What is a kidney ultrasound?

A kidney ultrasound is an imaging test that uses sound waves to look at your kidneys. It can check the size, shape, and location of your kidneys. It also lets your healthcare provider see how well blood is flowing to your kidneys.

The healthcare provider uses a device called a transducer to make the images of your kidneys. The transducer sends out sound waves that bounce off your kidneys. The sound waves are too high-pitched for you to hear. The transducer then picks up the bounced sound waves. These are made into pictures of your kidneys on a screen.

Your healthcare provider can add another device called a Doppler probe to the transducer. This probe lets your healthcare provider hear the sound waves the transducer sends out. They can hear how fast blood is flowing through a blood vessel and in which direction it's flowing. No sound or a faint sound may mean that you have a blockage in the flow.

Ultrasound is safe to have during pregnancy because it doesn't use radiation. It's also safe for people who are allergic to contrast dye because it doesn't use dye. It's considered a noninvasive test. This means it's not done with an incision or a tool that goes inside your body. Ultrasound doesn't usually cause any pain or discomfort.

Why might I need a kidney ultrasound?

You may need a kidney ultrasound if your healthcare provider thinks you may have a problem in your kidneys. These problems include:

• Cyst

• Tumor

• Abscess

• Blockage

• Collection of fluid

• Infection

• Kidney stone

You may also have a kidney ultrasound to help:

• Put a needle in place to take a tissue sample from the kidneys (biopsy)

• Drain fluid from a cyst or abscess

• Put a drainage tube in place

• See how blood is flowing to the kidneys through the renal arteries and veins

Your provider may also use ultrasound after a kidney transplant to see how well the transplanted kidney is working.

Your healthcare provider may have other reasons to recommend a kidney ultrasound.

What are the risks of a kidney ultrasound?

A kidney ultrasound has no risks of radiation. Most people have no discomfort from the transducer moving across the skin.

You may have risks depending on your specific health condition. Talk with your healthcare provider about any concerns you have before the procedure.

Certain things can make a kidney ultrasound less accurate. These include:

• Severe obesity

• Barium in your intestines from a recent barium test

• Intestinal gas

How do I get ready for a kidney ultrasound?

• Your healthcare provider will explain the procedure to you. Ask any questions you have about the procedure.

• You may be asked to sign a consent form that gives permission to do the test. Read the form carefully and ask questions if anything is not clear.

• You usually don’t need to stop eating or drinking before the test. You also usually will not need medicine to help you relax (sedation).

• The gel put on your skin during the test does not stain clothing, but you may want to wear older clothing. The gel may not be completely removed from your skin afterward.

• Follow all other instructions your healthcare provider gives you to get ready.

What happens during a kidney ultrasound?

You may have a kidney ultrasound as an outpatient or as part of your stay in a hospital. The way the test is done may vary depending on your condition and your healthcare provider's practices.

Generally, a kidney ultrasound follows this process:

1. You will be asked to remove any jewelry or other objects that may get in the way of the scan.

2. You may be asked to remove clothing. If so, you will be given a gown to wear.

3. You will lie on an exam table on your belly and you will be told when to move positions for different kidney views if needed.

4. The technologist will put a clear gel on the skin over the area to be looked at. The gel may feel cool or cold when it's first put on your skin.

5. The technologist will press the transducer against the skin and move it over the area being studied.

6. If blood flow is being looked at, you may hear a "whoosh, whoosh" sound when the Doppler probe is used.

7. If your bladder is looked at, you will be asked to empty your bladder after scans of the full bladder are done. You will have more scans done of the empty bladder.

8. Once the test is done, the technologist will wipe off the gel.

A kidney ultrasound is not painful. You may have some discomfort from having to remain still during the test or lying on your belly. The gel will also feel cool and wet. The technologist will use all possible comfort measures and do the scan as quickly as possible to lessen any discomfort.

What happens after a kidney ultrasound?

You don’t need any special care after a kidney ultrasound. You may go back to your usual diet and activities unless your healthcare provider tells you otherwise.

Your healthcare provider may give you other instructions, depending on your situation.

Next steps

Before you agree to the test or the procedure, make sure you know:

• The name of the test or procedure

• The reason you are having the test or procedure

• What results to expect and what they mean

• The risks and benefits of the test or procedure

• What the possible side effects or complications are

• When and where you are to have the test or procedure

• Who will do the test or procedure and what that person’s qualifications are

• What would happen if you did not have the test or procedure

• Any alternative tests or procedures to think about

• When and how you will get the results

• Who to call after the test or procedure if you have questions or problems

• How much you will have to pay for the test or procedure