Duplex kidney

This page explains about the causes, symptoms and treatment of duplex kidney, from Great Ormond Street Hospital.

The world ‘duplex’ is Latin for ‘double’ so having a duplex kidney literally means that your child has a double kidney on one side. Some of our patients at Great Ormond Street Hospital who have this condition are proud to boast that they have three kidneys!

The double section is usually limited to the part of the kidney where the urine collects (the collecting system or renal pelvis), before the urine passes down the bladder in the usual way via a tube called the ureter.

Ureter duplication

But in some cases there is also duplication of the ureter as well. This can be a partial duplication (so the ureter is a ‘Y’ shape) or there may be a completely separate extra ureter.

The limited duplex kidney (where only the collecting system is double) is usually an incidental finding and rarely causes problems. The more extensive duplication, however, does often cause problems and can typically mean a child is more prone to urine infections.

Also the extra ureter can insert into the bladder in an abnormal place or even in the urethra (the tube leading from the bladder to the outside), causing constant urinary dribbling.

The duplicated part of the kidney drained by that ureter has often not developed normally (it is known as ‘dysplastic‘) and thus has poor function.


The fact that your child was diagnosed at the age of two suggests that theu did have problems, such as an infection, and the fact that her duplex kidney contributes only 33 per cent to overall kidney function suggests that part of that kidney is either dysplastic or scarred from previous infections.

If this is the case, they should be seen by a specialist to determine further treatment, which may include surgical removal of the abnormal part.

If your child isn’t already under the care of a specialist kidney doctor (nephrologist), you could ask your paediatrician or GP to arrange a referral.

Last review date: 
March 2011