Abdominal Ultrasound

An abdominal ultrasound uses reflected sound waves to produce a picture of the organs and other structures in the upper abdomen. Occasionally a specialized ultrasound is ordered for a detailed evaluation of a specific organ, such as a kidney ultrasound. An abdominal ultrasound can evaluate the:

• Abdominal aorta, which is the large blood vessel (artery) that passes down the back of the chest and abdomen. The aorta supplies blood to the lower part of the body and the legs.
• Liver, which is a large dome-shaped organ that lies under the rib cage on the right side of the abdomen. The liver produces bile (a substance that helps digest fat), stores sugars, and breaks down many of the body's waste products.
• Gallbladder, which is a saclike organ beneath the liver. The gallbladder stores bile. When food is eaten, the gallbladder contracts, sending bile into the intestines to help in digesting food and absorbing fat-soluble vitamins.
• Spleen, which is the soft, round organ that helps fight infection and filters old red blood cells. The spleen is located to the left of the stomach, just behind the lower left ribs.
• Pancreas, which is the gland located in the upper abdomen that produces enzymes that help digest food. The digestive enzymes are then released into the intestines. The pancreas also releases insulin into the bloodstream; insulin helps the body utilize sugars for energy.
• Kidneys, which are the pair of bean-shaped organs located behind the upper abdominal cavity. The kidneys remove wastes from the blood and produce urine.

A pelvic ultrasound evaluates the structures and organs in the lower abdominal area (pelvis).

Abdominal ultrasound is done to:

• Determine the cause of abdominal pain.
• Detect, measure, or monitor an aneurysm in the aorta. An aneurysm may cause a large, pulsing lump in the abdomen.
• Evaluate the size, shape, and position of the liver. An ultrasound may be done to evaluate jaundice and other problems of the liver, including liver masses, cirrhosis, fat deposits in the liver (called fatty liver), or abnormal liver function tests.
• Detect gallstones, inflammation of the gallbladder (cholecystitis), or blocked bile ducts. See an illustration of a gallstone.
• Detect kidney stones.
• Determine the size of an enlarged spleen and look for damage or disease.
• Detect problems with the pancreas, such as pancreatitis or pancreatic cancer.
• Determine the cause of blocked urine flow in a kidney. A kidney ultrasound may also be done to determine the size of the kidneys, detect kidney masses, detect fluid surrounding the kidneys, investigate causes for recurring urinary tract infections, or evaluate the condition of transplanted kidneys.
• Determine whether a mass in any of the abdominal organs (such as the liver) is a solid tumor or a simple fluid-filled cyst.
• Determine the condition of the abdominal organs after an accident or abdominal injury and look for blood in the abdominal cavity. However, computed tomography (CT) scanning is more commonly used for this purpose because it is more precise than abdominal ultrasound.
• Guide the placement of a needle or other instrument during a biopsy.
• Detect fluid buildup in the abdominal cavity (ascites). An ultrasound also may be done to guide the needle during a procedure to remove fluid from the abdominal cavity (paracentesis).

Tell your doctor if you have had a barium enema or a series of upper GI (gastrointestinal) tests within the past 2 days. Barium that remains in the intestines can interfere with the ultrasound test.

Other preparations depend on the reason for the abdominal ultrasound test you are having.

• For ultrasound of the liver, gallbladder, spleen, and pancreas, you may be asked to eat a fat-free meal on the evening before the test and then to avoid eating for 8 to 12 hours before the test.
• For ultrasound of the kidneys, you may not need any special preparation. You may be asked to drink 4 to 6 glasses of liquid (usually juice or water) about an hour before the test to fill your bladder. You may be asked to avoid eating for 8 to 12 hours before the test to avoid gas buildup in the intestines. This could interfere with the evaluation of the kidneys, which lay behind the stomach and intestines.
• For ultrasound of the aorta, you may need to avoid eating for 8 to 12 hours before the test.

