The test is performed by placing a handheld device, also called a transducer, onto the skin over the organ(s) of interest. The transducer sends and receives sound waves through the body, then converts the waves into images on a monitor.
Normal and abnormal tissues and organs contain different acoustic properties which are recorded by the sound waves during an ultrasound. For example, an ultrasound would be able to show the presence of a gallstone or cyst, as well as the swelling of the liver. An abdominal ultrasound can be used to evaluate the gallbladder, liver, bile ducts, pancreas, spleen, and kidneys.
It depends on your symptoms. A gastroenterologist may order this test to determine the cause of abdominal pain, detect gallbladder or kidney stones, identify the cause of abnormal blood tests, or monitor tumors. Among many other reasons, your doctor may use an abdominal ultrasound to look for damage after an injury or the cause of a fever, fluid retention or swelling of an abdominal organ.
Usually patients are asked to not to eat or drink for 6 to 8 hours before the procedure; however, preparation for the procedure depends on your age and the nature of your examination. Your health care provider will advise you of your preparation instructions based on your specific needs.
Depending on which area is being examined, you may need to take off any jewelry or clothing that will interfere with the ultrasound images. You will be given a cloth or paper covering to wear during the test.
While lying down, a clear, water-based conducting gel is applied to the skin on your abdomen to help transmit the sound waves. The transducer is then pressed against your abdomen and moved back and forth over the organ(s) of interest. You will feel light pressure as it passes over your abdomen. Typically, an ultrasound is not uncomfortable, but if the test is being done to check for damage from a recent injury, the slight pressure of the transducer may be painful. You will not hear or feel the sound waves as they pass through your abdomen; however, a picture of the organs and blood vessels can be seen on a video monitor.
During the ultrasound, it is important that you remain very still. You may be asked to hold your breath for short periods of time during the examination in order to get the clearest images possible of your abdomen. You may be asked to change position so that different areas can be examined (for example, you may be asked to lie on your stomach for a kidney ultrasound). The procedure usually takes less than 30 minutes, but could take up to 60 minutes depending on why the procedure is being performed and which areas are being viewed.
There are no documented risks to having an ultrasound regardless of age or health.
Using abdominal ultrasound, the physician 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, an abdominal ultrasound cannot determine whether it is cancerous or noncancerous, and a biopsy may be needed. In that case, an ultrasound may be used during the biopsy to help guide the placement of a needle. The biopsied specimen will then be sent to a pathology lab for testing.
A continuous sound wave commonly known as “Doppler” may be used during the ultrasound procedure to evaluate blood flow to and from the intestinal tract or other organs. It can help diagnose many conditions including blood clots, decreased blood circulation or blocked arteries. A mesenteric Doppler ultrasound looks for any narrowing of the three main arteries that carry blood to the intestinal tract. Similarly, a Doppler ultrasound of the liver determines if the veins to and from the liver are narrowed or obstructed.