Kidney ultrasound

Learn about kidney ultrasounds including what to expect before, during, and after an ultrasound.
Medically reviewed by
AKF's Medical Advisory Committee
Last updated
November 10, 2023

What is a kidney ultrasound?

One way your doctor can look at your kidneys is by doing a kidney ultrasound. A kidney ultrasound (also called a renal ultrasound) is a safe and painless test that uses sound waves to make images of your kidneys.

Why have a kidney ultrasound?

Your doctor may use an ultrasound to look at your kidneys if they think there may be a problem with your kidneys. A kidney ultrasound can show:

  • Something abnormal in the size or shape of your kidneys
  • Blood flow to your kidneys
  • Signs of injury or damage to your kidneys
  • Kidney stones, cysts (fluid-filled sacs) or tumors
  • Your bladder (the organ that stores urine before it leaves your body)

Your doctor may also use a kidney ultrasound to:

  • Help guide needles during a kidney biopsy (a procedure where your doctor takes a very small piece of your kidneys and looks at it under a microscope)
  • Check on your transplanted kidney

What happens during a kidney ultrasound?

During the procedure:

  1. You will lie down on an exam table.
  2. The ultrasound tech (the person doing the ultrasound at your doctor's office) will spread a warm gel on your belly over your kidney area. The gel helps send sound waves from a probe.
  3. The tech will rub a small probe against your skin.
  4. A computer will measure sound waves as they bounce back from your body to create images. The tech may ask you to hold your breath several times or roll on your side while the computer is measuring the sound waves.

A kidney ultrasound takes about 20-30 minutes.

How do I get ready for a kidney ultrasound?

If your doctor thinks you need a kidney ultrasound, they will give you instructions on what to do. They may tell you to drink 24 ounces (3 cups) of water before the test to get better images. They may also tell you not to eat or drink hours before the test.

What can I expect after a kidney ultrasound?

After a kidney ultrasound, a radiologist (a doctor specially trained in reading ultrasound images) will read your ultrasound images and give the results to your doctor. Your doctor will have the results within 1-2 days. You and your doctor will go over the results and decide your next steps.

Your donation directly supports the fight against kidney disease

For 21 consecutive years Charity Navigator™ has rated us a Top Nonprofit. Your donations allow us to help more people than any other kidney organization – from making 150 kidney transplants possible every month to delivering financial relief to 1 in 7 dialysis patients. We also fund clinical research, provide financial assistance for kidney patients affected by natural disasters, and support a National virtual pediatric camp and a Kidney Health Coach community program.