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.
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.
UPJ obstruction can be caused by the following:
There is some suspicion that the problem can be inherited. However, this has not been proven conclusively.
Symptoms of UPJ in children include:
Currently, most cases of UPJ obstruction are detected by pregnancy ultrasound while the baby is still in the womb.
> 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:
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.
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.
There are no risks to others, as UPJ obstruction is not contagious.
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.
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.
Complications of surgical repair of UPJ obstruction can include:
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
Editor:Slon, Stephanie, BA
Reviewer:Gail Hendrickson, RN, BS
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