Ultrasound

Ultrasound is a non-invasive test to image structures within the body. It is used to diagnose and monitor a variety of conditions. There are also therapeutic uses for ultrasound.

Definition of ultrasound

Ultrasounds are non-invasive medical tests that can image a variety of structures within the body. A probe (transducer) is used to generate high frequency sound waves that bounce off tissues and return to the probe creating electrical impulses that are converted by computer into images of those tissues and organs.

The ultrasound probe is most often placed on the skin to generate the images, but some ultrasounds need to be placed closer to the organ being studied. In endoscopic ultrasound, the probe can be placed in the esophagus, stomach, vagina, or rectum to get images of organs deeper in the body.

Doppler ultrasound uses technology to see blood flow and is used to evaluate the heart and other blood vessels.

Therapeutic ultrasound can be used to treat arthritis, soft tissue injuries, and myofascial pain.

Lithotripsy is focused high intensity ultrasound that is used to break up kidney stones.

High intensity ultrasound in association with MRI can be used to target and destroy tissue, including some malignancies.

Point of care ultrasound (POCUS). Ultrasound machines are becoming more compact and powerful. Their use at the bedside is expanding and being used as adjuncts to the physical examination by the healthcare provider to help with diagnosis. This alleviates the need in some cases for the patient to go to a radiology department or special facilities.

FAST (focused assessment with sonography in trauma) is one use of POCUS to look for fluid where it does not belong, in the abdomen and around the heart, and is a scan done by an emergency physician or surgeon in the resuscitation of a trauma victim.

Ultrasound vs. sonogram

Ultrasound and sonogram are terms that are often used interchangeably. The ultrasound often refers to the machine, and the sonogram refers to the image produced (sono=sound + gram=image).

The procedure of making the image is called ultrasonography or sonography.

The person taking the images is the ultrasonographic/ultrasound technician. A variety of physician specialists may interpret the ultrasound images, depending on what structure is being evaluated. While radiologists interpret most ultrasounds, other specialists interpret some images. For example, cardiologists interpret heart ultrasounds (echocardiography) and obstetricians interpret fetal ultrasounds, and emergency physicians and surgeons interpret trauma point of care ultrasounds. In point of care ultrasound the clinician usually takes the images themselves.

What are the uses for ultrasound?

Ultrasound is a noninvasive test to image structures within the body. It is used to diagnose and monitor a variety of conditions. There are also therapeutic uses for ultrasound.

Examples of diagnostic uses for ultrasound

• Obstetrics – monitoring fetal development and screening for fetal and placenta abnormalities
• Cardiology – (echocardiography) assessing the anatomy of the heart (valves, muscle wall thickness, and other abnormalities), function of the heart (heart wall motion, ejection fraction), heart rhythms
• Blood vessels – aorta, including screening for aortic aneurysm, carotid arteries (assessing stenosis or narrowing), peripheral arteries (assessing peripheral vascular disease), peripheral veins [assessing for blood clots (deep vein thrombosis)]
• Breast – Ultrasound can be used to gather information in addition to mammography. For example, if a cyst is found, ultrasound can help determine if it is fluid filled or solid
• Chest – assessing pneumonia, effusion (fluid collections), heart failure, pneumothorax (collapsed lung)
• Abdominal structures – commonly imaged organs include the liver, gallbladder, bile ducts, pancreas, appendix and kidneys, bladder
• Gynecologic structures – uterus, ovaries, fallopian tubes
• The scrotum – differentiating between a testicular torsion (a twisted testicle), epididymitis and hydrocele (fluid in the scrotal sac)
• The neck – including the thyroid and parathyroid glands, and the carotid arteries
• Musculoskeletal system – includes bones, joints, muscles, and tendons
• The eye – checking for the size and shape of the eye globe, evaluating the retina for the presence of tears, measuring the thickness of the optic nerve sheath to indirectly measure pressure inside the brain

Screening uses for ultrasound

Some disease screening possibilities include:

Carotid artery stenosis looks for narrowing of the arteries that supply the brain with blood. Arteries that are significantly narrowed by plaque are a risk factor for transient ischemic attack and stroke.

The abdominal aorta has the potential to dilate, especially in people who have risk factors for coronary artery disease and peripheral vascular disease (e.g. high blood pressure, high cholesterol, smoking, diabetes). Ultrasound can be used to measure the aorta, and in patients who have a dilated or widened aorta, routine screening measurements are recommended. If the aorta continues to widen, aortic repair may prevent rupture.

Pregnancy is the most common use of ultrasound screening, allowing the health care provider and the expectant mother to follow the growth of the fetus and to look for any potential abnormalities that may develop in the fetus or the placenta.

Therapeutic uses for ultrasound

Ultrasound is useful in placing needles on catheters into the body.

Nurses and physicians routinely use ultrasound to place intravenous catheters. Physicians can use ultrasound to place catheters into veins and arteries located deeper in the body.

Ultrasound can be used to guide a needle into a cyst or abscess to drain it. It can also be used to place a needle near a mass for biopsy (the procedure to obtain a small piece of tissue).

Ultrasound may be used to place a needle near a nerve to inject medication to help with pain control.

Physical therapy uses ultrasound to generate heat in tissues to help with mobility and pain control, especially in patients with osteoarthritis or soft tissue pain.

There are many types of ultrasounds, and most do not need special preparation beforehand. Patients getting an ultrasound of the abdomen, especially of the gallbladder, are asked to fast for a few hours beforehand. Those getting a pelvis or vaginal ultrasound are asked to drink plenty of water beforehand to fill the bladder and make imaging of the uterus, ovaries, and tubes easier.

Any other special preparations are discussed well before the test.

What should you not do before an ultrasound?

For scheduled ultrasound tests, the patient will be given instructions on what to do or avoid in the hours before the test.

What is done during an ultrasound?

For most ultrasounds, a probe (transducer) is used to send sound waves into the body and receive the echoes that bounce back. A small amount of gel is used between the probe and the skin to help with image quality. The ultrasound technologist, or the physician, will use their knowledge of anatomy to direct the ultrasound beam to the area to be studied.

Endoscopic ultrasound uses a probe that is inserted into the body, usually the esophagus, vagina, or rectum. The principles of acquiring the image are the same, but for some studies the patient may need to be sedated.

How long does an ultrasound take?

It takes training and skill to interpret the pictures that are returned in real time, and adjust the ultrasound beam, making it narrower or wider, changing the direction and the depth, to visualize the area being studied and to get the information needed for the diagnosis. For that reason, the test may take a variable amount of time, depending upon the patient’s individual anatomy, the area studied, and the questions that need to be answered.

The time it takes to perform an ultrasound depends upon the situation. A scheduled ultrasound of the abdomen or extremity usually is completed in less than an hour. An echocardiogram, ultrasound of the heart, may take longer, depending upon the information that is needed regarding structure or function of the heart.

FAST performed emergently at the bedside of a trauma patient may only take a minute or two.

The ultrasound, like any other test, needs to be interpreted as part of the whole patient evaluation. The test may give the answer to a specific question that was asked, or it may provide direction for the next sequence of tests to be done.

Most often, the ultrasound technologist is the person who acquires the images, but it is the physician who prepares the final report. Sometimes, the physician is also involved in gathering the images. This is especially true in cardiology and obstetrics.

If a radiologist is involved, they will provide the ultrasound result report to the healthcare provider who ordered the test and that provider will discuss the results with the patient.

There are no known risks to ultrasound. That said, ultrasound should not be done for non-medical reasons. The American College of Obstetrics and Gynecology discourages the use of obstetric ultrasound for keepsake fetal videos.