Renal dysplasia (or kidney dysplasia) means that a kidney does not fully develop in the womb. The affected kidney does not have normal function – which means that it does not work as well as a normal kidney. It is usually smaller than usual, and may have some cysts, which are like bubbles or sacs filled with liquid.
Renal dysplasia can be broken down:
- renal: to do with one or both kidneys
- dys: not working properly
- plasia: to do with development.
It is one type of congenital anomaly of the kidneys and urinary tract. ‘Congenital’ means that the problem is present at birth and ‘anomaly’ means different than normal.
How common is it?
Renal dysplasia is rare. It affects around one baby in every 2,000.
Renal dysplasia may be picked up before birth on the 20 week antenatal ultrasound scan, or soon after birth. It may also be picked up in an older child who has some symptoms. An affected kidney is called a dysplastic kidney. Renal dysplasia rarely causes any problems during the pregnancy or in childbirth.
- If it happens in one kidney, it is called unilateral renal dysplasia. Although one of their kidneys will not work properly, most children have no serious problems, but will need monitoring for possible long-term effects.
- If it happens in both kidneys, it is called bilateral renal dysplasia. This is more serious, and will need follow-up during the pregnancy to find out how the baby is affected.
Renal dysplasia: causes
Renal dysplasia happens when part of the kidney does not develop properly in the womb.
Doctors understand that there are some possible causes of renal dysplasia, though it may not always be possible to identify the cause in your baby. Occasionally a specific cause is found.
Genetic mutations (inherited)
For one in five children, renal dysplasia is caused by a genetic change. These are problems in the genes (which are in each of our body’s living cells), which are passed on by the parents.
If your doctor thinks your baby has a problem that is caused by genetic mutations, you may be referred for genetic testing and counselling. Genetic testing usually involves getting a sample of blood or body tissue, which can be checked for a specific gene. Siblings of an affected child may also be offered genetic testing to see if they have the condition as well. Genetic counselling is a service that can give you information and guidance about conditions caused by genetic mutations.
Occasionally, renal dysplasia is part of a syndrome, which a collection of symptoms and signs caused by genetic mutations. These children may also have other problems, such as with their digestive system, nervous system, heart and blood vessels, muscles and skeleton, or other parts of their urinary system.
Medicines and other drugs
A few cases of renal dysplasia are caused by some medicines taken by the pregnant woman – including prescribed medicines for seizures (fits) or high blood pressure (such as angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs)). Speak with your doctor about the medicines that you are taking.
It may also be caused by some drugs, such as cocaine.
Renal dysplasia: tests and diagnosis
Antenatal ultrasound scan
The 20 week antenatal ultrasound scan looks at the baby growing in the womb. Renal dysplasia may be suspected if one or both of the kidneys look smaller than usual or otherwise look abnormal.
The scan cannot always diagnose (identify) the problem. Although your doctor will not always know how your baby will be affected at birth, they are less likely to have significant problems if:
- they are growing well in the womb
- no other problems have been found, and
- there is a normal amount of amniotic fluid.
You may need to go back to the hospital for more ultrasound scans during pregnancy.
Diagnosis later in childhood
Sometimes, renal dysplasia is only picked up after birth or when a child is older. It is usually found during a scan that a child is having for another reason, such as after a urinary tract infection (UTI) or after an accident.
Other conditions that look like renal dysplasia
Sometimes, renal dysplasia is thought to be another type of problem with the kidney(s).
- Renal hypoplasia – part of the kidney does not develop properly, and the kidney is smaller than normal.
- Multicystic dysplastic kidney (MCDK) – a more severe form of renal dysplasia. The whole of the affected kidney is a bundle of many cysts and does not work.
- Reflux nephropathy – damage to the kidney.
Other conditions associated with renal dysplasia
Sometimes, renal dysplasia can be seen with other conditions that happens in the womb.
- Antenatal hydronephrosis – one or both kidneys do not drain urine properly. In renal dysplasia, this is because the urine drainage system is ‘baggy’ and does not empty properly. The affected kidney becomes stretched and swollen. Antenatal hydronephrosis may get better at a later stage in the pregnancy, but your doctor will check how your baby is affected.
- Vesico-ureteric reflux (VUR) – when babies with VUR pass urine in the womb, some urine refluxes (goes back up) towards, and sometimes into, the kidneys. This can affect the fully working kidney and/or the dysplastic kidney.
- Posterior urethral valves (PUV) – a blockage in the back part of the urethra near the bladder in some boys.
Tests after birth
After your baby is born, they may need some imaging tests (scans). These use special equipment to get images (pictures) of the inside of the body. They are used to confirm that your child has renal dysplasia and look for any complications.
Unilateral renal dysplasia
In unilateral renal dysplasia, one kidney does not develop properly in the womb. (‘Unilateral’ means one side.) Most children born with one dysplastic kidney have no complications and do not need special treatment but will be followed up to monitor their progress. Sometimes the other kidney grows larger than normal to make up for the dysplastic kidney. However, they may be at risk of or urinary tract infections (UTIs) and/or hypertension (high blood pressure) later in life.
Bilateral renal dysplasia
In bilateral renal dysplasia, both kidneys do not develop normally. (‘Bilateral’ means two sides.) Some babies born with two dysplastic kidneys have no immediate complications. Others need more support at birth, including support to help them breathe.
All children with bilateral renal dysplasia need monitoring, as some may go on to develop the later stages of chronic kidney disease kidney failure. This occasionally happens while a baby or child is young, but is more likely to occur later in life, especially during puberty when children’s bodies grow quickly. Children need to attend follow up appointments at a hospital or clinic throughout childhood to check how well their kidneys are working. Treatment can be started as soon as it is needed, to help your child grow and remain healthy. Eventually the kidneys may stop working and kidney replacement therapy (dialysis or a transplant) may be needed.
Will it affect other family members?
Unless you have been told that your baby’s renal dysplasia was caused by a genetic mutation, it is unlikely that a future pregnancy will result in renal dysplasia, or other problems with the kidneys. If one of your children has renal dysplasia, it is unlikely another one of your children or family members will get it. Speak with your doctor for more information.