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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.

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. He or she 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 does not use dye.

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
  • 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. A kidney ultrasound is not painful. You may have some discomfort from having to remain still during the test. 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 minimize any discomfort. 

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.
  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.