Guide to an Ultrasound

What is an Ultrasound?

Ultrasound is a medical imaging test that uses sound waves to create images of organs. You may also hear ultrasound referred to as sonography. During an ultrasound, a transducer, which is passed over the skin, sends high-frequency sound waves into the body and receives echoes back. The echo patterns reflect changes in tissue density. A specialized computer program then translates the echoes to build an image. The pictures can immediately be viewed on a computer monitor.  

Ultrasounds are routinely used in prenatal care. But ultrasounds are also used to view the heart, kidneys, thyroid, spleen, blood vessels and breasts.

What to Expect During an Ultrasound

Before your procedure, you will be asked to change into a hospital gown. You’ll lie on the exam table, and a water-based gel will be applied to your skin over the area to be examined. The gel helps to create more precise images.

The tech will press the transducer firmly over the body part being examined and move the wand around. Compressing the tissue firmly allows for a better image. Although the technician may apply pressure when moving the transducer, usually no discomfort is involved.

If you have a transvaginal ultrasound, the technician will insert a special transducer called a vaginal probe into the vagina. The vaginal probe creates images of the ovaries, uterus and fallopian tubes. When the test is completed, the gel is wiped from your body, and you are free to get dressed.

How Long Does an Ultrasound Take?

The amount of time it takes to have an ultrasound performed may vary depending on what body part is being examined. In general, an ultrasound takes anywhere from about 15 to 45 minutes to complete.

Why is an Ultrasound Done?

Ultrasound is a noninvasive and efficient way to see internal structures of the body. It’s a useful tool to monitor and diagnose a variety of conditions. For example, an ultrasound can monitor a developing fetus and diagnose abnormalities.

A great deal of information on other organ systems, such as the heart, and kidneys, can also be learned. For instance, an ultrasound can differentiate between soft tissue and fluid and between clotted blood versus flowing blood. It can also determine how fast blood is flowing and detect structural abnormalities. The information gathered can help doctors learn a lot about how a particular organ is functioning.

Preparations Required by the Patient

The type of preparation needed for an ultrasound will depend on which part of the body is being examined. For instance, if you’re having an abdominal ultrasound, which includes the liver, spleen and gall bladder, you’ll be instructed not to eat any gas producing foods for 24 hours before the test. Examples of gas producing foods include cabbage, Brussel sprouts, broccoli and onions. If you’re having an abdominal ultrasound, you’ll also need to fast for six hours before the procedure. 

For a pelvic ultrasound, you’ll need to have a full bladder for the scan. You will be instructed to drink about 32 ounces of water before the test and avoid urinating. Since different types of ultrasounds may have different preparation requirements, consult with your doctor for specific instructions.


Are there any side effects to having an ultrasound? There are no known side effects to having an ultrasound. The use of high-frequency sounds waves is considered safe.

Why do I have to drink water before a pelvic ultrasound? A full bladder moves the uterus into a position where it can be viewed more clearly. A full bladder also pushes the bowels and intestines out of the way so the pelvic organs can be seen better.  

Are there risks to a developing fetus during an ultrasound? Unlike other medical imaging scans, ultrasound does not use radiation. It is considered safe to a developing fetus.

Can I find out the gender of my baby during a prenatal ultrasound? Depending on how far along you are in your pregnancy, you may be able to find out the gender of your baby. It will also depend on the position of your baby and whether an image of the genitals can be seen.

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