Ureteropelvic Junction (UPJ) Obstruction


Ureteropelvic junction (UPJ) obstruction occurs when the area connecting the renal pelvis (part of the kidney) to one of two tubes that connect with the bladder (ureter) becomes blocked, causing urine to build up, which damages the kidneys. A UPJ obstruction can also occur if a blood vessel is positioned incorrectly over the ureter.


Causes and Risk Factors for UPJ Obstructions

UPJ is usually present at birth (congenital) and is most frequently diagnosed during a prenatal ultrasound. If undiagnosed after birth, the child may have an abdominal mass or urinary tract infection. When UPJ occurs in older children or adults, it is usually due to scar tissue, abnormalities in muscles under the scar tissue, kidney stones, infection, or previous treatments or surgeries for a blockage. An obstruction also can be caused by compression of the UPJ by a blood vessel or irregularities in the fibrous bands around the ureter.

If undiagnosed or left untreated, chronic UPJ obstruction can lead to significant kidney damage and the gradual loss of kidney function. This is especially true of patients who are diagnosed later in life. Urinary tract infections become common and can be more serious than usual. Kidney stones in the urine that collect in the urinary tract as the result of blockage also become far more common.

Symptoms of UPJ Obstructions

Symptoms of UPJ obstructions include:

  • The renal pelvis and/or kidneys are dilated (hydronephrosis)
  • Urinary tract infection
  • Abdominal mass
  • Vomiting
  • Poor growth in infants (failure to thrive)
  • Back pain
  • Flank pain


A renal ultrasound is used to detect a UPJ obstruction prenatally. Further imaging tests may also be necessary depending on results of the ultrasound.

After birth (postnatally), a range of tests are used to diagnose such obstructions, including:

  • Urinalysis and culture
  • Complete blood count (CBC)
  • Nuclear scan of kidneys
  • Voiding cystourethrogram
  • CT Scan
  • Diuretic renal scan, in which a small amount of radioactive material is injected into a vein and kidney function is measured using the scanned images of the organ as it removes the radioactive material from the blood


Surgery is usually required if a UPJ obstruction is affecting kidney function. Either endoscopic techniques or open surgery can be used, although adults are better candidates for endoscopic procedures. Even though the success rate for endoscopy is lower, the risk of complications is less, and recovery time is shorter. In both surgical methods the ureter is cut to remove the blockage, then reattached to the renal pelvis.

Because there can be complications resulting from surgical repair of UPJ obstructions, regular follow-up visits with a physician are necessary.


To prevent infection, a physician may prescribe antibiotics for a newborn with UPJ obstruction, in addition to a renal ultrasound every three to six months to monitor the condition.

If a UPJ obstruction begins to cause a noticeable reduction in renal function, a pyeloplasty may be recommended. A pyeloplasty is a surgical procedure that removes scar tissue from the blocked area, then connects the healthy part of the kidney to the healthy ureter. Removing the obstruction improves urine flow and reduces the possibility of kidney damage. Until the patient heals, a tube (stent) may be inserted to drain urine from the kidney.

Follow-up care is necessary for several years after pyeloplasty, as well as regular testing to evaluate kidney function every 6 months to a year. Though there are some potential complications, there is an excellent success rate with this procedure.

Resources at Cedars-Sinai
  • Urology Academic Practice

© 2000-2022 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.
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