Imaging study · No radiation
Ultrasound
Also known as: sonography, ultrasound scan, Doppler, echo, point-of-care ultrasound, POCUS
High-frequency sound waves bounced off tissue give real-time, radiation-free images, used for pregnancy, the abdomen, the heart (echocardiography), blood vessels and guiding needles.
How it works
A hand-held probe sends pulses of high-frequency sound into the body and listens for echoes from tissue boundaries. The depth of each echo builds a live moving image. Doppler ultrasound measures the frequency shift from moving blood to show flow direction and speed in colour. It is safe, portable and real-time, but sound cannot cross bone or air.
What it shows
- Abdomen: gallstones, liver size and texture, kidney obstruction, aortic aneurysm, fluid
- Pelvis: pregnancy, ovaries and uterus, bladder volume, prostate (transrectal)
- Vessels: deep vein thrombosis, carotid narrowing, varicose veins, arterial blockages
- Heart: the echocardiogram
- Soft tissue: thyroid nodules, breast lumps, lymph nodes, tendons, muscle tears, abscesses
- Guidance for needles: biopsies, drains, injections, cannulas
Best for
- First test for the gallbladder, kidneys, thyroid, scrotum, pregnancy and leg veins
- Any test that must be repeated or done at the bedside
- Guiding procedures in real time
- Children and pregnancy
Not the right tool for
- Anything behind bone (brain in adults, spinal cord) or air (lungs beyond the surface, gas-filled bowel)
- Deep structures in larger patients (image quality falls with depth)
- A comprehensive survey: it shows what the operator points at, so quality depends on skill
What to expect
- Modality
- Ultrasound
- Preparation
- Fasting for gallbladder scans so it is full; a full bladder for pelvic scans; otherwise none.
- Duration
- 10-30 minutes.
- Radiation
- No ionising radiation; diagnostic ultrasound has no known harmful effects at the energies used.
- Contrast
- Microbubble contrast (tiny gas bubbles injected into a vein) improves characterisation of liver and kidney lesions.
- Risks
- None known; brief discomfort from probe pressure on a tender area.
Common uses
| Region | Typical question |
|---|---|
| Right upper abdomen | Gallstones, jaundice, abnormal liver tests |
| Kidneys and bladder | Kidney injury, obstruction, stones, bladder emptying |
| Leg veins | Suspected deep vein thrombosis |
| Neck | Thyroid nodules, lymph nodes, carotid stenosis after a stroke |
| Musculoskeletal | Tendon tears, joint effusions, guiding steroid injections |
Studies this page covers
Abdominal ultrasoundPelvic ultrasoundObstetric ultrasoundTransvaginal ultrasoundTransrectal ultrasoundThyroid ultrasoundBreast ultrasoundScrotal ultrasoundRenal ultrasoundBladder ultrasoundVascular Doppler ultrasoundCarotid Doppler ultrasoundVenous Doppler ultrasoundArterial Doppler ultrasoundPoint-of-care ultrasoundMusculoskeletal ultrasoundCarotid ultrasoundVenous duplex ultrasoundArterial duplex ultrasound
Named studies of the master test taxonomy that this modality page covers; each links to its test category.