What is Ultrasound?
Ultrasound uses sound waves to look at the internal organs of the body. A special instrument, called a transducer, has tiny crystals inside that, when excited by an electrical current, emit sound waves above the audible range of sound. The sound waves are sent into the body and bounce off internal organs. The transducer then picks up these rebounding sound waves and, with the aid of a computer, displays the returning sound waves as a picture representing the organ(s) of interest. There is no radiation involved in ultrasound. This unique feature is why so many doctors refer pregnant women for ultrasound examinations of their unborn baby. Ultrasound has had many advances in the last few years. Technologists can examine in detail other anatomical structures such as the baby’s heart.
What can Ultrasound do?
Ultrasound is very good at discerning cystic (fluid-filled) structures from solid structures within the body. It is a great tool for targeted examinations, and because of its relatively low cost, it is also a wonderful first line of testing. Ultrasound can look at solid internal organs (pancreas, spleen, liver), reproductive organs, thyroid, unborn babies, arteries and veins, and can even image the skin and muscles on the arms and legs. Ultrasound is also used as a guidance tool: the technologist can show the doctor the exact location of an organ for biopsy with a needle.
Why do I need to drink water before some exams?
When a patient needs to have their bladder, kidneys, unborn baby, and/or female reproductive system imaged, the patient must drink water, at least one hour prior to the examination, to fill the bladder. The bladder works as an “acoustic window”, which means it helps the sound waves get to the organ(s) that need to be imaged. Plus by having a full bladder, the intestines that usually live between the pelvic organs and the bladder are moved out of the way so the technologist has a clearer view. By filling the bladder, the doctor can also assess the bladder wall for irregularities, and watch to confirm that the kidneys are draining properly into the bladder.
Often, when scanning unborn babies, the baby’s head is very low in the mother’s pelvis. By filling the bladder, the baby’s head gets moved out of the mother’s lower pelvis, thus allowing the baby’s brain and skull to be imaged better.
Why do I need to fast for 6 hours before an abdomen examination?
Scanning the abdomen is very hard because of the intestines. In a normal person, the intestines are filled with air, fluid, and ingested food. These three things make imaging the abdominal organs nearly impossible. Ultrasound cannot image through air. By fasting for eight hours before the examination, the intestines are relatively empty, and the technologist can work around them to image the liver, gall bladder and bile ducts, main portal vein, pancreas, spleen, and kidneys. The other benefit of fasting for eight hours is that the gall bladder can be seen more readily. The gall bladder is a reservoir for bile and bile salts, which is made by the liver. When we eat and/or drink, the gall bladder contracts to expel bile into the small intestine to break down what we ingest. When the gall bladder is contracted, it is very hard to evaluate for possible problems. But by fasting for eight hours, the gall bladder is sufficiently full of bile and can be evaluated for size, shape, and irregularities.
When you are instructed to fast before an abdomen Ultrasound examination, it also includes no drinking, no chewing (gum, tobacco, etc), and no smoking. All of these will cause the gall bladder to contract, thus making Ultrasound identification next to impossible.
- Abdomen: Nothing to eat or drink for six hours prior to examination. This includes no tobacco products, and no chewing gum.
- Retroperitoneal (Kidneys): Nothing to eat for six hours prior to examination. Please drink 32 oz of water one hour prior to exam time.
- Pelvis: Please drink 32 ounces of water one hour prior to examination time. Do not use the bathroom before exam time. (Example: your appointment is at 9:00. You may use the bathroom before 7:30. From 7:30 to 8:00 drink all 32 ounces of water and do not use the bathroom again)
- Pediatric/Male Pelvis: Please drink at least 32 ounces of water one hour prior to exam time. Do not use the bathroom before exam time. Please see above for an example.
- First Trimester Obstetrical: No preparation necessary.
- Second/Third Trimester Obstetrical: Please drink 32 ounces of water one hour prior to examination time. Do not use the bathroom before exam time. Please see Pelvis preparation for an example.
- Thyroid: No preparation necessary
- Neo-Natal Intracranial: No preparation necessary
- Aorta: Nothing to eat or drink for six hours prior to examination time.
- Venous/Deep Vein Duplex: No preparation necessary
- Breast: No preparation necessary. If you are new to our imaging center and have had a Mammogram or Breast Ultrasound elsewhere please bring your prior films with you.
- Superficial: No preparation necessary.