Abdominal imaging - Ultrasound

Principle

Abdominal ultrasound is a radiation-free, widely available, relatively low-cost first-line imaging modality - particularly strong for the hepatobiliary system, kidneys, and free fluid detection, though limited by operator dependence and body habitus/bowel gas interference
Sound waves reflect differently off tissues of different density, producing real-time greyscale images; Doppler ultrasound adds flow assessment, useful for vascular patency (portal vein, hepatic veins, renal arteries) and characterising some lesions by their vascularity pattern

First-line test for suspected gallstone disease, and commonly used as an initial screen for hepatomegaly/splenomegaly, ascites, and renal tract pathology
Gallstone disease/cholecystitis, ascites, hepatosplenomegaly, renal tract obstruction, portal vein assessment

First-line for suspected biliary colic/cholecystitis (gallstones, gallbladder wall thickening, pericholecystic fluid, sonographic Murphy's sign) - excellent sensitivity for gallstones specifically
Limited by bowel gas (can obscure deeper structures, particularly pancreas) and body habitus (image quality degrades with increasing patient size) - a technically limited study should prompt consideration of CT/MRI rather than being treated as definitively normal
Bedside/point-of-care ultrasound increasingly used for rapid free fluid assessment (e.g. FAST scan in trauma) and guiding procedures (paracentesis, line insertion)

A technically difficult/limited ultrasound (obscured views) should be explicitly flagged as such, and cross-sectional imaging (CT/MRI) considered if clinical suspicion remains despite an apparently normal but technically limited study

Ultrasound's operator- and body-habitus-dependence means a "normal" study in a technically difficult patient carries less reassurance than the same result in an easily imaged patient - this caveat should be communicated when interpreting results, not assumed to be self-evident

4 more sections, plus exam facts

Premium unlocks every note across every specialty, and the full exam fact library behind it.