How to Read an Ultrasound

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There are many reasons why you might have an ultrasound examination, for example, to look at a baby that’s in your womb. If you’ve never had an ultrasound before or been involved in performing one, it can be a little scary. Not knowing what you’re looking at can be unsettling. However, being able to read the ultrasound images will put your mind at rest and make you more confident in the knowledge of the professional performing the examination. 

While doctors and radiologists have lots of training on how to read ultrasound images. However, ultrasound reading isn’t too challenging once you’ve made yourself aware of the basics. 

Thanks to medical imaging, the lives of millions of people have been transformed and potentially fatal illnesses prevented. Not only are ultrasound images used during pregnancy, but it is also used to diagnose and prevent a range of illnesses. You can also use it for other therapeutic purposes. 

If you’d like to know more about ultrasound images, how to read an ultrasound, and their interpretations to further your healthcare career, or because you’re a patient, now is the time to keep reading.     

Ultrasound Imaging Explained

Ultrasound Imaging Explained

Ultrasound imaging is a medical procedure that uses sound waves. The sound waves travel through the body and provide an ultrasound image of the body’s internal organs. Such ultrasound images allow medical professionals to check the condition of soft tissue, internal organs, and fluids in the body.

Doctors and other healthcare professionals use ultrasound readings to diagnose problems with a person’s internal organs and to determine the source of pain or inflammation in the body. 

Ultrasound imaging is also one of the most common testing methods when gynecologists and other healthcare professionals want to check or monitor the growth of a fetus.

Pregnancy ultrasound images are a popular method of testing and diagnosing because it is non-invasive and provides a real-time image. An ultrasound scan is also a very safe examination method.

An ultrasound machine works using high-frequency sound waves. The waves are emitted toward the body and they penetrate the skin. The soundwaves then bounce off a person’s tissue and inner organs. 

The ultrasound machine records these reflected sound waves and the patterns are then used to generate a visual image of a person’s internal organs and tissues. 

The typical frequency of ultrasound waves is between 2 MHz and 15 MHz. Frequencies that are higher produce a shorter wavelength and increased attenuation. When the frequency is reduced, the absorption allows the user to study body structures and various other features.     

What do the numbers mean at the top of an ultrasound image?

What do the numbers mean at the top of an ultrasound image

At the top of an ultrasound image, there are usually a series of numbers and other information. Ultrasound centers and hospitals tend to use this space for details such as:

  • The patient’s name
  • Hospital reference number
  • Ultrasound machine settings

These numbers and details also help you recognize the top of ultrasound images. However, it’s not always the case. The top of an ultrasound image depends on where the ultrasound probe is placed. You’ll be able to recognize a cone-like shape in the image. The ultrasound picture fans out from a small to a big section. The smaller end is the top of the ultrasound image. 

What Do different colors on an ultrasound mean?

Different colors are showcased depending on how the sound waves resonate off a substance. Most images are black and white, but you’ll notice different shades in an ultrasound scan. The different shades are the result of the sound waves passing through or resonating material densities. 

Traditionally, ultrasound images were black, white, and grayish shades. A breakthrough in medical ultrasound was the advent of the color Doppler. Using this new technique, healthcare professionals were able to directly observe the flow of blood, particularly within the heart. The colors represent the direction and speed of blood flow within a certain area. 

What does black on an ultrasound mean?

If tissues are filled with liquid, for example, amniotic fluid in the uterus, the image will be darker. 

What does white mean on an ultrasound?

White on an ultrasound indicates the presence of bone. 

Grayish Colors – Tissues

Grayish Colors - Tissues

Grayish colors indicate tissue and liquids. The brighter the shade of gray, the denser the tissue.  

What does the color orange mean on an ultrasound?

Orange colors are possible when using power Doppler ultrasound machines. It is used when analyzing slow flow. If you see the color orange, it generally indicates blood vessels. 

What does red or blue mean on an ultrasound?

Red and blue colors represent the movement of the blood. Blue represents blood flow away from the probe, while red represents blood that’s flowing towards the probe. 

If the image shows a combination of blue and red, it could be the result of circular flow, coherent flow, or turbulence. 

Different shades of blue and red indicate velocity. The lighter the shade, the higher the velocity. The darker the shade, the lower the velocity. 

What is Shown at the Top of the Ultrasound Image?

If you ignore the numbers and text that appear at the top of the screen or printed ultrasound picture, the top of the screen or printed image is where the ultrasound probe was placed. 

For example, if the ultrasound is of your uterus, at the top of the image you’ll see an outline of the tissues that are present in that area. As you move further down the screen or image, it shows the deeper tissue along with the lining of your uterus and amniotic fluid. With a fetal ultrasound, the top of the image looks like lots of dense tissue which corresponds with the top of your uterus along with tissue that’s above it. Just under this, there is generally a black area which is the amniotic fluid.    

What are Some Common Visual Effects?

An ultrasound picture doesn’t provide the clearest of images. It’s often the case that sound waves don’t bounce off surfaces in the body in an even manner. Because of this, there are visual effects that rely on the settings, density, and angles set by the doctor or radiologist. Some of the most common visual effects are:

  • Enhancement
  • Attenuation
  • Anisotropy  


An enhancement is when sections of the structure that are being examined look brighter than expected. This could be due to excess fluid in the area, for example, if there is a cyst. 


