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Ureteropelvic junction obstruction is a condition where blockage occurs at the junction where the ureter attaches to the kidney.

This results in decreased flow of urine down the ureter and an increase of fluid pressure inside the kidney.

If untreated, UPJ obstruction can lead to permanent loss of kidney function (kidney failure). Kidney stones or infection may occur in the affected kidney, even after treatment.


UPJ obstruction is often diagnosed during prenatal ultrasound, when the enlarged kidney is seen. For those that occur later or are not detected at birth, symptoms suggesting UPJ obstruction include hematuria (blood in the urine), urinary tract infection, kidney infection, kidney stones, and abdominal discomfort.

While the most common type results from a narrowing of the ureter as it forms in fetal development (usually because of an abnormality in the development of the muscle surrounding the UPJ), UPJ obstruction can also occur later in life and can be caused by other factors, including compression of the ureter by inflammation, kidney stones, scar tissue, abnormal blood vessels, or a tumor.

Diagnostic tests help to determine the degree of UPJ obstruction and whether surgery is necessary.


When the obstruction is mild, it is usually left to correct itself. Antibiotics may be used to prevent infection, and the patient is monitored every 3–6 months with a renal ultrasound. 

Because of the potential for kidney damage, more severe cases tend to require pyeloplasty, a surgical procedure that removes the blockage and reconnects the ureter and the renal pelvis.

The success rate is higher than 95 percent, and the procedure can often be done laparoscopically. The patient continues to be followed even after successful repair to ensure proper kidney function.

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