More than 2 Billion dollars is spent each year in the United States towards the referral, diagnosis, and treatment of suspected nephrolithiasis. The use of computed tomography (CT) for the diagnosis of renal stones has increased 10 times over the past 15 years and although the use of CT offers greater sensitivity, the increase risk related to radiation exposure provides the basis to consider ultrasound as the initial imaging modality of choice. There is no evidence that CT used an initial imaging choice is associated with improved patient outcomes.
The study referenced in the original article sought to understand if there would be any significant difference in patient outcomes, radiation exposure, or cost of care between patients who underwent ultrasound or cat scan as the initial diagnostic test ordered to rule out nephrolithiasis. In the study, 2759 patients from 15 geographically diverse academic emergency departments were randomly assigned to one of three imaging groups: ultrasound performed at point-of-care by an emergency room physician (908 patients), ultrasound performed in a Radiology department (893 patients), or an abdominal CT (958 patients). The patients recruited for the study were between ages 18 and 76 and were eligible for the study if they had presented to the emergency department with complaints of flank or abdominal pain and the treating emergency physician had decided to order imaging to rule out kidney stones. Patients who were considered to be at high risk for diagnosis such as appendicitis, aortic aneurism, acute cholecystitis, or bowel disorders, were not eligible. Additional disqualifying factors were patients with a history of renal transplant or single kidney, patients undergoing dialysis, pregnancy, and excessive weight.
The study examined three different points of data: additional serious diagnosis that could be related to missed or delayed diagnosis, overall cumulative radiation exposure from imaging, and the total cost of care. The cumulative radiation exposure examined the sum of the effective doses from all imaging sources that was performed within 6 months of the initial emergency room visit. The study also examined any return visits to the emergency department, all hospitalizations after initial discharge, serious adverse events related to the participation in the study, self-reported pain scores, and the diagnostic accuracy for the diagnosis of renal stones.
Of the 2759 patients in the study, 41.6% had a history of kidney stones, 63.3% had hematuria, and 52.5% had tenderness on physical exam. A small percentage of the participants had findings consistent with acute cholecystitis (1.3%) or appendicitis (3.6%) or were determined to be at high risk for aortic aneurysm (0.8%), appendicitis (3.1%), or bowel obstruction or ischemia (3.6%). When examining serious adverse events related to the participation in the study, it was noted that there were no significant differences among the study groups. In total, there were 12 related serious adverse events which occurred in 5 patients assigned to the CT group, 4 assigned to radiology ultrasound, and 3 patients assigned to point-of-care ultrasound. Of the 12 related serious events, 5 were patient deaths that occurred between 38 and 174 days after the randomization, none of which were considered to be related to participation in the study.
The authors summarized their study by stating that patients in the ultrasound groups were exposed to much lower amount of radiation as compared to patients in the CT group and with no significant differences in complications or related adverse events. Of also importance, were pain scores, hospital admissions, and emergency department readmissions during follow up that did not vary significantly between the groups. The authors did not suggest that ultrasound should be the only diagnostic study used to rule out nephrolithiasis, but it should be used as the initial diagnostic imaging test and further diagnostic testing ordered if deemed necessary by the physician. By replacing CT with ultrasound as the initial diagnostic test to rule out nephrolithiasis, patients will benefit from an overall reduction in radiation exposure and will not experience any significant differences regarding pain, return visits, hospitalizations, or subsequent serious adverse events.