If you’re having problems with your kidneys or bladder, or your doctor suspects you may have a kidney condition, you may be referred for a kidney CT scan. This detailed imaging test uses X-rays and advanced computer technology to create cross-sectional pictures of your kidneys, helping your doctor diagnose conditions such as kidney stones, infections, or kidney disease.
Whether you’ve been booked in already or just exploring your options, here’s everything you need to know about how a kidney CT scan works, what it’s like, and what it can show.
What is a Kidney CT Scan?
A kidney CT scan (also called a renal CT scan) is a type of computed tomography scan that takes a series of X-rays from different angles. It sends these images to a computer, which processes them to create detailed pictures of your kidneys, bladder, blood vessels, and surrounding organs and bones.
Compared to a standard X-ray, a kidney CT scan offers much more detailed information to your medical team. It can help spot problems that might be missed on a regular X-ray, such as small kidney stones, cysts, abscesses, or even signs of kidney cancer.
Depending on your condition, your radiologist may use a special contrast material (dye) during the CT scan. They’ll inject this into a vein in your hand or arm. The contrast dye helps highlight certain structures more clearly, especially blood vessels and urine flow through the kidneys.
Why Might I Need a Kidney CT Scan?
Your doctor may recommend a kidney CT scan if you’re experiencing symptoms that could be a sign of a kidney or urinary tract problem. These might include:
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Pain in your side, back or lower abdomen.
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Blood in your urine (haematuria).
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Persistent urinary infections.
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Swelling in your hands, feet or face.
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Unexplained weight loss.
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A metallic taste in your mouth.
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Nausea, vomiting or reduced ability to produce urine.
Your doctor may also recommend a CT scan to check for complications if you already have a diagnosis of kidney disease, diabetes or high blood pressure, all of which can affect your kidney function. CT scans can also help your doctor plan your treatment if you have a condition such as polycystic kidney disease, or they can use CT scans to investigate your risk of developing kidney failure.
If you’ve had an injury or accident involving your abdomen or lower back, a kidney CT scan can show whether your kidneys or any surrounding structures have been damaged.
What Can a Kidney CT Scan Diagnose?
Doctors use CT scans to help diagnose a wide range of problems because they’re so detailed, including:
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Kidney stones: CT scans are the gold standard for detecting kidney stones. They can pick up even very small stones that might not appear on a standard X-ray, and help your doctor decide on the best treatment.
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Kidney infections and abscesses: If you have a kidney infection or an abscess (a pocket of pus), a CT scan can show any swelling, inflammation or build-up of fluid.
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Polycystic kidney disease: This inherited condition causes fluid-filled sacs (cysts) to develop in the kidneys. Your doctor can use a CT scan to find out how many cysts you have and how large they are.
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Tumours or cancer: CT scans can detect abnormal growths in the kidneys and help tell the difference between benign (non-cancerous) and malignant (cancerous) tumours. They can also help your doctor see if cancer has spread to nearby blood vessels or lymph nodes.
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Kidney injury or trauma: If you’ve had an accident or fall, a CT scan can help check whether you have any internal damage and guide next steps in your treatment.
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Blocked urine flow: Known as hydronephrosis, this can happen if something is stopping urine from draining properly from the kidneys to the bladder, for example, a kidney stone, tumours or an enlarged prostate. CT scans can show the exact location and cause of the blockage.
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Bladder or urinary tract abnormalities: CT scans can be used to check for problems in other parts of the urinary system, such as the ureters or bladder.
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Kidney function: While your doctor can’t directly measure how well your kidneys are working, certain types of CT scans using contrast dye can help doctors understand blood flow and urine drainage patterns. This allows them to understand how well your kidneys are functioning.
What Different Types of Kidney CT Scans Are There?
One of several kinds of CT scans can be used to assess the kidneys, depending on what your doctor needs to find out:
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Non-contrast CT scan: This is usually the first choice for checking for kidney stones, as the scan can clearly show stones without needing contrast dye.
