Ultrasound

An ultrasound (also called a sonogram) is a diagnostic imaging test that uses high-frequency sound waves to create live pictures of the inside of your body. No radiation is involved, making it one of the safest imaging methods available.

A small handheld device called a transducer is placed on your skin. It sends out sound waves that bounce off your organs, tissues, and blood vessels. A computer converts the returning echoes into moving images on a screen, allowing the radiologist (a doctor who specialises in reading medical images) to see the shape, size, and movement of internal structures in real time.

Ultrasound is one of the most widely used diagnostic tools in medicine because it can examine many different parts of the body quickly and safely. Doctors request it when they need a closer look at an organ or structure without exposing the patient to X-ray radiation.

• Abdominal pain — to check the liver, gallbladder (the small sac that stores bile), pancreas, kidneys, and spleen
• Pregnancy monitoring — to check the baby's growth, position, heartbeat, and the placenta (the organ that feeds the baby in the womb)
• Thyroid gland problems — lumps or swelling in the neck
• Pelvic conditions — ovarian cysts (fluid-filled sacs on the ovary), fibroids (non-cancerous growths in the uterus), or prostate enlargement
• Blood vessel assessment — to detect narrowing or blockages using Doppler ultrasound (a technique that measures blood flow)
• Breast lumps — to help distinguish fluid-filled cysts from solid masses
• Guiding procedures — such as biopsies (tissue sampling) or draining of fluid collections
• Musculoskeletal problems — to look at tendons (the cords that connect muscles to bone) and joints

Ultrasound is not the best choice for every situation. Your doctor will consider other imaging methods when ultrasound is unlikely to give a clear enough picture.

• Structures hidden behind bone or air (such as the lungs or brain in adults), where sound waves cannot pass through easily
• Very deep structures in patients with a large body size, where image quality may be limited
• Conditions that require very detailed pictures of bone structure, where CT or MRI gives better information

Standard ultrasound carries virtually no known risks for most patients, because it uses sound waves rather than radiation.

• Mild skin discomfort — the gel applied to the skin can feel cold or slightly sticky
• Slight pressure — the transducer is pressed firmly against the skin, which may cause brief discomfort over a tender area
• Transvaginal or transrectal ultrasound (where the probe is inserted into the body) may cause brief pressure or discomfort, but serious complications are very rare
• In some cases, a very full bladder required for the preparation can feel uncomfortable before the scan begins
• The images may occasionally be unclear, requiring a repeat scan or a different type of imaging — this is a limitation, not a complication

Preparation depends on which part of the body is being examined. Your doctor or the radiology team will give you specific instructions beforehand. The general guidance below covers the most common situations.

For abdominal ultrasound, patients are usually asked to fast (eat and drink nothing except water) for several hours before the scan. This prevents gas from food from blocking the view of the organs. For a pelvic ultrasound, patients are often asked to arrive with a full bladder, as a full bladder pushes nearby organs into a better position for imaging. For other areas such as the thyroid, breast, muscles, or joints, no special preparation is usually needed. Your doctor will tell you whether to pause any medications, though this is rarely required for a standard ultrasound.

Before the scan, the radiology team may review recent blood tests or other imaging results. No special pre-procedure blood tests are usually required for a routine ultrasound, but your doctor may order them if the ultrasound is being used to investigate a specific condition.

Here is what typically happens during the procedure:

• You will be asked to change into a gown or expose the area being examined.
• You will lie on an examination table in a position that gives the best access to the area.
• A clear, water-based gel is applied to your skin over the area. This gel helps the sound waves pass into the body without interference from air.
• The sonographer (the technician trained to perform ultrasounds) gently moves the transducer across the gel-covered skin.
• You may be asked to hold your breath briefly, change position, or press on a specific area to help improve the image.
• The sonographer captures still images and short video clips throughout the scan.
• The gel is wiped off and you can get dressed. The scan itself is usually completed within a short time, though complex examinations may take longer.
• A radiologist reviews the images and sends a written report to your referring doctor, usually within hours to a few days depending on the facility.

Ultrasound requires almost no recovery time. Because it is non-invasive (nothing enters the body in a standard scan) and uses no radiation, patients can return to their normal activities immediately after the procedure. There are no wounds to care for and no medication effects to wait out.

• You can eat, drink, and move around normally as soon as the scan is finished, unless your doctor has told you otherwise for a separate reason.
• If a transvaginal or transrectal probe was used, some patients notice very mild spotting or discomfort for a short time; this usually settles quickly.
• No driving restrictions or activity limitations apply after a standard ultrasound.
• Wait for your results: the radiologist's report goes to your referring doctor, who will discuss the findings with you at a follow-up appointment.
• If the ultrasound was used to guide a biopsy or drainage procedure, aftercare instructions for that additional procedure will be given separately by your medical team.
• If you have any concerns about symptoms after the scan — however unlikely — contact your doctor rather than waiting.