Diagnostic ultrasound or sonography is an imaging method used to examine internal organs and soft body tissue. It is an important diagnostic tool in the medical field.
During an ultrasound examination, high-frequency sound waves bounce off of body structures, specifically organs and soft tissue, creating echoes. This mechanism reflects the size, shape and consistency of the targeted organs and tissue. As a result, a computer-generated image is produced.
Diagnostic Potential of Ultrasound
Ultrasound is used to assess many different parts of the body including, but not limited to:
- The womb during pregnancy, to confirm a due date, reveal if there are multiples, rule out an ectopic pregnancy, assess fetal position, determine birth defects or problems with the placenta
- Pelvic area including uterus and ovaries
- Gallbladder, liver, spleen and pancreas
- Kidneys and bladder
- Vascular system including the heart and blood vessels
- Breast abnormalities, often in conjunction with a mammogram
- Thyroid gland
- Prostate and testicle abnormalities
- Muscle and tendon issues
Ultrasound is also used during some procedures, such as a needle biopsy, to help guide a physician to the specific treatment site.
Preparing for an Ultrasound
Most ultrasound studies have no specific preparation. However, there are a few specialized ultrasound tests that do have some minor preparation, including the following:
- Gallbladder ultrasound requires that the patient have no food or liquids for six to eight hours before the exam. Food causes the gallbladder to contract, which makes it smaller and more difficult to visualize.
- Pelvic ultrasound requires that the urinary bladder be full so that it is lifted above the uterus, ovaries and/or prostate for better visualization. A full bladder also moves air-filled bowel away from the uterus to further improve visualization.
Comfortable clothing should be worn the day of the ultrasound. Sometimes, a patient does not need to undress for the test if the area being examined can be easily exposed.
What to Expect During the Test
Patients recline for a 30 to 60-minute ultrasound examination. A clear, water-based conducting gel is spread over the area being examined. The gel helps the hand-held transducer or wand transmit the sound waves through the body as it is gently moved along the skin. In some instances, the technologist presses the transducer firmly against the skin to get a clear image.
Most ultrasounds are painless. There are usually no needles or incisions involved. The exception is if the purpose of the ultrasound is to do a guided needle biopsy or transesophageal echocardiogram, which usually involves administering intravenous (IV) sedation for patient comfort.
There can be mild discomfort if the specific ultrasound involves the patient having a full bladder or is part of a more invasive study done with a transducer that is inserted into the vagina, rectum or esophagus.
There are several ultrasound studies that are performed by placing a specialized transducer or device within the body. They include:
- Transvaginal ultrasound, which evaluates a woman’s uterus and ovaries using a special vaginal transducer.
- Transesophageal echocardiogram during which a special transducer is inserted down the esophagus to get an unobstructed view of the heart. This ultrasound is done under intravenous sedation.
- Transrectal ultrasound, which looks at a man’s prostate using a rectal transducer.
The transducer sends the collected information to a computer, which creates detailed images. There are no specific physical restrictions after having an ultrasound.
A specially trained technologist does the ultrasound test. In the event of a pregnancy, the attending obstetrician most often does the ultrasound. A radiologist interprets the completed ultrasound images and sends a report of the findings to the ordering physician.
There are no true risks to having an ultrasound but there are a few limitations to the test:
- Sound waves travel poorly through bone and free air; hence an ultrasound is not a helpful diagnostic tool for areas of the body obstructed by bone or those with gas.
- Since sound waves cannot penetrate deep into the body, ultrasound studies for obese patients can result in poor imaging.
It is important to note that there is no radiation exposure during an ultrasound, which makes ultrasound a safe diagnostic choice.
Ultrasound studies provide valuable medical information for diagnostic and assessment purposes. It is important to discuss with your physician the option of using ultrasound for health screenings or guided procedures.