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Fetal Duplication of Collection Systems

DuplicateCollectingSys_s.gifIn a normal urinary system, there is one ureter (tube-like structure) connected to each kidney. The ureters' main function is to drain urine from the kidney into the bladder. A fetus that is diagnosed with duplication of collecting systems has two ureters for one kidney; each one drains separately into the bladder. This condition is often associated with fetal ureterocele, a balloon-like malformation of the area where the ureter enters the bladder.

In a fetal duplicated collecting system, the ureter affected by the ureterocele generally drains the top part of the kidney, while the other ureter drains the bottom part. The ureter affected by the ureterocele enters the bladder at a lower location than the other ureter. This may cause reflux (or back-flow) of urine into the other ureter.

Most commonly found in females, the condition generally affects 15% of all live births.


A fetal duplication of collecting systems is generally diagnosed by ultrasound examination before birth. Evaluation of the kidneys is part of the routine ultrasound examination done by many obstetricians as part of their prenatal care around the 20th week of pregnancy. 

Parents expecting a child with fetal duplication of collecting systems can receive a consultation in the Institute for Fetal Health.


Fetal duplication of collecting systems has no symptoms, but may be seen on ultrasound (sonogram) examination. Typically when children are born with this condition, they may have a urinary tract infection or develop urinary incontinence later in life.


Nothing can be done to treat fetal duplication of collecting systems before a baby is born. However, after birth, treatment will depend on how the duplication of collecting systems is affecting the urinary system. If an ureterocele is found, then the accumulated urine may need to be drained surgically. If the duplicated system is causing reflux, the second ureter may need to be removed. In some cases, the duplex system is not associated with reflux nor a ureterocele, so the child may just need continued observation.

Long-term Effects

After normal urine flow is established, children are watched carefully for infection, but the outlook for normal urinary function is very good.


Learn about fetal ureterocele.