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UPJ (Ureteropelvic Junction) Obstruction in Children

UPJ obstruction in children at a glance

  • Ureteropelvic juncture (UPJ) obstruction occurs when the normal flow of urine in a child’s kidney is slowed or stopped, which can damage the kidney.
  • UPJ obstruction is most often detected before birth with ultrasound testing.
  • Most cases of UPJ obstruction are birth defects, affecting 1 in 1,500 children.
  • The blockage usually occurs at the renal pelvis, where the kidney attaches to the ureter tube that carries urine from the kidney to the bladder.
  • UPJ obstruction can interfere with the function of the kidney and/or cause episodes of abdominal pain.
  • The problem may improve without treatment, usually by 18 months of age, or surgery may be required to remove the blockage.

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What is UPJ obstruction?

Ureteropelvic junction obstruction in children is a congenital defect involving a narrowing or obstruction in the child’s kidney that slows or stops the flow of urine from the kidney to the bladder. Most often only one kidney is affected.

The blockage forms as the kidney develops in the fetus and generally occurs at the renal pelvis, where the kidney attaches to the ureter tube. UPJ can also be due to a kinking of the ureter tube over blood vessels, which more often leads to cases of intermittent obstruction, when kidneys function normally at times but retain urine at others.

In UPJ, the urine can’t drain fast enough into the ureter tube and builds up in the kidney, causing it to swell (hydronephrosis). This causes the kidney to be noticeably enlarged on ultrasounds, so doctors are able to identify UPJ before birth in many cases.

When detected before birth, the child’s kidney is investigated for UPJ. The condition is also detected after a child is born, generally indicated by intermittent bouts of pain in the child’s abdomen. Many of these cases resolve under observation, generally before 18 months of age.

About 10 to 25 percent of UPJ cases require surgery to prevent damage to the kidney from hydronephrosis. Cases of intermittent abdominal pain with vomiting often require surgery, as these are signs that the child’s kidney is being damaged and may lose function.

UPJ can also occur in adults, though not as often as in children. Adults who have had kidney stones or surgery are more prone to UPJ.

Symptoms of UPJ obstruction

Most congenital cases of UPJ obstruction show up as an enlarged kidney on ultrasound prior to birth. In newborns, UPJ may not produce symptoms. When children do present symptoms, they may include:

In cases of intermittent blockage of urine, pain symptoms may come and go. Urologists generally consider that children with UPJ obstruction don’t experience pain unless urine is infected or the blockage in the kidney is getting worse.

Diagnosis and treatment of UPJ in children

Even if ultrasound before birth indicates UPJ obstruction, more tests are necessary to be sure. The urologist needs to know how effectively urine is draining in an infant or child and can assess this using the following tests:

  • Blood and urine analysis can determine if the kidney is properly filtering body waste into urine.
  • Nuclear renal scan uses nuclear material injected in the blood and special sensing instruments to see how well the kidneys function and to evaluate the extent of the blockage.
  • Intravenous pyelogram (IVP) is used less often than the newer nuclear renal scan. IVP involves dye injected into the bloodstream and x-rays showing how the dye passes through the kidneys. This indicates if the kidney, renal pelvis and ureters are normal.
  • Voiding cystourethrogram is an x-ray evaluation of kidney and bladder function conducted while the child is urinating to empty the bladder.
  • CT scans can also show the presence of an obstruction and are most often used when children experience severe pain, causing the parent to seek attention at an emergency room.

Treatment for ureteropelvic junction obstruction

Young patients with signs of enlarged kidneys receive repeated ultrasounds. Conservative treatment for infants and young children is often recommended, involving close monitoring and looking for indications of poor urine drainage or inadequate kidney growth.

Sometimes a nuclear renal scan, in which a radioactive isotope is injected into the bloodstream and absorbed by the kidneys, is used to assess kidney function. Improvement, sometimes sudden, can occur in UPJ cases. But if the child’s urine flow doesn’t improve due to a remaining obstruction, surgery is needed.

Open pyeloplasty involves removing the UPJ obstruction by traditional surgery through a 2- to 3-inch long incision. The ureter is properly re-attached to the renal pelvis, resulting in a wider opening. Urine then drains efficiently, relieving symptoms and reducing infection risk. The patient is under general anesthesia during surgery and usually stays in the hospital for a couple of days after surgery. Pyeloplasty has a success rate of 95 percent.

Laparoscopic pyeloplasty is a minimally invasive surgery that accomplishes the same thing as the open pyeloplasty. It involves special surgical instruments inserted through a small incision in the abdomen along with a lighted camera, offering the surgeon a clear view of the operating area. Robotic laparoscopic pyeloplasty utilizes a robotic surgical system controlled by the surgeon. Laparoscopic surgeries generally cause less bleeding, scarring, risk of infection and blood clots, and recovery time is faster.

Endopyelotomy is sometimes used and involves a wire inserted through the ureter tube to cut away the UPJ obstruction or widen the narrowed opening from the inside. This procedure may need to be repeated.

Risks of these surgical procedures include:

  • Problems from anesthesia
  • Blood loss
  • Blood clotting
  • Infection
  • Pain
  • Scarring.