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Contrast-enhanced CT scan: If your doctor wants a clearer view of the blood vessels, tumours or internal structures of your kidney, they may recommend a scan with contrast. The dye helps highlight different tissues and can improve your diagnosis.
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CT urography: This is a special kind of CT scan that looks at your entire urinary system, including the kidneys, ureters and bladder. Your doctor may recommend a CT urography if you have blood in your urine or lots of urinary infections.
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CT angiography: This scan focuses on the blood vessels around the kidneys. Doctors often use it before surgery or to look for narrowing (stenosis) or aneurysms.
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Delayed phase CT: This scan happens several minutes after the contrast injection to show how well your kidneys collect and drain the dye. It helps spot blockages, scarring, or issues with urine flow.
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Triple-phase CT (triphasic CT): This scan takes images at three different time points after you have the contrast dye injected. It shows how blood flows through the kidney tissue over time.
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CT with 3d reconstruction: Advanced CT scanners can even create three-dimensional models of your kidneys, helping doctors plan surgeries or biopsies.
What Does the Scan Involve?
A kidney CT scan is done using a large, doughnut-shaped CT scanner. You’ll lie on a narrow table that slides in and out of the centre of the scanner. Inside the ring, an X-ray tube rotates around your body, sending out beams of X-rays from different angles. These are picked up by detectors and sent to a computer, which creates detailed images of your kidneys, bladder, and surrounding organs.
You may be asked not to eat or drink for a few hours before the scan, especially if you’re having a scan with contrast dye.
Let your radiographer or radiologist know if you’re pregnant, have diabetes, kidney disease, or if you’ve ever had a reaction to contrast dye or iodine.
Your radiologist will ask you to remove any jewellery, piercings or metal objects, as these can interfere with the scan. They’ll also ask you to change into a hospital gown.
During the Scan
If you need a contrast dye, your radiologist will give you a small injection into a vein in your arm or hand via a small, plastic tube called a cannula. The injection might give you a cold sensation, and can cause a brief metallic taste in your mouth. Some people might feel a warm flush or mild nausea, but this usually passes quickly.
You might hear clicking sounds as the machine works. Your radiologist will ask you to lie very still during the scan. They might also ask you to hold your breath for a few seconds at a time to reduce the risk of blurred images.
After the Scan
If you had contrast dye, your radiologist may ask you to stay briefly in case of any side effects. These are rare, but can include sweating, itching, swelling, or redness at the injection site.
Drink plenty of water afterwards to help flush the dye from your system.
Most people can go home straight after the scan and carry on with their usual activities.
Are There Any Risks?
CT scans use a small amount of ionising radiation, which can slightly increase the risk of developing cancer later in life. However, the amount of radiation exposure is generally low, and the benefits of getting a clear diagnosis often outweigh any risks.
If you're pregnant, your doctor may recommend a different type of imaging test that doesn’t involve radiation, such as an ultrasound or MRI.
Some scans use a contrast dye that contains iodine, which can sometimes cause allergic reactions. These are usually mild, but it’s important to tell your healthcare team if you’ve had any reactions in the past.
People with kidney problems or diabetes may be at a higher risk of developing contrast-induced nephropathy, a rare condition where kidney function worsens after exposure to contrast dye. Your doctor will weigh up the risks and benefits before going ahead with the scan and may order blood tests to check your kidney function first.
How to Prepare for a Kidney CT Scan
Your hospital or imaging centre will give you specific instructions ahead of your scan, but here are some general tips:
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Let your doctor know about any medicines you're taking, especially metformin for diabetes, as you may need to stop it temporarily after the scan.
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Drink plenty of water before and after the scan unless you’ve been told not to.
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Avoid wearing clothes with zips, buttons, or metal fastenings.
When Will I Get My Results?
Once your scan is complete, a specialist doctor called a radiologist will review the images and prepare a report. This will be sent to your doctor, who will then discuss the results with you and talk you through any next steps or treatment options.
