What is abdominal ultrasound?
Ultrasound uses high frequency sound waves generated electronically using special crystals in a probe. The sound travels through your body, and bounces off different tissues and back to a receiver on the same probe. The sound waves are then interpreted into a digital image.
Abdominal ultrasound is when your abdomen is examined by a radiologist or sonographer using this machine to ‘see inside you’.
What are the common uses?
To evaluate the liver, gallbladder, kidneys, pancreas, spleen, abdominal aorta and other blood vessels of the abdomen; and diagnose a variety of conditions such as cysts, tumours (abnormal growths and enlarged abdominal organs), calcifications (like kidney stones or gallstones), areas of infection (like abscesses), aneurysms and malformations.
Functional checks, like blood flow in the liver, kidneys and spleen can also be done.
How should I prepare?
Wear comfortable loose-fitting clothing. Remove all clothing and jewellery in the area to be examined; and you may be asked to wear a gown during the procedure.
For a study of the liver, gallbladder, spleen, pancreas and aorta, you may be asked to eat a fat-free meal on the evening before the exam and avoid eating for 12 hours beforehand.
For an exam of the kidneys (urinary tract), you may be asked to ensure a full bladder and avoid eating for 12 hours before the exam.
How is the procedure performed?
You'll lie on your back on the examination table. A clear gel is applied to the skin on your abdomen, and the radiologist presses the transducer firmly against your body, moving it back and forth over the area of interest until the desired and optimal images are acquired. Sometimes it is slightly uncomfortable as the radiologist or sonographer passes over an area that is tender, but this is transient. The radiologist may stop occasionally to take measurements or do other assessments of organs or other lesions. They may ask you to lie on one side or another at certain stages of the exam, in order to 'see' certain areas better. Most ultrasound examinations are painless, fast and easy.
The ultrasound examination is usually completed within 30 minutes and the gel will be wiped off your skin.
You may be asked to wait in the waiting room while the radiologist or sonographer analyses the images, and a written report is given to you for your referring doctor. The radiologist may discuss preliminary results with you at the end of your exam if you so request.
What are the benefits vs risks?
The abdominal ultrasound is non-invasive (no needles or injections). It is widely available, easy to use and less expensive than other imaging methods. It uses no ionising radiation and provides clear pictures of soft tissues that do not show up well on X-ray images; in addition the ultrasound provides real-time imaging, thus making it a good tool to guide minimally invasive procedures such as needle biopsies and needle aspirations of fluid or abscesses for further evaluation.
There are no known harmful effects for the standard diagnostic ultrasound examination, and it is even safe to perform during pregnancy.
What are the limitations of the procedure?
The sound waves used by the ultrasound do not penetrate air and are in fact reflected by air or gas, therefore it is not ideal for examination of the bowel. In addition, these elements may prevent proper visualisation of deeper structures and lesions lying beneath the bowel. Patients who are obese may be more difficult to image because the sound waves weaken as they pass deeper into the body.
Some lesions may be visible, but the exact nature or pathology may not be clear and may need further evaluation, for example with needle biopsy or CT.