.
  • Many of these blockages are small enough that they won’t damage your child’s kidney.
  • Severe blockages can impair the kidney’s ability to drain urine, which can lead to permanent kidney damage.
  • If your child’s UPJ obstruction is severe enough to put her kidney at risk, a single surgical procedure can be performed to remove the blockage.

What are the symptoms of a UPJ obstruction?

Mild: Most babies won’t have any symptoms at all. If your child’s UPJ obstruction has been seen on a prenatal ultrasound, it’s probably because they have hydronephrosis (or extra urine in the kidney). This is a fairly common condition that often goes away on its own after birth.

Moderate to severe: More severe UPJ obstructions may be associated with blood in the urine or abdominal pain in older children.

Severe pain in your child’s side is also a possibility, especially after being hit there during a contact sport or accident.

If a large UPJ obstruction has caused a lot of urine to build up in your child’s kidney, she may also experience some or all of the symptoms of kidney failure:

  • hemorrhage (heavy bleeding)
  • fever
  • rash
  • bloody diarrhea
  • severe vomiting
  • abdominal pain
  • no urine output or high urine output
  • pale skin
  • edema (swelling)
  • swelling around the eye
  • detectable abdominal mass

What causes UPJ obstructions?

The exact cause of UPJ obstructions is not known, but they are congenital (present at birth) and are often discovered during a routine prenatal ultrasound, which suggests that they arise from problems in the development of your child’s urinary tract.

There are a few ways an obstruction can form while your baby is developing:

  • A portion of your child’s ureter doesn’t fully develop, leading to a narrow section that can easily become blocked.
  • There can be a part of the muscle in the ureter wall that doesn’t squeeze properly.
  • Your child may have what is called a “crossing vessel,” which means that there is an extra artery that feeds the kidney. In this situation, that secondary artery can cause kinking or blocking of the ureter.

The condition has been known to run in families, which indicates a genetic component, although specific genes have not yet been identified.

Are there any complications associated with UPJ obstructions?

If a UPJ obstruction is detected early, it can be treated fairly easily. If left untreated or misdiagnosed, however, the chronic backup of urine into the kidney can do permanent damage to your child’s kidneys and urinary system. That’s why it’s vital to see a specialist in urology for an accurate, timely diagnosis.

What is the long-term outlook for my child?

Every child is unique, and your child’s long-term health depends upon her exact condition. But the bottom line is that with an accurate diagnosis, appropriate treatment and close management of your child's treatment and care, your child should go on to achieve normal urinary function.

How we care for UPJ obstructions

One benefit to being at Boston Children’s Hospital is the presence of our excellent Maternal Fetal Care Center. If your baby is diagnosed before birth with a UPJ obstruction, our multidisciplinary team will follow the condition closely from gestation through birth and beyond.

If your child’s doctor determines that your child needs surgery, you’ll meet with your child’s doctor and work together to design a treatment plan that fits your child and the condition. Boston Children's is home to the largest pediatric Urology Department in the world; we perform more than 3,100 surgical procedures each year and care for almost 18,000 children from throughout the country and all over the world.

We have pioneered the use of robotic surgery for complex procedures through small incisions, reducing pain, recovery time, and hospital stays. Today we perform more pediatric robotic surgeries than any other hospital in the world, and train physicians from around the country and the world.

Ureteropelvic junction obstruction: Reviewed by Richard N. Yu, MD, PhD
© Boston Children’s Hospital; posted in 2012