What to Expect at a Kidney Ultrasound

In This Article

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.

Ultrasound wand and machine
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Additionally, kidney ultrasounds don’t routinely require that you fast or prepare the bowel, which can be a necessity for other tests. Occasionally, your health care 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 machine—known as a transducer—comes in contact with the skin.

Reasons for a Kidney Ultrasound

There are several reasons that you may need to have a kidney ultrasound, according to the University of Rochester Medical Center:

  • 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 how a kidney is functioning in post-transplant patients

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

  • Guiding the insertion of the needle for biopsies
  • Draining cysts or abscesses
  • Placing a nephrostomy, or a drainage tube into your kidneys


Your doctor will give you specific instructions to follow before your ultrasound and answer any questions you may have. However, some general basics are as follows:

  • Your physician may request that you drink a minimum amount of liquid before the procedure, such as 24 ounces of water or more.
  • You might be asked to hold your bladder for the test. If you must void before the ultrasound, you may need to drink water while in the waiting room to maintain a full bladder.
  • In most cases, you can eat before your appointment, since you’re normally not required to fast. But there could be case-by-case instances where your doctor asks you to modify your diet leading up to the ultrasound.
  • Ordinarily, sedation isn’t required for the procedure.
  • Prior to the kidney ultrasound, you may be asked to read and sign a consent form granting the technician permission to go ahead with the test. If there’s something you don’t understand or that makes you feel uncomfortable, don’t hesitate to ask questions.
  • Wear comfortable clothing. The technicians must use a gel on your skin, which aids in the conduction of the sound waves. The gel won’t stain your clothes, but it can be sticky and messy to wipe off of your skin.
  • Sometimes, the technician will ask you to remove your clothing and wear a hospital gown instead.
  • Consider leaving your jewelry or other valuable items at home.
  • Allow 30 to 60 minutes for the completion of the kidney ultrasound.
  • Make sure you follow any additional instructions your healthcare provider gives you.

What to Expect

Your doctor 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 for the procedure, but there are a few standard guidelines you’ll probably encounter.

  • The technician will have you lie on your stomach to locate the kidneys during the ultrasound.
  • As mentioned earlier, the technician will apply a gel to your skin to facilitate the transmission of the sound waves and obtain an image.
  • The clinician will place a transducer on your skin over the particular areas of interest or concern.
  • The transducer doesn’t hurt, but you might feel some pressure on your skin as the technician attempts to gain the best view of your kidneys and takes a picture.
  • You may be asked to hold a position for a few moments, or, you might be asked to adjust your position for a clearer image.
  • You may hear a “whoosh” sound during the ultrasound if the technician is looking at the blood flow to your kidneys. This sound is perfectly normal.
  • If your bladder is being scanned, you might need to take some images with a full bladder, void, then have additional images taken with an empty bladder.
  • When the kidney ultrasound is over, the technician will wipe the gel off or your skin. Afterward, you likely can get dressed and leave.
  • Your physician will contact you with the results and any additional steps you may need to take.

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 shouldn’t experience any side effects following the procedure. In rare occurrences, a patient may notice some mild tenderness over the areas that have been examined, but this should subside within a couple of hours following the procedure.

A Word From Verywell

Kidney ultrasounds generally don't cause pain. If you experience discomfort while lying down, be sure you let your technician know. Often, they can support your body with extra pillows, blankets, or towels. Following a kidney ultrasound, many patients are able to resume regular activities, but you’ll want to adhere to the individualized recommendations your doctor gives you.

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Article Sources
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  1. Johns Hopkins Medicine. Kidney Ultrasound.

  2. Cleveland Clinic. Kidney ultrasound: Test details. Updated June 1, 2014.

  3. University of Rochester Medical Center. Kidney ultrasound.

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