In some cases, you may get the results within a day or two. In others, it can take up to a week, especially if further analysis is needed.
If your CT scan shows something abnormal, your doctor will explain what it means and what happens next. Depending on the results, you might need further tests, specialist referrals, or a change to your treatment plan.
If the scan identifies kidney stones, your doctor may offer you medication, advice on increasing your water intake, or procedures to break up or remove the stones. They may recommend antibiotics or drainage procedures if there are signs of infection or abscesses.
In cases where a tumour is suspected, your doctor may order additional imaging, a biopsy, or refer you to a specialist for cancer treatment.
How Much Does a Kidney CT Scan Cost?
If you’re having your scan on the NHS, it will be free. If you choose to go privately, the cost can vary depending on the type of scan, whether contrast dye is used, and the clinic you visit. Private CT scans typically range from £420 to around £800 in the UK.
While it’s natural to feel a little anxious before any scan, knowing what to expect – and understanding why it’s being done – can help you feel more confident and prepared.
How Can I Get a Kidney CT Scan?
You can book a private kidney CT scan near you today with Scan.com. We can help you fast-track your diagnosis with no GP referrals required and expert clinical consultations within days. Choose from over 250 centres nationwide with flexible appointment times and get fast online results, including a digital imaging report. It’s easier than ever to skip the waiting lists and get your health back on track.
FAQs
How Long Does a Kidney CT Scan Take?
The scan usually takes between 15 and 30 minutes, but it’s a good idea to factor in more time for preparation and recovery if you have a contrast dye.
What Does a Kidney CT Scan Show?
A kidney CT scan gives your doctor a detailed picture of your kidneys, bladder and the surrounding organs. It can spot kidney stones, cysts, tumours, abscesses, or signs of infection, all things that might not show up on a standard X-ray. It’s especially helpful if you’ve been having pain, blood in your urine, or many urinary infections.
A CT scan can also show swelling, blockages, or any damage caused by long-term kidney problems like polycystic kidney disease or diabetes.
Can Kidney Stones Be Missed on a CT Scan?
While CT scans are highly sensitive, in rare cases, very small stones or certain types, like uric acid stones, can be missed, especially if image quality is poor or the scan settings aren't ideal. That said, it’s uncommon for this to happen. A CT scan is still one of the most accurate ways to confirm or rule out kidney stones.
What Can Be Mistaken for Kidney Stones on a CT Scan?
CT scans are highly accurate at detecting kidney stones, with standard scans identifying them correctly over 95% of the time and ruling them out more than 98% of the time.
Sometimes, things that look like kidney stones on a CT scan turn out to be something else. For example, tiny calcium deposits in the blood vessels near the kidney, lymph nodes with calcification, or even certain types of scarring can sometimes be misinterpreted as kidney stones. However, your radiologist is trained to spot subtle differences and avoid misdiagnosis.
What Is a Triple-Phase CT Scan for the Kidneys?
A triple-phase (or triphasic) CT scan takes images of your kidneys at three different time points after contrast dye is injected. This helps doctors understand how blood flows through your kidneys and can highlight any unusual changes or abnormalities.
Sources
Can a CT Scan Accurately Diagnose Kidney Stones? (2022). https://www.healthline.com/health/kidney-health/ct-scan-for-kidney-stones
Computed Tomography (CT or CAT) Scan of the Kidney. (n.d.) https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/ct-scan-of-the-kidney
CT Scan of the Kidney. (n.d.) https://www.cedars-sinai.org/health-library/tests-and-procedures/c/ct-scan-of-the-kidney.html
Kidney Scan. (2022). https://www.webmd.com/a-to-z-guides/kidney-scan-what-to-expect
Harry, M. R., et al. (2023). Correlation of Kidney Volume on CT-Scan with Kidney Function Tests in Patients with Normal Kidneys at Haji Adam Malik Hospital Medan in 2020-2021