Ureteropelvic Junction Obstruction

What is Ureteropelvic Junction Obstruction?

Ureteropelvic junction (UPJ) obstruction is when part of the kidney is blocked. Most often it is blocked at the renal pelvis. This is where the kidney attaches to one of the ureters (the tubes that carry urine to the bladder). The blockage slows or stops the flow of urine out of the kidney. Urine can then build up and damage the kidney. Sometimes surgery is needed to improve the flow of urine and other times the problem will improve on its own.

What Happens under Normal Conditions?

Kidneys make urine by filtering the blood, and removing waste, salts and water. The urine drains from the kidney into the renal pelvis and then into the ureter. Each kidney must have at least 1 working ureter (some have 2) to carry the urine from the kidney to the bladder.


Most often UPJ obstruction is congenital. This means that children are born with this health issue. It is not known how to prevent it. One in 1,500 children are born with this problem. The blockage occurs as the kidney is forming. Today most cases are found using ultrasound before birth. Though it occurs less often in adults, UPJ obstruction may happen after kidney stones, surgery or upper urinary tract swelling.
In UPJ obstruction, the kidney makes urine faster than it can be drained through the renal pelvis into the ureter. This causes urine to pool in the kidney, which leads to kidney swelling (hydronephrosis). Often, only 1 kidney is affected. The enlarged kidney is easily seen on ultrasound. For this reason, a doctor can often predict UPJ obstruction before a baby is born.


With the use of ultrasound, most cases are found long before birth. After birth, signs in infants and children are:
• abdominal mass
• urinary tract infection with fever
• flank pain (pain in the upper abdomen or back, mostly with fluid intake)
• kidney stones
• bloody urine
• vomiting
• poor growth in infants
UPJ obstruction may also cause pain without an infection.
Some cases of UPJ obstruction are not clear. Urine may drain normally at times, and at other times be blocked. This causes pain that comes and goes. The general belief is that most children are not in pain unless the urine becomes infected or the blockage gets worse.


While ultrasound helps your doctor see the kidneys, more tests are needed to confirm UPJ obstruction. To make a proper diagnosis, your urologist must see how well urine is produced and drained. There are several tests that can be done.
Blood samples and urine samples may be taken. The BUN (blood urea nitrogen) and creatinine tests find if the kidney is working well as it filters the blood.
An intravenous pyelogram (IVP) was often used in the past. In this test, a dye is injected into the bloodstream. An X-ray is used to see the kidneys remove the dye from the blood. As the dye passes through urine, your doctor can see if the kidney, renal pelvis and ureter look normal.
A nuclear renal scan is similar to an IVP but is more modern. This test uses radioactive material instead of dye. The material can be seen with a special camera. This test gives the doctor good information about how the kidney is working and how much blockage there is.
CT scans are sometimes used in the emergency room to find out why children are having severe pain. A CT scan can easily show the obstructed kidney if that is the cause of the pain. Magnetic resonance imaging (MRI) is also used to look at the kidneys, ureters and the bladder. But MRI is expensive and not used everywhere.
Siblings need screening for UPJ obstruction only if they show signs. There have been some cases in which several members of a family have UPJ obstruction, but the majority of cases are individual.


Treatment is not always necessary, and experts have different opinions. It is important to know that poor drainage in infants and children younger than 18 months may be temporary. Many infants with good kidney function and poor drainage at first will have much improvement after a few months. On the other hand, in some infants the obstruction won’t improve it will get worse.
Young patients with an enlarged kidney are first followed with repeat ultrasounds and, if there is any concern, repeat nuclear scans. Sudden improvement can occur. If so, it often occurs in the first 18 months of life. If urine flow does not improve for an infant and obstruction remains, then surgery is needed. Adults may find treatment in other ways.

Open Surgery

The classic treatment for infants is an operation called pyeloplasty. In this surgery the UPJ is removed, and the ureter is reattached to the renal pelvis to create a wide opening. This lets the urine drain quickly and easily. It also relieves symptoms and the risk of infection. The surgeon’s cut is usually 2 to 3 inches long, just below the ribs. This process usually takes a few hours with a great success rate (95% success). The patient may have to stay in the hospital for a day or 2 after surgery. Drainage tubes can be used to promote healing.

Minimally Invasive Surgery

Newer surgical options are less invasive, such as:
1. laparoscopic pyeloplasty with or without a surgical robot, or
2. internal incision of the UPJ using a camera and scope inserted through the bladder

Laparoscopic Pyeloplasty

In this method the surgeon works through a small cut in the abdominal wall. A surgical robot can help guide the tools. The clear advantages of this method are less pain and nausea, especially in older children and adults. But scarring in the abdomen can result. This treatment has led to very successful results.

Internal Incision

With this option a wire is inserted through the ureter. This wire is used to cut the tight and narrow UPJ from the inside. A special ureteral drain is left in for a few weeks and then removed. The UPJ heals in a more open manner but the surgery may need to be repeated. The success rates are lower than with open or minimally invasive surgery. But the advantages also include less pain and nausea.