Every woman in Wales is offered a fetal anomaly scan when they are between 18 and 20 weeks pregnant.
The aim of this scan is to:
The finding from your scan does not necessarily mean that your baby has a problem with any of their organs.
Published January 2022, 3rd edition.
― Renal pelvis dilation
― What is a RPD?
― What will happen next?
― What care will I be offered?
― What will the next scan tell me?
― If my baby needs a follow-up after they are born, what does this mean?
― Further information
Renal pelvis dilatation is also known as RPD. RPD is found in less than 1 in 100 (less than 1%) anomaly scans performed in Wales.
The renal pelvis is the area in your baby’s kidney where urine collects. If the renal pelvis looks wider (more dilated) than usual, the sonographer will measure it. If it measures over 5 millimetres (mm), this is classed as dilated. RPD can be seen in just one kidney (unilateral) or both kidneys (bilateral).
You will be seen by a midwife who specialises in antenatal screening or your hospital doctor (obstetrician) who will explain what care you will be offered next.
If the RPD measured between 5.1mm and 10mm, you will be offered a further scan when you are 30 to 32 weeks pregnant. If the measurement was 10.1mm or above, this is known as hydronephrosis and you will be given an appointment with an obstetrician who will discuss this in more detail with you. You will also be offered a further scan when you are 30 to 32 weeks pregnant.
If the next measurement is 7mm or below
If the measurement following the next scan is 7mm or below, there will be no need for any further follow-up. In Wales this happens in around 8 out of 10 (80%) babies. These babies have about the same chance of going to hospital with a kidney problem during childhood as babies who did not have RPD seen on the anomaly scan.
If the next measurement is above 7mm
If the scan at 30 to 32 weeks shows that the RPD measures over 7mm, an appointment will be made for you to discuss this with a doctor who will explain this in more detail.
In Wales, in around 2 out of 10 (20%) babies with RPD at the anomaly scan, the renal pelvis remains dilated. For these babies, the risk of going to hospital with a kidney problem during childhood is around 20 times more likely than for babies with no RPD on the anomaly scan (38 in 100 children compared with 2 in 100 children).
The doctor will arrange for your baby to be seen by a paediatrician (baby doctor) after your baby is born.
The paediatrician may offer you some antibiotics for your baby to prevent a possible infection. They will also arrange another scan for when your baby is around two weeks old to see if the renal pelvis remains wider (dilated).
You can get more information from the hospital midwife who specialises in antenatal screening or your hospital doctor (obstetrician).
Antenatal Results and Choices (ARC)
Helpline: 0845 077 2290 or 0207 713 7486 from a mobile