Ureteropelvic Junction Obstruction

The main jobs of the kidney are to filter the blood, remove waste products and deliver waste products (urine) through the ureter to the bladder. But what happens when the area where the ureter and the renal pelvis meet becomes blocked in children? The following information should help you recognize this problem before it causes serious damage.

What happens under normal conditions?
Kidneys produce urine by filtering the blood and removing wastes, salts and water. The urine must then drain from the kidney through an internal collecting system that ends in a funnel-shaped structure called the renal pelvis and into a natural tube called the ureter. Each kidney must have at least one functional ureter (some have two) to carry the urine from the kidney to the bladder.

What is UPJ obstruction?
The most common cause of obstruction (blockage) in the urinary tract in children is a congenital obstruction at the point where the ureter joins the renal pelvis — the ureteropelvic junction (UPJ). This problem occurs in approximately one in 1,500 children. These obstructions develop prenatally as the kidney is forming, and today most are diagnosed on prenatal ultrasound screening. In UPJ obstruction, the kidney produces urine at a rate that exceeds the amount able to drain out of the renal pelvis into the ureter, and this causes accumulation of urine within the kidney. This accumulation, also called hydronephrosis, is easily visible on ultrasound.

Although encountered less frequently in adults, UPJ obstruction may occur as a result of kidney stones, previous surgery or disorders that can cause inflammation of the upper urinary tract.

What are the symptoms of UPJ obstruction?
Symptoms of UPJ obstruction may be an abdominal mass; a urinary tract infection with fever; flank pain, especially with increased fluid intake; stones and bloody urine. Patients with UPJ obstruction also may have pain without an infection. Some UPJ obstructions are irregular in nature, and urine may drain normally at one time and be completely obstructed at others, producing sporadic pain.

How is UPJ obstruction diagnosed?
Although ultrasound is a very useful screening test, it is not diagnostic of UPJ obstruction. In order to make the diagnosis, it is necessary to perform a functional test, or one that measures the ability of the kidney to produce and drain urine. The classic examination is called the intravenous pyelogram (IVP). In this test, a dye is injected into the bloodstream, and the kidneys remove this substance from the blood. The dye passes into the urine and eventually out of the bladder. The dye is visible on X-ray, and the physician can see the shape of the kidney, renal pelvis and ureter. Although IVPs continue to be helpful, a more useful examination in children is the furosemides renal scan. This test is done in a fashion similar to the excretory urogram except that a radioactive material is used instead of X-ray dye. The material can be followed with a special camera, and this test can give more accurate information about kidney function and drainage.

How is UPJ obstruction treated?
Once the diagnosis of UPJ obstruction is established and there is no further reasonable chance of improvement, the condition requires surgical treatment.

The classic treatment of UPJ obstruction is an open operation to remove the UPJ and to reattach the ureter to the pelvis of the kidney, creating a wide junction between the two. This operation, called a pyeloplasty, allows rapid and easy drainage of urine produced by the kidney and relieves symptoms and the risk of infection. The procedure usually takes a few hours and has a success rate in excess of 95 percent with one operation. Hospitalization after surgery depends on age of the patient. A variety of drainage tubes can be used to promote healing, and the choice of which one to use is dependent on the surgeon's preference. The incision usually is just below the ribs and just behind a line that would pass from the patient's arm to the leg on the affected side. The incision usually is two to three inches long.

Newer treatment of UPJ obstruction involves minimally invasive surgery. Laparoscopic surgery is done by placing several instruments through the abdominal wall and performing the surgical procedure. This procedure is most often done through the abdominal cavity and has the disadvantage of potentially causing scarring or adhesions within the abdomen. The clear advantages of laparoscopic surgery are less pain and nausea, especially in older children and adults. Success rates of laparoscopic pyeloplasty are just being determined.

What can be expected after treatment for UPJ obstruction?
After repair of UPJ obstruction, there usually is swelling of the ureter and continued poor drainage of the kidney for a period of time. This usually changes as the area heals. The surgeon normally obtains a functional test a few weeks after the procedure to evaluate how well the kidney is working. Patients typically recover quickly from any of the procedures, but some have pain for a few days after surgery. Occasionally, a drainage tube must be left in place to help drain the kidney while it heals. The appearance of the kidney can continue to improve for years, but usually it never looks normal on ultrasound or other studies. Once repaired, a UPJ obstruction almost never recurs. There is nothing that the family can do to prevent further problems with the kidney. Patients may have a slightly increased risk of developing stones and infection throughout their lives because many of the kidneys still contain some pooled urine even though their overall drainage is improved after surgery.

Pediatric urologic surgeons who treat UPJ obstruction:

Paul F. Austin, M.D.

Douglas E. Coplen, M.D.

For an appointment with a Washington University pediatric urologic surgeon, call (314) 454-6034.