To distinguish if a structure seen on ultrasound is a rib or a mass, which maneuver should you perform?

• A. Apply color Doppler
• B. Turn 90 degrees on it
• C. Reposition the patient
• D. Increase gain

Answer: (B)

Distinguishing a rib from a mass hinges on recognizing bone features and how they appear when you change the probe orientation. A rib is a bone with a bright cortical margin that follows the chest wall and creates posterior acoustic shadowing. To confirm if the structure is part of the rib, rotate the transducer 90 degrees and view it in a different plane. If it’s a rib, you’ll still see the bright cortical line tracing the rib and the shadow continuing along its length as you change angles. A soft-tissue mass, by contrast, will not show a persistent bone-like cortical margin or the same predictable shadow pattern when viewed from another angle, and its echotexture may appear more heterogeneous.

Color Doppler, repositioning the patient, or simply increasing gain can provide useful information in other contexts, but they don’t offer the same definitive plane-dependent distinction between bone and soft tissue as rotating the probe to re-evaluate the structure’s relationship to the rib.