Management of stone disease often involves imprecise diagnoses as well as inadequate stone localization and sizing. Enter into the picture the novel approach of using the acoustic shadow width to determine stone size by ultrasonography. Using this method stone size was estimated with significantly greater accuracy, regardless of whether ray line, spatial compound or harmonic imaging was used. Indeed, accuracy of sizing to within 1 mm was obtained in 78% of cases.
Is this the Holy Grail? One limitation of ultrasonography is it is 2-dimensional, leaving the possibility that the largest dimension may be missed or stone volume underestimated. In more than half of stones smaller than 5 mm, a shadow width was not able to be reported. As stones become deeper (ie patients get bigger), the resolution of ultrasonography decreases, leading to more challenges in differentiating stone or shadow from the background scatter.