A ureteropelvic junction (UPJ) obstruction is a blockage that occurs where the kidney’s urine collection system meets the ureter, the tube that carries urine to the bladder. After the kidney filters waste products from the blood to create urine, the urine collects in a bowl-shaped area of the kidney called the renal pelvis. The renal pelvis narrows down to become the ureter, the tube that carries urine to the bladder.

Without proper drainage, urine will eventually collect in the kidney, causing a condition known as hydronephrosis. UPJ obstruction can cause permanent kidney damage if left untreated.

What Causes UPJ Obstruction?

According to the American Urological Association, UPJ obstruction occurs in approximately 1 in 1,500 children. In most cases, the obstruction is congenital, which means it develops while the urinary tract is forming before the child is born.

There are two main causes of UPJ obstructions:

• An abnormal narrowing or a kink in the ureter, perhaps caused by pressure from a nearby blood vessel.
• A weakness in part of the ureter muscle that makes it unable to contract properly and send urine down the ureter to the bladder. This allows urine to collect within the kidney.

UPJ obstruction does not appear to have a genetic component, does not run in families and is not associated with gender, race or ethnicity.

What Are the Symptoms of UPJ Obstruction?

Thanks to the widespread use of ultrasounds during pregnancy, most cases of UPJ obstruction are detected even before a child is born. This can allow specialists to monitor your baby’s development and begin initial planning for care after delivery.

Infants and children with UPJ obstruction may experience a wide range of symptoms, including:

• Lower back or side pain
• Urinary tract infections, especially with fever
• Blood in the urine
• Lump or mass in the abdomen
• Kidney stones
• Vomiting

It is also possible to have a UPJ obstruction without symptoms.

How Is UPJ Obstruction Diagnosed?

During a prenatal ultrasound, the technician or physician examines all of your baby’s developing body parts, including the kidneys. If one or both kidneys appear dilated on ultrasound, the physician will suspect UPJ obstruction. In all but the most severe cases, a definite diagnosis will wait until after you deliver and we can examine your child directly.

We may start by sending a urine sample to test for infection, but blood tests are usually not needed. We will also order an ultrasound to determine whether your child’s kidney is dilated. We also need to gauge how effectively the kidney is functioning.

Tools used to diagnose UPJ obstruction include:

• Nuclear renal scan in which dye is injected to measure how well the kidneys work and observe the dye’s process through the urinary tract
• MRI scan, in cases of complex anatomy or where other imaging does not yield enough information
• CT scan, for children whose symptoms could also indicate other conditions like kidney stones

How Is UPJ Obstruction Treated?

UPJ obstructions may resolve on their own during the first 18 months of a child’s life. Once a definite diagnosis is made, we will monitor your child closely during this time even if no immediate treatment is needed. In children whose UPJ obstructions do not self-heal and do not receive appropriate treatment, permanent kidney damage can occur.

If necessary, UPJ obstruction treatment can consist of a type of surgery known as pyeloplasty. Bruce Lindgren, MD, Director of Minimally Invasive Urological Surgery and attending physician in Urology, notes that several different surgical options are available at Lurie Children’s. “Essentially, in pyeloplasty, we precisely identify and remove the area of blockage, then reattach the healthy part of the renal pelvis to the healthy ureter,” he says. “The type of surgical technique we recommend is based on patient size and surgeon preference.”

In infants, especially those less than 6 months of age, open-field surgery is typically preferred and involves a small incision just below the child’s rib cage on the affected side. Another option at is minimally-invasive pyeloplasty using the da Vinci® robot-assisted system, which is particularly well-suited for complex intra-abdominal procedures and reconstructive urological surgery.

According to Dr. Lindgren, "We do the same thing laparoscopically with the robot as we do open, we're just able to do it with smaller incisions. This results in less pain, the patients go home sooner and are back to normal activities in a couple of days, and parents are back to work sooner," he says. "The robotic advantage is we can do this very precise manipulation and reconstruction through very tiny incisions." 

Regardless of which technique we use, expect your child to stay one or two nights in the hospital. During the stay, they will likely have one or more catheters or stents to drain urine.

Children who have laparoscopic pyeloplasty may not even need pain medication by the time they go home and typically return to normal activities within a week. Children who have open-field surgery may need some pain medication but also are typically back to normal daily activities in about a week.