Duplex kidneys: tests, diagnosis and treatment

Duplex kidneys may be suspected before the child is born on a routine pregnancy ultrasound scan or identified in an older child as part of investigations for urinary tract infections.

Duplex kidneys: tests in pregnancy

Duplex kidneys can be found on a routine pregnancy ultrasound scan. The 20-week pregnancy ultrasound scan will look at the baby growing in the womb.

If duplex kidneys or other findings are found then further antenatal (before the baby is born) ultrasound scans may be required during the pregnancy. The infant will also have another ultrasound scan after he / she is born.

Duplex kidneys: tests after birth

If duplex kidneys are found on antenatal ultrasound scans your baby will need further scans after he/she is born. How soon the child has an ultrasound scan after they are born will depend on what the antenatal ultrasound scan shows. It may be within the first week of life or at around 4-6 weeks of age. The timing of this will be discussed with you by your healthcare teams.

Tests may include (depending on the findings of the ultrasound scans):

DMSA scan (Dimercaptosuccinic Acid)

This is a type of radionucleotide scan. This means that a substance that gives out a type of radiation called gamma rays is injected into the blood stream. This substance is taken up by the kidneys and a special camera takes some pictures. This allows us to see how well the kidneys are functioning.

MAG3 scan (mercaptoacetyltriglycine)

This is another type of radionucleotide scan. In this scan a substance called mercaptoacetyltriglycine is injected into the blood stream. It is also linked to a substance that gives out a type of radiation called gamma rays. It is taken up by the kidneys and then a special camera takes pictures. This type of scan gives us information on how well the kidneys are functioning, but also on how well urine is draining from the kidneys down into the bladder.

MCUG (micturating cysourethrogram)

This is usually for babies and children who are suspected of having vesicoureteric reflux (urine travelling back up the tubes from the bladder to the kidneys). A special X-ray machine takes a series of images of the bladder while your baby is passing urine.

Urine tests

You, or a nurse, would need to collect some of your child’s urine in a small, clean container for a urine test. A dipstick will be dipped into the urine – this is a strip with chemical pads that change colour depending on what substances are in the urine. The sample may also be sent to a laboratory for more accurate tests.

Blood tests

As well as various scans, your child may have some blood tests. This gives an idea of how well the kidneys are working.

If you are told during your pregnancy that your baby may have duplex kidneys you may have further ultrasound scans during the pregnancy and after he/she is born.

If these scans show no other abnormalities, and your child is well, no further intervention or follow-up is needed. However, it is important to monitor your child for symptoms of urinary tract infections (temperature, unsettled, vomiting, poor feeding, pain on passing urine, blood in urine) and seek medical advice should these occur.

If these scans show abnormalities, what happens next will depend on what these abnormalities are. If there is dilatation (enlargement) of the drainage system (hydronephrosis) of the duplex kidney (hydronephrosis), your child may be started on an antibiotic to reduce the chances of getting a urinary tract infection. This is called a prophylactic antibiotic. The precise type and dose of antibiotic will be discussed with you by your doctor.

If your child continues to have hydronephrosis or it is getting worse on follow-up ultrasound scans you may be referred to an urologist for a review. A urologist is a surgeon who specialises in the urinary tract system.

Duplex kidneys: surgery

Occasionally, surgical procedures are required due to complications such as recurrent urinary tract infections or because of problems with urine drainage caused by ectopic ureters, ureterocoeles, or vesicoureteric reflux.

Surgical interventions, if required, will be discussed with you by your urologist. The type of surgery will depend on how the duplex kidney is affecting your child. Examples of surgical interventions are:

Endoscopic (key hole) anti-reflux procedure

If there is vesicoureteric reflux, sometimes surgeons do operations to reduce the amount of urine going back up to the kidneys. This can sometimes be done as an injection next to the ureter opening to make it less wide open by an endoscopic (key hole) procedure.

Ureteric re-implantation

If there is an ectopic ureteric opening (opening in the wrong place) below the sphincter (valve that holds the wee in), sometimes surgeons have to join the two drainage tubes together and/or take out the one that opens in the wrong place. Re-attaching the ureter to the bladder in a different position can sometime be needed. This is called a ureteric re-implantation.

Puncture or excision of ureterocele

If the ureterocele is causing problems with urine drainage from either kidney, or interfering with bladder emptying it is sometimes advisable to puncture it by keyhole (endoscopic) surgery or remove it completely.

Partial nephrectomy

If there is an abnormal part of the duplex kidney and it is causing problems, sometimes it is advisable to remove the problem part. This is called a partial nephrectomy or sometimes a ‘heminephrectomy’.

About the future

In most cases, duplex kidneys do not cause any problems for the pregnancy or childbirth, and the baby and mother will not have any long-term problems.

Your child will be able to do all of the things that other children their age do. He or she can go to nursery and school, and can play with other children and stay active. 

Your healthcare team will speak with you and your family about any long-term effects.

Follow up

Some babies and children with duplex kidneys need follow-up. Your child may need to go back to the clinic or hospital for more tests and to see the doctor. 

Further support 

This may be a difficult and stressful experience for you and your family. If you have any concerns or need additional support, speak with your doctor or nurse.