What are duplicated ureters?

Duplicated ureters, also known as duplicated collecting system or duplex kidney, is the most common birth defect related to the urinary tract. Both boys and girls are affected but the condition is more common in girls.

Ureters are long, narrow tubes that drain urine from the kidneys to the urinary bladder. Normally one ureter leads from each kidney to the bladder. In the case of duplicated ureters, two ureters drain a single kidney. One ureter drains the upper part of the kidney and the other drains the lower part. This condition may affect one or both kidneys.

Duplicated ureters can take one of two forms:

  • Incomplete: Two separate ureters are attached to the same kidney but join together at some distance away from the kidney to form a single ureter that enters the bladder.
  • Complete: Two separate ureters lead away from the same kidney and remain separate.

How common are duplicated ureters?

About 0.7% of the healthy adult population and 2% to 4% of patients with urinary tract symptoms have duplicated ureters. Incomplete duplication is three times more common than complete duplication, which is estimated to appear in about one of every 500 people.

What causes duplicated ureters?

Duplicated ureters are a result of errors in cell division that occur during the development of a fetus, the baby inside the mother’s womb. There is no proof that anything during pregnancy causes the defect. However, there is evidence to show that the condition can be passed from parent to child. If one parent has a duplicated ureter the child has a 50-50 chance of also being born with this condition.

What are symptoms and complications of duplicated ureters?

As long as duplicated ureters drain normally into the urinary bladder they should not cause any symptoms. If symptoms do occur, it is usually in the case of complete duplicated ureters.

Duplicated ureters can occur with other abnormalities of the urinary system. One of the more common is ureterocele. With this condition, the end of the ureter does not develop properly, and urine flow is obstructed. This results in a balloon-like swelling as urine builds up at the point where the ureter and bladder connect. In addition, urine can reflux back toward the kidney through the second ureter, which often has a weak valve because it joins the bladder in an abnormal location.

A number of symptoms can also occur when one of the ureters is ectopic, which means it drains to somewhere other than the bladder. Symptoms of an ectopic ureter include:

  • Hydronephrosis: An ectopic ureter is usually narrower than it should be, leading to an obstruction in the flow of urine. The urine gets backed up and causes the kidney and ureter to swell.
  • Urinary tract infection (UTI): Poor drainage makes it easier for bacteria to enter urine and travel to the bladder. UTIs result in painful urination.
  • Vesicoureteral reflux: Urine backs up and flows in the wrong direction (up toward the kidney instead of down toward the bladder). It is important for a doctor to grade the amount of reflux, as a child may be able to outgrow a small amount of reflux but may need more extensive treatment if the reflux is large. Kidney infections or other damage can result from reflux.
  • Incontinence (inability to control urination):
    • In boys, this symptom may not be present because the ureter drains inside the body. However, other signs such as swelling or UTIs may occur.
    • In girls, even those that have been toilet-trained, there is a general wetness with urine. Rather than being caused by losing bladder control, the dampness is due to a steady leakage of urine.

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