The value of ultrasound in predicting non-visualization of the gall-bladder on OCG: implications for imaging strategies in patient selection for non-surgical therapy of gallstones.

Gall-bladder visualization on oral cholecystography (OCG) is required for most non-surgical therapies of gallstones. In this study we attempted to establish sonographic criteria which will predict non-visualization of the gall-bladder on OCG. For this purpose we compared the results of ultrasound (US) and OCG in 171 patients with gallstones being assessed for non-surgical therapy. Sonographic criteria for non-visualization were a contracted gall-bladder and stone impaction in the gall-bladder neck or cystic duct. In detecting findings which predict non-visualization on OCG, US had a sensitivity of 78.3% and a specificity of 97.6%. The predictive values were: positive findings 92.3% and negative findings 92.4%. The overall accuracy was 92.4%. We conclude that US can be used as a first step in selecting patients for non-surgical therapy and if US indicates a contracted gall-bladder, 11% of the patients can be excluded from further diagnostic imaging.