Ureteropelvic Junction (UPJ) Obstruction Symptoms & Causes


What is a UPJ obstruction?

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. 

What are the different types of severity of UPJ obstructions?

UPJ obstructions range in severity from mild to severe: 

  • Mild: Many UPJ obstructions are small and only minimally affect the flow of urine. In these cases, the condition usually goes away on its own as your child grows. 
  • Moderate: Some obstructions are intermediate and the flow of urine is partially affected. In these cases, it is unclear whether the obstruction will improve or worsen, so the doctor will monitor the condition of your child’s kidneys. 
  • Severe: We don’t see larger obstructions very often, but when they occur they can cause recurring urinary tract infections. There is also a greater risk for kidney damage because of the pressure that the trapped urine puts on your child’s kidney.


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 her 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.

Signs and symptoms 

What are the symptoms of a UPJ obstruction?


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 she has 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

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 her treatment and care, your child should go on to achieve normal urinary function.