A kidney ultrasound (renal KUB ultrasound) is an imaging test that allows your radiologist 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 radiologist information about the health of your kidneys and helps them diagnose certain diseases and conditions.

Why would I need a kidney ultrasound?

Your treating physician / surgeon 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 treating physician / surgeon order a kidney ultrasound if they suspect any of the following:

1. Kidney stones.
2. Kidney infection.
3. A blockage or obstruction.
4. Kidney tumor.
5. Kidney cysts.
6. An abscess.
7. Pee building up in your kidney (hydronephrosis).
8. Kidney disease.
9. Injury or trauma.
10. Irregularities to the size or shape of your kidneys.
11. Issues with how blood flows to your kidneys.

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

Test Details

How does a kidney ultrasound work?

A kidney ultrasound is safe, noninvasive and doesn’t hurt. Your radiologist 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 radiologist can see on a screen. Your radiologist 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 radiologist 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 treating physician / surgeon needs a post-void residual urine test (PVR), you’ll need to drink 1 to 1.5 liters of water an hour before the ultrasound and not use the restroom until after. This test helps evaluate your bladder function and capacity.

An radiologist 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:

1. You’ll pull-up your top up to chest or remove your clothes and change into a hospital gown.
2. You’ll lie down on a padded exam table.
3. Anradiologist 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.
4. 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.
5. 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 treating physician / surgeon.

How long does an ultrasound of the kidneys take?

Typically, a kidney ultrasound will take about 15-20 minutes to complete.

What can I expect after a kidney ultrasound?

In most cases, the results of your ultrasound are available within 24 hours after the test.

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.

Results and Follow-Up

What do results of a kidney ultrasound mean?

Your treating physician / surgeon 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 radiologist will order additional imaging tests, kidney function tests (KFT), NCCT KUB, CT/MR Urography, kidney biopsy.

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

Can you see a tumor in a kidney with ultrasound?

Yes, your radiologist 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 radiologist may order additional imaging tests to take an even closer look at that specific area.

When should I call my healthcare provider?

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

Additional Common Questions

Do you really need to drink 1-1.5 liters 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 Achyutam Ultrasound

An ultrasound is a safe and effective imaging tool 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 radiologist can let you know what to expect, including if you need to come with a full bladder. Your radiologist 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.