What Is An Ultrasound?

Ultrasound is a procedure that uses high-frequency sound waves to view internal organs and produce images of the human body. The human ear cannot hear the sound waves used in an ultrasound. Ultrasound is: Noninvasive, which means it does not penetrate the skin or body openings, and Diagnostic, which means it is used to determine what disease or condition is present The technical term for ultrasound imaging is sonography. Ultrasound technology was originally developed as sonar to track submarines during World War I. It was first used medically in the 1950s and is considered very safe. The original ultrasound scanners produced still images, but modern scanners produce moving pictures, which are easier to interpret.

When Is Ultrasound Needed?

Ultrasound is useful for a variety of conditions, including:

  • Obstetric (related to pregnancy) uses for ultrasound
  • Non-obstetric uses for ultrasound

Specialized ultrasound imaging procedures include:

  • Echocardiography
  • Doppler echocardiography
  • Ultrasound for biopsy

Obstetric Uses For Ultrasound

One of the most common uses for ultrasound is to view the uterus (the muscular organ in a woman’s abdomen that holds the fetus) and fetus (unborn child) during pregnancy. Ultrasound scanning is often performed at about 16 to 18 weeks into the pregnancy.

  • If the date of conception is known, the scan can demonstrate whether or not the fetus is of expected size. If the date of conception is unknown, or the mother is uncertain, ultrasound of fetal size can help establish the accurate date of conception.
  • Ultrasound can reveal a multiple pregnancy (for example, twins or triplets).
  • Ultrasound is valuable in identifying some fetal abnormalities.
  • Congenital heart disease (malformation of the heart) can sometimes be detected, enabling both the parents and the doctor to prepare for specialized care during delivery.
  • Ultrasound is used for amniocentesis, a procedure that uses a needle to remove amniotic fluid for analysis.

Some of the other conditions during pregnancy for which ultrasound is valuable include:

  • Position of the placenta (special tissue that provides nutrients to the fetus)
  • General health of the fetus
  • Ectopic pregnancy (presence of an embryo outside the uterus)
  • Impending miscarriage
  • Early fetal death

Ultrasound also can help to view the fallopian tubes, ovaries and other reproductive organs in instances of infertility, or to look for cysts or other foreign objects.

Non-Obstetric Uses For Ultrasound

Ultrasound is used for many non-obstetric conditions or disorders, including the following:

  • Scanning of the brain in a newborn
  • Examining of the internal organs, including the appendix in possible appendicitis (rupture of the appendix)
  • Scanning of the liver to determine cirrhosis (liver inflammation) and liver cysts (fluid filled sacs), abscesses (infections), or tumors (masses of cells)
  • Locating gallstones in the gallbladder or bile ducts
  • Scanning of the pancreas for cysts, tumors, or pancreatitis (inflammation of the pancreas)
  • Evaluating the eyes
  • Scanning of the kidneys for congenital defects, tumors, and hydronephrosis (swelling of the kidney due to urine outflow obstruction)
  • Scanning of the thyroid gland, breasts, bladder, testicles, ovaries, spleen, and eyes for cysts, tumors, or foreign objects
  • Identification of the cause of enlargement of the abdomen or other organs
  • Investigation of tendon tears
  • Review of the outcome of a procedure
  • Determining if a person is a good candidate for angioplasty (reopening or reconstruction of a blood vessel) or other procedures


Echocardiography is a specialized type of ultrasound that is used to look at the action and function of the heart.

This type of ultrasound is a major diagnostic technique that can detect structural and some functional abnormalities of the heart wall, valves, and large blood vessels. Blood flow across the valves can also be measured.

An echocardiography is especially valuable for studying disorders of the heart valves. Abnormal opening and closing of these valves can be detected because they differ from normal patterns of movement.

Other diagnostic uses of echocardiography include:

  • Detection of congenital heart disease (a malformation of the heart or blood vessels near the heart)
  • Detection of problems with the large blood vessels
  • Detection of any enlargement or damage of the heart muscle, a condition called cardiomyopathy
  • Swellings caused by weakening of the heart wall or the blood vessel walls (aneurysms)
  • The presence of a blood clot in one of the chambers of the heart
  • Pericarditis, a condition in which the pericardium, the membrane that covers the heart, becomes inflamed.

Doppler Echocardiography

Doppler echocardiography is a recently developed ultrasound technique that indirectly measures the flow velocity of blood as it passes through the heart. It is used in assessing malfunctioning valves in aortic stenosis (narrowing of the aortic valve opening) or mitral insufficiency (failure of the mitral heart valve to close properly) and in assessing patients with congenital heart disease.

Ultrasound For Biopsy

Another increasingly common use for ultrasound is in conjunction with fine-needle biopsy (inserting a very thin and hollow needle into an organ to remove tissue or fluid for examination). Ultrasound provides a real time, moving image. So, the image is valuable in helping to guide the needle accurately to a specific spot.

