Ureterolthiasis has become a poster child for over-utilization of advanced imaging. Despite the relative level of distress kidney stones cause our patients, the use of computed tomography has never been associated with improved outcomes – yet, CT is widespread for its diagnostic utility, contributing substantially to $2 billion in annual healthcare expenditures for this condition in the U.S. alone.
This, however, is a comparative effectiveness evaluation promoting ultrasound for the diagnosis of ureterolithiasis in the Emergency Department, a three-pronged evaluation comparing CT, formal ultrasonography by radiology technicians, and bedside Emergency Department ultrasonography. Essentially, the objective of this study was to compare safety – regarding, in a sense, whether the additional information supplied by CT was valuable for the detection of life-threatening alternative diagnoses. And, with respect to this outcome all strategies had, essentially, the same number of “misses” during the follow-up period – mostly acute cholecystitis, one case of appendicitis, and a smattering of other thoracoabdominal diagnoses. And so – ultrasonography, even our amateur sort in the ED, is “just as good”.
Of course, there are a few oddities associated with this publication. There are, bizarrely, three “primary outcomes”, and the authors explicitly choose to report only two of them. Total costs of care was intended to be an outcome, but the authors simply state those results will not be reported in this paper. This study also has an interestingly low incidence of ~33% confirmed ureterolithiasis – which may result from their lack of a “gold standard” for diagnosis of stone, relying on patient-reported stone passage or follow-up for stone removal. Or, it could be enrollment of a population with an oddly low incidence of hematuria – only ~63% of enrolled patients exhibited this common finding with a sensitivity of >80%. I’d be curious to see the incidence of hematuria in the cases with alternative diagnoses, although there would likely be too few to draw any substantial conclusions.
There was also substantial crossover from the ultrasonography cohorts. 40.7% of those randomized to ED ultrasonography and 27.0% randomized to radiology ultrasonography ultimately underwent CT. And, this crossover reveals the limitation of ED ultrasonography: a “sensitivity” of 54%, compared with a “sensitivity” of 88% for CT (the unreliable gold standard for diagnosis limits test characteristic calculations). There was also a major exclusion relevant to the U.S. population: women over 250 lbs and men over 285 lbs. Unfortunately, a substantial portion of the U.S. exceeds such superlative mass – and the generalizability of these results to that population is open to reasonable variability.
The take home point, however, is a little less reliable. Yes, if you select patients for imaging similarly to these authors and visualize unilateral hydronephrosis in the setting of suspected ureterolithiasis, it is fair to terminate your diagnostic pathway. However, the primary fallacy of this study design is predicated on the debatable necessity of performing imaging for all suspected ureterolithiasis. One can make a very reasonable argument ureterolithiasis can be adequately diagnosed on clinical grounds, and advanced imaging is required only in the minority of cases, regardless of the findings on bedside ultrasound. The vast majority of ureterolithiasis carries a relatively benign prognosis of recurring and remitting pain of a few weeks duration, and return precautions or outpatient follow-up for persistent symptoms is likewise a reasonable course of action.
“Ultrasonography versus Computed Tomography for Suspected Nephrolithiasis”