In bilateral renal hypoplasia, both kidneys are smaller than usual because they have not fully developed in the womb. (‘Bilateral’ means two sides.)

Before birth

Bilateral renal hypoplasia may be suspected on the 20 week antenatal ultrasound scan, which looks at your baby growing in the womb.

The scan also measures the amount of amniotic fluid (or liquor), the fluid that your baby floats in. The baby’s kidneys start making urine and pass this out into the amniotic fluid. This fluid protects your baby from getting hurt from the outside and helps his or her lungs mature so he or she is ready to breathe after birth.

If there is not enough amniotic fluid (oligohydramnios), this may be a sign that the kidneys are not working well, and that there may be problems breathing after birth.

You may need more ultrasound scans during the pregnancy to find out how the hypoplasia is affecting your baby.


If bilateral renal hypoplasia is suspected, you will be referred to specialist healthcare professionals as early as possible in the pregnancy. They may include:

  • foetal medicine specialist – a doctor who specialises in the health of unborn babies (foetuses)
  • obstetrician – a doctor who specialises in pregnancy, delivering babies and the care of women after childbirth
  • paediatrician – a doctor who treats babies, children and young people
  • paediatric nephrologist – a doctor who treats babies, children and young people with kidney problems
  • neonatologist – a doctor who specialises in newborn babies.


In most cases, there is no treatment needed before birth.


Very rarely, there is concern that the problems with the baby’s kidneys and/or lungs are very severe, and may mean that he or she will not be able to live a normal life.

In the most severe cases, these problems can be life threatening and the baby may have kidney failure from birth. A team of healthcare professionals experienced in delivering babies and treating newborn babies with these problems will give you support. They will discuss with you all the options, and agree a plan for the remainder of the pregnancy and the delivery.

Tests after birth

After your baby is born, he or she may need some imaging tests (scans). These use special equipment to get images of the inside of the body. They are used to confirm that your child has bilateral renal hypoplasia and look for any complications.

  • An ultrasound scan is usually done first. This looks at the shape and size of your baby’s kidneys and other parts of the urinary system. A small handheld device is moved around your child's skin and uses sound waves to create an image on a screen.

If problems are found on the ultrasound scan, your doctor may recommend other tests, which may include the below.

  • DMSA – looks at the kidneys to check for any damage. A chemical that gives out a small amount of radiation is injected into one of your child’s blood vessels. This chemical is taken up by healthy parts of the kidney and a special camera takes pictures.
  • MAG3 scan – for babies who also have antenatal hydronephrosis, this shows how much blood is going into and out of their kidneys, and whether they are passing urine normally. As in the DMSA test, a chemical that gives out a small amount of radiation is injected into a blood vessel, and a special camera takes pictures.
  • Cystourethrogram or MCUG (sometimes called a VCUG) – usually for babies and children who are suspected of having vesicoureteral reflux (VUR). In this condition, some urine refluxes (goes back up) towards, and sometimes into, the kidneys. This test can check how your child is passing urine. A special X-ray machine takes a series of images of the bladder while your baby is passing urine.

Bilateral renal hypoplasia complications and treatment

A small number of children have complications if the hypoplasia is severe in both kidneys.

Support for newborn babies

If your doctors think that your baby might have problems from birth, he or she will be reviewed by healthcare professionals experienced in looking after newborn babies. Your baby may need to be admitted into a neonatal unit, a special ward of the hospital for newborn babies. The team of healthcare professionals will measure how much urine your baby is passing, and how much he or she is growing.

In rare cases, babies are not able to breathe properly after birth because their lungs have not developed properly. This is more likely in babies who had very little amniotic fluid (or liquor) when growing in the womb.

If your baby needs help breathing, he or she can be given oxygen or ventilation, using a machine that moves breathable air in and out of the lungs. Many of these babies improve as they begin to grow but occasionally in very severe cases this is not the case.

Kidney function

Usually – even if the hypoplastic kidneys are not working as normal – they are working well enough that there are no symptoms at birth. Because hypoplastic kidneys may not grow normally, children will need blood tests throughout their life to measure kidney function (how well their kidneys are working).

Children who have long-term problems with how their kidneys work are said to have chronic kidney disease (CKD). A team of healthcare professionals will make sure your child gets the right tests, treatments and monitoring as they grow, according to how well his or her kidneys are working.

Kidney failure

Your child’s kidney function may get worse as the kidneys cannot grow as the child’s body grows. In some children, this progresses to kidney failure, when the kidneys cannot support the body.

It is very rare for a baby to be born with kidney failure. Occasionally, a young baby or child has kidney failure. It is more likely during puberty or the start of the teenage years, when children go through a growth spurt and the smaller kidneys are no longer able to work for the bigger body.

Babies and children in kidney failure need specialist treatment. This may include dialysis, which uses special equipment or a machine to remove waste products and extra water from the body, and/or a kidney transplant, in which a healthy kidney from another person is transplanted into a patient’s body.

Long-term complications and treatment

High blood pressure

Some children develop hypertension, blood pressure that is too high.

If your child has hypertension, he or she will need to reduce their blood pressure so it is in the healthy range. Your child will probably need to eat a no-added salt diet, and may need to take medicines, to control the blood pressure. It is also recommended that all children, especially those with hypertension, keep to a healthy weight and exercise regularly.

Rarely, children who have a hypoplastic kidney that is not working well and have blood pressure that cannot be controlled, will need the hypoplastic kidney removed in an operation called a nephrectomy. You may be referred to a paediatric urologist, a surgeon who treats children with problems in the urinary system, to discuss the operation.

Urinary tract infections

Some children get urinary tract infections (UTIs), when germs get into the urine and travel up the urinary tract (or system) and cause an infection, usually in the bladder. Babies and children with UTIs may become irritable, have a fever, have pain on weeing, feel sick or be sick.

If your child has a UTI, he or she will need to take antibiotics, medicines that kill the germs.

If you think your child has a UTI, seek medical advice.

About the future

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

Follow up

Your child will need to go back to the hospital or clinic for follow-up appointments throughout his or her life. It is important to go to these appointments even if your child seems well. You will also have the opportunity to ask any questions. At these appointments your child will have:

  • his or her blood pressure measured
  • urine tests – to check for for protein in his or her urine (proteinuria), which may be a sign of problems in the kidney. You or a nurse will collect some of your child’s urine in a small, clean container. A dipstick is dipped into the urine – this is a strip with chemical pads that change colour if there is protein in the urine.
  • blood tests – to measure his or her kidney function
  • his or her height and weight checked in childhood, to measure how much he or she is growing.

Further support

This can 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.

More information

  • Tests and diagnosis

    Find out more detail about some of the tests used to diagnose or investigate kidney conditions.

  • Chronic kidney disease (CKD)

    A life-long condition in which the kidneys stop working as well as they should over time. A team of healthcare professionals will support your child.

  • Urinary tract infection (UTI)

    Urinary tract infections happen when germs get into the urine (wee) and travel into the urinary tract.