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

OBJECTIVE: 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.

MATERIALS AND METHODS: 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.

RESULTS: 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.

CONCLUSION: Plain radiography is of limited value for detecting small renal stones <5 mm.