What is an ultrasound?

An ultrasound is an imaging test that uses sound waves to make pictures of organs, tissues, and other structures inside your body. It allows your health care provider to see into your body without surgery. Ultrasound is also called ultrasonography or sonography. Ultrasound images may be called sonograms.

Ultrasound can be used to treat certain medical conditions. But it's mostly used to help:

• Monitor the health and development of an unborn baby during pregnancy. Pregnancy ultrasound can help check if your baby is growing normally. It can screen for certain conditions, such as birth defects that can be seen in images. It can also check for pregnancy problems. For example, an ultrasound can show if your placenta (the organ that brings oxygen and nutrients to the baby) is in the right position. Pregnancy ultrasound may also be called "prenatal ultrasound," "fetal ultrasound," or "obstetrical ultrasound."
• Diagnose the cause of a wide variety of medical conditions. Ultrasound is best used to learn about conditions that involve soft tissues, such as organs, glands, and blood vessels. Diagnostic ultrasound may be used if you have signs or symptoms of a problem, and an ultrasound may help diagnose or rule out possible causes.
• Guide certain biopsy procedures. Some biopsies use a needle to remove a sample of fluid or tissue from the body for testing. An ultrasound can find the abnormal area and guide the needle to the right place to collect the sample.

There are different types of ultrasounds. One type, called Doppler ultrasound, can show movement in your body. For example, it can show your heart beating and the speed and direction of blood flowing through your blood vessels. It can also show the beating heart and movement of an unborn baby. Another type of ultrasound can create 3-D (three-dimensional) images.

Other names: sonogram, ultrasonography, pregnancy sonography, fetal ultrasound, obstetric ultrasound, diagnostic medical sonography, diagnostic medical ultrasound

What is it used for?

A pregnancy ultrasound may be used to:

• Check the size, position, heart rate, and age of the unborn baby
• See if there is more than one baby
• Screen for:
  • Genetic disorders, such as Down syndrome
  • Birth defects in the heart, brain and spinal cord, or other parts of the body
• Check the amount of amniotic fluid (the liquid in the sac surrounding an unborn baby) and the location of the placenta
• Guide the collection of test samples taking during amniocentesis and chorionic villus sampling (CVS)

Diagnostic ultrasound has many uses. For example, ultrasound can help:

• Find the cause of pain, swelling, and other symptoms
• Look for blockages, growths, and structural problems in organs, glands, and blood vessels
• Tell the difference between cysts (fluid-filled sacs) and solid tumors

Ultrasound may help diagnose medical conditions that involve many parts of the body, such as the:

• Heart and heart valves
• Blood vessels
• Organs in the abdomen (belly), including the liver, gallbladder, pancreas, or spleen
• Organs in the pelvis, including the urinary tract, and male and female reproductive organs
• Thyroid and parathyroid glands
• Kidneys
• Breasts
• Brain, spine, and hips in infants

Why do I need an ultrasound?

If you're pregnant, it's common to have a routine ultrasound between weeks 18 and 22 of pregnancy to check on the health of your baby. If your provider suspects a problem, you may need an ultrasound at other times during your pregnancy.

You may need a diagnostic ultrasound if you have signs or symptoms of certain types of medical conditions and your provider needs to look inside your body to help find the cause. If you're having a needle biopsy to remove fluid or tissue for a test, you may have an ultrasound as part of the procedure.

What happens during an ultrasound?

An ultrasound is often done by a sonographer, a health care professional who has special training to do ultrasound exams. Ultrasounds may be done in different ways depending on the part of your body that's being examined. Most ultrasound exams include these general steps:

• You will remove clothing from the area that will be examined and lie on a table.
• The sonographer will spread a special gel on your skin over the area that will be examined.
• The sonographer will hold a wand-like device, called a transducer, and move it across your skin. The device sends sound waves into your body. The gel prevents air from getting between the device and your skin, which would block the soundwaves from entering your body. The sound waves are a very high pitch, so you can't hear or feel them.
• The soundwaves "bounce" off the structures inside your body. The ultrasound device picks up the echoes and turns them into images on a computer screen. You may be able to see the images on the screen during your exam.
• After the exam is over, the sonographer will wipe the gel off your skin.

For certain ultrasound exams, the ultrasound device is placed inside a body opening to get a clearer image. Depending on the organs being checked, the device may be placed in the:

• Vagina. This is called a transvaginal ultrasound. It helps view the uterus and ovaries.
• Rectum. This is called a transrectal ultrasound. It's usually done to view the prostate gland.
• Esophagus (the tube that connects your mouth and stomach). This is called a transesophageal echocardiogram (TEE). It's done to get clear images of the heart.

Will I need to do anything to prepare for the test?

Preparations for an ultrasound exam depend on what part of your body is being checked. Some ultrasound exams require no preparation at all. Your provider will tell you if you need to prepare for your ultrasound and what to do.

For example, if you're having an ultrasound to view your urinary tract, you may need to drink water so that you have a full bladder. You will have to hold your urine (pee) until the test is over. For other ultrasounds, you may need to fast (not eat or drink) for several hours before your test.

Are there any risks to the test?

Ultrasound has not been linked to any health harms. It's generally considered safe when trained sonographers use it correctly. Ultrasound doesn't use ionizing radiation like x-rays use, which makes it safer than x-ray. That's why ultrasound is the most widely used medical imaging method for viewing an unborn baby during pregnancy.

But in certain cases, ultrasound can affect fluids and tissues in the body. That's why most medical experts recommend using ultrasound only when it's needed to provide important medical information.

What do the results mean?

The results of your ultrasound depend on the type of ultrasound you had. Your provider can explain what your results mean for your health.

If you had a pregnancy ultrasound, normal results mean that your baby appears to be developing normally. But an ultrasound can't guarantee you'll have a healthy baby. If your results weren't normal, you may need more tests, including another ultrasound exam.

Learn more about laboratory tests, reference ranges, and understanding results.