Tests and scans
A CT urogram is a test using a CT scan and special dye called a contrast medium to look at the urinary system. The contrast medium helps show up the more clearly.
You have a CT scan of your:
kidney
bladder
tubes that connect the kidneys to your bladder (ureters)
A CT scan uses x-rays to take detailed pictures of your body from different angles. A computer then puts them together to make a 3 dimensional (3D) image. It can see details like the soft tissues and blood vessels.
CT stands for computed tomography.
You usually have a CT urogram in the x-ray (radiology) department as an outpatient. A operates the scanner. The whole appointment can take up to an hour and a half.
Find out more about having a CT scan
You might have a CT urogram to:
find out the cause of your symptoms
check how well your kidneys and the rest of your urinary system are working
check how well treatment is working
You can usually eat and drink normally for this test. Follow the instructions given to you by your hospital.
Usually, you have to drink a certain amount of water before you arrive for your CT scan. This is so your bladder can get bigger and be seen more clearly on the pictures.
When you have a CT urogram you usually have an injection of contrast medium. This is a type of dye that shows up body tissues more clearly on the scan. You have the injection through a small thin tube called a cannula, into your arm. The cannula stays in place until after your scan. This is in case you have any problems such as an allergic reaction after having the injection.
Let the radiology department know if you:
are on medication for diabetes
have an allergy to contrast medium or iodine
are pregnant or think you might be
have any kidney problems
are on blood thinning medicines such as warfarin
You can usually take all other medications as normal, unless you are told otherwise by the staff in the scanning department.
When you arrive you usually fill out a checklist or questionnaire with the radiographer. They will ask about your medical history and check if you have any allergies. They also explain what to expect during your CT urogram. This is a good time to ask any questions you may have.
Your radiographer may ask you to drink more water when you are in the scanning department.
Before the scan you remove jewellery and other metal objects, such as piercings around the area being scanned. Metal interferes with the images produced by the scanner. You usually change into a hospital gown.
The radiographer inserts the cannula into your arm.
When it’s time, your radiographer or an assistant takes you into the scanning room.
A CT scanning machine is large and shaped like a doughnut.
Your radiographer gives you an injection of contrast medium through your cannula. They will let you know when exactly during your scan, you have this.
The contrast medium can make you:
feel hot and flushed for a minute or two
have a metallic taste in your mouth
feel like you're passing urine but you aren't - this feeling is common and passes quickly
A CT scan is quite open, but some people can feel claustrophobic. Let the radiographer know if this will be a problem for you.
You usually lie down on the machine couch on your back. But sometimes you may need to lay on your front.
Your radiographer makes sure you're in the right position. They sometimes use foam shapes and cushions to do this.
They leave the room and talk to you through an intercom. They can see you through a window from the control room.
The couch slowly slides backwards and forwards through the hole of the scanner. The machine takes pictures as you move through it.
The scan is painless but can be uncomfortable because you have to stay still. Tell your radiographer if you’re getting stiff and need to move.
You’ll hear a whirring noise from the scanner.
Your radiographer will ask you to hold your breath at times.
They may stop the scan and ask you to walk around for several minutes. Or they may ask you to go to the toilet to empty your bladder (have a wee). Then you carry on with the scan.
If your radiographer wants you to move position they'll talk to you through the intercom. Or they'll come back into the room to help you.
When the scan is over, your radiographer comes back into the room and lowers the couch so you can get up.
The 2-minute video shows what happens when you have a CT scan.
You stay in the department for about 15 to 30 minutes if you had an injection of contrast medium. This is in case it makes you feel unwell, which is rare.
Your radiographer removes the cannula from your arm before you go home.
You should be able to go home, back to work or the ward soon afterwards. You can eat and drink normally.
A CT urogram is a safe test for most people but like all medical tests it has some possible risks. Your doctor and radiographer make sure the benefits of having the test outweigh these risks.
Some of the possible risks include:
Rarely, people have an allergic reaction to the contrast medium. This most often starts with weakness, sweating and difficulty breathing. Your radiographer will ask if you have any allergies before you have the contrast medium. Tell them immediately if you feel unwell.
You might get a small bruise around the area where they put the needle in for the cannula.
There's a risk that the contrast medium will leak outside the vein. This can cause swelling and pain in your hand or arm but it’s rare.
There is a small risk that the contrast medium can affect your kidneys. Your radiographer checks your most recent blood test results before your scan. This is to make sure your kidneys are working well.
Pregnant women should only have CT scans in emergencies. Contact the department as soon as you can before the scan if you are pregnant or think that you might be.
Exposure to radiation during a CT scan can slightly increase your risk of developing cancer in the future. Talk to your doctor if this worries you.
You should get your CT urogram results within 1 or 2 weeks.
Ask your doctor, radiographer or nurse how long it will take to get them. Contact the doctor who arranged the test if you haven’t heard anything after a couple of weeks.
Waiting for test results can be a worrying time. You might have contact details for a specialist nurse. You can get in touch with them for information and support if you need to. It may help to talk to a close friend or relative about how you feel.
We have more information on tests, treatment and support if you have been diagnosed with cancer.
Last reviewed: 09 May 2025
Next review due: 09 May 2028
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A CT scan is a test that uses x-rays and a computer to create detailed pictures of the inside of your body. Find out how you have it and what happens afterwards.
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