Is fasting required for a liver color Doppler ultrasound?

Yes, liver ultrasound (also known as hepatic ultrasound or abdominal ultrasound focusing on the liver) is typically performed after an overnight fast—usually for at least 8 hours. Fasting is recommended because food intake stimulates gallbladder contraction and increases intestinal gas and gastric contents, both of which can significantly degrade image quality. A full gallbladder serves as an important acoustic window, helping to visualize the liver’s posterior segments and adjacent structures more clearly. Additionally, fasting reduces bowel gas and peristalsis, minimizing artifacts that obscure hepatic anatomy and Doppler assessment of intrahepatic vessels. While some modern ultrasound systems and experienced sonographers may obtain diagnostic images in non-fasted patients, adherence to standard fasting protocols remains the best practice to ensure optimal sensitivity and specificity—particularly when evaluating for diffuse liver disease, focal lesions, steatosis, or biliary pathology.