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Ultrasound
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Ultrasound

An ultrasound is an imaging test that uses sound waves to create pictures of internal organs, tissues, and structures without the need for surgery.

What is an ultrasound?

An ultrasound, also called ultrasonography or sonography, uses sound waves to visualize the inside of the body. The resulting images are called sonograms. It is primarily used to monitor pregnancy, diagnose medical conditions, and guide biopsy procedures.

Types of Ultrasound

  • Doppler ultrasound: Shows movement, such as blood flow through vessels or a beating heart.
  • 3-D ultrasound: Creates three-dimensional images.
  • Transvaginal/Transrectal/Transesophageal: Devices placed inside body openings to obtain clearer images of specific organs.

What is it used for?

Pregnancy ultrasound is used to check the baby's size, position, heart rate, and age, as well as to screen for genetic disorders or birth defects. Diagnostic ultrasound helps identify the cause of pain or swelling, detect blockages or growths, and distinguish between fluid-filled cysts and solid tumors in organs like the heart, liver, kidneys, and thyroid.

What happens during an ultrasound?

Most ultrasound exams follow these steps:

  • You lie on a table and remove clothing from the area being examined.
  • A sonographer spreads a special gel on your skin to prevent air from blocking sound waves.
  • A wand-like device called a transducer is moved across the skin, sending high-pitch sound waves into the body.
  • The device picks up echoes of these sound waves and converts them into images on a computer screen.

Are there any risks?

Ultrasound is generally considered safe and does not use ionizing radiation like X-rays. However, because ultrasound can affect fluids and tissues in the body, medical experts recommend using it only when necessary to provide important medical information.

Frequently Asked Questions

You must remove metal jewelry from the area being examined because metal can block or reflect the sound waves, creating shadows or artifacts on the image that obscure the organs of interest. Loose-fitting clothing is recommended to make it easier for the sonographer to access the skin and apply the gel without having to cut or stretch tight garments, ensuring a smooth and efficient examination process.
For most abdominal and pelvic ultrasounds, yes, you will need to drink 32 to 48 ounces of water one hour before the appointment and hold it until the exam is finished. A full bladder acts as an acoustic window, pushing the intestines out of the way and providing a clear view of the bladder, uterus, ovaries, or prostate. However, for a transvaginal ultrasound, you are usually asked to empty your bladder just before the procedure to improve image clarity.
Ultrasound is considered safe for both the mother and the fetus because it uses sound waves rather than ionizing radiation like X-rays. There is no known limit to the number of times it can be performed. Most patients receive a dating scan in the first trimester, a detailed anatomy scan around 20 weeks, and additional growth scans later in pregnancy if needed, but the frequency depends on your specific medical history and the recommendations of your obstetrician.
standard ultrasound uses sound waves to create static images of the structure and shape of organs, helping to detect masses, cysts, or abnormalities in size. A Doppler ultrasound specifically measures the speed and direction of blood flow within vessels and organs. This type is often used to check for blockages in arteries or veins, assess blood flow to the placenta during pregnancy, or evaluate the function of the heart and kidneys.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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