Fetal Renal Pelvic Dilatation

What is a Renal Pelvic Dilatation?

Renal Pelvic Dilatation is one of the most common findings found on anomaly ultrasounds. We see this appearance in approximately 1 in 100 pregnancies at 20 weeks.

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. Renal Pelvic Dilatation can be seen in just one kidney (unilateral) or both kidneys (bilateral).

How is it diagnosed?

At approximately 20 weeks of pregnancy, your anomaly ultrasound scan may show some babies have more fluid than normal within the renal pelvis (collecting system) of one or both of their kidneys.

What does it mean for your baby?

There is not necessarily a problem with your baby. The enlargement may become less obvious or may increase over the course of pregnancy. It can be a normal variation or can be associated with some degree of blockage in the urinary tract (kidney, ureters, urethra and bladder). In some babies there is a backflow of urine from the bladder into the kidneys (this is called reflux).

Further investigations

You will be given the opportunity to discuss these findings with a midwife should you wish. If the renal pelvis is measuring between 5mm and 10mm, we will arrange a further scan at 34 weeks to repeat your baby’s kidney measurement.

If, at your anomaly scan, the measurement is greater than or equivalent to 10 mm, or there are any additional findings related to your baby’s urinary tract, you will be seen by a fetal medicine consultant within three working days. This is usually carried out at the Royal Victoria Infirmary (RVI) in Newcastle. An appointment will also be made to discuss your baby’s care after birth with one of our specialist doctors.

How can Renal Pelvic Dilatation affect my baby?

In the majority of cases, the condition remains stable or resolves in the neonatal period. However, in some cases this enlargement can make babies more prone to urinary tract infections after birth and in early childhood. To prevent such infections, a low dose of antibiotics can be given. This will be commenced before you go home with your baby. In case there are any additional findings, the detailed management will be discussed with you.

How can Renal Pelvic Dilatation be treated?

Your baby will be started on antibiotics. We will also arrange for your baby to have a kidney ultrasound scan in the first few weeks of life. You will then be offered an appointment for the Paediatric clinic a month or two after baby’s birth to discuss the scan and whether the antibiotics should be continued.

What about future pregnancies?

If this is an isolated incident then there is a low risk of reoccurrence in future pregnancies. In future pregnancies you will receive the routine screening the same as you did in this pregnancy.

What happens next?

We have booked you a follow up scan in the obstetric ultrasound department at 34 weeks. If at this scan your baby’s renal pelvic dilatation measures 7mm or less, no further follow up is needed.

Where can I get more information and support?

Our team are always happy to discuss any concerns you may have: You can contact staff on Maternity Assessment.

Maternity Assessment
08:30 – 20:30 daily, 7 days a week.
Telephone: 08:30 – 20:30 daily, 7 days a week.

Other useful sources of information

The Fetal Medicine Foundation
Website: https://fetalmedicine.org/

Comments, concerns, compliments or complaints

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Leaflet feedback

This leaflet has been produced in partnership with patients and carers. All patient leaflets are regularly reviewed, and any suggestions you have as to how it may be improved are extremely valuable. Please write to the Clinical Governance team, North Tees and Hartlepool NHS Foundation Trust, University Hospital of North Tees, TS19 8PE or:

Email: [email protected]

Leaflet Reference: PIL1404
Date for Review: 08/02/2026