There have been claims that cholesterol stones cannot be detected via ulstrasound. It appears that this is not the case. I have posted several links to other articles supporting the detection of these stones but figured they might get lost in the convolutions of the thread below. I figured another debate topic would be a good idea. here is a pretty good article where detection is 100%:
Prediction of gall stone composition by ultrasound: implications for non-surgical therapy
BS Kapoor, AK Agarwal and NN Khanna
Department of Surgery, University Hospital, Banaras Hindu University, Varanasi, India.
Oral cholecystography is the basic radiodiagnostic procedure required to assess chemical composition of Gallstones as well as functional status of gall bladder prior to non-surgical management of gallstones. However, the value of ultrasound in non-surgical management of Gallstones is yet to be proved. In this study we attempt to establish sonographic criteria which will predict the composition of Gallstones prior to their non-surgical treatment. For this purpose the ultrasonographic characteristics of 233 patients with gallstone disease and functioning gall bladders were studied and an effort was made to correlate cholesterol and calcium content of different types of stones (as estimated by X-Ray powder diffraction study and atomic absorption spectrophotometry) with their ultrasonographic characteristics. Sonographic criteria for the presence of cholesterol stones were those which were floating and gallstones producing acoustic shadowing without internal echoes from within the stone. In detecting findings which would predict the presence of cholesterol stones on ultrasound, ultrasound had a sensitivity of 72.90% and a specificity of 100%. The predictive values of positive findings and negative findings were 100% and 93.4%, respectively. The demonstration of typical features of cholesterol stones on ultrasound obviates the need for oral cholecystography.
And here is another example: Most notable is this phrase:
"Stones usually sink to the dependent portions of the gallbladder, but cholesterol stones may float.
So not only can they detect them but their buoyancy characteristics are easy to see on ultrasound.
The procedure of choice for gallstone diagnosis is real-time ultrasonography, replacing oral cholecystography. Accuracy of detection is greater than 95%. The gallbladder is normally an echo-free structure on the undersurface of the liver. Characteristic findings of gallstones include moveable, discrete, echogenic foci within the dependent portion of the gallbladder and acoustic shadows emanating directly below the echogenic foci. Stones usually sink to the dependent portions of the gallbladder, but cholesterol stones may float. Occasionally collections of weaker echoes without acoustical shadowing are found within the gallbladder lumen, representing biliary sludge. Sludge can be found in fasting patients, nonambulatory patients, patients on total parenteral nutrition. and patients with cirrhosis or extrahepatic biliary obstruction.
Noncalcified stones can be difficult to detect despite CT being more sensitive than plain film. Noncalcified stones can be recognized as subtle areas of slightly lower or higher attenuation within the bile.
Magnetic Resonance Imaging
Stones can be observed as areas of low signal intensity within the higher signal intensity of the gallbladder bile. The accuracy of this technique relative to other imaging modalities is currently unknown.