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What is megaureter?

Megaureter is an abnormality of one or both of the ureters of a child. Ureters are the two funnel-shaped tubes that carry urine from the kidneys to the bladder. A megaureter refers to an expanded or widened ureter that does not function normally. Whereas a normal ureter is about 3-5 mm, the size of a megaureter is usually greater than 7 mm in diameter.

What causes a megaureter?

A megaureter can be associated with the reverse flow of urine (vesicoureteral reflux, VUR). A megaureter can also be associated with an obstruction. The obstruction can either be the result of a Megaureter
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Megaureter Illustration
ureterocele or narrowing where the ureter meets the bladder (ureteral vesical junction obstruction, UVJO). The goal with megaureters is to determine which are obstructed, which have reflux, and which have both.

A megaureter that is not associated with other problems occurs during fetal development. It occurs when a section of the ureter — which is normally a muscular layer of tissue — is replaced by stiff, fibrous tissue. In the absence of a muscular layer, normal peristalsis (worm-like movement of the ureter that propels urine toward the bladder) cannot occur.

How is megaureter diagnosed?

The severity of the problem often determines how a diagnosis is made. Often a megaureter is diagnosed before birth by ultrasound. After birth, some children may have other problems that may suggest the presence of megaureter. This may prompt our team in the Division of Urology to perform further diagnostic tests, which may include the following:

Our approach to treating megaureter

Through research in the Division of Urology, we have shown that as long as kidney function is not significantly affected and urinary tract infections do not become an issue, some megaureters can be managed medically. (Journal of Urology, Prenatally Detected PMU, 2005. Read the abstract»). This may involve the use of antibiotic prophylaxis and radiology observation with repeated ultrasounds.

When the dilation is severe without showing signs of improvement, or kidney function is affected, surgical repair may be necessary.

Surgical options

Cutaneous distal ureterostomy: This may be necessary in a newborn with massive ureteral dilation or poor renal function. The ureter is surgically brought to the surface of the skin to allow it to drain urine freely into the diaper. This allows the affected kidney and ureter to decompress. Around 18 months of age, the ureter is then reimplanted into the bladder.

Ureterovesical junction obstruction: This surgical procedure involves removing the section of the ureter that is abnormal, reducing it and reconnecting the ureter. The segments of most megaureters regain tone once they are unobstructed.

Reviewed by: Division of Urology
Date: May 2011

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