An abdominal ultrasound uses reflected sound waves to produce a picture of the organs and other structures in the upper abdomen. Sometimes 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 small sac-shaped organ beneath the liver that 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 producesenzymes 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 use 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).
Why It Is Done
Abdominal ultrasound is done to:
- Find the cause of abdominal pain.
- Find, measure, or monitor an aneurysm in the aorta. An aneurysm may cause a large, pulsing lump in the abdomen.
- Check 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.
- Learn the size of an enlarged spleen and look for damage or disease.
- Find problems with the pancreas, such as a pancreatic tumour.
- Look for blocked urine flow in a kidney. A kidney ultrasound may also be done to find out the size of the kidneys, detect kidney masses, detect fluid surrounding the kidneys, investigate causes for recurring urinary tract infections, or check the condition of transplanted kidneys.
- Find out whether a mass in any of the abdominal organs (such as the liver) is a solid tumour or a simple fluid-filled cyst .
- Guide the placement of a needle or other instrument during a biopsy .
- Look for 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 ).
How To Prepare
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. Gas 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.
How It Is Done
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 take off any jewellery 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.
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 (or back) to improve the quality of the sound waves. A small hand-held unit called a transducer is pressed against your abdomen.
You may be asked to change positions so more scans can be done. 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.
After the test
You may be asked to wait until the radiologist has reviewed the information. The radiologist may want to do more ultrasound views of some areas of your abdomen
How It Feels
The gel may feel cold when it is put on your skin 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. But if the test is being done to check 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.
The size and shape of the abdominal organs appear normal. The liver, spleen, and pancreas appear normal in size and texture. No abnormal growths are seen. No fluid is found in the abdomen.
The diameter of the aorta is normal, and no aneurysms are seen.
The thickness of the gallbladder wall is normal. The size of the bile ducts between the gallbladder and the small intestine is normal. No gallstones are seen.
The kidneys appear as sharply outlined bean-shaped organs. No kidney stones are seen. No blockage to the system draining the kidneys is present.
An organ may appear abnormal because of inflammation, infection, or other diseases. An organ may be smaller than normal because of an old injury or past inflammation. An organ may be pushed out of its normal location because of an abnormal growth pressing against it. An abnormal growth (such as a tumour) may be seen in an organ. Fluid in the abdominal cavity ( ascites ) may be seen.
The aorta is enlarged, or an aneurysm is seen.
The liver may appear abnormal, which may point to liver disease (such as cirrhosis or cancer).
The walls of the gallbladder may be thickened, or fluid may be present around the gallbladder, which may point to inflammation. The bile ducts may be enlarged because of blockage (from a gallstone or an abnormal growth in the pancreas). Gallstones may be seen inside the gallbladder.
The kidneys or the tubes that drain the kidneys ( ureters ) may be enlarged because of urine that is not draining properly. Kidney stones are seen within the kidneys (not all stones can be seen with ultrasound).
An area of infection ( abscess ) or a fluid-filled cyst may appear as a round, hollow structure inside an organ. The spleen may be ruptured (if an injury to the abdomen has occurred).
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
- Stool, air (or other gas), or contrast material (such as barium) in the stomach or intestines.
- Not being able to remain still during the test.
- Extreme obesity .
- Having an open or bandaged wound in the area being viewed.
What To Think About
- Other tests, such as a computed tomography (CT) scan , may be needed to follow up abnormal ultrasound results. To learn more, see the topic Computed Tomography (CT) Scan of the Body.
- X-rays are not recommended during pregnancy because of the risk of damage to the 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 checked.
- In rare cases, gallstones may not be found by ultrasound. Other imaging tests may be done if gallstones are suspected but not seen on the ultrasound.
- Gallbladder Scan
- Endoscopic Retrograde Cholangiopancreatogram (ERCP)
- Abdominal X-Ray
- Using abdominal ultrasound, a doctor can usually distinguish among a simple fluid-filled cyst, a solid tumour, or another type of mass that needs further evaluation. If a solid tumour is found, abdominal ultrasound cannot determine whether it is cancerous (malignant) or non-cancerous (benign). A biopsy may be needed if a tumour 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. But 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.
- Computed Tomography (CT) Scan of the Body
- 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. To learn more, see the topic Pelvic Ultrasound.
Other Works Consulted
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.