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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

Ureteropelvic Junction Obstruction | Diagnosis & Treatments

How is a UPJ obstruction diagnosed?

  • A UPJ obstruction can often be diagnosed before birth if your doctor sees too much urine in your developing baby’s kidney — a condition called hydronephrosis — during a prenatal ultrasound study. This accumulation of urine in the kidney can be caused by a UPJ obstruction that blocks the flow of urine from the kidney
  • If an ultrasound indicates that your child has hydronephrosis, your obstetrician may monitor your pregnancy more closely and may perform more ultrasounds to check for any changes over time.
  • The good news is that often these blockages don’t cause any problems — and many go away on their own without any treatment.

If hydronephrosis has been seen during a prenatal ultrasound, your doctor will typically perform the following tests within a few weeks after your baby is born:

  • Renal ultrasound: Your new baby will have her own ultrasound test to look at the kidneys. This study gives a good picture of how serious the hydronephrosis is.
  • Voiding cystourethrogram: This special kind of x-ray is used to show the anatomy of your child’s bladder and urethra. Using a small tube called a catheter, doctors will fill your child’s bladder with a liquid containing iodine. As the bladder fills and your child urinates, the flow of the liquid will be visible on video x-ray images.
  • Renal scan: This test helps to measure the difference in function between the two kidneys and estimate the degree of blockage in the urinary system. After a tiny amount of radioactive material (radioisotope) is injected into your child’s bloodstream, a special camera called a gamma camera is used to take pictures of the kidneys, showing how well they are filtering and draining.
  • Blood tests: These let the doctor see how well your child’s kidneys are working.
  • Urinalysis and urine culture: Laboratory tests that examine the urine. These tests can indicate microscopic blood or protein in the urine, other chemicals, or evidence of a UTI.

After we complete all necessary tests, our experts meet to review and discuss what they have learned about your child's condition. Then we will meet with you and your family to discuss the results and outline the best treatment options for your child.

How is a UPJ obstruction treated?

In general, your child's treatment depends on the severity of the blockage. In mild cases, the flow of urine is affected only minimally and your child will likely not experience any symptoms at all. If the obstruction is larger, your doctor may choose to closely monitor your child with repeated ultrasound tests. In the most severe cases, where your child's kidney is at risk of damage from chronic backup of urine, surgery may be necessary.

Mild to moderate cases

  • When you hear that your child has a ureteropelvic junction (UPJ) obstruction, it doesn't necessarily mean that they will need surgery. Some children may outgrow their UPJ obstructions without any treatment.
  • If your child has a mild or moderate obstruction, your doctor may recommend a series of follow-up imaging studies to make sure the condition isn't getting worse or causing any kidney problems.

How often will my child need to be seen?

Infants may be seen within the first three to four months of life to figure out the severity of the obstruction. If we're comfortable that it's not causing any harm to your child's kidneys, we'll likely repeat the ultrasound study within a few months.

Severe cases

  • If your child has a more severe obstruction, your doctor may prescribe antibiotics to prevent urinary tract infections. We'll also keep doing ultrasounds and renal scans until the condition has either gotten better on its own or worsened to the point that your doctor decides that surgery is necessary to fix it.
  • Children with more severe cases of UPJ obstruction may require surgery. The most common reasons we recommend surgery to correct a UPJ obstruction are recurrent kidney infections, worsening of kidney swelling, or decline in kidney function.
  • Should your child's doctor decide that he needs surgery, our surgeons have vast experience in both traditional open and minimally invasive robotic-assisted surgical procedures. You'll meet with your child's doctor and work together to design a customized plan of treatment that fits your child and the condition.

Are antibiotics safe to take for an extended period of time?

Yes. We have treated thousands of children with preventive antibiotics for many years with very few severe side effects. The preventive antibiotics used are very low dose. There are some risks associated with any medication, but we believe that the benefits of preventing urinary tract infections and kidney damage in children with more severe UPJ obstructions outweigh any small risks from taking the antibiotics for long periods.

Don't children become ‘immune’ to the antibiotics?

Children do not become immune to antibiotics. Their immune systems continue to effectively fight off infections. However, the bacteria (germs) that live on and inside of human beings can become resistant to certain antibiotics.

My child needs surgery. What's the procedure like?

The goal of the surgery is to remove the blockage in the ureter and allow urine to flow properly. If your child has a blockage, our surgeons locate the blockage, remove the blocked segment, and reconnect the drainage system.

What are the different options for surgical procedures?

There are two types of surgeries we can do to treat your child's UPJ obstruction:

Robotic surgery

We often perform state-of-the-art robotic surgery to treat UPJ obstructions. Your child's surgeon will make small incisions in his abdomen, which are then used to perform the reconstructive procedures under the guidance of a small camera, also inserted through an incision. The total length of all incisions added together is typically smaller than that used in open surgery.

Open surgery

If your child's doctor decides that it's best to perform a traditional open procedure, the incision will be larger and your child will typically stay in the hospital for a few more days, but the procedure has proven very effective over the years and the results will be very similar.

How might a UPJ obstruction affect my child's long-term health?

If they are detected early, most UPJ obstructions don't cause many problems. Even larger obstructions can be fairly easily removed, and your child should go on to have good urinary function. If left untreated, however, the chronic backup of urine into the kidney can damage your child's kidneys.

Ureteropelvic Junction Obstruction | Research & Clinical Trials

Research & Innovation

Proteomics and biomarkers

  • Proteomics, the study of an organism's proteins, picks up where the Human Genome Project left off. Proteins are everywhere in the body, but not all proteins encoded in the genome are expressed—and each organ in the body expresses a different set of proteins.
  • In Boston Children’s Hospital’s Department of Urology, Rosalyn Adam, PhD, Keith Solomon, PhD, Richard Lee, MD, and colleagues are working to categorize the entire collection of urine proteins and understand what is different in children with in urologic diseases like congenital UPJ obstructions. They are also using proteomics to detect changes in bladder tissue that may be associated with disease progression. 

Managing pain after surgery

  • Boston Children’s has been a pioneer in anesthesia for children, and our urologists and anesthesia doctors have worked together to develop highly effective pain management techniques for children who have surgery.
  • Using these methods, most children recover quickly after surgery and their pain is kept to a minimum. Most children can go home one or two days after surgery. In addition, we have been leaders in development of less invasive methods of correcting UPJ obstructions. Our pioneering surgeons have used laparoscopic and robotic-assisted laparoscopic surgery to successfully correct UPJ obstructions in many children.

Ureteropelvic Junction Obstruction | Programs & Services