Ultrasound may be a viable alternative to CT scanning as an initial investigation for suspected nephrolithiasis, the findings from a study in the United States suggest. A total of 2,759 patients aged 18-76, presenting to an emergency department with suspected renal colic were randomly assigned to either initial diagnostic ultrasound carried out by an emergency physician (908), ultrasound by a radiologist (893), or abdominal CT scan (985).