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What is a duplex kidney?

A duplex kidney is where a child is born with a double kidney on one side (“duplex” is Latin for “double”). The part of the kidney that is duplicated is usually the collecting system (or renal pelvis), which is where urine collects before it is passed into the ureter (tube) that leads to the bladder. This rarely causes problems and may only be noticed by chance during a scan of the patient.

In more extensive duplex kidneys, the ureter may be duplicated as well. This may be a partial duplication, with the two ureters joining together in a Y-shape, coming together before connecting to the bladder. However, there can also be a complete second ureter, which can be problematic. It may connect to the bladder in an unusual place, which can cause vesicoureteral reflux, or it may even connect directly to the urethra (the tube leading from the bladder out of the body), bypassing the bladder completely, and causing a constant dribble of urine.

Symptoms of a duplex kidney

Duplex kidneys and duplicated ureters that drain directly into the bladder rarely cause any symptoms.

However, if there is a complete second ureter, this often functions poorly and can be connected to a number of problems:

Medical tests to diagnose a duplex kidney

Duplex kidneys are usually diagnosed with imaging tests, such as ultrasound, CT or MRI scans. However, if they are asymptomatic, they may not be noticed until adulthood.

Treatments for duplex kidneys

Duplex kidneys that are not causing problems do not require treatment. However, if they are causing symptoms and affecting the patient’s health or quality of life, doctors may recommend one of the following:

Which type of specialist treats duplex kidneys?

Urologists and paediatric urologists treat duplex kidneys in adults and children respectively. The condition is more commonly treated in children, as if it causes symptoms it will usually do so from birth.