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What is a megaureter?

Ureters are the tubes that drain urine from the kidneys into the bladder. A megaureter is an enlarged ureter that does not function normally. While normal ureters are about 3 to 5 millimeters in diameter, a megaureter usually has a diameter of 8 millimeters or more. Megaureters can be both refluxing (meaning fluid backs up and goes in the opposite direction it should) and obstructed (blocked).

What causes a megaureter?

There are several conditions that can contribute to or cause a megaureter:

  • Ectopic ureter: This is a condition where the ureter does not connect properly to the bladder and drains somewhere outside the bladder. In boys, the ectopic ureter may drain into the bladder neck or urethra near the prostate. In girls, the ectopic ureter may drain into the bladder neck, urethra, or reproductive organs. This is often associated with a duplicated kidney (duplex collecting system), where one kidney has two separate drainage systems. In this case, one ureter may drain normally into the bladder while the second does not.
  • Non-obstructed megaureter: In some cases, the ureter may be enlarged but not associated with other problems. This may happen if a section of the ureter does not develop normally before a baby is born. This condition may be isolated or can be associated with other conditions involving smooth muscle defects, such as Eagle-Barrett syndrome.
  • Ureterovesical junction obstruction: This is a condition where the ureter is narrowed and partially blocked where it joins the bladder.
  • Ureterocele: This is a congenital condition where there is a cystic ballooning of the ureter within the bladder.
  • Vesicoureteral reflux: This is a condition where the flap valve in the bladder is not long enough, causing urine to back up towards the kidney as the bladder fills.

Who gets megaureters?

Megaureters are relatively rare and usually occur during fetal development, so they are present in newborns. Many of the conditions associated with megaureter, such as vesicoureteral reflux and ectopic ureter, are more common in females.

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