Ultrasound
A non-invasive imaging technique using sound waves to visualize soft tissue structures in real time. Used for abdominal organ evaluation, cardiac assessment (echocardiography), and guided tissue sampling.
Ultrasound (ultrasonography) uses high-frequency sound waves to create real-time images of internal soft tissue structures. A transducer emits sound pulses that bounce off tissue interfaces and return to the probe, generating a two-dimensional image. Unlike radiographs, ultrasound involves no ionizing radiation and provides detailed internal organ architecture.
Abdominal Ultrasound
Abdominal ultrasound is the primary tool for evaluating:
- Liver: parenchymal texture, masses, biliary mucocele, vascular abnormalities (portosystemic shunt)
- Spleen: nodules, masses (hemangiosarcoma screening), torsion
- Kidneys: size, architecture, stones, cysts, pyelonephritis, chronic kidney disease staging
- Bladder: wall thickness, masses, stones not visible on radiograph
- Pancreas: pancreatitis (enlarged, hypoechoic pancreas with hyperechoic surrounding fat)
- Adrenal glands: size and symmetry (Cushing’s disease evaluation)
- Gastrointestinal tract: wall layer thickness, masses, foreign bodies, lymph node enlargement
- Reproductive tract: pregnancy diagnosis, pyometra
Cardiac Ultrasound (Echocardiography)
Echocardiography is a specialized cardiac ultrasound that evaluates:
- Chamber dimensions and wall thickness
- Valve structure and function (mitral valve disease)
- Myocardial contractility (dilated cardiomyopathy)
- Pericardial effusion
- Blood flow patterns (Doppler mode)
Board-certified veterinary cardiologists perform and interpret echocardiograms. This is different from abdominal ultrasound, which general practitioners or internists may perform.
FAST Scan Protocol
Focused Assessment with Sonography for Trauma (FAST) is a rapid, point-of-care ultrasound protocol used in emergency settings. The veterinarian places the probe at four standard locations to detect free fluid (blood, urine, effusion) in the abdomen (AFAST) or chest (TFAST). A positive FAST scan indicates internal hemorrhage, ruptured bladder, or effusion requiring immediate intervention.
FAST scans take 3-5 minutes and can be life-saving in trauma, hemangiosarcoma rupture, and pericardial effusion cases.
Ultrasound-Guided Sampling
Ultrasound guidance allows precise tissue sampling without surgery:
- Fine needle aspirate (FNA): a needle is guided into a mass or organ for cytology
- Tru-cut biopsy: a larger needle obtains a tissue core for histopathology
- Abdominocentesis/thoracocentesis: guided fluid drainage
This makes ultrasound both a diagnostic and interventional tool.
When Ultrasound Is Recommended
- Abnormal blood work suggesting organ disease
- Cancer screening and staging (splenic, hepatic, renal masses)
- Follow-up on abnormalities found on radiograph
- Monitoring known disease progression
- Senior dog screening protocols (abdominal ultrasound every 6-12 months after age 7-8)
- Any unexplained weight loss, vomiting, or abdominal pain
Limitations
Ultrasound cannot penetrate bone or air-filled structures well. It does not replace radiographs for skeletal evaluation or lung assessment. Image quality depends heavily on operator skill and equipment quality.