Abdominal Ultrasonography

(Abdominal Ultrasonography, Abdominal Sonography, Abdominal Echography)

Procedure overview

An abdominal ultrasound is a noninvasive procedure used to assess the organs and structures within the abdomen, such as the liver, gallbladder, pancreas, bile ducts, spleen, and abdominal aorta. Ultrasound technology allows quick visualization of the abdominal organs and structures from outside the body. Ultrasound may also be used to assess blood flow to abdominal organs.

An abdominal ultrasound uses a handheld probe called a transducer that sends out ultrasonic sound waves at a frequency too high to be heard. When the transducer is placed on the abdomen at certain locations and angles, the ultrasonic sound waves move through the skin and other body tissues to the organs and structures of the abdomen. The sound waves bounce off the organs like an echo and return to the transducer. The transducer picks up the reflected waves, which are then converted into an electronic picture of the organs.

Different types of body tissues affect the speed at which sound waves travel. Sound travels the fastest through bone tissue, and moves most slowly through air. The speed at which the sound waves are returned to the transducer, as well as how much of the sound wave returns, is translated by the transducer as different types of tissue.

Prior to the procedure, clear, water-based gel is applied to the skin to allow for smooth movement of the transducer over the skin and to eliminate air between the skin and the transducer.

By using an additional mode of ultrasound technology during an ultrasound procedure, blood flow within the abdomen can be assessed. An ultrasound transducer capable of assessing blood flow contains a Doppler probe. The Doppler probe within the transducer evaluates the velocity and direction of blood flow in the vessel by making the sound waves audible. The degree of loudness of the audible sound waves indicates the rate of blood flow within a blood vessel. Absence or faintness of these sounds may indicate an obstruction of blood flow.

Ultrasound may be safely used during pregnancy or in the presence of allergies to contrast dye, because no radiation or contrast dyes are used.

Other related procedures that may be performed to evaluate the abdomen include abdominal X-rays, computed tomography (CT scan) of the abdomen, and abdominal angiogram. Please see these procedures for more information.

Reasons for the procedure

Abdominal ultrasound may be used to assess the size and location of abdominal organs and structures. Ultrasound can detect cysts, tumors, abscesses, obstructions, fluid collection, blockages (clots) in blood vessels, and infection within the abdomen. The size of the abdominal aorta can be measured by ultrasound in order to detect an aortic aneurysm. Calculi (stones) of the gallbladder, kidneys, and ureters may be detected by ultrasound.

Abdominal ultrasound may be performed to assist in placement of needles used to biopsy abdominal tissue or to drain fluid from a cyst or abscess. This procedure may also be used to assess blood flow within the abdomen.

There may be other reasons for your doctor to recommend an abdominal ultrasound.

Risks of the procedure

There is no radiation used and generally no discomfort from the application of the ultrasound transducer to the skin.

There may be risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.

Certain factors or conditions may interfere with the results of the test. These include, but are not limited to, the following:

• Severe obesity

• Barium within the intestines from a recent barium procedure

• Intestinal gas

Before the procedure

• Your doctor will explain the procedure to you and offer you the opportunity to ask any questions that you might have about the procedure.

• You may be asked to sign a consent form that gives your permission to do the procedure. Read the form carefully and ask questions if something is not clear.

• Any prior preparation, such as fasting or sedation, will be determined by the specific area to be examined. Your doctor will give you instructions if required.

• Although the gel applied to the skin during the procedure does not stain clothing, you may wish to wear older clothing, as the gel may not be completely removed from your skin afterwards.

• Based on your medical condition, your doctor may request other specific preparation.

During the procedure

An abdominal ultrasound may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your doctor's practices.

Generally, an abdominal ultrasound follows this process:

1. You will be asked to remove any clothing, jewelry, or other objects that may interfere with the scan.

2. If asked to remove clothing, you will be given a gown to wear.

3. You will lie on an examination table. You will lie either on your back or on your stomach, depending on the specific area of the abdomen to be examined.

4. A clear gel will be placed on the skin over the area to be examined.

5. The transducer will be pressed against the skin and moved around over the area being studied.

6. If blood flow is being assessed, you may hear a "whoosh, whoosh" sound when the Doppler probe is used.

7. Once the procedure has been completed, the gel will be wiped off.

While the abdominal ultrasound procedure itself causes no pain, having to lie still for the length of the procedure may cause slight discomfort, and the clear gel will feel cool and wet. The technologist will use all possible comfort measures and complete the procedure as quickly as possible to minimize any discomfort.

After the procedure

There is no special care required after an abdominal ultrasound. You may resume your usual diet and activities unless your doctor advises you differently. Your doctor may give you additional or alternate instructions after the procedure, depending on your particular situation.