What to Expect at a Kidney Ultrasound

A kidney ultrasound is a non-invasive way to take images of your right and left kidneys. Unlike an X-ray, ultrasound technology doesn’t use radiation. Instead, it uses sound waves that are undetectable by the human ears.

The sound waves echo off the organs and create images that allow your healthcare provider to see the size, shape, location, and, in some instances, the blood flow to your kidneys.

Because kidney ultrasounds don’t emit radiation or use contrast dye as part of the testing process, they are safe for children, pregnant women, and people who may have an allergy to dyes.

Additionally, kidney ultrasounds don’t routinely require that you fast or prepare the bowel, which can be a necessity for other tests.

Occasionally, your healthcare professional may want you to come to the test with a full bladder, so the volume of the bladder can be evaluated before and after you urinate (called pre- and post-residual PVR).

Typically, a kidney ultrasound isn’t painful, though you might feel some pressure on the spots where the hand-held device—known as a transducer—comes in contact with your skin.

Reasons for a Kidney Ultrasound

There are several reasons that you may need to have a kidney ultrasound, including:

• Infections
• Kidney stones
• Blockages in the kidneys (called hydronephrosis)
• Kidney tumors
• An abscess in the kidney
• Cysts on or in the kidney
• Tumors
• A buildup of fluid on the kidneys
• To assess post-transplant kidney function

Furthermore, kidney ultrasounds may also be used to assist in medical procedures like:

• Guiding needle insertion for biopsies
• Draining cysts or abscesses
• Placing a nephrostomy (drainage tube) into your kidneys

Preparation

Your healthcare provider will give you specific instructions to follow before your ultrasound and answer any questions you may have. You may be asked to:

• Drink 24 or more ounces of water
• Hold your bladder for the test
• Wear comfortable clothing or change into a hospital gown

If you have to use the bathroom before the ultrasound, you may need to continue drinking water in the waiting room to maintain a full bladder.

The technicians will put gel on your skin because it helps conduct the sound waves. The gel won’t stain your clothes, but it could make a gooey mess of them.

Other thing to think or ask about include:

• Can I eat before my ultrasound? In most cases, you can. However, your healthcare provider may ask you to modify your diet beforehand.
• Will I have to take off my jewelry? You may be asked to, so consider leaving jewelry and other valuable items at home.
• Will I be sedated? Ordinarily, sedation isn’t required for an ultrasound.
• How long will it take? Most ultrasounds take between 30 and 60 minutes.

Make sure you follow any additional instructions your healthcare provider gives you.

What to Expect

Your healthcare provider may order a kidney ultrasound as an outpatient test, or,  if you’re staying in the hospital, it might be part of your inpatient diagnostic testing.

Each hospital, clinic, or facility will have its own protocol that they’ll want you to follow, but there are a few standard things you’ll probably encounter.

• You'll probably lie on your stomach throughout the procedure.
• The technician will apply gel to your skin.
• Then they'll run the transducer over your skin to view and photograph the kidneys.
• You should feel pressure but not pain.
• You may be asked to hold still for a few moments or adjust your position.
• You may hear a “whooshing” sound, which is perfectly normal, if the technician is looking at the blood flow to your kidneys.
• If your bladder is being scanned, you might need to take a break, empty your bladder, then have more images taken.
• When it's over, the technician will wipe off the gel or give you something to remove it with.
• Then, usually, you can get dressed and leave.

Most of the time, your healthcare provider will contact you later with the results and instructions.

Risks and Side Effects

A kidney ultrasound is a safe way to examine a patient and obtain vital images without the risk of exposure to radiation. Most people don't experience any side effects.

In rare instances, you may notice some mild tenderness over the areas that have been examined, but this should subside within a couple of hours.

A Word From Verywell

Kidney ultrasounds generally don't cause pain. If you're uncomfortable while lying down, be sure you let your technician know. They may be able to support your body with extra pillows, blankets, or towels.

Following a kidney ultrasound, many people are able to resume regular activities, but you should adhere to the your healthcare provider's recommendations.