What Is Megaureter?
Ureters are the two tubes that transport urine from the kidneys to the bladder. A megaureter is an enlarged, swollen ureter that is about double the normal size. This condition occurs congenitally (present at birth) in about 0.4 of each 1,000 births.
The word “hydroureteronephrosis” is sometimes used describe an enlarged ureter. This is a more broad term for swelling in the urinary tract, when the underlying cause is unknown.
Types of Megaureter
Megaureters are classified as either “refluxing” or “non-refluxing.”
- Refluxing, non-obstructed megaureter: Most often seen with high-grade vesicoureteral reflux (VUR), but it can also occur as a result of posterior urethral valves (PUV) in boys, or due to neurogenic bladder (lack of bladder control caused by a neurological condition).
- Refluxing, obstructed megaureter: Occurs with an ectopic ureter (ureter that is implanted in the wrong place, outside the bladder), ureterocele, or with reflux during voiding. This is a rare condition.
- Primary megaureter: A ureter that is enlarged, even though no reflux or obstruction is present. This can be caused by polyuria (excessive urination) or an infection, or it can be a postoperative result from a procedure. Sometimes the cause is not known.
- Non-refluxing, obstructed megaureter: Occurs due to a ureteral obstruction or a mass/tumor. This is a rare condition.
Causes of Megaureter
The two most common causes are:
- Vesicoureteral reflux (VUR)
- Ureterovesical junction obstruction (UVJ). This is an obstruction in the area where the ureter meets the bladder.
Other conditions can cause megaureter, including neurogenic bladder, ectopic ureter, ureteroceles, or other bladder-outlet obstructions (posterior urethral valves, urethral polyps, or Prune Belly Syndrome).
How Is Megaureter Diagnosed?
The diagnosis is usually made when the baby is still in utero, when hydroureteronephrosis is detected during a routine anatomy-scan ultrasound. Once the baby is born, testing is typically performed to confirm the diagnosis.
Renal Ultrasound (RU)
This type of ultrasound examination assesses the degree of swelling in the kidneys and urinary tract, and looks for any abnormalities in the bladder.
Voiding Cystourethrogram (VCUG)
This imaging exam looks at the urinary tract to determine the cause for hydroureteronephrosis. This test may be used to rule out VUR as a cause for hydroureteronephrosis.
VCUG may be performed when babies have a prenatal diagnosis of hydroureteronephrosis (especially if the baby also has a febrile urinary tract infection), or when there is dilation of both kidneys.
MAG3 Lasix Scan
If the urologist has ruled out VUR or a bladder-outlet obstruction (with RUS and VCUG procedures), this test is usually the next step.
The MAG3 Lasix Scan evaluates kidney function, including how well the kidneys drain. This test will show the percentage of how well each kidney is functioning relative to the other. Each kidney should contribute 45 percent to 55 percent of total function (totaling 100 percent of function). If one kidney functions at less than 40 percent or the function is declining by more than 5 percent, surgery is usually necessary.
How Is Megaureter Treated and Managed?
Your child's treatment and management plans will depend on the underlying cause and the specific symptoms of megaureter. Most infants will need to be started on prophylactic antibiotics to prevent a urinary tract infection (UTI). For boys with megaureter, circumcision may be considered to decrease the risk of infection.
Sometimes repeat renal ultrasounds are necessary, and some cases may need surgical intervention. Surgery may be necessary if any of the following conditions exist:
- Recurrent febrile UTIs
- Loss of kidney function (less than 40 percent, or greater than 5 percent decline on a subsequent study)
- Worsening hydronephrosis or urinary tract dilation