This test is done by a doctor who specializes in performing and interpreting imaging tests (radiologist) or by an ultrasound technologist (sonographer) who is supervised by a radiologist. It is done in an ultrasound room in a hospital or doctor's office.

You will need to remove any jewelry that might interfere with the ultrasound scan. You will need to take off all or most of your clothes, depending on which area is examined (you may be allowed to keep on your underwear if it does not interfere with the test). You will be given a cloth or paper covering to use during the test.

You will lie on your back (or on your side) on a padded examination table. Warmed gel will be spread on your abdomen to improve the quality of the sound waves. A small handheld unit, called a transducer, is pressed against your abdomen and moved back and forth over it. A picture of the organs and blood vessels can be seen on a video monitor.

You may be asked to change positions so additional scans can be made. For a kidney ultrasound, you may be asked to lie on your stomach.

You need to lie very still while the ultrasound scan is being done. You may be asked to take a breath and hold it for several seconds during the scanning. This lets the sonographer see organs and structures, such as the bile ducts, more clearly because they are not moving. Holding your breath also temporarily pushes the liver and spleen lower into the belly so they are not hidden by the lower ribs which makes it harder for the sonographer to see them clearly.

Abdominal ultrasound usually takes 30 to 60 minutes. You may be asked to wait until the radiologist has reviewed the information. The radiologist may want to do additional ultrasound views of some areas of your abdomen.

The gel may feel cold when it is applied to your stomach unless it is first warmed to body temperature. You will feel light pressure from the transducer as it passes over your abdomen. The ultrasound usually is not uncomfortable. However, if the test is being done to assess damage from a recent injury, the slight pressure of the transducer may be somewhat painful. You will not hear or feel the sound waves.

There are no known risks from having an abdominal ultrasound test.

An abdominal ultrasound uses reflected sound waves to produce a picture of the organs and other structures in the abdomen.

Factors that can interfere with your test and the accuracy of the results include:

• Stool, air (or other gas), or contrast material (such as barium) in the stomach or intestines.
• The inability to remain still during the test.
• Extreme obesity.
• Having an open wound in the area being viewed.

• Additional tests, such as a computed tomography (CT) scan, may be needed to investigate abnormal ultrasound results. For more information, see the medical test Computed Tomography (CT) Scan.
• X-rays are not recommended during pregnancy because of the risk of damage to the developing baby (fetus). Because ultrasound is safe during pregnancy, it generally is used instead of an abdominal X-ray if a pregnant woman's abdomen needs to be evaluated.
• On rare occasions, gallstones may not be detected by ultrasound. Other imaging tests may be done if gallstones are suspected but not seen on the ultrasound. For more information, see the medical tests Gallbladder Scan, Endoscopic Retrograde Cholangiopancreatogram (ERCP), and Abdominal X-ray.
• Using abdominal ultrasound, a doctor can usually distinguish among a simple fluid-filled cyst, a solid tumor, or another type of mass that needs further evaluation. If a solid tumor is found, abdominal ultrasound cannot determine whether it is cancerous (malignant) or noncancerous (benign). A biopsy may be needed if a tumor is found. Ultrasound may be used during the biopsy to help guide the placement of the needle.
• Ultrasound is less expensive than other tests, such as a CT scan or magnetic resonance imaging (MRI) scan, that also can provide a picture of the abdominal organs. However, for some problems, such as abdominal masses or an injury, a CT scan or MRI may be a more appropriate test. Also, these tests may be done if the abdominal ultrasound is normal but abdominal pain persists. For more information, see the medical tests Computed Tomography (CT) Scan and Magnetic Resonance Imaging (MRI) of the Abdomen.
• A pelvic ultrasound will be used to produce a picture of the lower abdominal (pelvic) organs and other structures inside the pelvis. For more information, see the medical test Pelvic Ultrasound.

Other Works Consulted

• Fischbach FT, Dunning MB III, eds. (2004). Manual of Laboratory and Diagnostic Tests, 7th ed. Philadelphia: Lippincott Williams and Wilkins.

• Pagana KD, Pagana TJ (2006). Mosby’s Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby.