What is a duplex collecting system?
In children with a duplex collecting system, also known as ureteral duplication, a kidney has two ureters (tubes that carry urine from the kidney to the bladder) rather than one.
- Children with this condition often also have a ureterocele, an enlargement of the portion of the ureter closest to the bladder due to the ureter opening being very tiny. This obstructs urine flow into the bladder, causing urine to back up the ureter toward the kidney.
- In a duplex collecting system, the ureter with the ureterocele generally drains the top half of the kidney, while the other ureter drains the lower half. The ureter with the ureterocele may enter the bladder lower than the other ureter, which may cause a backflow of urine (reflux) into the higher ureter.
- A duplex collecting system can result in frequent urinary tract infections, backflow of urine into the kidney, and sometimes kidney damage.
Richard Lee, MD — Urologist
What causes ureteral duplication?
Ureteral duplication is much more common in girls than in boys. No one knows the cause of ureteral duplication; some cases have been reported in siblings, suggesting a genetic component.
What are the symptoms of ureteral duplication?
- pain in the side
- urinary tract infection
How Boston Children’s approaches a duplex collecting system
A duplex collecting system and ureterocele are generally treated in tandem. Treatment of the ureterocele often depends on the size of the constriction and how well the kidney that the ureter drains is functioning.
Duplex Collecting System | Diagnosis & Treatments
How are ureteral duplication and ureterocele diagnosed?
Often they are noticed before birth, when a prenatal ultrasound exam shows swelling (hydronephrosis) of a kidney. If a ureterocele isn't detected during pregnancy, it may not be detected until your child has recurrent urinary tract infections.
If your child has a history of frequent urinary tract infections, your child's physician may recommend the following tests:
- Ultrasound of the entire urinary tract: This imaging test helps your child's doctor view internal organs as they function and to check the blood flow through various vessels.
- Intravenous pyelogram (IVP): A special x-ray of the kidneys, ureters, and bladder, IVP uses a liquid called contrast that helps reveal the rate and path of urine flow through the urinary tract.
What sort of treatment will my child receive?
Specific treatment recommendations for a ureterocele or ureteral duplication will depend on your child's individual situation.
If your child is ill from a urinary tract infection, intravenous fluids and antibiotics may be administered. Once the urinary tract infection is resolved, the ureterocele will be addressed.
If the area of the ureter has a great deal of urine accumulation, it may need to be surgically drained.
- Larger ureteroceles that cause a great deal of backflow into the ureter may need to be removed. (The normal duplicate ureter is often left alone.)
- A small ureterocele may not require medical intervention if the kidney is functioning without difficulty.
If your child's kidney has been damaged, part of it may need to be removed. For more information on that procedure, see our page on nephrectomy.
For more information, see our page on ureterocele.