Ultrasound Characteristics and Stone Composition
This 1.2 cm stone that is echogenic, mobile, and casts acoustic shadow is most likely NOT a pure cholesterol stone, but rather a mixed or calcified stone. The ultrasound features described are more consistent with stones containing significant calcium content rather than pure cholesterol composition.
Key Distinguishing Features
Typical Cholesterol Stone Characteristics
According to the American College of Emergency Physicians guidelines, cholesterol stones are often small, less echogenic, may float, and may demonstrate "comet tailing" rather than prominent acoustic shadowing 1. This contrasts significantly with your described findings.
Your Stone's Characteristics Suggest Mixed/Calcified Composition
Size (1.2 cm): This is relatively large for a pure cholesterol stone, as cholesterol stones tend to be smaller 1
Strong echogenicity: Pure cholesterol stones are typically "less echogenic" compared to mixed or pigmented stones 1
Prominent acoustic shadowing: While cholesterol stones can shadow, the presence of strong, well-defined acoustic shadowing typically indicates calcium content within the stone 1
Mobility: This feature is consistent with both cholesterol and mixed stones, so it does not help differentiate 1
Supporting Evidence from Stone Composition Studies
Research demonstrates that ultrasound characteristics can predict stone composition with 72.9% sensitivity and 100% specificity when specific criteria are met 2. The criteria for predicting pure cholesterol stones include:
- Floating stones
- Acoustic shadowing WITHOUT internal echoes from within the stone
- Generally smaller size 2
Your stone's strong echogenicity and prominent shadowing suggest it likely contains calcium bilirubinate or calcium salts mixed with cholesterol 3, 4. Most gallstones (approximately 80-90%) are actually mixed composition rather than pure cholesterol 3, 4.
Clinical Implications
The distinction matters less for surgical management but would be relevant if considering:
- Medical dissolution therapy: Only effective for small (<5-10mm), radiolucent, pure cholesterol stones 5
- Your 1.2 cm stone with these ultrasound features would NOT be a candidate for oral litholysis with ursodeoxycholic acid 5
Important Caveat
Definitive stone composition can only be determined by chemical analysis after cholecystectomy 2, 6. Ultrasound provides probabilistic prediction but cannot definitively establish composition in all cases 2.