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PUJ Obstruction - UPJ Obstruction

Overview, Causes, & Risk Factors

The renal pelvis is the structure that drains urine from the kidneys. The tube that carries the urine from the renal pelvis into the bladder is called the ureter. The narrow area where these two structures meet is called the ureteropelvic junction (UPJ). A blockage in the UPJ can inhibit the flow of urine.

What is going on in the body?

Blockage of the UPJ can be present from birth. It is a common urinary tract abnormality. Most of the time the problem appears in childhood. In some people, however, symptoms may not show up until after puberty. Obstruction can also result from a kidney stone lodged in the area or from injury.

In between 10 and 40 percent of cases, UPJ obstruction occurs on both sides of the body. Twenty to forty percent of children with this condition have a backflow of urine into the kidney.

What are the causes and risks of the condition?

UPJ obstruction can be caused by the following:

  • abnormalities in the muscles of the ureter
  • scar tissue in the ureter
  • compression of the UPJ by a blood vessel leading to the kidney
  • kinks in the ureter
  • fibrous bands around the ureter
  • kidney stones
  • external trauma, or injury to the body over the kidney area
  • injury during endoscopy or surgical procedures
  • There is some suspicion that the problem can be inherited. However, this has not been proven conclusively.

    Symptoms & Signs

    What are the signs and symptoms of the condition?

    Symptoms of UPJ in children include:

  • fever
  • abdominal distress
  • nausea and vomiting
  • a poor growth rate, known as failure to thrive
  • Currently, most cases of UPJ obstruction are detected by pregnancy ultrasound while the baby is still in the womb.

    Diagnosis & Tests

    How is the condition diagnosed?

    > The healthcare provider will suspect a UPJ obstruction if the renal pelvis and kidneys are dilated. This dilation is known as hydronephrosis, and can be detected with a pregnancy ultrasound. It should be confirmed with another ultrasound after the baby is born.

    Other diagnostic tests include:

  • Doppler ultrasound to measure the blood flow to the kidney
  • intravenous pyelogram, which allows the kidneys to be visualized under x-ray
  • renal scintigraphy, involves the injection of radio-nuclide tracer into a vein in the arm. The images produced from technique are helpful in assessing kidney function.

  • Prevention & Expectations

    What can be done to prevent the condition?

    There is no known prevention for this condition. However, if UPJ is due to a kidney stone, it may be helpful for a person to drink plenty of fluids.

    What are the long-term effects of the condition?

    Chronic obstruction can lead to the gradual loss of kidney function. Urinary tract infections are common with UPJ. They can be serious when this condition is present. Also, kidney stones are prone to form in the urine that collects in the urinary tract when there is a blockage.

    What are the risks to others?

    There are no risks to others, as UPJ obstruction is not contagious.

    Treatment & Monitoring

    What are the treatments for the condition?

    If a UPJ obstruction is clearly present and is affecting kidney function, surgery is needed to repair it. This operation involves cutting the ureter to remove the blockage, then reattaching it to the renal pelvis. This procedure can be done through an endoscope or with open surgery.

    Endoscopic techniques are frequently performed with adults. They are less commonly used with children. They carry a slightly lower success rate than open surgery. However, there are few complications and the person is able to recover more quickly.

    What are the side effects of the treatments?

    There are possible side effects with any surgery. These include bleeding, infection, and allergic reaction to the anesthesia. Stents and tubes placed in the urinary tract following surgery may cause discomfort, and an increased risk for infection. The person may also need to urinate frequently.

    What happens after treatment for the condition?

    Complications of surgical repair of UPJ obstruction can include:

  • bleeding
  • infection
  • damage to the kidney or ureter
  • How is the condition monitored?

    Follow up visits with the surgeon will be necessary if surgery has been performed. Any new or worsening symptoms should be reported to the healthcare provider.


    Author:Stuart Wolf, MD
    Date Written:
    Editor:Slon, Stephanie, BA
    Edit Date:05/10/00
    Reviewer:Gail Hendrickson, RN, BS
    Date Reviewed:07/05/01


    The Merck Manual of Medical Information, Home edition, 1997

    Professional Guide to Diseases, Sixth Edition. Springhouse: Springhouse Corporation, 1998

    Tierney, Lawrence, editor, "Current Medical Diagnosis and Treatment, 39th edition", 2000