Hydronephrosis is a condition where one or both kidneys become stretched and swollen as the result of a build-up of urine inside them.

It can affect people of any age and is sometimes spotted in unborn babies during routine pregnancy ultrasound scans. This is known as antenatal hydronephrosis.

Hydronephrosis does not generally cause any long-term problems if it's diagnosed and treated promptly.

Babies with the condition may not require any treatment at all.

The condition can increase your chances of getting urinary tract infections (UTIs).

In severe cases that are left untreated, the kidneys may become scarred, which could lead to loss of kidney function (kidney failure).

Antenatal hydronephrosis in babies

Antenatal hydronephrosis (ANH) is increasingly being found in unborn babies during routine ultrasound scans.

It's estimated to show up on at least 1 in every 100 pregnancies.

As a parent, it can be worrying to learn your baby has a problem with their kidneys. But most cases of hydronephrosis in babies are not serious and should not affect the outcome of your pregnancy. Sometimes, babies born with ANH may need to be treated with antibiotics to prevent kidney infections, but most babies born with ANH will have no lasting problems.

Find out more about diagnosing antenatal hydronephrosis and treating antenatal hydronephrosis.

Signs and symptoms

Antenatal hydronephrosis does not usually cause any symptoms. It is often found during pre-natal scans or in tests that are being done for other reasons.

Symptoms for children and adults can include:

You should see your doctor or contact 111 if you have any of these symptoms.

They may refer you for an ultrasound scan to assess your kidneys.

Antenatal hydronephrosis in babies does not usually cause symptoms after birth, but you should seek medical advice as soon as possible if your baby develops signs of a possible UTI, such as a high fever without any other obvious cause.

Find out about diagnosing hydronephrosis.

What causes hydronephrosis?

Antenatal hydronephrosis

Antenatal hydronephrosis diagnosed in pregnancy is usually mild. It's thought to be caused by an increase in the amount of urine your baby produces in the later stages of pregnancy.

In more severe cases, it may be caused by a blockage in the flow of urine from the kidneys to the bladder, backflow of urine from the bladder to the kidneys, or a blockage in the flow of urine out of the bladder.

Adult hydronephrosis

In adults, hydronephrosis is commonly caused by:

Find out about the causes of hydronephrosis.

Treating hydronephrosis

If you have hydronephrosis, your treatment will depend on what's causing the condition and how severe it is. 

Pregnant women and babies with the condition may not require any treatment.

In adults, the first stage of treatment is often to drain the urine out of your kidneys by inserting a tube called a catheter into your bladder or kidneys.

This will help relieve the pressure on your kidneys.

Once the pressure has been relieved, the cause of the build-up of urine may need to be treated.

The treatments used will depend on why the condition developed.

For example:

Find out about how hydronephrosis is treated.

Page last reviewed: 11 December 2021
Next review due: 11 December 2024