How Does An Ultrasound Work?

Ultrasound imaging uses the principles of sonar developed for ships at sea. As sound passes through the body it produces echoes, which can identify distance, size and shape of objects inside.

  • During the ultrasound examination, a machine called a transducer is used to view the target organ and produce pictures for study. The transducer emits sound and detects the returning echoes when it is placed on or over the body part being studied.
  • When the emitted sound encounters a border between two tissues that conduct sound differently, some of the sound waves bounce back to the transducer, creating an echo.
  • The echoes are analyzed by a computer in the ultrasound machine and transformed into moving pictures of the organ or tissue being examined.
  • Ultrasound waves pass easily through fluids and soft tissues, making the procedure especially useful for examining fluid-filled organs such as the uterus in pregnancy, as well as the gallbladder, and soft organs like the liver.
  • Ultrasound waves are unable to penetrate bone or gas, so ultrasound is of limited use for examining regions surrounded by bone, or areas that contain gas or air. Even so, ultrasound has been used to examine most parts of the body.

Nice To Know:

What are the benefits and limitations of ultrasound?

  • Ultrasound is a noninvasive imaging technique. It is a painless procedure.
  • Ultrasound is widely available, low cost and easy to use.
  • Because it does not use radiation, the side effects of radiation are not an issue. So, ultrasound is the preferred technique for monitoring pregnant women and their unborn children.
  • Real-time images are generated by ultrasound, so it is a good tool for guiding invasive procedures like needle biopsies.
  • Ultrasound can display the movement and actual function of the body’s organs and blood vessels.
  • There are no known harmful effects of standard ultrasound imaging.
  • The main limitation of ultrasound imaging is that it does not reflect clearly from bone or air. Therefore, other imaging techniques are preferred for areas such as the lungs and the bones.

How Do You Prepare For An Ultrasound Scan?

No special preparation is required for a routine ultrasound. Wear loose comfortable clothing to your ultrasound appointment.

For a liver or gallbladder scan, the patient is usually asked to fast (take nothing by mouth) for several hours before the test.

For a scan in early pregnancy, the woman is usually asked to drink several glasses of water and not to pass urine for a few hours before the test. A full bladder helps to improve the view of the uterus by displacing nearby loops of intestine.


What Happens During An Ultrasound Procedure?

You will probably be asked to lie down on a bed or table for the scan. Clothing over the area to be scanned is removed, and a special warm oil or gel is applied to the skin. This is to achieve good contact as the transducer is passed back and forth.

Ultrasonic waves are inaudible and cause no sensation, though pressure from the transducer may be uncomfortable. The scan usually takes about 15 minutes. During the procedure, you will probably be able to watch the ultrasound images on the screen attached to the scanner.

When a scan is performed in conjunction with a biopsy, a local anesthetic reduces or eliminates any discomfort.

Normal activities can be resumed immediately after the test.

Ultrasound is very safe and painless, so there is little risk.

Need To Know:

Getting your results

Your ultrasound images will be analyzed by a radiologist, a physician who specializes in ultrasound and other radiology testing. The radiologist will send a signed report which includes an interpretation of the image to your primary physician. You may receive your results right after your scan. If not, you will receive information on the report through your primary care physician.

Frequently Asked Questions

Here are some frequently asked questions related to ultrasound:

Q: Is an abdominal ultrasound ordered for any condition other than pregnancy?

A: There are several reasons the doctor requests an abdominal ultrasound. These include:

  • Finding the cause of stomach pain
  • Looking for stones in the gallbladder or kidney
  • Diagnosing enlargement of an abdominal organ
  • Pyloric stenosis, one cause for vomiting in babies
  • Suspicion of appendicitis

Q: If ultrasound cannot penetrate bone, is an ultrasound of the head ever done?

A: While ultrasound is usually ineffective for organs encased in bone, like the brain, cranial ultrasound is sometimes performed on infants who still have a soft spot (called the anterior fontanelle) in their skulls.Some indications for cranial ultrasound include:

  • Screening for bleeding in the bran
  • Signs of infection
  • Cranial abnormalities

Q: Is ultrasound ever ordered for a hip?

A: Hip ultrasound is ordered when the diagnosis is dislocated or underdeveloped hips, especially on babies.

Q: Why is kidney ultrasound ordered?

A: Ultrasound does not test kidney function. When kidney ultrasound is ordered, it is to take pictures of both the kidneys and the urinary bladder in order to detect the following conditions or disorders:

  • Urinary tract infection
  • The cause for blood in the urine
  • High blood pressure
  • Back or abdominal pain
  • Known or suspected kidney stones
  • A family history of kidney disease

Q: Is ultrasound ever ordered for the spine?

A: A spinal ultrasound is usually ordered to take pictures of the spinal cord in a baby three or four months old or less. A baby is usually referred for spinal ultrasound because of a dimple, hair patch, or discoloration of the skin. The study is done to look for an abnormality of the spinal cord.