This effect is also known as shadowing and makes the area being scanned appear darker than expected. 


This visual effect is related to the probe’s angle. For example, when the probe is held at right angles it can make the area look brighter. This is particularly relevant when sound waves hit tendons. To stop this from happening, the probe’s angle must be readjusted so that it contacts the body perpendicularly. 

How to Understand Which Side of Your Body is Left and Which is Right?

How to Understand Which Side of Your Body is Left and Which is Right?

Not all ultrasound equipment produces the same kind of image. Some produce a mirror image while others do not. However, it’s relatively easy to determine whether you’re looking at a mirrored ultrasound image or one that’s a straight shot. 

Understanding the difference means you’re not going to be confused about which side of the image is the left side of your body and which is the right. Of course, there’s always the option of asking the ultrasound technician for clarification.

On the whole, most ultrasound images produced in clinical settings have a mirror-like effect. In other words, what you see on the left of the ultrasound screen or ultrasound picture is the left side of your body.

However, there are clinical ultrasounds that use straight shot imaging instead. One of the most common is transvaginal ultrasound imaging. In this situation, the left side of the body is on the right side of the ultrasound screen.  

Knowing How to Read Pregnancy Ultrasounds

Knowing How to Read Pregnancy Ultrasounds

Ultrasound procedures are performed for a variety of reasons, but one of the most common is to check the development and growth of a baby during pregnancy. Ultrasound tests are very safe during such an important stage in a person’s life because, unlike x-rays, they don’t penetrate bones. Rather than using radiations, ultrasounds use sound waves or echoes to create the image of the fetus or baby. 

An ultrasound image reading can be very helpful at various stages of pregnancy, for example:

  • First trimester: Within the first three months of pregnancy, an ultrasound is used to check the growth of an embryo, confirm the number of embryos, check the amniotic fluid, and calculate gestational age and estimated date of delivery (EDD). 
  • Second trimester: Ultrasounds taken during weeks 18 and 20 allow an ultrasound technician to check the development of the fetus and take fetal measurements, its limbs, spine, internal organs, baby’s head, and brain. It’s also possible to check the location and size of the placenta, the gestational age of the fetus, and a baby’s gender if the parents want to know. 
  • Third trimester: Ultrasounds after week 30 of a pregnancy can be used to determine the baby’s average continued growth. Checks can be made on the location of the placenta, to ensure that there are no problems with it blocking the cervix.

Locate Your Womb

If you’re performing or looking at an ultrasound during pregnancy, one of the first things you should know is where the womb is. 

It’s easy to locate the womb by looking at the light gray or white line that is around the outside of the ultrasound image. Within those lines, there will be a large area that’s black. This indicates the amniotic fluid. 

Depending on how the ultrasound doctor has positioned the transducer, your womb may or may not take up the whole of the sonogram image.  

Locate Your Baby

The next thing to notice during ultrasound interpretations is the baby. It will look either gray or white on the image. It will be located inside the darker area of the image, which is the amniotic fluid. The amount of detail you’re able to see will depend on the pregnancy state and the development of the baby. Some of the things you might be able to recognize include:

  • 8th week of pregnancy: You’ll see an image of a fetus that looks around the same size as a baked bean.
  • 12th week of pregnancy: The ultrasound image will clearly show the baby’s head.
  • 20th week of pregnancy and later: You’ll be able to recognize the baby’s feet, heart, eyes, spine, and much more.   

How can you tell gender on an ultrasound picture?

How can you tell gender on an ultrasound picture?

If you want to know your baby’s sex, you’ll be able to find this out with an ultrasound between 18 and 20 weeks of pregnancy. Ultrasound technicians will be looking for three lines that signify a penis or labia. 

Some ultrasound signs are gender-specific.

Girl ultrasound signs

  • Hamburger sign: A girl’s labia lips look similar to a hamburger bun, while the clitoris resembles a hamburger patty. 
  • Sagittal sign: Each different sex has a different sagittal sign. You can find this sign by looking at a profile view of the fetus, otherwise known as the midline sagittal plane. At the end of the spine, you’ll see a nub, which is called the caudal notch. It indicates a girl if it points downward at a 10-degree angle.  

Boy ultrasound signs 

  • Sagittal sign: If the caudal notch points upwards at more than a 30-degree angle it indicates the fetus is male. 
  • Urine flow: Sometimes it’s possible to spot the flow of urine. If the flow is upward it is more likely the fetus is a boy. 
  • Male genitalia: By weeks 18 and 20, male genitalia can sometimes be seen. For example, you might be able to see the penis, scrotum, and testicles.  

Determining a baby’s sex using traditional ultrasound is a very good way to do it, but it’s not 100% accurate. For example, some visual effects could interfere with ultrasound interpretations.  


Now you know a little bit more about how to read an ultrasound, you won’t feel so nervous when undertaking such an examination, whatever side of the machine you sit on.  


Does cancer show up white or black on an ultrasound picture?

Cancerous tissue shows up as black during an ultrasound, whereas dense tissue is much lighter. 

What does the CM mean on an ultrasound picture?

CM is commonly used when referring to the depth of the scan.  

What does shadow on ultrasound mean?

A shadow simply means that the sound waves were reflected. It can be caused by many things such as calcifications, air, and very dense masses or tissue.