Ureteropelvic Junction Obstruction
Our kidneys are the organs responsible for filtering our blood to remove waste products. These waste products, also known as urine, must travel through the urinary tract to exit our body. Urine leaves the kidney and enters the renal pelvis, which is a collecting system for the kidney. It passes through the "funnel" of the renal pelvis and then flows down tubes called ureters to the bladder, where it is stored until urination occurs.
The ureteropelvic junction (UPJ) is the "funnel" or point at which the kidney's collecting system and ureter meet. The UPJ is the most common site for a blockage or obstruction in the upper urinary tract. The blockage may be severe (high grade), minimal (low grade), or intermittent. About 15% of children with UPJ obstruction will also have a condition called Vesicoureteral Reflux (VUR). VUR occurs when urine in the bladder flows backwards into the ureters and often back into the kidneys.
Causes of Ureteropelvic Junction Obstruction
UPJ obstruction is most often due to an anatomic narrowing at the point where the collecting system of the kidney meets the ureter. Other causes of obstruction include crossing blood vessels, a fibrous band, or abnormal positioning of the ureter on the renal pelvis.
A UPJ obstruction makes it difficult for urine to flow freely out of the kidney into the ureter, which may cause the kidney and its collecting system to become enlarged and filled with fluid. This is a condition called hydronephrosis. Prolonged blockage may be harmful to kidney function, especially if associated with infections.
Symptoms of Ureteropelvic Junction Obstruction
Hydronephrosis, which is commonly due to a UPJ obstruction, can often be detected before birth through prenatal ultrasound. Newborns and infants may have an abdominal mass or become very sick because of urine infections. Older children may experience abdominal pain, nausea, or urinary tract infections related to the obstruction.
Treatment of Ureteropelvic Junction Obstruction
Testing to determine the degree of obstruction and if VUR is present will be necessary. Mild blockages can be managed with preventative antibiotics and periodic testing to monitor kidney growth. Surgical correction may be necessary if the blockage is interfering with the normal growth and development of the kidney. Surgical repair of an obstruction usually involves the removal of the abnormal UPJ and reattachment of the ureter to the renal pelvis.