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Ureteropelvic Junction Obstruction

What is ureteropelvic junction obstruction (UPJ)?

The urinary system is made up of two kidneys, two ureters, the bladder and a urethra. The kidneys are the bean-shaped structures located just below the rib cage that make urine and filter waste products from the blood. The ureters are thin tubes that carry the urine from the kidneys to the bladder where it is stored until leaving the body. The urethra is the tube that carries urine from the bladder out of the body.

The area where the ureter connects to the kidney is the ureteropelvic junction (UPJ). A narrowing of this junction can cause a blockage which can prevent the normal flow of urine from the kidney, causing swelling (dilation) of the kidney (a condition called hydronephrosis). Prolonged blockage may be harmful to kidney function, especially if it is associated with infections.


UPJ obstruction is most often caused by a narrowing at the point where the ureter is connected to the kidney. UPJ obstruction can also be caused by a blood vessel or tissue crossing over the ureter causing a blockage.


Because of the increased use of prenatal ultrasound, UPJ obstructions can often be detected before birth. UPJ obstruction may be found in newborns and infants with abdominal fullness or urinary tract infections. Older children with this issue may have abdominal pain with nausea and vomiting, blood in their urine, or urinary tract infections with fever.

Testing, diagnosis and treatment

When a UPJ obstruction is suspected at any age, tests to determine the degree of blockage will be performed, including kidney ultrasound (painless test that takes pictures of the kidney and ureter) and possibly a kidney scan.

Mild blockages can be followed to monitor kidney growth but often resolve on their own without intervention. Surgery may be recommended if the blockage is slowing the growth or function of the kidney or causing infections. A treatment plan will be determined with your child’s urology team based on your child’s individual needs.

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