What is megaureter?

The urinary system is made up of two kidneys, which filter out wastes and extra water from the blood to make urine. Urine flows out of the kidneys and into the bladder through two narrow tubes called ureters.

In most cases, the ureters are normally about 1/4-inch wide. Megaureter (or “large ureter”) occurs when a ureter is larger than 3/8-inch wide. Megaureters are usually discovered in pre-birth imaging tests.

Left untreated, megaureter can lead to infections, blocked urine flow and possibly serious damage to the kidneys.

How common is megaureter?

The exact number of the occurrence of megaureters isn’t known, but the condition is found in males about four times more often than in females.

What causes megaureter?

There are two main types of megaureters:

• Refluxing megaureter: In this type, the urine flows back up the ureter from the bladder. This backflow, known as vesicoureteral reflux, expands the ureter.
• Primary obstructed megaureter: The ureter is too narrow where it enters the bladder, causing a blockage of urine flow at that point.

There are also combinations of the two main types:

• Primary non-obstructed, non-refluxing megaureter: This occurs when there is neither reflux nor obstruction.
• Refluxing obstructed megaureter: This rare condition occurs when there is both reflux and obstruction.

The two most common types are refluxing megaureter and primary non-obstructed, non-refluxing megaureter.

Another class of megaureters is known as secondary megaureters. These are caused by health problems that include:

• A blockage in the male urethra.
• Prune belly syndrome (the absence of abdominal muscles at birth).
• Neurogenic bladder (a poorly functioning bladder due to damage to the nerves that control the bladder).

What are the symptoms of megaureter?

Usually, megaureters don’t cause any symptoms. Many are found on prenatal imaging.

When symptoms occur, they may differ among different people or in how much discomfort they cause. Even when symptoms aren’t present, a suspected megaureter should be evaluated by a doctor in order to avoid possible kidney damage.

In some cases megaureters are found during treatment of a child for a urinary tract infection. Possible symptoms in such cases include fever, back pain, or vomiting.

How is megaureter diagnosed?

• Ultrasound: This imaging test uses sound waves to form a picture of the structure of the kidneys, ureters and bladder.
• Voiding cystourethrogram (VCUG): A dye is dripped through a tube inserted into the urethra. The dye can be traced by an X-ray to see if it remains in the bladder or travels up the ureter.

How is megaureter treated?

• Most patients don’t require intervention and outgrow the condition over time.
• Ultrasound testing is done on a regular schedule to make sure the kidneys are growing normally.
• Initial treatment of megaureters of all types usually includes the use of antibiotics to reduce the chance of urinary tract infections.
• Surgery may be needed for megaureters that don’t resolve with time, that have had a worsening in dilation or have developed infections.

Left untreated, megaureter can lead to infections, blocked urine flow and possibly serious damage to the kidneys.

What can be expected after treatment for megaureter?

Some problems after surgery include bleeding and, in about 5% of cases, a blockage or backflow of urine. These may go away by themselves after some time. After surgery the size of the ureter may not be corrected immediately. Your child may still require regular ultrasound testing to evaluate their kidneys.

How can megaureter be prevented?

There is no known way to prevent megaureter. More information on what causes the condition is needed. Researchers are still trying to determine if it’s genetic.