Q: What are the disadvantages of ultrasound?

A: The main disadvantage of ultrasound is the inability of the sound waves to penetrate bone and gas.

Putting It All Together

Here is a summary of the important facts and information related to ultrasound:

  • Ultrasound is a diagnostic procedure that uses painless and harmless high frequency sound waves inaudible to the human ear to view internal organs and produce images of the human body
  • One of the most common uses for ultrasound is to view the uterus and fetus during pregnancy. Ultrasound scanning is often performed about 16 to 18 weeks into the pregnancy.
  • Echocardiography is a specialized type of ultrasound that is used to look at the function and action of the heart. Among other conditions, echocardiography is used for the following:
  • To detect structural and some functional abnormalities of the heart wall, valves, and large blood vessels
  • To measures blood flow across the heart valves
  • Doppler echocardiography is a recently developed ultrasound technique that indirectly measures the flow of blood as it passes through the heart. Among other conditions, Doppler echocardiography is used to assess:
    • Malfunctioning heart valves in aortic stenosis or mitral insufficiency
    • Congenital heart disease
  • Ultrasound is being used more frequently in conjunction with fine-needle biopsy. The ultrasound is valuable in helping the doctor to guide the needle accurately to a specific target.
  • No special preparation is required for a routine ultrasound.
  • During the ultrasound examination, a machine called a transducer that both emits the sound and detects the returning echoes is placed on or over the body part being studied. The transducer sends the information it collects to the scanner, which generates the ultrasound image.
  • Normal activities can be resumed immediately after the test.
  • An ultrasound imaging procedure is safe and painless.


Here are definitions of medical terms related to ultrasound:

Aorta: The main artery of the body, arising directly from the left ventricle of the heart to supply oxygen-carrying blood to all other arteries (except the pulmonary artery, which carries deoxygenated blood from the heart to the lungs).

Aortic stenosis: Narrowing of the aortic valve opening, causing obstruction of blood flow into the circulation. The condition causes the heart to work harder and the muscle in the wall of the left ventricle (lower chamber) to thicken.

Biopsy: A procedure to remove cells to investigate a condition.

Congenital Heart Disease: A malformation of the heart or blood vessels near the heart.

Cyst: A closed sac, usually filled with fluid.

Diagnostic: Pertaining to the investigation to find a specific identifiable condition or disease.

Fine needle biopsy: A procedure using a very small needle to remove cells or objects from small areas such as the blood vessels.

Fetus: The developing cells in the uterus that will become a child.

Heart: An organ positioned centrally in the chest, with the right margin directly underneath the right side of the sternum, or breastbone. The rest of the heart points to the left, with the lowest point located directly underneath the left nipple.

Heart action and function:

  • Deoxygenated blood (blood that has had the oxygen portion removed) arrives from the body via the vena cava, in the right atrium, or upper heart chamber.
  • There it is transferred to the right ventricle, or lower chamber, and is pumped by the pulmonary artery to the lungs.
  • The lungs reoxygenate the blood and return it by way of the pulmonary vein to the left side of the heart, where it enters the left atrium and is transferred to the left ventricle.
  • From the left ventricle, blood is pumped via the aorta to all parts of the body.

Infertility: The inability to have a child.

Invasive: Going under the skin to into an orifice.

Mitral insufficiency: Failure of the mitral valve of the heart to close properly, which allows blood to leak back into the left atrium (upper chamber) when pumped out of the left ventricle (lower chamber). Also known as mitral incompetence or mitral regurgitation.

Mitral stenosis: Narrowing of the opening of the mitral valve in the heart. This narrowing causes the atrial portion of the left side of the heart to work harder to force blood through the valve. The consequences are similar to those of mitral insufficiency, which may accompany stenosis.

Mitral valve prolapse: A common slight deformity of the mitral valve, situated in the left side of the heart that can cause mitral insufficiency (leakage of the valve). Also known as “floppy valve syndrome.” Mitral valve prolapse causes a characteristic heart murmur that may be heard by the physician through a stethoscope during a routine examination.

Noninvasive: Not going under the skin or into the orifices.

Pyloric stenosis: Narrowing of the pylorus (the lower outlet from the stomach) that blocks the passage of food into the duodenum (the first part of the small intestine). The condition can occur in both babies and adults.

Transducer: The hand-held portion of the ultrasound imaging machine, which sends sound waves into the body, and records echoes produced by the waves.

Vena cava: Either of two large veins into which all the circulating deoxygenated blood drains. The veins are nearly an inch in diameter and are located deep within the chest and abdomen.

Additional Sources Of Information

Here are some reliable sources that can provide more information on ultrasound:

Radiology Info – A public information website of the Radiological Society of North America, and the American College of Radiology 

American College of Radiology – Provides information primarily for professionals, but provides a search for accredited facilities 
Phone: (800) ACR-LINE
Phone: (800) 227-5463

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