Pediatric Urology

Home » Pediatric Urology » Ureteropelvic Junction Obstruction, Causes, Treatment

Overview

The organ that produces urine (kidney) and the tube that carries urine from the kidney to the bladder (ureter) join at the ureteropelvic junction (UPJ). Narrowing (stricture) at this junction reduces the flow of urine from the kidney and can result in enlargement of the kidney caused by the backup of urine into the renal pelvis (hydronephrosis) and kidney damage. UPJ obstruction can be severe, minimal, or intermittent and is often diagnosed during prenatal ultrasound. It is the most common cause of hydronephrosis in utero and in newborns.

Incidence and Prevalence
Approximately 1% of prenatal ultrasounds detect hydronephrosis in the fetus. In 50% of these cases, UPJ obstruction causes the condition. UPJ obstruction is more common in males and affects the left kidney more often than the right. About 20–30% of cases occur in both kidneys (bilaterally).

Causes

Congenital abnormalities are the most common cause of UPJ obstruction in young children. The condition often results from an abnormality in the muscles that surround the UPJ. It may also be caused by an abnormality in the structure or position of the ureter, kidney, and renal blood vessels.

In older children, UPJ obstruction may be caused by the following:

• Compression of the ureter caused by inflammation
• Condition in which scar tissue forms in the renal cavity (retroperitoneal fibrosis)
• Kidney stones
• Scar tissue from previous surgery to correct UPJ obstruction

Signs and Symptoms

Symptoms of UPJ obstruction include the following:

• Back pain
• Blood in the urine (hematuria)
• Failure to thrive
• Flank pain
• Flank mass
• Kidney infection (pyelonephritis)
• Urinary tract infection (UTI)

Diagnosis

UPJ obstruction that causes hydronephrosis is usually diagnosed by prenatal ultrasound. Neonatal patients suspected to have this condition are evaluated for the obstruction using renal ultrasound. Other imaging tests may also be required.

Other diagnostic tests used to evaluate kidney function and determine the severity of the blockage include the following:

• Creatinine, BUN (blood urea nitrogen), and electrolyte levels
• Complete blood count (CBC)
• Diuretic renal scan
• Urine culture
• Voiding cystourethrogram (VCUG; used to rule out vesicoureteral reflux)

In diuretic renal scan, a small amount of radioactive substance is injected into a vein and kidney function is assessed using scanned images of the organ as it removes the substance from the blood.

Treatment

Newborns with UPJ obstruction and hydronephrosis are placed on antibiotics to prevent infection and are monitored with renal ultrasound every 3 to 6 months. If UPJ obstruction causes a significant reduction in renal function, a surgical procedure called pyeloplasty is performed to remove the obstruction, improve urine flow, and reduce the risk for kidney damage. Pyeloplasty involves removing the blockage and reattaching the ureter to the renal pelvis. A temporary device that holds the ureter open (stent) may be inserted to drain the kidney.

Complications include the following:

• Adverse reaction to anesthesia
• Kidney infection (pyelonephritis)
• Narrowing of the ureter (stricture)
• Recurrent UPJ obstruction
• Urine leakage into surrounding tissue
• UTI (e.g., cystitis)

Patients require follow-up care for several years following pyeloplasty. Tests to evaluate kidney function are performed regularly (6 months to 1 year).

Prognosis

The success rate for patients who undergo pyeloplasty is higher than 95%.

Prevention

Ureteropelvic junction obstruction cannot be prevented.

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