The Utility of the Kidneys-ureters-bladder Radiograph as the Sole Imaging Modality and Its Combination With Ultrasonography for the Detection of Renal Stones

Abstract

To investigate the efficacy of plain radiography and ultrasonography, each as the sole imaging tool as well as combined, for detecting renal stones using unenhanced computed tomography as a standard reference. Ultrasonography and plain radiography of the kidneys, ureters, and bladder are often used for urinary tract stone detection, but the effectiveness of each method used alone, or the 2 methods used together, remains controversial. From January 2012 to September 2014, 822 patients underwent plain radiography, ultrasonography, and unenhanced computed tomography on the same day. The sensitivity and specificity of the 2 modalities to detect stones were evaluated. We compared the sizes of stones on plain radiography and ultrasonography with their size on unenhanced computed tomography. Of 1644 kidneys, unenhanced computed tomography detected at least 1 stone in 994 kidneys. Ultrasonography and plain radiography detected at least 1 stone in 882 and 488 kidneys, yielding a sensitivity of 88.7% and 49.1% and a specificity of 68.3% and 99.1%, respectively. Of 488 stones detected by plain radiography, 476 stones were also detected by ultrasound, with a sensitivity of 89.9% and specificity of 68.1% for the combination of the 2 modalities. The detection rate for plain radiography for stones <5 mm was low. Stone sizes measured by the 2 modalities positively correlated with those obtained by computed tomography, and the concordance rate based on size was similar. Plain radiography is of limited value for detecting small renal stones <5 mm.