Originally published by Harvard Health.
What Is It?
Ultrasound uses sound waves instead of radiation to generate snapshots or moving pictures of structures inside the body. This imaging technique works in a manner similar to radar and sonar, developed in World War II to detect airplanes, missiles, and submarines that were otherwise invisible.
A radiologist or ultrasound technician places an ultrasound transducer, which looks like a microphone. The transducer sends sound waves into your body and picks up the echoes of the sound waves as they bounce off internal organs and tissue. A computer transforms these echoes into an image that is displayed on a small screen.
Doppler ultrasound is a variation of this technique that not only shows internal structures but also examines the flow of blood through blood vessels. Doppler ultrasound is useful in detecting blockages to blood flow, such as a blood clot blocking a vein, or narrowing of the blood vessels due to cardiovascular disease.
What It’s Used For
Abdominal ultrasound is most useful in viewing and evaluating the following organs:
- abdominal aorta and other blood vessels in the abdomen
Using an abdominal ultrasound, a doctor can detect gallstones, check the liver for cancers, examine the kidneys for cancers or for blockages in the flow of urine, measure the size of the spleen or the width of the aorta (the body’s largest artery), and look for fluid around the abdominal organs.
Ultrasound waves do not travel well through air or gas, so abdominal ultrasound is not useful in examining the intestines. Ultrasound can also be difficult to conduct on patients who are severely overweight or obese. Sound waves weaken as they travel through the outer tissues of the body, and may not reach the organs in a person with excess body mass.
You must fast on the day of the test. Digesting food causes your intestines to fill with extra air, which make the ultrasound image less sharp. Tell your doctor if you take insulin, because insulin can make your blood sugar drop after a period of fasting.
How It’s Done
Abdominal ultrasound can usually be done quickly and painlessly. As you lie on your back on an examination table, a technician or doctor squirts some clear jelly onto your lower abdomen. This jelly helps the ultrasound transducer slide around easily on your skin and helps create a seal between the transducer and your skin, reducing air pockets that can make the ultrasound picture less clear.
When the transducer is placed against your skin, an image of your abdominal organs appears on a video screen, and the technician or doctor moves the transducer back and forth across your abdomen to see specific organs from different views. It’s helpful for you to mention any soreness during the test — for example, if you’re tender while the transducer pushes against a particular area, such as your gallbladder or appendix.
If a Doppler ultrasound is performed, you may also hear the pulse-like sound of blood rushing through the blood vessels as blood flow is evaluated.
If your doctor performs the ultrasound, you may get preliminary results immediately. In many cases, though, the test is performed by a technician who won’t be able to provide any results. In either case, the test is recorded on videotape or digital disc so that it can be reviewed later by a radiologist. Your doctor should have the radiologist’s report in one to four days, and can provide you with complete results then.
Abdominal ultrasound (like all ultrasound) does not involve the use of ionizing radiation and poses no documented health risks, even when performed repeatedly.
When to Call a Professional
Because harmful side effects are not expected, people typically need to call their doctors only for abdominal ultrasound results.
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