Most people are born with two kidneys. Renal agenesis (or kidney agenesis) means one or both kidneys do not develop while a baby is growing in the womb.
About the name
Renal agenesis can be broken down:
- renal: to do with one or both kidneys
- agenesis: part of the body does not develop
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.
Renal agenesis 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.
- If one kidney has not developed, this is called unilateral renal agenesis. Many children and adults live with one kidney with no serious problems. They may need to go to follow-up appointments to check for any possible long-term effects.
- If both kidneys have not developed, this is called bilateral renal agenesis. If this is suspected your antenatal scan, you will need to go back to the hospital for more scans to confirm the problem. Sadly, babies with no kidneys are unable to survive.
Renal agenesis: tests and diagnosis
During pregnancy
The 20 week antenatal ultrasound scan looks at your baby growing in the womb. Renal agenesis may be suspected if one or both kidneys cannot be seen on this scan. You may need to go back to the hospital for more scans or other tests to check whether this is affecting your baby.
Your obstetrician may refer you to a paediatrician, a doctor who treats babies, children and young people, or a paediatric nephrologist, a doctor who treats babies, children and young people with kidney problems.
After your baby is born, he or she may need an ultrasound scan or other tests to confirm whether there is renal agenesis.
Unilateral renal agenesis
In unilateral renal agenesis, one kidney has not developed. (‘Unilateral’ means one side.) Many children with only one kidney have no symptoms or complications and do not need treatment. Sometimes the other kidney grows larger than normal to make up for the missing kidney. However, children may be at risk of urinary tract infections (UTIs) and/or hypertension (high blood pressure) later in life.
Your child may need to visit your family doctor to for urine tests and blood pressure measurements.
Bilateral renal agenesis
In bilateral renal agenesis, both kidneys have not developed. (‘Bilateral’ means two sides.) If this is suspected, you will need to go back to the hospital for more scans to confirm the problem. Sadly, babies with no kidneys are unable to survive.
In such situations, some people decide to terminate (stop) a pregnancy. This is a very personal decision. A healthcare professional will speak with you and support whatever decision you make.
Doctors understand that there are some possible causes of renal agenesis, though it may not always be possible to identify the cause in your baby. It is not usually caused by anything that the mother does during her pregnancy.
How common is renal agenesis?
Unilateral renal agenesis is relatively common – it is estimated that one baby in a thousand is born with only one kidney.
Bilateral renal agenesis is much rarer. Although there are a few known causes of renal agenesis, most of the time we cannot identify a specific cause.
Causes of renal agenesis
Renal agenesis happens in the womb when one or both kidneys do not develop. It is estimated that one baby in a thousand is born with only one kidney. However, it is very rare that both kidneys do not develop.
It is not always possible to know why renal agenesis happens. In the majority of cases, it is not caused by anything that the mother does during her pregnancy, and it is unlikely that a future pregnancy will result in renal agenesis or other problems with the kidneys.
Occasionally a specific cause is found.
Genetic mutations (inherited)
Most cases of renal agenesis are not inherited from the baby’s mother or father. However, some cases are caused by genetic mutations. 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. Genetic counselling is a service that can give you information and guidance about conditions caused by genetic mutations.
Occasionally, the renal agenesis is part of a syndrome, which a collection of symptoms and signs. These children also have other problems, such as with the digestive system, nervous system, heart and blood vessels, muscles and skeleton, or other parts of the urinary system. These may be caused by genetic mutations.
Medicines and other drugs
A few cases of renal agenesis are caused by some medicines taken by the pregnant woman – including medicines for seizures (also called convulsions or fits) or high blood pressure (such as ACE inhibitors (angiotensin-converting enzyme inhibitors) and angiotensin receptor blockers inhibitors) and angiotensin receptor blockers (ARBs)). Speak with your doctor about the medicines that you are taking during pregnancy.
It may be caused by some illicit drugs, such as cocaine.
Will renal agenesis affect other family members?
Unless you have been told that your baby’s renal agenesis was caused by a genetic mutation, it is unlikely that a future pregnancy will result in renal agenesis, or other problems with the kidneys. If one of your children has renal agenesis, it is unlikely that another of your children or family members will get it. Your doctor or healthcare professional will be able to give you more information.