Prediction of stone composition from plain radiographs: A prospective study

Background and Objectives: Stone composition, as reflected in radiographic appearance, is important to help choose between SWL and percutaneous/endosc opic procedures. Predicting a stone's composition accurately from a plain r adiograph would be a useful tool in clinical decision-making. However, the ability of physicians to predict composition has not been adequately assess ed. A prospective study was designed to quantify the accuracy of a panel of physicians who routinely deal with stones in classifying stone composition solely from radiographs, 'Materials and Methods: A panel of six members was created to review 100 pl ain-film radiographs from patients with renal stones of known composition, The panel consisted of two urologists, two radiologists, and two nephrologi sts, all of whom have expertise in stone disease. If the composition guesse d was at least 40% of the total stone composition, the response was deemed correct, Results: Overall, there was an average 39% correct response score among the six panelists. When the stones were divided by size, 35% were <1 cm, and 6 5% were larger. The accuracy of chemical composition determination did not improve with greater stone size, nor was there a difference in accuracy for pure and mixed stones. The most frequently misclassified stone was calcium phosphate, with only 14% being correctly diagnosed. Conclusions: With a random sampling of plain radiographs, a panel of physic ians specializing in stone disease correctly diagnosed the composition of r enal calculi less than half of the time without being given clinical inform ation.