Treatment for hydronephrosis depends on what's causing the condition and how severe it is.

In adults, the aims of treatment are to:

• remove the build-up of urine and relieve the pressure on your kidneys
• prevent permanent kidney damage
• treat the underlying cause

Most people with hydronephrosis will have a procedure called urinary catheterisation to drain the urine from their kidneys.

Depending on the underlying cause, medication or surgery may be needed afterwards to correct the problem.

If the condition is severe or causing problems such as a urinary tract infection (UTI), you may to be treated soon after you're diagnosed.

In less severe cases, it may be safe to delay treatment for a short period.

The first stage in treating hydronephrosis is to drain the urine out of your kidneys.

This will help ease your pain and prevent any further damage to your kidneys.

A thin tube called a catheter may be inserted into your bladder through your urethra (the tube that carries urine out of the body). Or a catheter may be inserted directly into your bladder through a small cut in your tummy (abdomen). This is called a suprapubic catheter

Find out about urinary catheterisation.

In a few cases where one of the kidneys has already been severely damaged, it may be better to remove the affected kidney. 

Most people can function normally with just one working kidney, which will not usually have a significant effect on your health or lifestyle.

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

Some possible causes and their treatments are described below:

• kidney stones can be removed during an operation or broken up using sound waves – read more about treating kidney stones
• an enlarged prostate can be treated with medication or surgery to remove some of the prostate – read more about treating prostate enlargement
• narrowing of the ureter (the tube that runs from the kidney to the bladder) can be treated by inserting a hollow plastic or metal tube called a stent, which allows urine to flow through the narrowed section – this can often be done without making cuts in your skin
• cancer that's causing hydronephrosis may be treated using chemotherapy, radiotherapy or surgery to remove the cancerous tissue

If hydronephrosis happens because you're pregnant, you will not usually need any treatment because the condition will pass within a few weeks of giving birth.

In the meantime, catheters can be regularly used to drain urine from the kidneys.

Painkillers and antibiotics can also be given if you're in pain or develop a UTI.

Most babies diagnosed with antenatal hydronephrosis (ANH) before they're born will not need any treatment because the condition will improve before they're born or within a few months of their birth.

There's usually no risk to you or your child, so labour should not need to be started early.

After the birth, your baby may be examined to check for any obvious problems, such as swollen kidneys, but normally you'll be able to take them home with you.

Your baby may need to return to hospital for some scans during the next few weeks to check there aren't any continuing problems.

These scans may include:

• an ultrasound scan – where sound waves are used to create a picture of your baby's kidneys
• a micturating cystourethrogram (MCUG) – where a thin tube is used to pass a special type of liquid that shows up clearly on X-rays into your baby's bladder while a series of X-rays are taken
• a dimercaptosuccinic acid (DMSA) scan or MAG-3 scan – where your baby is injected with a substance that shows up on a special device called a gamma camera; the camera is then used to take pictures of your child's kidneys

In most babies, antenatal hydronephrosis will get better as they get older. But until scans show there's no longer a problem, your child may need to take antibiotics to reduce their chances of developing a UTI. This is because the urine inside their kidneys can make them more vulnerable to infection.

If ANH does not get better by itself, your child may need to keep taking antibiotics. Surgery is not usually needed.