In colour Doppler ultrasound, the colour coding convention is that blood flowing TOWARDS the transducer is displayed in RED and AWAY from transducer in BLUE. This is remembered by the acronym:

• A RABA — Red Away, Blue Approaching
• B ABCD — Away Blue, Coming Downward
• C BART — Blue Away, Red Towards ✓
• D DARE — Doppler Away Red, Expected

Explanation

The standard colour Doppler convention is BART — Blue Away, Red Towards. Blood flowing towards the transducer produces a positive Doppler frequency shift and is assigned red colour; blood flowing away from the transducer produces a negative shift and is assigned blue. This is a convention (not anatomy — arteries are not always red or veins blue). Power Doppler displays only the amplitude/intensity of Doppler signal (not direction) and is more sensitive for slow flow detection. In portal vein assessment, hepatopetal flow (towards liver/transducer) = red; hepatofugal flow (reversed, away) = blue — an important sign of portal hypertension.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.