Kidney Ultrasound

What is a kidney ultrasound?

A kidney ultrasound (renal ultrasound) is an imaging test that allows your healthcare provider to look at your kidneys and bladder.

An ultrasound is an imaging test that uses sound waves to make pictures of your organs. It allows your healthcare provider to see your organs on a screen. Your kidneys filter the waste products out of your blood, which then leave your body as urine (pee). Your bladder holds your pee until it leaves your body.

A kidney ultrasound gives your healthcare provider information about the health of your kidneys and helps them diagnose certain diseases and conditions.

Why would I need a kidney ultrasound?

Your healthcare provider recommends a kidney ultrasound when they need more information about what could be causing a kidney problem. A kidney ultrasound typically includes images of your bladder, too.

Your healthcare provider may order a kidney ultrasound if they suspect any of the following:

• Kidney stones.
• Kidney infection.
• A blockage or obstruction.
• Kidney tumor.
• Kidney cysts.
• An abscess.
• Pee building up in your kidney (hydronephrosis).
• Kidney disease.
• Injury or trauma.
• Irregularities to the size or shape of your kidneys.
• Issues with how blood flows to your kidneys.

Your healthcare provider may also use an ultrasound when they perform a kidney biopsy or check on a transplanted kidney.

How does a kidney ultrasound work?

A kidney ultrasound is safe, noninvasive and doesn’t hurt. Your healthcare provider moves a device called a transducer over the top of your skin. The transducer releases sound waves which penetrate your skin and bounce off your internal organs and tissues. These sound waves create echoes that transform into images or videos your healthcare provider can see on a screen. Your provider then looks at the ultrasound images and analyzes them for any potential problems.

How do I prepare for a kidney ultrasound?

In most cases, you don’t need to prepare for a kidney ultrasound. You can typically eat or drink as usual on the day of your test. In some situations, your provider asks that you avoid eating after midnight on the day of your test. They’ll let you know if this applies to you.

If your healthcare provider needs a post-void residual urine test (PVR), you’ll need to drink 30 to 32 ounces of water an hour before the ultrasound and not use the restroom until after. This test helps evaluate your bladder function and capacity.

An ultrasound technician typically performs your kidney ultrasound. If you have any questions leading up to your ultrasound appointment, call your provider’s office to learn more about how to prepare.

What happens during the kidney ultrasound?

A kidney ultrasound follows these steps:

• You’ll remove your clothes and change into a hospital gown.
• You’ll lie down on a padded exam table.
• An ultrasound technician will apply a water-soluble gel to your skin where they plan to place the transducer. This gel is safe and doesn’t stain your clothes or hurt your skin. It may feel slightly cold at first.
• A radiologist places the transducer on your skin around your abdomen. They’ll gently press down and move it around very slowly with one hand. With the other hand, they’ll control the ultrasound machine and take the images.
• You may have to hold your breath several times or roll on your side during the test. Your technician may also ask you to leave the room to go to the bathroom during the test so they can get images of your bladder when it’s full and when it’s empty.

A radiologist reviews your images and then discusses their findings with your healthcare provider.

How long does an ultrasound of the kidneys take?

Typically, a kidney ultrasound will take about 20 to 30 minutes to complete.

What can I expect after a kidney ultrasound?

In most cases, the results of your ultrasound are available within 24 to 48 hours after the test. This can depend on how quickly your healthcare team can review and analyze the images.

Your healthcare provider will discuss the test results and next steps at either a follow-up appointment or with a phone call. After you leave your ultrasound appointment, you can go about your normal activities.

What are the risks of a kidney ultrasound?

There isn’t any risk involved with an ultrasound. Because it uses sound waves and not radiation, ultrasound is very safe.

What do results of a kidney ultrasound mean?

Your healthcare provider will review the results of your test with you. The results you receive are unique to your situation and depend on why you had the ultrasound. There’s a small chance your provider will order additional imaging tests, kidney function tests or a kidney biopsy.

After getting all your test results, your healthcare provider can make a diagnosis or create a treatment plan to help you. Always ask your provider if you have concerns about your results and what they mean.

Can you see a tumor in a kidney with ultrasound?

Yes, your healthcare provider can detect a tumor or another mass on your kidney with an ultrasound.

What does a dark spot on a kidney ultrasound mean?

A dark spot on a kidney ultrasound typically appears because sound waves can’t bounce off anything. This happens when waves hit liquid or other materials that aren’t solid. If your provider sees a dark spot on your kidney, it could point to something like a cyst or abscess. Your provider may order additional imaging tests to take an even closer look at that specific area.

When should I call my healthcare provider?

Contact your healthcare provider if you have questions about your kidney ultrasound, including how to prepare and when to expect test results. Always let your provider know if you have any concerns about your test results or the next steps in your treatment plan.

Do you really need to drink 32 oz of water before an ultrasound?

In most cases, your healthcare provider will ask you to come to the test with a full bladder so that they can see how much your bladder holds before and after you empty it. If you’re unsure, either call your provider ahead of time or arrive at your test with a full bladder to be safe.

A note from Cleveland Clinic

An ultrasound is a safe and effective imaging tool healthcare providers use to get a better look at your organs. If you need a kidney ultrasound, rest assured that the test is typically painless and relatively quick. Your healthcare provider can let you know what to expect, including if you need to come with a full bladder. Your provider will go over the results of your ultrasound with you and let you know if additional tests are necessary to help find out what’s causing your symptoms.